Hydropower Terminology Definitions - by Hobo Maps - Go Back to Hydropower Projects Web Page - - - Home
Lao language terms below:
Ban = village or town
Buak (Buek) = man-made pond
Don = island or sandbar in a river such as Mekong
Houay (Huay) = small river or stream that may be dry part of the year
kip = monetary currency of Laos
Luang = may refer to a populated flat area in mountainous terrain
Muang (Meuang) = district
Nai Ban = village chief or head man
Nam = river or lake
Nong = natural low-area pond
Pak = town or village located at junction where a river or stream joins a larger river
Phou or Pha = mountain or hill
Sathani rot fai = railway station
Tad = waterfall or cascade
Talad = traditional market
Xe = river (in southern Laos - pronounced as "say")
Terminology below edited and conformed to terms used in Lao PDR hydropower projects.
1995 Mekong Agreement - Agreement signed by Governments of Cambodia, Lao PDR, Thailand and Viet Nam that established the Mekong River Commission in 1995.
3-phase power - is a three-wire ac power circuit with each phase signal 120 electrical degrees apart
3S Basin - drainage basin for 3 large rivers in southern Laos & Cambodia with "S" names - Sekong, Sesan and Srepok
abatement - the reduction or elimination of pollution
abiotic - relating to things in the environment that are not living
abstraction - the process of taking away or removing characteristics from something in order to reduce it to a set of essential characteristics.
abutment - the edge of a hill or solid high ground against which a dam is constructed to resist the forces of movement.
accretion - growth or increase by gradual accumulation
ac generator - an alternator
AC motor - uses stationary coils of wire to rotate the rotating magnet around on its shaft
Acoustic Doppler Current Profilers - instruments used to measure water velocities, direction of flow and depth.
acre - 1 acre is equal to about 4,000 square meters or .4 hectare
acre-foot - The volume of water that would cover one acre to a depth of one foot. 1 acre-foot= 43,560 cubic feet or 326,000 gallons.
active power - the amount of electric power in an AC electric circuit which is actually consumed or utilized. Also called true power or real power and is measured in Watts.
active storage – also known as active volume, regulating capacity or live storage - the portion of a reservoir that can be drawn down and removed by drainage gravitation. Contrary to dead storage that must be pumped out.
adit tunnel – a nearly-horizontal passage dug for access to an underground tunnnel or mine. Used for ventilation, haulage, drainage, repairs or other access.
aerate - to force or introduce additional air into a material such as water
aeration weir – a weir designed to aerate the water flowing over it.
aerator - a forced-air system used to aerate water
aerobic - living, active, or occurring only in the presence of oxygen
affermage - lease agreement where the lesee takes over operational responsibility of an enterprise but the assets remain the property of the lessor.
afforestation - the planting of new forests on lands where the preceding vegetation or land did not contain forests.
air - so-called "pure" or "natural" air is a mixture of gases containing about 78% nitrogen, 21% oxygen, less than 1% carbon dioxide, argon and other gases and varying amounts of water vapor.
Air Quality Index (AQI) - a numerical index used for reporting severity of air pollution levels to the public. For current levels in Laos see https://www.iqair.com/laos .
algal bloom or algae bloom - a rapid increase or accumulation of algae in freshwater or marine water systems often noticed by color change in the water.
alluvial - made up of sand and earth deposited by rivers, floods, etc.
alternating current (ac) - electric current that reverses its direction of flow several times per second, as contrasted with direct current which travels in only one direction.
alternator - alternating current generator; ac generator
American Wire Gauge - is the US standard measure for the diameter of electrical conductors.
ampacity - the maximum current in amperes that a conductor can carry continuously without exceeding its safe temperature limit
ampere - a measure of electric current flow. May be compared to the measure of water flow volume as cubic feet or gallons per second
amphibia - a class of vertebrates that live on land but breed in water such as frogs, toads, salamanders, etc.
Anadromous fish - fish that begin their life cycle in freshwater, then migrate as juveniles to the ocean where they grow into adults and finally migrate back into freshwater to spawn.
anaerobic - without oxygen
angled bar racks - structural guidance systems used to direct downstream migrating fish toward bypasses and sluiceways rather than passing through a hydropower turbine. They do not physically exclude fish from powerhouse intakes but create conditions that discourage fish from entering the intakes.
Annual daily peak flow - the largest daily flow recorded in a year (m3/s).
Annual Recurrence Interval - the average annual rate of occurrence of an event; it is equal to the 1/exceedance probability
annunciator - indicator lights designed to secure a human operator’s attention by blinking and sounding an alarm when an automated process changes into an abnormal state.
anoxia - the absence or near absence of oxygen in water or body tissue (can be fatal)
anoxic - a condition in which the aquatic (water) environment does not contain dissolved oxygen
apparent power - kVA is a measure of apparent power and measures the total amount of power in use in a system. In a 100% efficient system kW = kVA.
appurtenant facilities - the non-integral components or aspects of a hydropower facility such as substations and transmission lines.
aquifer - an underground body of saturated rock through which water can easily move
arch dam - a type of dam structure formed as a single curved wall facing upstream to transmit most of reservoir water pressure to the abutments.
armature - the component of an electric rotating machine that contains the main current-carrying winding where the electromotive force produced by magnetic flux rotation is induced; it may be rotating or stationary.
Association of Southeast Asian Nations (ASEAN) - regional political and economic intergovernmental institution with 10 members in southeast asia.
aquaculture - the activity of breeding, growing and harvesting fish and other aquatic plants.
aquatic biomonitoring - the science of inferring the condition of rivers, lakes, streams and wetlands by examining the organisms that live there (such as fish, invertebrates, insects, plants and algae).
Arc Fault Circuit Interrupter - device that senses power fluctuations when sparking ("arcing") occurs between contact points in a wire connection and may trip or break the circuit
aseismic - not characterized by earthquake activity.
aspirator - an apparatus for moving for removinflg fluids, commonly by suction
asynchronous - when two electric systems do not have the same alternating current frequency and are said to be out of phase.
asynchronous motor (induction motor) - an AC electric motor where the electric current in the rotor needed to produce torque is obtained by electromagnetic induction from the magnetic field of the stator winding
attraction flow - additional water flow supplied at a fish passage entrance (fish ladder) that creates hydraulic signals for fish to sense the fishway as a safe route and entice them to pass through it.
average return interval - the average annual rate of occurrence of an event
avulsion - the sudden transfer of land from one legal owner to another such as when a change in the course of a borderline river moves land claims from one country to another.
axial flow turbine - a type of turbine that has water flowing through in a direction parallel to the turbine shaft
axial thrust - in hydraulic pumps, the summation of unbalanced impeller forces acting in the axial direction.
backwater effect - upstream effects caused by the impoundment of reservoir water behind a dam structure.
baffle - a shallow weir or blocking fixture added to a water channel's floor and walls to deflect water and lower flow velocities. Used to ease fish passage and provide resting zones for migrating fish.
baht - the monetary currency of Thailand
ball valve - a shut-off valve that controls the flow of water by means of a rotary ball with a bore hole. Can be opened or closed by rotating the ball a quarter turn (90 degrees).
Ban - a village in Lao language
bankable contract - when a contract such as a PPA is sufficiently robust to enable a project to reach financial close and have tradeable value.
bankable project - a project that has favorable terms in its contracts such that banks are willing to provide financing at reasonable rates and give the project good profit potential.
bar - water pressure is measured in bars, with 1 bar being the force needed to lift water up 10 meters in elevation. A concrete hydropower headrace pipe may have about 11 bars pressure while a high-pressure steel penstock may have about 34 bars pressure.
barrage (dam) - a type of dam with gates that channel water flows through the structure rather than over the structure as with an overflow weir. The submerged gates allow fine adjustment of water levels in a reservoir or head pond and may allow intake at multiple water levels.
barrel (Imperial) - unit of liquid measure equal to about .16 cubic meters or 36 imperial gallons
barrel (U.S.) - unit of liquid measure equal to about 5.61 cubic feet or 42 U.S. gallons
base load - The minimum amount of electric power needed to be produced and supplied to the electrical grid over a certain time period. The unvarying (or slowly varying over many hours) portion of electric demand.
base load plant – a type of power plant intended to operate at maximum output all of the time to send continuous maximum energy into the grid.
base load power generation - power generation intended to run continuously and not just for peak-load demand
basic project costs - direct costs that excludes indirect costs and standard costs
basin - a region drained by a certain river and the tributary streams that flow into it. Also called a watershed or drainage basin.
bathtub spillway - double side-channel spillway
Battery of Asia - term referring to Laos as a major electricity exporter to Southeast Asian countries, popularized by a Thaksin Shinawatra speech in 2005.
behind-the-meter systems - privately-owned renewable energy systems located at homes or businesses
benthic – bottom-dwelling (describing fish species that prefer to feed and stay near the bottom of a water body)
benthic zone - the lowest levels of a water body
bifurcation - division of water flow into two branches such as when one penstock flow is split to drive two water turbines.
biocultural rights - a community's long-established customary right to be involved in the management of nearby lands, waters and resources.
biodiversity - all the different kinds of life found in one area
bioenergy - energy derived from organic materials such as biomass, biofuel, biogas & waste-to-energy
biofilm - a rough layer of living and reproducing microorganisms (such as bacteria) that form on and coat surfaces (such as inner walls of water pipes which may lead to the lowering of flow velocity and power production).
biofouling - undesirable biological accumulation of living organisms on surfaces exposed to water that causes operational inefficiency (such as barnacles on a ship's hull or microorganisms inside a water pipe)
biofuel - any fuel that is derived from biomass
biogas - gas which is produced from biomass
biomass - organic matter including wood, agriculture waste and other organic materials
biomonitoring - Inferring the ecological condition of rivers, lakes, streams and wetlands by examining the health of organisms (fish, invertebrates, insects, plants, and algae) that live there. Helps to assess environmental contamination of air and water.
biosphere - the atmospheric zone at and near the earth's surface where life exists; all living organisms of the earth.
blackout - a complete power loss affecting many electricity consumers over a large geographical area for a significant period of time
black-start - the process of restarting a shut-down power station to full operation without relying on external electric power.
blade-strike survival - fish survival rates for hydropower systems due to turbine blade-strike of downstream moving fish can be as high as 96% (Romero-Gomez and Richmond 2014). Slowly rotating turbines with large gaps between blades are design options.
boat lock (ship lock) – a navigation lock used to transit boats through a hydropower dam structure.
boilerplate provisions - standardized provisions in a contract that usually appear at the end of the agreement and arre included in many similar agreements
bombie - unexploded ordnance from a cluster bomb
bonneted gate - a type of enclosed water gate used to regulate flow in dam outlets and remove silt through flushing.
brackish water - water occurring in a natural environment that has more salinity than freshwater but not as much as seawater.
British thermal unit (Btu) - a measure of the heat content of fuels or energy sources; 1 Btu equals 0.000293 kilowatt hour
brownout - a controlled power reduction in which an electricity provider decreases the voltage on the power lines so customers receive weaker electric current. Used when total power demand exceeds the maximum available supply. A typical household would not notice the difference.
buckets (impulse blades) - are curved buckets on a rotating turbine runner that are impacted by a water jet and spin the runner converting almost all of the kinetic energy from the water to mechanical energy or torque
build–own–operate–transfer (BOOT) – a type of concession agreement that allows a developer to build a facility, operate it for a certain time period and then turn ownership over to the government that issued the concession agreement.
build–operate–transfer (BOT) – concession agreement that allows someone to build a facility, operate it for a time period and then turn it over to the government that issued the concession agreement.
bulb turbine- a type of propeller turbine with the turbine and generator both sealed in a streamlined watertight bulb mounted in the center of the water passageway. Used for very low head projects with low unit output.
bulkhead gate - a type of water gate used to isolate a certain area from water intrusion and primarily used for dewatering and maintenance. The gate is almost always opened and closed under balanced pressure.
bus - An electrical conductor or bar that serves as a convenient means of connecting switches and other equipment into various arrangements.
busbar (also bus bar) - a metallic bar used for electric power distribution inside switchgear, panel boards and busway enclosures .
butterfly valve - a type of valve that regulates water flow by a quarter-turn rotation of a disk. It works like a ball valve for quick shutoff but a butterfly valve can also open and close incrementally.
buttress dam - a type of dam structure that transfers the load to foundation rock through individual buttress footings. It uses the combined weight of the impounded water and the structure itself to provide resistance against movement.
Buyer's Credit - a loan made by a lender to an importer for the purchase of imported goods or services. A finance agency guarantees the loan, eliminating the risk of nonpayment for the exporter.
bypass - a channel or conduit through or around a dam structure that channels river flow and acts as a route for fish to pass without going through the turbines.
capability - the maximum load which a generator, turbine, transmission circuit, apparatus, station or system can supply without exceeding acceptable limits of temperature, stress, etc..
capacitance - the capability of a material object or device to store an electric charge
capacitor - A dielectric device that temporarily absorbs and stores electrical energy by accumulating electric charges on two closely-spaced surfaces that are insulated from each other.
capacitor bank - helps maintain voltage control to accommodate variable renewable energy generation.
capacity - the maximum output of electricity that a generator can produce under ideal conditions. The maximum load which a generator, turbine, transformer, transmission circuit, station or system is designed for.
capacity charge - a charge or fee paid for the capacity of a power plant being available to an offtaker, regardless of whether the offtaker actually takes power
capacity factor - the ratio of the energy that a plant actually produces to the energy that would be produced if it were operated at full capacity continuously throughout a given period, usually a year. Also sometimes called the plant factor or load factor, it is expressed as a percentage of the nameplate capacity or in decimal form (e.g. 30% or 0.30).
capacity reserve margin - is (capacity minus peak demand) divided by peak demand. A capacity reserve margin of 15% is typically considered adequate
captive power plants - supply power to specific businesses that would otherwise rely on the grid for their power supply.
carbon dioxide - CO2 - a colorless gas having a faint sharp odor and a sour taste. It is a greenhouse gas linked to global warming and is formed in thhe combustion of carbon-containing materials, in fermentation and in respiration of animals. It is absorbed by plants in the photosynthesis of carbohydrates.
Carbon Dioxide Equivalent (CDE) - a term used in the global warming potential (GWP) system that compares the emissions from various greenhouse gases based on their global warming potential using carbon dioxide as the base for comparison. For example, the CDE for methane is 24.5 which means it has 24.5 times more GWP than carbon dioxide.
cascade - a series of descending waterfalls, rapids or dams along a river
cascade management - when all dams in a particular cascade have their operations coordinated and managed tagether.
cascade reach - the portions of a cascading river where new dams have impounded reservoirs and the former rapids are inundated and cease to exist.
cascading failure - a failure in a system of interconnected parts where the failure of one part leads to the failure of other parts (domino effect)
catchment area – drainage basin – watershed - the land area that channels runoff from rainfall or other precipitation into a certain stream or river. A common drainage system
cavitation - noise or vibration that causes damage to turbine blades as a result of bubbles that form in the water as it goes through the turbine - causes capacity loss, head loss and efficiency loss.
celsius (C) - Formerly known as Centigrade. A temperature scale based on 0 degrees as freezing point and 100 degrees as boiling point of water. To convert Celsius to Fahrenheit, multiply the number by 9, divide by 5, and add 32. For example: 10 degrees Celsius x 9 = 90; 90 / 5 = 18; 18 + 32 = 50 degrees Fahrenheit.
check dam - a small weir-like overflow dam used to slow water flows, reduce erosion, create ponds, act as stream crossing, etc.
China Datang - China Datang Overseas Investment Co., Ltd.
circuit breaker - an electrical switching device that can automatically close or break the flow in an electrical circuit while current is flowing through it
circular mil - a unit of area equal to the area of a circle with a diameter of one mil (one thousandth of an inch or 0.0254 mm).
civil works - heavy construction work associated with weirs, dams, tunnels, canals, conduits, intakes, penstocks, powerhouse structures, tailrace, access roads, bridges and other hydropower site improvements.
Clean Development Mechanism – a system under the Kyoto Protocol used to subsidize new non-polluting power production that is hoped to displace older polluting production and eliminate the need to build more polluting power plants.
closing structure - a dam or weir that blocks a river's water flow and creates a head pond or reservoir
coffer dam - a temporary water-blocking structure used to prevent water from interfering with dam construction
cogeneration - the use of waste or excess heat from a non-hydropower process as a by-product to drive turbine generators for electricity generation. The sequential use of energy for the production of electrical and useful thermal energy.
cold-load pickup - extra effort needed to restore load that has been off for a while
cold reserve capacity - reserve electrical generating capacity not currently in operation but available for generation on demand.
collecting gallery - a place where fish are guided to in a fish-pass system at a hydropower dam facility
comfort letter - a business document that assures the recipient that another party is able to meet the terms of an agreement being considered.
commercial operation date – the date that a new hydropower facility is deemed to be complete and ready for full operation. The date can be decided by agreement after completion of a ramp-up period when 100% production is achieved and often is used as the official start of a consignment period.
commutator - a device that will allow the current generated by an AC generator to mimic a DC generator's output and have the flow travel in one direction only.
computational fluid dynamic(s)- the numerical method of simulating fluid motion using computational methods and hardware.
concession agreement - an agreement between a government and a private entity which grants certain business rights to a private entity for a limited period of time.
concessionary - when investors are willing to make some financial sacrifice to achieve their social goals by taking greater risks or accepting lower returns.
concession period – the number of years a concession agreement is in force.
conductivity - the measure of the ease at which an electric charge or heat can pass through a material
conductor - conducting material such as copper or aluminum wire or cable that is used to carry electricity.
conduit - a pipe, tube, tunnel or canal used for the conveyance of water, electric cables, etc..
confluence - intersection and merging of two rivers
connection fee - cost for households to initially electrify their homes - includes in-house wiring, the connection from the house to the post, the meter and the box.
consumer energy resources - renewable energy systems commonly located at homes or businesses - also referred to as distributed energy resources (DER) or behind-the-meter systems.
consumption - the end use and application of energy such as electricity which is typically measured in kilowatt-hours.
control board - hydropower plants are operated either locally with a unit control board or remotely through a central control room and/or dispatching center.
core of power plant - turbine and generaator
counterpoise - grounding rods or buried grounding wires; a factor or force that balances or neutralizes another.
covenant - a formal and binding provision in an agreement such as a contract.
crest gate - a type of gate located on the crest (top) of a spillway used to control water discharge. These gates are hinged at the bottom and open by rotating from vertical to horizontal.
cross-flow turbine - is drum-shaped and uses a nozzle that directs water flow against curved vanes on a cylinder runner. The turbine directs water to flow through the blades twice. On the first pass water flows from outside of the blades to the inside while on the second pass water flows from the inside back out.
crowding mechanism - a procedure to move fish upstream over or through a blocking dam by having a crowding boat push fish into and through a boat lock structure along with the boats transiting the lock.
crustacea - any of various types of animal that live in water and have a hard outer shell such as lobsters, shrimps, crabs, etc.
cryogenic storage - storage at extremely low temperatures such as for LNG or Liquified Natural Gas
cubic centimeter (cm3) = a measure of volume equal to 0.000001 cubic meter or .061 cubic inches
cubic feet per second (cfs) = liquid flow rate of one cubic foot per second or 450 gallons per minute (gpm)
cubic foot (ft3) = dry measure of volume equal to .028 cubic meters or 1,728 cubic meters
cubic feet per second (ft3/s) = liquid flow rate equal to one cubic foot per second or about .0283 cubic meter per second
cubic inch (in3) = dry measure of volume equal to 16.38 cubic centimeters or .000578 cubic foot
cubic meter (m3) = dry measure of volume equal to 35.3 cubic feet; liquid measure of volume equal to 1,000 liters, 6.11 imperial barrels or 220 imperial gallons
cubic meters per second (m3/s) = liquid flow rate equal to one cubic meter per second or about 35.3 cubic feet per second
cubic yard (yd3) = dry measure of volume equal to .765 cubic meters or 46656 cubic inches
cumec = a measure of the rate of flow of fluid, especially through a pipeline, equal to one cubic metre per second (m³/s).
cure period - the time period during which a defaulting party has a chance to correct a breach which would otherwise lead to an event of default.
current (electric) - the flow of an electric charge (electrons) through a conductor or circuit, usually measured in amperes as the amount of charge that passes a given point every second as it is travels through the conductor (wire).
current transformer - a type of transformer used to measure the current (usually high voltage) passing through the circuit.
cut slope – a slope in land created by excavation such as beside a hydropower dam structure or along a roadway
dam - a structure used to impound water typically made of earth, rock or concrete constructed across a river or flowing water channel to create a reservoir for water storage.
dam cascade - where multiple dams are constructed on the same river, one above the other.
dam cascade management - when all dams in a particular cascade have their operations coordinated and managed tagether.
dampener - something that dampens or reduces the force or effect of something such as a shock absorber. Hydraulic damping isolates vibration of a rotating shaft or drive train to protect against overloads.
DC motors - require the use of brushes to make electrical contact with moving coils of wire
dead flow - wastewater and oversupply of irrigation water to farmlands
dead storage – the volume of water in a reservoir that is below the lowest outlet and cannot be used to generate power or be removed by drainage.
debt service - periodic principal and interest payments required to be made on the debt used to finance a project.
decimal degrees - method of using purely digital numeric data for coordinates of geographic position location instead of degrees, minutes and seconds method
decommissioning - the dismantling of a power plant and clean up the project site
Delft3D - a 3-dimensional modelling tool used to investigate hydrodynamics, sediment transport, morphology and water quality for fluvial, estuarine and coastal environments.
deforestation - large-scale removal of nearly all trees from an established forest
degrees, minutes and seconds - traditional method of writing geographic position coordinates
deloading - decreasing or reducing load
deloading rate - the rate at which an electricity generator decreases output below minimum stable generation.
demand - the amount of electric energy requested to be received by recipients
demand-side management - efforts by utility providers to modify consumer demand with incentives for consumers to use less energy during peak hours
demining - removal of unexploded ordnance
dendritic - having a branched form resembling a tree
design head - the amount of head (elevation drop) at which a specific turbine is designed to provide maximum efficiency, often measured in feet or meters.
desilting basin - pond for suspended silt to settle out
dewatering – process of removing water from something such as an enclosure, structure or system.
diadromous - a general category describing fish who spend portions of their life cycle in both fresh water and salt water. These represent both anadromous and catadromous fish.
dielectric liquids - are used as electrical insulators in high voltage applications, e.g. transformers, capacitors, high voltage cables and switchgear
dielectric material - insulating material or a very poor conductor of electric current, often used for capacitors
diffuser - a device that spreads out something in many directions such as in the dilution of water discharged from a turbine
Dipterocarp/Dipterocarpaceae - a type of mainly tropical lowland rainforest trees
direct current (dc) - electric current that travels in only one direction as contrasted with alternating current which reverses its polarity or direction of flow several times per second. Direct current transfers only active power with lower losses than alternating current which transfers both active and reactive power.
discharge sluice - a water gate and channel that carries away water discharged from a powerhouse.
dispatchability - the ability of a given power source to increase and decrease output quickly on demand
dispatchable plant - a power plant that is capable of responding to the instructions of the transmission company on demand to vary its output on short notice.
dispatchable power generation – electricity generation that can be quickly and easily turned on or off to efficiently manage a power distribution grid system.
dispatching center - guides and manages power generation
displacement – relocation of people away from their residence to allow construction of new hydropower facilities and inundation of lands
distributed energy resources - privately-owned renewable energy systems located at homes or businesses - behind-the-meter systems
diversion – diverting the flow of water from one drainage basin into a different basin.
diversion system - the system used to divert water from its source and transport it to a turbine
downramping - decreasing or powering down
draft tube - a water conduit that maintains a column of water from the turbine outlet to the downstream water level. The tube carries water from a turbine runner to the tailrace and is designed to maximize head and power generation.
drawdown - the advance of funds from the lender to the borrower in the context of a loan
dry season months - the six calendar months from December to May in the Lower Mekong Basin
dynamic pressure or dynamic head - the usable force of water as it reaches the turbine
dynamo – also called a generator; a device that converts mechanical energy from a rotating turbine shaft to electrical energy. Electricity is induced when magnetized coils of wire on a rotating rotor sweep past a stationary magnetized coil (stator).
earth dam - a type of dam structure in which more than 50% of the total volume is formed of compacted earthen materials which are generally smaller than 3-inch size.
earthing switch - a disconnect used to connect equipment to grounded electrical conductors buried in the earth for safety
ecosystem - (ecological system) the interaction of all living organisms with non-living features within a certain geographic environment.
efficiency - a percentage obtained by dividing the actual power or energy produced by the maximum power or energy that theoretically could be produced. It represents how well a hydropower plant converts the kinetic energy of the water into electrical energy.
effective head – a reduced value for Hydraulic Head when normal operating inefficiency losses such as friction losses are subtracted.
Electricité du Cambodge (EDC) - a state-owned electricity utility responsible for electricity generation, transmission and distribution in Cambodia
Electricité du Laos (EDL) - Lao PDR state-owned electricity utility responsible for generation, transmission, distribution and services to customers in the country.
Electricity of Vietnam (EVN) - Vietnam state-owned electric power entity
electric current - the rate of flow of an electric charge (electrons) through a conductor or circuit, often measured in amperes.
electric energy - energy defined as the movement of electrons from one point to another, commonly measured in kilowatt-hours or megawatt-hours.
electrical grounding - the process of safely directing excess electricity to the ground (earth) via a grounding wire to prevent injury or fires.
electromagnetic - characterized by electric currents that give rise to magnetic fields and magnetism
Electro-Mechanical Works - Turbines, Generators, Inlet valves and regulators, Control systems, Condensers and switchgears, Protection systems, Transformers, Hydraulic actuators, valves and pumps.
El Niño phenomenon - when above-average sea surface temperatures in the tropical Pacific Ocean cause low-level surface winds to weaken or change direction. This causes disruption of normal weather patterns even in SE Asia.
embankment dam ( earth dam) - a type of dam structure in which more than 50% of the total volume is formed of compacted earth materials which are generally smaller than 3-inch size.
endemic - relating or referring to species found only in a specific geographic region
Energy China - Gezhouba Group or China Gezhouba Group Corporation
Energy Efficiency Ratio - for air conditioners, the ratio of output cooling energy (in BTUs) to input electrical energy (in watt-hours)
engineering, procurement and construction contract (EPC) - a contract in which a contractor agrees to deliver a completed project, ready to use, on a turnkey basis.
entrainment - occurs when fish are inadvertently drawn into a powerhouse intake structure and pass through a turbine conduit risking blade-strike.
environmental flow - the amount of water flow needed in a river to maintain a healthy ecosystem
erosional wave - the slow wave-like loss of river-bottom sedimentation that progresses downstream over time after a new dam is built due to the lack of sediment discharge which causes loss of sandy deposits overlying river-bottom bedrock.
escrow account - an account where funds are held by a 3rd party in trust while two or more parties complete a transaction
estuarine - regarding an estuary or a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it and a free connection to the open sea.
estuary - a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it and a free connection to the open sea.
evacuate - remove air, water or other contents from (a container)
evapotranspiration - transfer of water (vapor) to the atmosphere by evaporation or by transpiration from plants.
excitation system - a system that provides a regulated DC current to the field windings of a generator to produce a magnetic field for electric power generation.
exciter - is usually a small generator that supplies the magnetic field for the main generator
execution date - the date on which a legal agreement is signed by both Parties and becomes effective
extirpation - the localized extinction of species
Fahrenheit (F) - a temperature scale where the boiling point of water is 212 degrees and its freezing point is 32 degrees.
fathom - water depth measure equal to 6 feet or 1.83 meters
fauna - all the animal life in a particular region or habitat
fertilizer - a chemical or natural substance [such as Nitrogen (N), Phosphorus (P) and Potassium (K)] added to soil or land to increase its fertility
FIDIC Contract = is a French language acronym for Fédération Internationale Des Ingénieurs-Conseils, which means the international federation of consulting engineers.
fill dam - type of dam made entirely of compacted earthen materials such as soil and rock
fish crowder - a device that guides fish to safe passage areas at a hydropower dam
fish elevator - mechanism that allows fish to swim upstream without having to leap over an obstacle or navigate a fish ladder. At the dam, fish are encouraged to swim into a collection area where they are nudged into a device that lifts them into waters above the dam or barrier.
fish guiding - guiding fish to safe passage areas at a hydropower dam
fishing gear - major types used in Lao PDR are hook and line, gill nets, lift nets, scoop nets, seine nets, cast nets & basket traps.
fish ladder - A series of pools arranged like steps that allow fish to pass upstream and transit through a dam structure. Often includes a series of pools that allow fish to rest as they climb the ladder.
fish lift or fish elevator- a mechanism that allows fish to swim upstream without having to leap over an obstacle or navigate a fish ladder. At the obstruction, fish are encouraged to swim into a collection area where they are nudged into a device that lifts them into waters above the dam or barrier.
fish lock - operates like a navigation lock for boat passage. It attracts fish into a lock chamber and releases them at a different water level on the other side of an obstruction such as a dam structure.
fish migration facilities - are intended to sustain the life cycle and populations of the long distance migratory fish species found in the part of the river where the dam is located
fish pass - any conduit, channel, lift, other device or structure which facilitates the free passage of migrating fish over, through or around a dam or other obstruction, upstream or downstream
fish passage - method that allows fish to swim past or through hydropower project barriers on a river, going either upstream or downstream.
fish screen - a barrier installed to divert downstream-migrating fish into a safe bypass around a blocking structure.
fishway - any structure created to facilitate safe and timely fish movement past an obstacle, allowing fish to move through a water system
flap gate - a water flow gate hinged at the top and opening one-way only, often placed in a water channel to close automatically on reversal of flow
flood gate - a water flow gate used to control flood releases from a reservoir.
flood pulse - the natural cycle of periodic seasonal floods on a river
flood season months - the four calendar months from July to October in the Lower Mekong Basin
flood storage capacity - the portion of reservoir capacity reserved for the temporary storage of floodwaters.
flora - all of the plants in a particular region or habitat
flow rate - the volume of water passing a certain place in a given amount of time usually expressed as cubic feet or cubic meters per second.
flow volume - doubling the diameter of a pipe increases its flow volume 4 times
flume - a man-made structure for conveying water in an open gravity chute with side walls raised above the surrounding terrain.
flushing (of sediment) - removal of sedimentation from reservoirs or impoundments by hydraulic flushing or other means
flushing effect - sediment flushing activities cause a total reallocation of sediments within the impoundment and cause habitat destruction and the loss of food sources for fish and other aquatic organisms.
fluvial processes - are processes associated with rivers and streams and the deposits and landforms created by them.
foot (feet) - 1 foot = 12 inches or .3048 meters; 3 feet = 1 yard; 5,280 feet = 1 mile; 3.28084 feet = 1 meter; 3,280.84 feet = 1 kilometer
Force majeure - unforeseeable circumstances beyond control that prevent someone from fulfilling a contract such as war, flood, earthquake, change in law, etc.
forebay - the impoundment immediately above and upriver from a dam structure. A pool of water placed upriver of a larger body of water to control siltation in the larger reservoir.
fossil fuel - Fuel such as oil, coal, natural gas and their by-products that was formed in the earth in prehistoric times from remains of living-cell organisms.
Francis turbine - a type of reaction turbine used in medium head and large output projects that can be positioned horizontally or vertically and comprised of a runner with fixed blades, scroll case, wicket gates and a draft tube.
free board - extra height of a canal sidewall that allows water flows to exceed the design flow
free-flow turbines - utilize flowing water's natural pathway and do not require diversion of water through man-made channels. They generate electricity from the kinetic energy present in flowing water rather than the potential energy from head. These systems can operate in rivers, channels, tidal waters or ocean currents.
friction loss - for piped water there is friction between the water and the inner surface of the pipe which causes pressure drop while the water is moving.
fuse box - a metal box that contains screw-in fuses that act as safety circuit breakers
fusegate - a set of units placed on a weir sill or spillway crest to form a watertight barrier that raises the height of the sill or crest and allows additional storage capacity in the pond or reservoir.
Gabion weir - a permeable weir structure composed of rip-rap materials formed into steps and held together by wire mesh, etc.
gallery - collecting gallery - a place where fish are guided to in a fish-pass system at a hydropower dam .
gallon - a unit of volume. A U.S. gallon has 231 cubic inches or 3.785 liters or .8327 Imperial gallons
gallons per minute (gpm) - liquid flow rate equal to one gallon per minute or about 3.79 liters per minute
galvanometer - a device used on electrical circuits to know and measure the intensity and direction of an electric current.
genset - also known as a generator set, is a portable power supply source that consists of an engine and a generator that can be used as a black start power source to ensure the normal restart operation of a shut down hydropower station.
Gantry crane - a type of sliding overhead crane used to lift and move objects from above.
gauging station - installed to measure water flow or discharge at a certain section of a river by continuously measuring and recording the water level.
generating capacity (also known as installed capacity or nameplate capacity) - is the maximum rated output of a generator or generating plant in normal operating conditions
generation - the process of converting different forms of energy such as kinetic, thermal, mechanical, chemical or nuclear into electricity.
generator – also called a dynamo; a device that converts mechanical energy to electrical energy. Electricity is induced when magnetized coils of wire on a rotating rotor sweep past a stationary magnetized coil (stator) and through its magnetic field.
1. Rotor - the moving part of an electric generator – the rotor's outer surface is covered with electromagnets and as the rotor turns inside the stator the electrons in the stator’s copper windings "vibrate" such that their movement generates an electric current.
2. Stator - the stationary part of an electric generator and is a series of copper coils nestled in the slots of an iron core - as the rotor spins its magnetic field induces a current in the stator's windings thereby generating electricity.
geomorphic - relating to the earth's surface
geomorphological - relating to the form or surface features of the earth
geopolitical - relating to international political relations as influenced by geographical factors.
Gezhouba Group - China Gezhouba Group Corporation or Energy China
gigawatt (GW) - a measure of electric power equivalent to 1,000 megawatts or 1 million kilowatts. A gigwatt of electricity is enough to power about 750,000 average homes in the USA.
gigawatt-hours (GWh) - a measure of electric energy equivalent to 1,000 megawatt-hours or 1 million kilowatt-hours.
global warming - the gradual long-term increase in the temperature of earth's surface and atmosphere when gasses from human activities, such as carbon dioxide from the burning fossil fuels, trap heat from solar radiation in the atmosphere (analogous to the greenhouse effect) by reducing reflection of infra-red radiation and heat back out and away from the earth's atmosphere into outer space
global warming emissions from reservoirs - after an area is flooded with a new hydropower reservoir in tropical areas the covered vegetation and soil decompose and release carbon dioxide and methane which contributes to global warming over the lifetime of the reservoir .
global warming potential (GWP) - A measure system used to compare various greenhouse gases global warming potential using carbon dioxide as the base for comparison. The GWP for methane is 24.5 which means it pollutes 24.5 times more than carbon dioxide.
governor - a device that measures and regulates turbine speed by adjusting water flow to the turbine which affects rotation speed and output and allows synchronous inclusion of output into a grid.
gravity concrete (gravity mass concrete) - a type of concrete structure where the weight of the structure materials itself is considered sufficient to resist external forces.
Greater Mekong Subregion (GMS) - comprises Cambodia, Lao PDR, Myanmar, Thailand and Viet Nam along with the Guangxi Zhuang Autonomous Region and Yunnan Province of the People’s Republic of China.
Greenfield hydropower project – a new hydropower plant built in an area that doesn’t have adequate existing hydropower plants.
greenhouse effect - the tendency of some transparent materials (such as glass) to transmit radiation with relatively short wavelengths (such as sunlight) and block radiation of longer wavelengths (such as heat and infra-red). This tendency leads to a heat build-up within the space enclosed by such a material on sunny days. By analogy is also called global warming as greenhouse gases allow incoming solar radiation to pass through the Earth's atmosphere but prevent most of the outgoing infra-red radiation from the surface and lower atmosphere from escaping into outer space.
greenhouse gas - Any gas that absorbs infra-red radiation in the atmosphere such as carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), halogenated fluorocarbons (HCFCs) , ozone (O3), perfluorinated carbons (PFCs), and hydrofluorocarbons (HFCs).
grid - a regional or nation-wide network of high-voltage electric transmission lines that brings power to users from sources such as hydropower plants, wind turbines and solar generators.
grid code - the technical specifications which a facility connected to a public electric grid has to comply with to ensure safe, secure and proper functioning of an electric system
ground disconnect - an earthing switch used to connect equipment to electrical conductors buried in the earth for safety
grounding - electrical grounding is the process of safely directing excess electricity to the ground (earth) via a grounding wire and grounding rod so that the excess (such as a lightning strike) doesn't cause injury or fires.
grounding electrode conductor - a bare copper wire that connects the neutral/ground bus bar to a ground rod driven into the earth near the service panel which allows stray electrical current (such as a surge created by lightning) to pass safely into the surrounding soil.
grounding rod - a conducting metal rod connected to a grounding wire that is placed in the ground to dissipate excess static electricity and external high voltages like lightning strikes.
ground fault - an inadvertent contact between an energized conductor and ground or a grounded equipment frame that may trip a circuit breaker
groundwater - underground water contained in saturated zones beneath the land surface
Gulf - Gulf Energy Development Public Company Limited (Thai)
habitat - the natural home or environment of an animal, plant or other organism
harmonic distortion - a change in the waveform of a supply voltage from the ideal waveform that causes distortion such as flickering lights, tripped breakers, etc.
harmonics – harmonics is used to describe a distortion in the fundamental voltage and/or current waveform within an electric system.
head - The difference in elevation between the intake level and the discharge point of water flowing through a hydropower plant for power generation. 1 foot of water head = 0.43 psi of pressure
head pond (intake pond) - a reservoir created behind a small dam or weir from which water is taken to a powerhouse to drive turbines.
headrace / headrace channel - a conduit above a penstock that conveys water to turbines in a powerhouse.
head tank - surge tank
headwater - the initial source area of a river or stream. also can refer to impounded water located on the upstream side of a dam structure.
headworks - a generic term for structures, pipes, channels and other constructed works located above a hydropower plant that channels water toward the turbines and generating equipment.
Health Impact Assessment = describes impacts a new hydropower project may have on the health and well-being of people in affected areas.
hectare - 1 hectare is equal 10,000 square meters or 2.5 acres or 6.25 rai (Thailand)
helical - spiral
hermetically-sealed - sealed tightly for safe submersion in water without intrusion
Hertz - the standard unit of frequency in the International System of Units; commonly stated as cycles per second.
Horsepower (HP) - A unit for measuring the rate of doing work. One horsepower equals about three-fourths of a kilowatt (745.7 watts).
Houay / Huay – Lao language term for a stream or small river that may not have water flow in the dry season
hungry water - water that has been released into a river from a dam reservoir deprived of sediments that causes "eating away" erosion of downstream channel beds and banks
hybridization = combining the qualities of two different systems into one such as installing floating photovoltaic panels on a hydropower reservoir.
hydration = adding, providing with or absorbing water
hydrate = to add, absorb or provide with water
hydraulic transients - (water hammer or pressure surges) are created when sudden changes in flow rates of water occur in pumping and pipeline systems. The pressures created may be high enough to damage or cause catastrophic failure of pipelines.
hydraulics - a mechanical function that operates through the force of liquid pressure. fluid mechanics
hydro - a combining word form meaning "water"
hydroacoustics - the study of sounds travelling through water. A method of surveying fish populations by analyzing the sounds created by fish movements
hydroacoustic camera - a camera used for fish monitoring in downstream areas of fish passage systems by analyzing the sound of fish travelling through water
hydrobiology - the biology of bodies of water; the science of life and life processes in water.
hydrocarbons - organic chemical compounds composed entirely of hydrogen and carbon atoms (e.g. fuels and lubricants).
hydro-connected solar - solar power development on the property of a hydropower facility
hydrodynamics - the study of water in motion; the study of forces that act on or are produced by liquids
hydroelectric power – power generated by capturing the potential (kinetic) energy of falling water through the use of a water wheel (turbine) to spin rotating magnets in a generator which induces an electric current.
hydrogenerators - hydropower generators that convert the mechanical energy from the spinning turbine shaft into electrical energy using an excitation system.
hydrokinetics - using a device to harness energy from an flowing stream of water and convert the hydrokinetic energy into mechanical energy.
hydrokinetic conversion device - a device used to extract some of the kinetic energy from a flowing stream of water
hydrokinetic turbine - a turbine that transforms the kinetic energy of a stream of water into mechanical energy
hydrologic - relating to the circulation, distribution and conservation of the earth's water.
hydrologic cycle or water cycle - the global cycle of energy from the sun causing water evaporation from lakes and oceans, the forming of clouds, precipitating as rain or snow and finally flowing back down to the ocean.
hydrology - the scientific study of the movement, distribution and management of water.
hydrometeorological - regarding transfers of water and energy between the land surface and the lower atmosphere
hydrometerology - a branch of meteorology and hydrology that studies the transfer of water and energy between the land surface and the lower atmosphere
hydrometric - regarding the monitoring of components of the hydrological cycle including rainfall, groundwater characteristics, as well as water quality and flow.
hydrometry - monitoring of components of the hydrological cycle including rainfall, groundwater characteristics, water quality and flow characteristics of surface waters
hydropeaking – operating a hydropower plant to generate more power and release more water in peak-demand hours and less in non-peak hours.
hydropolitics - the study of conflict and cooperation between states over transboundary water resources. The political dimensions of transboundary water resources usage.
hydropower - the harnessing of gravitational kinetic energy in flowing water to create energy that can be captured via a turbine to power machinery or generate electricity.
hydrosocial - regarding the social, environmental and political dimensions of water resources usage.
hydrosocial cycle - the process by which water and society influence and transform each other in a circular manner since problems surrounding water resources are fundamentally social and political issues. Analyzes how water and society make and remake each other over space and time.
impedance - the effective resistance of an electric circuit or component to alternating current, arising from the combined effects of ohmic resistance and reactance.
impeller - the rotating component of a turbine, blower, fan, etc.
impoundment - (noun) a pond or reservoir confined by a dam, dike, floodgate or other artificial barrier.
impoundment - (verb) the action of creating a pond or reservoir by flooding land. (noun) a body of water confined by a dam, dike, floodgate or other artificial barrier.
impulse turbine - a turbine that uses kinetic energy from a high-velocity water jet to rotate the turbine shaft.
incandescent lamp -an electric lamp in which a filament is heated by an electric current until it emits visible light.
incident controller - the person in charge of dealing with an incident such as a breakdown or shutdown.
incident response team - special group formed to deal with an incident such as a breakdown or shutdown.
inertia - a property of matter by which it remains at rest or in uniform motion unless acted upon by some external force. Inertia energy stored in a rotating generator can for a few seconds temporarily make up for the power lost from the failed generator which allows time for the mechanical control systems to detect and respond to the failure.
Independent Power Producer (IPP) – a privately-owned (non-governmental) energy producer in the business of generating electricity for sale and profit.
Indochina - mainland Southeast Asia; combined land of Singapore, Malaysia, Thailand, Cambodia, Laos, Vietnam and Myanmar
Indochinese Peninsula - mainland Southeast Asia; combined lands of Singapore, Malaysia, Thailand, Cambodia, Laos, Vietnam and Myanmar
induction – the process involving magnetism where coils of wire on a rotor sweep past a generator’s stationary coil (stator) and an electricit current is induced.
induction motor ( asynchronous motor) - an alternating current electric motor in which the electric current in the rotor needed to produce torque is obtained by electromagnetic induction from the magnetic field of the stator winding.
installed capacity - (also known as nameplate capacity or generating capacity) - the maximum output of a generator or generating plant in normal operating conditions
intake - the entrance structure that directs water flows from a reservoir into a turbine unit at a hydroelectric dam. Multi-level water intakes help to ensure that water released from the reservoir comes from multiple levels of the reservoir, rather than just the bottom (which is the coldest and has the lowest dissolved oxygen).
intake pond or head pond - for run-of-river projects; a reservoir behind a small dam or weir from which water is taken to a powerhouse to drive turbines.
intake screens - devices such as bar racks or trash racks installed in front of water turbine intakes to keep unwanted items from flowing into the turbines.
intake structure - the structure that takes in water from a reservoir or river to drive turbines at a hydroelectric power plant.
Integrated Control Panel - uses the CPU to perform integrated operations of control, operations of protective equipment and storage of operation records for the powerhouse.
Integrated Demand Side Management - an approach that uses all the resources utilities have at their disposal to plan, generate and supply electricity in the most efficient manner possible.
intermittent energy - energy that is not continuously available due to a factor outside of direct control (i.e wind blowing, or sun shinning)
inundation - the condition of being flooded and covered with water
invertebrates - animals that have no spine or backbone
inverter - device that converts direct current (DC) power to alternating current (AC)
Joule - a unit of work or energy equal to the amount of work done when the point of application of force of 1 newton is displaced 1 meter in the direction of the force. It takes 1,055 joules to equal a British thermal unit.
Joule effect - energy loss when electricity is transmitted over electric lines and heat is created in the conductors.
juristic person - an entity such as a corporation or joint venture that is recognized as having legal personality.
Kaplan turbine - a type of propeller turbine that allows adjustment of the wicket gates and the angle of the blades. Often used for low head operation with small unit output
kilo - a decimal unit prefix in the metric system denoting multiplication by one thousand
kilogram (kg) - measure of weight equal to 1,000 grams or 2.2 pounds
kilometer (km) - measure of distance equal to 1,000 meters or .621 miles or 1,093.6 yards
kilovolt (kV) - one thousand volts
kilovolt-ampere (kVA) rating - the output in kilowatts of a generator divided by the power factor. In a 100% efficient system kW = kVA
kilowatt (kW) - a measure of electric power equal to 1000 watts or 1.341 horsepower.
kilowatt-hour (kWh) - A measure of electric energy; the equivalent of 1,000 watt-hours. Ten 100-watt light bulbs shining for one hour will use one kilowatt-hour of electricity (the equivalent of 3,412 Btu of heat energy).
kinetic energy – gravitational energy in hydropower terms - the energy potential of water at a high elevation that can be partially captured as it flows to a lower elevation.
kip - the monetary currency of Lao PDR
Kyoto Protocol - an international agreement intended to reduce earth’s greenhouse gas emissions by subsidizing the construction of new non-polluting power plants. It is hoped this new clean power production will create enough supply to eliminate the need for building more polluting power plants and encourage displacement and closure of older polluting power plants.
lacustrine - referring to a lake or relating to a lake or reservoir
Lancang – the Chinese name for the Mekong River inside China
Lancang Cascade – the mainstream Mekong/Lancang dams in China
Lancang Jiang - a name for the Mekong River inside China.
Lancang-Mekong Cooperation - established in 2016 for cooperation between the riparian states of the Lancang/ Mekong River to boost trade between China, Myanmar, Thailand, Laos, Cambodia and Vietnam.
Lao Cascade - all of the Mekong mainstream hydropower projects located within Lao PDR or on its border
Lao(s)-China Railway - in Laos is powered by rainfall
Lao Holding State Enterprise – a Lao PDR government entity responsible for the state’s financial holdings in hydropower projects, especially those involving foreign and private investors.
Latitudes - horizontal lines that measure distance north or south of the equator such as 18°26'09"N = 18 degrees, 26 minutes, 9 seconds north latitude.
Letter of Credit - a loan made by a lender to an importer for the purchase of imported goods or services. A finance agency guarantees the loan, eliminating the risk of nonpayment for the exporter.
levelized cost (per unit produced) - is calculated as present value of lifetime costs divided by total lifetime units of energy produced. Used to compare kilowatt hour cost for different types of production such as water power, wind power, solar power, etc.
Levelized Cost of Energy - lifetime per-unit cost - the present value of lifetime costs divided by lifetime units produced. Used to compare kilowatt hour cost for different types of power production.
levelized tariff - lifetime per-unit tariff - the present value of lifetime tariffs divided by lifetime units subject to various tariff rates.
Light-Penetrating Effect - where sunlight penetration into water is increased due to a reduction in suspended sediments or decreased flow velocity.
limnology - the study of inland waters including lakes (both freshwater and saline), reservoirs, rivers, streams, wetlands and groundwater.
Liquefied Natural Gas (LNG) - Natural gas that has been condensed to a liquid by cryogenically cooling the gas to about minus 260 degrees Fahrenheit (below zero).
Liquefied Petroleum Gas (LPG) - a mixture of gaseous hydrocarbons, mainly propane and butane, that change into liquid form under moderate pressure. LPG or propane is commonly used as a fuel for homes and transportation.
liter (litre) - A metric unit of capacity equal to one cubic decimeter or about 33.814 fluid ounces
liters per minute (lpm) - liquid flow rate equal to one liter per minute or about .264 gallons per minute
lithology - the study of the general physical characteristics of rocks
littoral - refers to the area of a waterbody closest to shore where sunlight can reach sediment and support growth of aquatic flora.
live storage – or active storage - the portion of a reservoir that can be drawn down and used for flood control, power production, navigation and downstream releases.
load - the combined amount of electrical energy required to meet customer demand on a certain system at any moment. The “consumer” of electric energy is referred to in the industry as load.
load center (service panel) - the box that is the distribution point for electricity and contains the main breaker and branch circuit breakers.
load dispatch center - central authority that manages power inputs into the grid
load electrical - the amount of electrical power drawn from a power line, generator or other power source. The total amount of electricity on a specific power system required to meet customer demand at any moment.
load factor - the ratio of the average load during a certain period of time to the peak or maximum load occurring in that period.
load following - situation where power generation is adjusted throughout the day in response to fluctuating demand for electricity.
load-following plant (Intermediate Peaking Plant) – A power plant that operates at variable power output settings to more efficiently meet varying energy demand.
load-serving entity - a company or other organization that supplies load (electricity) to a customer.
load shedding - rolling blackouts - temporarily cutting off power supply to certain customers to avoid overloading the entire system. A type of demand response when the demand for electricity exceeds the power supply capability of the network.
load shifting – adjustment of a hydropower plant’s output in order to match electricity output to demand changes throughout the day.
lock - navigation lock - a structure in a river or waterway built to allow navigation passage for boats between two waterways which are not at the same level, such as with a dam structure.
lock fish passage - using a navigation lock for fish passage as well as for boat passage by moving a ‘crowder’ screen through the lock to drive fish through the lock structure as the lock operates for boat passage.
log boom (trash boom) - a floating rope-like device placed in reservoir water to block logs and other unwanted materials from entering turbine intakes
Longitudes - vertical lines that measure east or west of the meridian in Greenwich, England such as 102°56'49"E = 102 degrees, 56 minutes, 49 seconds east longitude
louver racks - angled bar racks and louvers used to direct fish toward bypasses and sluiceways at hydropower plants. These devices that do not physically exclude fish from intakes but create conditions to divert fish away from the intakes.
Lower Mekong Basin - the Lao, Thai, Cambodian & Vietnamese portions of the Mekong River and its drainage basin.
manifold - the section of a pipeline that divides water flow from a single penstock into several smaller penstocks to distribute and feed multiple turbine generator units
marginal loss - the incremental increase in power distribution losses for each additional unit of electricity generated.
marine energy - energy derived from naturally-moving water to produce renewable power from river and ocean currents, waves, tides etc.
megavolt ampere - A measure of bulk power with one megavolt ampere equal to one megawatt
megawatt (MW) - A measure of bulk power; the equivalent of 1,000 kilowatts or 1 million watts; the unit is generally used to describe the output of a generator.
megawatt-hour (MWh) - A measure of electric energy; the equivalent of 1,000 kilowatt hours or 1 million watt hours; megawatt-hours are determined by a hydropower plant’s capacity and how long the plant is running. A 1,000-megawatt power plant running at full power for one hour produces 1,000 megawatt-hours (MWh) of electricity.
Mekong Dam Monitor - an online platform managed by the Stimson Center that uses remote sensing, satellite imagery and GIS analysis to provide near-real time reporting of hydrologic indicators in the Mekong Basin. https://www.stimson.org/project/mekong-dam-monitor/ .
merchant power plant - a power plant that sells electricity to a competitive wholesale market instead of under a PPA
meter (metre) - a measure of length equal to 1.0936 yards
metric ton - a unit of mass equal to 1000 kilograms
methane -CH4- a potent greenhouse gas that can be created from decomposition of vegetation under water
micro hydro – very small hydropower projects that generate less than 100 kilowatts output.
mil - measure of length devised to measure wire conductor sizes in absolute terms (without the insulation) equal to one thousandth of an inch or 0.0254 mm.
mile - distance measure equal to 1,769 yards or 1,609 meters or 1.609 kilometers
miter gate - boat transit lock gates that swing out from the side walls and meet at an angle pointing toward the upper level
mitigation - the reduction of something harmful and its harmful effects.
mobile commons - such as water in transboundary rivers and the sediments it carries
mole drain - an underground cylindrical drainage channel cut by a special plough to drain excess water from heavy agricultural soil
Mollusca (Mollusks) - a class of soft-bodied spineless creatures typically protected by a hard shell such as snails, scallops, oysters, etc.
monoculture - a cultivation system of only one organism
morphology - the study of shapes and forms of things
motor-generator - used in pumped storage plants to generate electrical energy and to drive pump turbines.
multi level intake - a type of water intake structure that is able to draw water from more than one level of a reservoir into a turbine unit at a hydroelectric dam. Multi-level water intakes help to ensure that water released from the reservoir comes from multiple levels of the reservoir, rather than just the bottom which is the coldest and has the lowest dissolved oxygen.
Nam – Lao language term for river or water.
nameplate capacity (also known as installed capacity or generating capacity) - the maximum output of a generator or generating plant in normal operating conditions
nappe - a sheet or curtain of water that flows over a weir or dam
natural gas- hydrocarbon gases found in the earth composed of methane, ethane, butane, propane and other gases.
natural gas liquids - mainly ethane, propane, butane, isobutane or natural gas
navigation lock (navigation structure) - a structure in a river or waterway built to allow safe navigation passage for boats between two waterways which are not at the same level. Lifts boats over a dam structure.
nephelometer - an instrument used to measure the turbidity of water
nephelometric - regarding the measurement of water turbidity using an instrument called a nephelometer
net head - is equal to gross head minus the hydraulic losses of the channeling waterways
net metering - when electricity consumers who operate their private energy generators such as wind or solar receive credit for the electricity they generate and place into the grid system
Newton’s Law -for every action there is an equal and opposite reaction
nexus - connection or causal link
Nitrogen (N) - a colourless, odourless, tasteless gas that is the most plentiful element in Earth's atmosphere and is a constituent of all living matter - useful as fertilizer
nitrous oxide - a type of greenhouse gas; also used as an inhalation anaesthetic
non-concessionary loan - loan with a market-based interest rate and substantially less generous terms than concessional loans where investors are willing to make financial sacrifice to achieve their social goals by taking greater risks or accepting lower returns.
non-dispatchable technologies - technologies where power is not available on demand but only when the energy is available such as from wind and solar.
novation - an agreement between contracting parties to allow the substitution of a new party for an existing one.
nutrient load - the amount of nutrients contained in water, usually bound to suspended sediments
OCR Rate - Official Cash Rate of interest on loans, often used by Asian Development Bank
off-take – to purchase and receive electric power from a producer
off-taker – a purchaser and receiver of electric power from producers
ogee - a serpentine-like shape with a double curve
ohm - the unit of electrical resistance in the International System of Units. One volt can produce a current of one ampere through a resistance of one ohm.
oscilloscope (informally scope or O-scope) - an electronic test instrument that displays varying electrical voltages as a two-dimensional plot of signals as a function of time. The main purpose is to capture information on electrical signals for debugging, analysis or characterization.
overshot gates - dam crest gates on a hydropower dam structure that allow overflow releases from the impoundment.
ozone - an inorganic molecule with the chemical formula O₃. It is a pale blue gas with a distinctively pungent smell.
peaking - the mode of operation of a power plant whereby power is produced in accordance with electricity demand.
peaking capability - the maximum peak load that can be supplied by a generating unit, power plant or power system in a stated time period. Sometimes called peaking capacity.
peaking capacity - the maximum peak load that can be supplied by a generating unit, powerplant or power system in a stated period of time.
peak load power generation - refers to the mode of operation of a power plant where power is produced in accordance with peak electricity demand.
Pelton turbine - a style of turbine preferred where the water flow for driving turbines has relatively high hydraulic head and low volume.
penetration - the amount of electricity generated by a single source when compared to the total generated by all sources
penstock – a closed conduit or pipe that carries water under pressure to drive turbines in a powerhouse.
permeable - allowing liquids or gases to pass through it
pH - a number used to express acidity and alkalinity on a scale whose values run from 0 (highest acidity) to 14 (highest alkalinity) with 7 being neutral
phosphorus (P) - a poisonous yellowish-white non-metallic chemical element that glows slightly and burns when in contct with air - useful as fertilizer
photovoltaic cell - or solar cell - a device that converts sunlight energy into electricity by photovoltaic effect.
photovoltaic floating - technology application in which solar cell systems are situated on sructures floating on bodies of water.
phytosanitary - relating to the health of plants , especially with regard to the requirements of international trade
phytosanitary certificate - verifies that agricultural products have been inspected and are free of pests and disease.
PIANC - a global organisation providing guidance and technical advice for a sustainable waterborne transport infrastructure
pick-up rate - percentage of residential households that have electricity grid connection
pico hydropower - a term used to for very small-scale hydropower plants with electrical output of five kilowatts or less (sometimes 10 kW).
piezometer - a device used to measure liquid pressure in a system
pit turbine - is a variation of the bulb turbine and has application in the head range of 1.5 to 10 meters and unit capacity below 15 MW. The generator (with a speed-increasing gearbox) is contained within the upstream pit providing easy access to all components. Pit turbine efficiency is better than S-type tubular turbine units and its cost is lower than a bulb tubular unit.
plant capacity factor - the ratio of actual output to the total amount that could have been produced under ideal conditions.
plant factor - the ratio of the energy that a power plant produces to the energy that would be produced if it were operated at full capacity throughout a given period. Sometimes called the capacity factor or load factor it is expressed as a percentage of the nameplate capacity or in decimal form (e.g. 30% or 0.30).
plunge pool - a pool used to dissipate the energy of free-falling water
political ecology - a theoretical approach that analyzes the complex interaction between humans and nature
polluting power plant - a power plant that produces and releases significant amounts of harmful greenhouse gases into the atmosphere (such as carbon dioxide) while generating electric power. Plants that burn fossil fuels are considered polluting plants while most hydropower plants are not.
pollution standards index - a numerical index used for reporting severity of air pollution levels to the public. For current levels in Laos see https://www.iqair.com/laos .
porosity - a measure of the void (empty) spaces within a material
potable water - also called drinking or tap water, is used for sanitary purposes such as drinking, showers, cooking, etc
Potassium (K) - a silvery-white metallic element that oxidizes rapidly in contact with air and whose compounds are used as fertilizer
potential energy - energy in a stored form
pounds per square inch (psi) - a unit of pressure resulting from a one pound force applied to an area of one square inch - 1 foot of water head = 0.43 psi of pressure
powerhouse - the physical structure of a hydroelectric generating facility that usually contains turbines and hydroelectric control equipment.
power grid - system of transmission lines and stations used to bring electric power to consumers and ultimate users.
power factor (p.f.) - the ratio of working power measured in kilowatts (kW) to apparent power measured in kilovolt amperes (kVA). A measure of opposing power in a circuit that flows back into the source due to flows not being 100% efficient. A power factor of .97 or 97% is common.
Preferential Buyer's Credit - a low-interest loan made by a lender to an importer for the purchase of imported goods or services. A finance agency guarantees the loan, eliminating the risk of nonpayment for the exporter.
preparatory survey - comprehensive description of a proposed new hydropower facility
pressure shaft – a conduit for water under pressure.
pressure surges - or hydraulic transients are created when sudden changes in flow rates of water occur in pumping and pipeline systems. The pressures created may be high enough to damage or even cause catastrophic failure of pipelines.
pressure tower (surge tower or surge tank) - a water storage device used as a pressure neutralizer to dampen pressure variance in a penstock or tunnel. A column of water in the tank reduces the effect of water hammer from sudden gate closing and opening.
pressure tunnel – a lined or unlined underground tunnel used as a conduit for water under pressure.
Programmable Logic Controller ( PLC) - a computer used to automate electro-mechanical processes. At hydropower plants they are often used to monitor and control key functions such as impoundment levels, minimum flow releases, turbine operation and gate operation.
Project Completion Report (PCR) - a tool used for accountability and learning.
Project Development Agreement (PDA) - a legal agreement between the Government of Lao and a hydropower project developer that includes provisions for the development, financing, construction and operation of a hydropower project in Lao PDR.
propeller turbine - type of turbine having a runner with three to six blades where flowing water contacts all of the blades constantly. The pitch of the blades may be fixed or adjustable. Major components are a runner, scroll case, wicket gates and draft tube.
protocol - a formal system of rules and procedures to be followed in certain situations
pumped storage hydropower - hydropower system that pumps water from a lower reservoir to an upper reservoir for storage and later power generation. Many pumped storage systems use energy from solar cells to pump water up to a higher reservoir in daytime. The system acts like a battery to store energy since the lifted water can be released to drive turbines below to generate electrical power whenever needed as a demand-flexible source for peak load.
race - a channel that transports water away from hydraulic apparatus (such as a tailrace that takes flows out of a powerhouse).
radial flow turbine - a type of turbine in which the water flows perpendicular to the shaft
radial gate - a water control gate with a curved upstream plate and radial arms hinged to piers or other supporting structure.
radial thrust - in hydraulic pumps, the summation of unbalanced impeller forces acting in the radial direction.
rai (in Thailand) - 6.25 rai (Thailand) equals 1 hectare
ramping capability – the ability of a power plant to efficiently scale-up and scale-down its output.
ramp rate - the maximum allowable rate of change in output from a power plant established to prevent undesirable effects resulting from rapid changes in loading or discharge.
ramp-down period – shut-down period; the time it takes to shut down an operation completely.
ramp-up period – start-up period; the time it takes to activate an operation and reach 100% operating level.
rated capacity - The name plate ratings of electrical apparatus. The maximum load that a generator, turbine, transformer, transmission circuit, apparatus, station or system is designed for.
rated head - the net hydraulic head at which a turbine produces a generator's rated output.
reactance - the opposition presented to alternating current by inductance and capacitance
reaction turbine - generic term for hydraulic turbines where water enters under pressure and interacts with the turbine runner in such a way that hydraulic energy rotates the turbine shaft.
reactive power - electric power that flows back into the source (such as from the inductors and capacitors) due to not being 100% efficient. This opposing power affects the power factor of a circuit.
reforestation - re-establishing native tree cover on lands that were previously forested but now have less than 10 percent tree canopy cover
Regional Grid Code - Multi-national electricity transmission code that regulates Governance, Connections, Operations, Markets, Metering & Operations.
regulating capacity or live storage - the portion of a reservoir that can be drawn down and used for flood control, power production, navigation and downstream releases.
regulating dam / re-regulating dam – an auxiliary dam constructed downstream of the outflow from turbines to temporarily store the discharged water and release it in a continuous and regular manner to even-out downstream flows.
regulating pond / re-regulating pond - a pond created not far below the outflow from turbines to temporarily store the water and release it in a continuous and regular manner to even-out downstream flows.
reinforced concrete - concrete which has metal such as rebar or mesh embedded to strengthen the cured concrete in resisting forces.
relocation or resettlement – relocation of people away from their residence to allow construction of new hydropower facilities and inundation of lands - dam-induced displacements.
renewable energy – energy that can be captured from an endless constantly-recharging system such as from the earth’s water cycle, the sun, wind, wood, tidal, geothermal, etc.
Renewable Energy Project - Project that generates and delivers energy from non-fossil and non-depletable energy source such as hydropower
reserve - additional unused capacity of a power system available to deal with contingencies such as forced outages and abnormal loads.
reservoir – a body of water impounded on a river or stream behind a dam, weir or other blocking structure.
reservoir active storage - also known as active volume or live storage - the portion of a reservoir that can be drawn down and used for flood control, power production, navigation and downstream releases.
reservoir dead storage - the portion of a reservoir that can not be used for flood control, power production, navigation or downstream releases.
reservoir stratification - the layer-like variation in temperature and quality of reservoir water as some water is warmed by the sun and rises while colder water sinks to lower levels.
resettlement – relocation of people away from their residence to allow construction of new hydropower facilities and inundation of lands - dam-induced displacements.
residence time - the time it takes for flowing water to transit the entire length of a cascade reach or other river section.
resistance (electrical) - the property of all electric conductors to resist the flow of current and turn some of the energy into heat. The smaller the cross section of a conductor the greater the resistance and its temperature; the hotter the cross section the greater its resistance.
resistive losses - energy transmission loss in conductors due to resistance which turns some of the energy into heat
reversible pump/turbine - a dual-purpose hydraulic device that operates as a pump in one direction of rotation and as a turbine in the opposite direction.
revetment structures - riverbank structures installed to reduce or eliminate erosion from flowing water.
riffles - the shallower and faster moving sections of a stream or river.
riparian area - the area that connects and interfaces nearby land with a river or stream.
riparian communities - communities that are situated along a river or lake shore.
riparian rights - traditional rights that attach to waterfront property by virtue of that property meeting waters edge.
ripple effect - occurs when an initial disturbance to a system spreads outward to disturb an increasingly larger portion of the system, like ripples in a pond.
riprap - large stones or concrete chunks placed for the purpose of protecting a slope from water erosion
River Continuum Concept (RCC) - a model for classifying and describing flowing water based on width, depth, velocity and sediment load while taking into account biological factors.
riverine = relating or referring to a river, resembling a river, located near a river
River Information System - provides info to aid safe river travel (water levels, oncoming vessels size and speed, incidents and accidents, weather forecast and reports)
roller-compacted concrete (RCC) - a type of concrete tha has the same ingredients as conventional concrete but is applied as a drier mix and compacted by rollers. It doesn't need joints, forms, metal reinforcing or finishing.
rolling blackouts or load shedding - temporarily cutting off power supply to certain customers to avoid overloading the entire system. A type of demand response when the demand for electricity exceeds the power supply capability of the network.
rotating-armature generator - consists of a rotating armature (a coil of wire in a loop shape) that rotates between two magnets. This generates an electromagnetic force that is then fed through slip rings and brushes to what it is powering, often referred to as the lead.
rotating-field generator - in this design, the armature is stationary with the loop of wire fixed (often referred to as a stator). The magnets then rotate around the stator creating a changing magnetic field that generates the electromagnetic force.
rotor - the rotating inner component of a generator consisting of windings surrounding the field poles.
runaway speed - the maximum rotational speed that a certain turbine can theoretically attain
run-of-river / run of the river - a type of hydropower project with a small dam and water storage capacity that allows river flows to pass through the project at roughly the same rate and time as the natural flow of the river. Except for during floods, the reservoir will constantly be kept at full supply level and the discharge through the power station and spillway is equal to the incoming flow.
runner - the rotating part of the turbine that converts the energy of falling water into mechanical energy.
runoff - the portion of fallen precipitation that flows over the land surface and forms streams and rivers.
saddle dam - an auxiliary dam constructed to confine the reservoir created by a primary dam. It permits a higher water elevation and more reservoir storage capacity. A subsidiary dam of any type constructed across a saddle or low point on the perimeter of a reservoir.
saline - regarding water that contains a high concentration of dissolved salts
salinity - the degree to which water contains concentrations of dissolved salts
sand flushing gate – a gate near the bottom of a dam structure used to release water from a reservoir in a way that helps scour and flush out accumulated sediment near the gate.
scoping phase or stage - initial stage for people to get a detailed understanding of a program
scour gate – a gate near the bottom of a dam structure used to release water from a reservoir in a way that helps scour and flush out accumulated sediment near the gate.
scouring - occurs when fast-moving water erodes sediments around structures for dams, bridges, roads, etc.
scroll case - a spiral-shaped water-intake device that guides a flow of water into the wicket gates next to the turbines.
sedimentation pond (settling basin or stilling basin) - a pond used for settling suspended materials in water out by the materials own weight. Used to prevent or minimize suspended sediment inflow into turbines.
sediment deposition - depositing of reservoir sedimentation
sediment-flushing gate – a gate installed near the bottom of a dam structure to be used for periodic sediment-flushing operations.
sediment flushing - removal of reservoir sedimentation by hydraulic flushing, usually by periodic sediment flushing maintenance operations.
sediment scouring - removal of sedimentation by fast-flowing water
sediment sluicing - a slow form of sediment flushing
sediment starvation - effect created downriver from a dam that traps most suspended sediment in its impounded waters.
sediment trapping - effect upriver of a new dam site where coarser sediments are unable to move through the dam structure and settle in the head pond or reservoir
seismic - relating to earthquakes or other vibrations of the earth and its crust.
service outage - shutdown of a generating unit, transmission line or other facility for inspection, maintenance and repairs.
service panel - the metal box that is the distribution point for electricity and contains the main breaker and branch circuit breakers.
servo motor - an electrical device that rotates parts of a machine with precise control of velocity, acceleration and angular or linear position.
SESAMEE - proprietary spreadsheet model used to evauate hydropower projects and value the positive and negative social and environmental impacts
settling basin or pond (stilling basin) - a pond used for settling suspended load materials out by their own weight. Used to prevent or minimize suspended sediment inflow into turbines.
ship lock - a navigation lock for boats on a river to transit past or through a hydropower dam.
short circuit - dangerous and inadvertant contact between the hot and neutral wires in a circuit that may trip a circuit breaker
shotcrete lining (sprayed concrete) - a type of concrete that is applied by spraying from a pneumatic hose under high pressure and can be applied to non-horizontal areas such as tunnel surfaces.
shunt (shunt resistor) - a device used to provide a low-resistance path for an electrical current in a circuit.
shunt reactor - a device used in high voltage energy transmission systems to stabilize the voltage during load variations.
siphon pit - a hydraulic structure that may be used to seal the downstream end of pressurized water systems and provide a stable back pressure during operation
skimmer wall - blocks floating debris from entering turbines
sluice - a water channel controlled at its head by a movable gate called a sluice gate. An opening for releasing water from below the static head elevation of an impoundment. Usually equipped with a gate to control the flow and sometimes used for downstream fish passage.
sluice gate – a movable gate allowing water to flow under it. When a sluice gate is lowered water may spill over the top in which case the gate operates as a weir.
sluicing mode - when shutting down power generation the turbines can be placed in sluicing mode where there is almost low pressure gradient and the blades will rotate slowly allowing safe fish passage.
slurry - a slushy, semi-liquid mixture of water and suspended substances such as cement, clay or coal
small hydro - hydropower projects that are able to generate 10 MW or less of power.
social discount rate - used for computing the present value of social project funds costs and benefits.
Social Impact Assessment – a document that details the characteristics and conditions of people living in areas that will be affected by a new hydropower project and describes impacts the project may have on them.
solar cell - or photovoltaic cell - a device that converts the energy of sunlight directly into electricity by photovoltaic effect
solar farm floating – a technology application in which solar cell systems are situated on sructures floating on bodies of water.
solar thermal electricity generation – systems that collect and concentrate sunlight to generate electricity by focusing sunlight onto a receiver where a heat-transfer fluid is heated and used to produce steam which powers a generator to produce electricity.
spatio-temporal - regarding both space and time
spawning - the reproduction process of aquatic animals such as fish when both sexes release eggs and sperm in the same place at the same time
spill - the release of water from a dam or hydropower project without passing it through the powerhouse. Typically a situation to be avoided as water “spilled” is lost power- generation revenue.
spillway - a structure used to release surplus water from a river or reservoir into a downstream area.
spiral case - a steel-lined conduit connected to the penstock or intake conduit that evenly distributes water flow to the turbine runner.
spot market - the wholesale electricity market into which the project company can sell electricity other than under a PPA.
square centimeter (cm2) - a measure of area equal to .155 square inches
square foot (ft2) - a measure of area equal to .093 square meter or 144 square inches
square inch (in2) - a measure of area equal to 6.45 square centimeters
square kilometer (km2) - a measure of area equal to 1,000,000 square meters or .386 square mile
square meter (m2) - a measure of area equal to 19.76 square feet
square mile - a measure of area equal to 2.59 square kilometers or 259 hectares or 640 acres
square yard (yd2) - a measure of area equal to 9 square feet or .836 square meter
S type turbine - a tubular turbine where water flow route from the inlet to the outlet looks like the letter “S”. This type of turbine is suitable for run-of-river generating stations where the river flow varies considerably.
stakeholders – persons or entities that would be impacted by a proposed new hydropower project.
static head - the pressure resulting from a non-moving column of liquid acting under gravity, often measured in meters of elevation drop
static pressure - where horizontal water pressure in a pipe remains the same or static without any loss of pressure for any distance when the water is not flowing.
stator - the stationary outer portion of a generator consisting of a frame, laminated magnetic core and armature windings.
stator armature - a stator that includes the main current-carrying winding in which electromotive force produced by magnetic flux rotation is induced.
step down - decrease voltage
step-in rights - rights of a secured lender in a default situation to step-in and take control of the secured project.
step up - increase voltage
stilling basin (settling pond) - a pond used for settling out suspended load in water by its own weight. Used to prevent or minimize suspended sediment from flowing into turbines. Stilling basins are also used to dissipate the energy of water discharged from a powerhouse to avoid undermining of the dam structure.
stratification - the variation in temperature and quality of water levels in a body of water as water near the surface is warmed by the sun and rises (fostering biologic growth) while colder oxygen-depleted water sinks to lower levels.
stress test - a modelling test to determine how robust a system is and at what point failure is likely to occur.
structural guidance systems - fish passage structures such as angled bar racks that create hydraulic conditions to discourage downstream migrating fishfish from entering powerhouse intakes while not physically excluding fish from entering intakes.
substation (S/S) - An electrical facility where the voltage of incoming and outgoing electric power is modified and controlled. Voltage is stepped up when power is sent through long-distance transmission lines and is stepped down when power is sent to local distribution lines.
subtransmission lines - carry voltages reduced from the major transmission line system
supersaturation – the change in water quality that occurs when turbulent water passes over a spillway and absorbs air. This increases nitrogen levels in the water and fish can be injured or killed when the nitrogen gas produces bubbles in their bloodstream. This effect is similar to “the bends” that can occur in human divers.
surcharge capacity - the storage capacity of a reservoir above the spillway crest that cannot be regulated
surge arrester - a protective device for limiting voltage on equipment by discharging or bypassing surge currents
surge shaft (surge tank or surge tower) - a water storage devic provided at the beginning of a headrace tunnel to dampen harmful effects when turbine valves are closed suddenly and the incoming water under pressure creates a vibrating effect (water hammer) that may damage the pipe and other parts of the system.
surge tank (surge tower) - a water storage device used as a pressure neutralizer to dampen pressure variance in a penstock or tunnel. A column of water in the tank reduces the effect of water hammer from sudden gate closing and opening.
sustainable development - development that meets the needs of the present without compromising the ability of future generations to meet their needs. Socio-economic change that does not undermine the ecological and social systems upon which societies depend.
swidden agriculture - shifting cultivation; slash-and-burn cultivation; rotational farming
switchgear - is composed of electrical disconnect switches, fuses and circuit breakers used to control, protect and isolate electrical equipment. Used both to de-energize equipment to allow work to be done and to clear faults downstream.
switchyard - the set of facilities next to a power plant in which voltage is transformed and electricity flow is directed onto transmission lines.
synchronous - when two electric systems have the same alternating current frequency (usually 50/60 Hz). When new output is connected to the grid its frequency is "locked" to the same frequency as everyone else connected.
synchronous generator - a synchronous machine that converts mechanical power into AC electric power through the process of electromagnetic induction. Synchronous generators are also referred to as alternators or AC generators.
T-Line - Transmission Line
tailrace / tailrace channel - the downstream channel that carries water away from a dam or powerhouse.
tailwater - the water released downstream of a powerhouse or dam.
take-and-pay clause – in a purchase contract, a provision that allows a buyer to purchase an amount of off-take electric power that it wishes without requiring a minimum.
take-or-pay clause – in a purchase contract, a provision that commits a buyer to purchase a minimum amount of off-take electric power or pay a financial penalty.
tariff - 1) a tax or duty paid to a government 2) a rate of payment such as from a power purchaser to a power provider under a PPA
tertiary - 3rd in order or level
terawatt - a measure of electric power equivalent to 1,000 gigawatts or 1 billion kilowatts; the unit is generally used to describe generating capacity at national or international levels.
terawatt-hour - a measure of electric energy the equivalent of 1,000 gigawatts or 1 billion kilowatts; the unit is generally used to describe generating capacity at national levels.
terrestrial - relating to the earth and dry land rather than waters or in the air
terrestrial fauna - animals living on land or using land (including aquatic systems) for all or part of their lives
thalweg (talweg) - the line of lowest elevation within a valley or watercourse; the lowest points along a line
thermal energy - when heat energy is converted to electric power such as by combustion of fossil fuels which creates steam to drive turbines
thermal power plant - a power plant in which heat energy is converted to electric power, such as by combustion of fossil fuels which creates steam to drive turbines
three-phase power - is a three-wire ac power circuit with each phase signal 120 electrical degrees apart
topography - the study of the forms and features of land surfaces.
transbasin diversion - man-made conveyance systems that divert water from one river basin to another basin
transboundary & transborder - crossing or extending across a border between two countries
transboundary commons - concept defining how common resources such as water are governed across geographical contexts and national borders
transducer - an electronic device that converts energy from one form to another.
transformer - an electromagnetic device used to change electricity to higher or lower voltages.
transients - hydraulic transients, or pressure surges, are created when sudden changes in flow rates occur in pumping and pipeline systems. The pressures created may be high enough to damage or even cause catastrophic failure of pipelines.
transmission – the transfer of electric power from a generation facility to end users as a one-way delivery system.
transpiration - the passage of watery vapor out from a living body (animals and plants)
trash boom - a floating rope-like device placed in reservoir water to block trash and other unwanted materials from entering turbine intakes.
trash fish - undesired fish caught along with desired fish that are often used as aquaculture feed rather than being discarded
trashrack - a rack or screen of parallel bars used near intake structures to prevent debris from entering the turbine intake.
trash screens – a screen placed in water used to block trash and other unwanted materials from entering turbine intakes
tributary - a river or stream that flows into a larger river or stream.
trifurcation - division of water flow into three branches such as when one penstock flow drives three water turbines.
tunnel boring machine (TBM or mole) - a machine used to dig underground tunnels by automated boring (alternative to mechanical excavation by drilling and blasting)
turbidity - the extent to which water has become clouded or unclear as a result of suspended sediments.
Turbine - A rotary engine that converts the kinetic energy of a flow of water into mechanical energy (spinning shaft).
1. Pelton turbines for high head applications and large output - an impulse type water turbine
2. Francis turbines for the medium net head range and large output up to 800 MW per unit
3. Kaplan turbines for low head operation with small unit output. often used for run-of-river projects
4. bulb turbines for very low head and low unit output.
5. reaction turbine - a wheel that operates like a rotating lawn sprinkler where water under pressure enters at a central point and escapes from the ends of the blades causing rotation of a shaft.
6. impulse turbine - a wheel where flowing water strikes its buckets or blades to cause rotation.
7. pump turbine - used for pumped storage hyropower plants - able to reverse the water flow and operate as a pump to fill a higher located reservoir in off-peak periods and then revert to a classical water turbine for power generation during peak demand.
8. tidal turbine - designed to handle both direction flows up to 5 meters per second. Tidal turbines are deployed on the seabed for water depths down to 100 meters and kept in position by gravity, pins or pilings.
9. cross-flow turbine - is drum-shaped and directs water flow against curved vanes on a cylinder runner so that water flows through the blades twice. Water flows from outside of the blades to the inside and then water goes from the inside back out.
10. propeller turbine - has a runner with three to six blades. Water contacts all of the blades constantly.The pitch of the blades may be fixed or adjustable. Major components are a runner, scroll case, wicket gates and draft tube. There are several different types of propeller turbines.
11. free-flow turbines - utilize flowing water's natural pathway and do not require man-made channels. They generate electricity from the kinetic energy present in flowing water rather than the potential energy from the head. The systems can operate in rivers, channels, tidal waters or ocean currents.
12. pit turbine - is a variation of the bulb turbine and is used in the head range of 1.5 to 10 meters and unit capacity below 15 MW. The generator (with a speed-increasing gearbox) is contained within the upstream pit providing easy access to all components. Pit turbine efficiency is better than S-type tubular turbine units and its cost is lower than a bulb tubular unit.
13. S-type turbine - a tubular turbine where water flow from the inlet to the outlet looks like the letter “S”. This type of turbine is suitable for run-of-river generating stations where the river flow varies considerably. Installation is almost exclusively with a direct connection to the generator.
14. Aerating turbine - installed to increase dissolved oxygen in the water released from the reservoir rather than just the bottom which is the coldest and has the lowest dissolved oxygen.
turnkey basis - a construction contract where a contractor plans, designs and builds a project making it functional and 'ready to use' for a buyer at an agreed price.
Tyrolean weir - a water intake structure which diverts water and some of the sediment carried by the river to a collection channel through a screen.
undershot gates - submerged gates in a hydropower dam structure that allow underwater releases from the impoundment.
unit control board - hydropower plants are operated either locally with a unit control board or remotely through a central control room and/or dispatching center.
usufruct - a legal right granted to a person or party which grants a temporary right to use/derive income/benefit from the property of another individual
utilization factor - the ratio of energy output to available energy within the capacity and characteristics of a hydropower plant.
Upper Mekong Basin - the portion of the Mekong (Lancang) River drainage basin within China and bordering Myanmar.
valve - a closure device for controlling the flow of water.
vane - guide vanes are turbine blades that can be adjusted to increase or reduce the flow rate of water through the turbine.
vertebrates - animals that have a well-developed internal skeleton of cartilage and bone and a highly developed brain
voltage - a measure of the pressure that pushes electric current through a conductor measured in volts or kilovolts. One volt is the force required to send one ampere of electric current through a resistance of one ohm.
volt-ampere - VA - a measurement of power in a direct current (DC) electrical circuit.
volts alternating current - VAC - a measure of the strength of an alternating electric field.
vortex - a mass of air or water like a whirlpool that spins around very fast and pulls objects into its empty center.
Wat - a Buddhist monastery or temple
water clarity effect - an increase in water clarity of a river due to sediment trapping in dam impoundments that results in low-sediment discharges and clearer river flow downriver from the dam.
water cycle or hydrologic cycle - water constantly moves through a vast global cycle, evaporating from lakes and oceans, forming clouds, precipitating as rain or snow, then flowing back down to the ocean. The energy of this water cycle, which is driven by the sun, can be tapped to produce electricity or for mechanical tasks.
water hammer effect – also called hydraulic shock – can occur in a pipe when water under pressure and in motion is forced to stop suddenly, such as when a valve closes too quickly, creating harmful pressure waves that vibrate in the pipe.
water intakes at multi-level can help ensure that water released from the reservoir comes from all levels of the reservoir, rather than just the bottom (which is the coldest and has the lowest dissolved oxygen).
water pressure - the force exerted by water on the walls of its container or anything in its path. It is typically measured in pounds per square inch (psi) but may also be measured in bars with 1 bar being the force needed to lift water up 10 meters in elevation.
water-retaining structures - dams, barrages, dikes, berms, etc.
water temperature effect - a change in a river's water temperature due to dam impoundments and storage where water temperature is stratified and altered which results in discharged water having abnormal temperature and altered river temperatures downriver from the dam.
watershed - the land area that channels runoff from rainfall or other precipitation into a certain stream or river in a common drainage system
waterwheel - a vertical wheel on a horizontal shaft that revolves by the action or weight of flowing water on the rim.
Water Quality Index - shows the pressure exerted by human activities on the water quality of the Mekong River. MRC program.
watt - A measure of electric power; standard light bulbs are rated at 25, 40, 60 or 100 watts. One watt is equal to one ampere of current per second.
weir - a type of overflow dam structure used in a river channel to create a reservoir or head pond for intake and water transfer. Water flows over the weir dam rather than through submerged gates.
wet season months - the six calendar months from June to November in the Lower Mekong Basin
wheeling - the delivery of energy from a generator to an end-user located in another area through the use of an existing distribution or transmission networks.
wheeling charges - charges for transfer of power services payable to the owner of the transmission network.
wicket gates - adjustable gates that control the flow of water from a scroll case into a turbine passage.
World Bank Guarantees - cover a wide array of government-related risks, such as: Contractual risk (payment risk, performance risk, etc.) Regulatory risk (change in law, negotiation or cancellation of license, tariff adjustments, etc.) Currency risk (convertibility, transferability, etc,) Political risk (expropriation, war and civil disturbance, etc.) In general, World Bank Guarantees are suitable to cover any government-related risk which is not of a purely commercial nature.
Xe – Lao language term for “river” used mostly in southern Laos instead of “Nam”.
yard - 1 yard = 3 feet or .9144 meter