GLOSSARY

A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | R | S | T | U | V | W

A

Abutment - The point of contact between objects or parts that are adjacent or next to each other.

Acre-foot - The amount of water that would cover one acre of land one foot deep. One acre-foot equals 325,900 gallons, 43,560 cubic feet, or 1,233 cubic meters.

Afterbay - A storage reservoir downstream of a power plant or large reservoir. It is used to regulate stream flow, provide a storage buffer, or control tailwater depths.

Alluvial - Sediment deposited by flowing water, such as in a riverbed.

Ampere - The basic unit of electric current flow. The SI symbol is A.

Anadromous - Any fish that spends a portion of its life cycle in freshwater and a portion in the sea.

Aqueduct - A conduit (such as a pipeline) or artificial channel (such as a concrete-lined canal) for transporting water.

Aquifer - An underground layer of rock, sediment, or soil that is filled or saturated with water.

B

Backfill - To refill an excavated area with construction material; or the material itself that is used to refill an excavated area.

Beneficial use (of water) - The use of water for any beneficial purpose often defined by statute or court decisions. Such uses include domestic use, irrigation, fish and wildlife, fire protection, navigation, power, industrial use, etc.

Bifurcation - To divide or fork into two branches, such as the section of the California Aqueduct that divides into the East Branch and West Branch, or division of a penstock into two pipes upstream of a power plant.

Bond - A certificate of debt issued by the government or corporation guaranteeing payment of the original debt plus interest by a specified future date. These certificates were used to finance the construction of SWP facilities.

Brackish - Water containing too much salt to be drinkable but having less salt than ocean water. Salinity may range from 0.5 to 17 parts per thousand.

Butterfly valve - A valve that uses a turnable disk element to regulate flow in a pipeline.

Bypass system - Provides for the diversion of flood flows into floodways that carry a portion of floodwater and hence decrease the flow in the main channel downstream of the point of diversion. Also a diversionary flow path to avoid some device or obstruction. Also used to direct or divert fish in a flow path away from an intake screen.

C

Capability - The maximum load which a machine, apparatus, station, or system can carry under specified conditions for a given period of time.

Capacity - The greatest load for which a piece of machine, apparatus, station, or system is rated or can safely serve. Also for hydroelectric plants it is the maximum power which can be developed by the generators at normal head at full flow. For pumping plants, it is the maximum amount of flow that can be moved at normal head.

Capital expenditures - Funds spent for permanent facilities and additions or improvements to plants or equipment.

Carry-over storage - Storage of precipitation held over in a water storage reservoir from surplus years to supply deficiencies of flow during dry years.

Central Valley Project - The largest water conveyance project in California with 20 reservoirs, 11 power plants, 500 miles of canals, and other facilities. Operated by the federal government, the CVP can deliver up to 7 million acre-feet annually. Its primary purpose is to provide water for irrigation within the state's Central Valley, as well as provide urban water supply in portions of the valley and the San Francisco Bay area, water quality, flood control, power, recreation, and fish and wildlife enhancement.

Channel - A course, such as a trench or aqueduct, through which water is moved or directed; the bed of a river or stream.

Check pool - A segment of the canal between two check or control structures. These segments, or pools, in the SWP are identified by sequential numbers.
Check structure - A structure that regulates water flow in an open channel. For the State Water Project, check structures consist of steel radial gates that open or close by remote control to maintain the water level in the aqueduct at design depth during normal operation.

Chute - A steep-sloped conduit conveying water at high velocities to a lower level. Usually of an open channel box-shape and constructed of reinforced concrete; conveys water such as spillway flows over the crest of a dam or between major changes in open channel elevation.

Conduit - Any channel or pipe used for conducting the flow of water or protecting electrical wires or cable.

Conjunctive use - A water management strategy that combines the use of surface and groundwater resources.

Conservation storage - That portion of water, stored in a reservoir, which is impounded for later use.

Consolidation - Adjustment of a saturated soil in response to increased load; involves squeezing water from the voids and a decrease in void ration.

Consumptive use - Quantify of water discharged to the atmosphere (elevation), or incorporated in the products of processes connected with vegetative growth, food processing, or industrial processes. Or the total annual land water loss in an area due to evaporation, plant and industrial process loss.

Control system - (for DWR) Real-time computers in plants and water control structures connected through communication links to Area Control Centers (ACC) and the Project Operations Center (POC).

Conveyance facilities - Facilities, such as aqueducts and channels, used to transport or carry water from one location to another.

Criteria - Water quality conditions which are to be met in order to support and protect desired uses. Could also be criteria for operations, flood control, etc.

Crest (dam) - A line running between abutments describing the upper limit of a dam.

Cubic feet per second (cfs) - A unit of measurement describing the flow of water. A cubic feet is the amount of water needed to fill a cube that is one foot on all sides, about 7.5 gallons.

Culvert - A transverse drain, concrete box culvert, pipe culvert, etc. That takes a water course below ground level.

Curtain grouting - The process of pressure grouting deep holes under a dam or in an abutment to form a watertight barrier and effectively seal seams, fissures, fault zones, or fill cavities in the foundation or abutment.

Cutoff wall - A wall of impervious material (e.g., concrete, asphaltic concrete, steel, impervious curtain grouting, etc.) located in the foundation beneath an embankment dam and which forms a water barrier and reduces seepage under a dam or spillway.

D

Dam - A barrier built across a valley or river for storing water.

Dead storage (dead capacity) - The reservoir capacity from which stored water cannot be evacuated by gravity; inactive storage.

Demand (electrical) - The load that the terminals of an installation or system averaged over a specified interval of time. Demand is expressed in kilowatts, kilovolt amperes, or other suitable units.

Demand (water) - The amount of water necessary to satisfy reasonable local requirements of a given community or agricultural area.

Delivery (water) - The amount of water DWR conveys to a contracting agency according to specified conditions.

Design head - The head at which a hydroelectric facility is designed to operate at maximum efficiency. Also refers to the water pressure or water elevation a facility may be designed to withstand, measured from the free surface level to the free discharge point.

Detention dam - A dam built to store streamflow or surface runoff, and to control the release of such stored water. The SWP contains two detention dams that are used for flood control.

Dewater - Removing water by pumping, draining or evaporation, usually from a work site.

Discharge - Rate of flow or volume per unit time of liquid flowing along a channel or through a pipe at a given instant.

Discharge capacity - The entire discharging capacity of a power plant's turbines or pumps; the maximum amount of water that can safely be released from a given waterway. .

Discharge head - Height between the water level at the pump intake and level at which it discharges freely to the atmosphere .

Discharge valve - Valve used to control flow through a pipe.

Diversion - Refers to water diverted from a water source.

Diversion capacity - The rate of flow which can be passed through a diversion facility under normal design conditions.

Diversion dam - A weir or barrier created for the sole purpose of diverting flow away from its course.

Diversion inlet - A conduit or tunnel upstream from an intake structure. Diversion inlet may be integral with the outlet works or be part of a separate conveyance structure that will only be used during construction.

Diversion tunnel - A channel made to divert the flow of water from one course to another, or around a construction site.

Drainage basin - The area drained by a river and all its tributaries; watershed.

Drainage layer - A layer of pervious material in an earthfill dam to relieve pore pressures or to facilitate drainage of the fill.

Drawdown - The magnitude of the change in water surface of a reservoir or canal pool as the result of the withdrawal of water.

E

Earthfill dam - An embankment type dam in which more than 50 percent of the total volume is formed of compacted fine-grained material.

Earthfill dam, homogeneous - An embankment type dam constructed of only one type of material.

Earthfill dam, zoned - An embankment type dam composed of zones of selected materials where the permeability of the material increases to the upstream or downstream face of the relatively impermeable core material.

Ecosystem - A functional system formed by the interaction of a community of organisms with its environment.

Effluent - Partially or completely treated wastewater flowing out of a treatment facility, reservoir, or basin.

Elevation - Refers to the height of a particular object, measured from sea level to a specific point on the object.

Embankment - Fill material, usually earth or rock, constructed above the surrounding terrain to carry a roadway or to hold back water.

Embankment dam (see earthfill dam) - Any dam constructed of excavated natural materials.

Emergency spillway - A spillway which provides for additional safety should emergencies not contemplated by normal design assumptions be encountered, i.e. unanticipated amounts of flood flows. The crest is usually set at maximum design water surface.

Energy dissipator - A structure that reduces the force of water flowing down a spillway or through a channel to prevent erosion or other damage to the facility.

Enhancement - Improvement of a facility beyond its originally designed purpose or condition.

Entitlement - Amount of water a cooperator is entitled to buy from the Department of Water Resources over a specified time period, usually one year.

Entrainment - Process by which aquatic organisms, suspended in water, are pulled through a pump or other device.
Environmental impacts - factors that affect organisms and the surroundings of organisms.

Erosion - The wearing away of the land surface by wind, water, ice, or other geologic agents. Erosion occurs naturally from weather or runoff but is often intensified by human land use practice.

Estuary - A semi-closed coastal body of water which has a free connection to the open sea and within which seawater is diluted with fresh water.

Export - Refers to an amount of water transported from one source or location to another.

F

Fallow - Land plowed and tilled and left unplanted.

Fault - A fracture in rock along which the adjacent rock surfaces are differentially displaced.

Fill - Manmade deposits of natural soils or the process of the depositing; an earth or broken rock structure or embankment.

Fish hatchery - A facility where salmon and other fish are artificially spawned and raised to be released in lakes, rivers, or estuaries.

Fish ladder - An inclined trough which carries water from above to below a dam so that fish can easily swim upstream.

Firm power - Power intended to have assured availability to the customer to meet load requirements.

Fixed operating costs - Costs, other than those associated with investment in facilities, which do not vary or fluctuate with changes in operation or use of facilities.

Floodplain - A strip of relatively level land bordering a stream or river and is often inundated during times of highwater.

Flood storage capacity - That portion of the reservoir capacity which is reserved for the temporary storage of flood waters to reduce downstream peak flows.

Flow - Refers to the movement of water through an open or closed channel or conduit, usually measured in cubic feet per second.

Flow control valve - A valve with a flow opening that is controlled by the rate of fluid through it.

Flume - An open channel or chute of wood, steel, or reinforced concrete for carrying water.

Fluvial - Refers to streams and stream processes.

Forebay - A storage reservoir upstream from a generating or pumping plant.

Foundation - The soil or rock that supports a dam or other structure.

Freeboard - The height between the normal water level at design flow and the top or storage capacity of a canal lining or dam.

G

Gallery - A passageway within the body of a dam, its foundation, or abutments.

Gate - A device that controls the flow in a conduit, pipe, or tunnel without obstructing any portion of the waterway when in the fully open position.

Gauge (gauging station) - Specific locations on a stream where systematic observations of hydrologic data are obtained through mechanical or electrical means.

General obligation bonds - Bonds issued and backed by the State of California; was used to raise revenues for construction of the State Water Project.

Generation - The gross energy generated in kWh at a generating plant.

Generator - A machine powered by a steam or water turbine which produces electric current.

Groundwater - The inflow to a ground water aquifer. Water may be placed into the aquifer by artificial or natural means.

Groundwater - Water held in pores and crevices of the subsoil, mainly derived from rain or other water source that percolates (drains or seeps) from the surface.

Grout curtain - Rows of holes drilled vertically downwards beneath the cut-off wall of a dam. These holes are spaced and filled with grout under pressure to fill voids and prevent water leakage.

H

Habitat - The natural environment of a plant or animal; a place that is natural for the life and growth of an organism.

Head - Refers to pressure exerted by a confined liquid, gas, or other substance used to produce energy.

Head, gross - The difference between headwater level and tailwater level at the powerhouse.

Head loss - The energy per unit weight of water lost due to friction, transitions, bends, etc.

Head, net - That part of the gross head which is directly available for the turbines.

Head pressure - Positive pressure at a given point in a liquid system, normally expressed in feet of water or pounds per square inch.

Headwall - Concrete retaining wall at an entrance to a conduit to stop erosion and seepage along the conduit. It usually acts as a transitional structure.

Head water - The water upstream from a powerhouse, or generally water upstream from any hydraulic structure creating a head.

Headworks structure (pumping plant) - Structure at high point of discharge penstocks to prevent backflow or siphoning of upper pool back through the pumping plant.

Heel of dam - The junction of the upstream face of a gravity dam with the ground surface. For an embankment dam, the junction is referred to as the “upstream toe of the dam.”

Horsepower (hp) - The English unit of power, equal to work done at the rate of 550 foot-pounds per second, approximately 746 watts.

Hydraulic fill - Fill material that is transported and deposited using water.

Hydraulics - The physical science and technology of the static and dynamic behavior of fluids. Operated or affected by the action of water or other fluid.

Hydroelectric power - the electric current produced by water power.

Hydrologic cycle - Also known as the water cycle; the complete cycle of water passing (evaporation) from the oceans, through the atmosphere to the land (precipitation) and back to the ocean

Hydroelectric powerplant - A facility in which the energy of falling water is used to drive generators to produce electricity.

I

Impermeable - Having a texture that does not permit water to pass through.

Imported water - Water brought into an area from a distant source, such as from one part of a state to another via an aqueduct.

Impoundment - A body of water confined by a dam, dike, floodgate, or other barrier for future use.

Impeller - Rotating wheel of a turbine; also known as a rotor.

Impervious - See impermeable

Inflow - Water that flows into a body of water.

Inlet structure (channel) - Concrete-lined portion of the spillway between the approach channel and gate or crest structure.

In-line - Part of a system of pumping plants arranged in a straight line.

Installed capacity - Maximum runoff of a hydroelectric facility that can be constantly maintained and used by equipment; the total of the capacities as shown by the name plates of the pumping or generating units in a station or system.

Intake - A hydraulic structure built at the upstream end of the diversion canal; a tunnel or power plant for controlling the flow and preventing silt and debris from entering the diversion.

Intake tower - A pressure tunnel intake erected separately in the reservoir for housing the flow control valves or gates.

Interconnection - A link between power systems, enabling them to draw on one another's reserves if necessary; a tie permitting a flow of energy between the facilities of two electric systems.

Irrigated acreage - The irrigable acreage actually irrigated in any one year. It will include irrigated crop land harvested, irrigated pasture, crop land planted but not harvested, and acreage in irrigated rotation used for soil-building crops.

J

Joint-use facility - A facility that is operated by the Department of Water Resources in cooperation with another agency or company. For example, the federal/State San Luis facilities.

K

Kilovolt (kV) - One thousand volts.

Kilovolt-ampere (kVA) - One thousand volt-amperes.

Kilowatt-hour (kWh) - A unit of energy equal to 1,000 watt-hours. The corresponding SI term is megajoule (MJ). 1 kWh = 3.6 MJ

L

Land retirement - Permanent removal of land from agricultural production.

Length (of dam) - The distance, measured along the dam's axis or centerline crest at the top of the dam's main body or of the roadway surface on the crest, from abutment contact to abutment contact. (The length includes the spillway if it lies wholly within the dam.)

Levee - A natural or manmade earthen barrier along the edge of a stream, river, or lake to prevent the flow of water out of its channel.

Lift - The amount of water that is raised in elevation by a pumping plant.

Lining - A layer of clay, concrete, brick, or other material placed over the bed of a canal to protect inner surfaces and reduce scour or leakage.

Live storage - All water storage above dead storage; active storage.

Load (electrical) - The amount of electric power drawn from a power line, generator, or other power source.

Load base - The minimum electrical load over a given period of time.

M

Main channel - The deepest or central part of the bed of a stream, containing the main current.

Maintenance - All routine and extraordinary work necessary to keep the facilities in good repair and reliable working order to fulfill the intended design project purposes.

Manifold - A branch pipe arrangement connecting and gathering the discharge from several pumps to a common discharge line or for connecting a penstock to several generating units.

Maximum operating storage - see Operating Storage, Maximum

Minimum operating storage - see Operating Storage, Minimum

Mitigation - When used in the context of an environmental assessment, it refers to an action designed to lessen or reduce adverse impacts due to a project's implementation.

Morning glory spillway - A circular or glory hole form of a drop inlet spillway. Usually free standing in the reservoir and so called because of its resemblance to the morning glory flower.

Motor - A device that converts any form of energy into mechanical energy. An electric motor uses forces produced by magnetic fields on current-carrying conductors.

Multipurpose reservoir - A reservoir capable of use for more than one purpose. Such purposes can include conservation, power, flood control, recreation, fish and wildlife, navigation, etc.

N

Nameplate - Power generation capacity of a generator that can be guaranteed under continuous operation.

Nonconsumptive water uses - Water uses that do not substantially deplete water supplies, including swimming, boating, waterskiing, fishing, maintenance of streamrelated fish and wildlife habitat, and hydropower generation.

Nonpoint source - A contributing factor to water pollution that cannot be traced to a specific spot.

Normal water surface - The highest elevation that water is normally stored, or that elevation which the reservoir should be operated for conservation purposes.

O

Ogee - A double curve shaped like an elongated S, usually associated with a spillway configuration designed with optimal overflow characteristics.

Off-peak energy - Electric energy supplied during period of relatively low system demands as specified by the supplier. Typically, these periods include nights and weekends.

On line - Synchronized and connected electrically with the system usually referring to a power generating facility.

On-peak energy - Electric energy supplied during periods of relatively high system demands as specified by the supplier. Typically, these periods include weekdays during daytime hours.

Operating surface - The level of water in a reservoir or canal under normal operating conditions.

Operating storage - Water stored in a reservoir or similar facility within a normal operating range.

Outage - Period during which a generating unit, transmission line, or other facility is out of service.

Outflow - The amount of water passing a given point downstream of a structure, expressed in acre-feet per day or cubic feet per second.

Outlet works - Usually a pipe or tunnel under a dam that allows water to be drawn from the reservoir as needed.

Output - The current, voltage, power, driving force or information delivered from a piece of equipment, station, or system.

Overchute - Drainage structure passing local drainage over a canal.

Overload - A load greater than the rated load of an electrical device.

Overload capacity - The maximum load that a machine, apparatus, or device can carry when operating beyond its normal rating but within the limits of the manufacturer's guarantee.

P

Panoche formation - Refers to geologic formation consisting mostly of sandstone, shale, and minor conglomerate.

Peak load - The maximum load consumed or produced by a unit or group of units in a stated period of time.

Pelton wheel (turbine) - An impulse hydraulic turbine in which water pressure is converted by a few stationary nozzles to a high velocity water jet, which hits a series of buckets mounted on the rim of a wheel. Usually used at high head power plants.

Penstock - A pressurized pipeline conveying water between an intake and power plant.

Pervious - Permeable, having openings that allow water to pass through.

Pervious zone - A part of the cross section of an embankment dam comprising material of high permeability

Phase (electric) - The fraction of the period of an alternating current which has elapsed since the current passed through the zero point of reference.

Potable water - Drinkable water.

Power - The time rate of transferring or transforming energy. The normal electrical unit is watt (W). Mechanical power is often expressed in horsepower (hp).

Power plant - An installation that contains turbines and generators for the production of electrical power. Also known as a powerhouse.

Power pool (electric) - Two or more electric systems interconnected and operating on a regional basis.

Precipitation - A deposit on the earth of hail, rain, mist, sleet, or snow. It is the common process by which atmospheric water becomes surface or subsurface water.

Preconsolidation - Refers to any number of earthwork methods to consolidate (I.e., settle) the ground prior to the consolidation that will occur during the construction of a facility. Areas of subsidence along the aqueduct's alignment were preconsolidated using pools of water to accelerate soil settlement and slow or reduce subsidence when the canal was constructed.

Pump - A machine used to raise or impel liquids through a pipe.

Pumped-storage - Refers to an operation in which a pumping-generating plant generates electricity for peak load, but, at off peak, water is pumped from the tailwater pool to the headwater pool for future use.

Pumping-generating plant- A plant with reversible turbine units that may be used to pump water or generate electricity, usually in pumped storage developments.

Pump lift - The vertical distance that a pump will raise water.

Pumping plant - An installation that contains motors and pumps for lifting water.

R

Raceway - A channel designed for holding wires, cables, or bus bars. Also a unidirectional flow channel to hold and raise fish at a fish hatchery.

Radial gates - Used to control the flow of water from a reservoir or through a channel. They are watertight cylindrical-faced gates supported on a steel framework and pivoted on a horizontal axis on the downstream end of the gate. Each gate can close under its own weight and is operated independently by remotely controlled motors. Also called tainter gates.

Rating - A designated limit of operating characteristics of a machine or device based on defined conditions.

Reach - On the California Aqueduct, a specific segment of the canal, identified by a number.

Reclaimed water - Wastewater that has been cleaned so that it can be reused for most purposes except drinking.

Release - Water freed from storage for specified purposes such as delivery, water quality improvement, or fish and wildlife enhancement.

Repayment period - Refers to the length of the long-term contracts that water agencies have with the State of California to pay back, with interest, the costs of the SWP conservation facilities. It ends in the year 2035.

Reserve generating capacity - Extra generating capacity available to meet unanticipated capacity demand for power in the event of generation loss due to scheduled or unscheduled outages of regularly used generating capacity.

Reservoir - An artificial lake, pond, tank, or basin (natural or human made) into which water flows and is stored for future use.
Reservoir capacity - Total storage space in a reservoir, below a designated elevation.

Revetment - An embankment or wall of sandbags, earth, etc., constructed to restrain material from being transported away. A facing of stone, cement, sandbags, etc., to protect a wall or embankment.

Rewind - Act of putting new copper insulated wire in the armature windings of a generator.

Riparian - Living on or adjacent to a water supply such as riverbank, lake, or pond. Of, on, or pertaining to the bank of a river, pond, or lake.

Riprap - A layer of large uncoursed stones, broken rock, boulders, or precast blocks placed in random fashion on the upstream and downstream faces of embankment dams, stream banks, on a reservoir shore, on the sides of a channel, or other land surfaces to protect them from erosion caused by current, wind, wave, and/or ice action. Very large riprap is sometimes referred to as “armoring.”

Rockfill Dam - An embankment type dam in which more than 50 percent of the total volume is comprised of compacted or dumped cobbles, boulders, rock fragments, or quarried rock.

Rolled fill dam - An embankment dam of earth or rock in which the material is placed in layers and compacted by the use of rollers or rolling equipment.

Runoff - Water that drains or flows off, such as rain water flowing off from the land or water from snow draining from a mountain range.

S

Sacramento-San Joaquin Delta - A 738,000-acre region, interlaced with hundreds of miles of waterways, which receives runoff from 40 percent of the California's land area, including runoff and flood flows from the Sacramento, San Joaquin, Mokelumne, and Cosumnes rivers. As part of an interconnected estuary system that includes Suisun Marsh and San Francisco Bay, the Delta supports hundreds of species of fish, wildlife, and plants. It also serves as part of an important water transport system which includes the SWP.

Saddle dam - A subsidiary dam of any type constructed across a saddle or low point on the perimeter of a reservoir.

Salinity - Measure of saltiness.

Scheduled outage - Shutdown of a generating unit, or other facility, for inspection or maintenance, in accordance with an advance schedule.

Scour - Erosion of a river bed or bank or of a sea coast by action of flowing water and waves.

Seepage - Water that has passed, flowed, or oozed gradually through a porous medium, such as a levee or the materials in a dam.

Sill - Horizontal overflow line of a measuring notch or spillway. Also a horizontal member on which a gate rests when closed.

Siphon - Of an inverted enclosed pipeline structure to convey the water under roads, drainage channels, rivers, etc. Also used by DWR to describe a pipeline where water moves from a higher to a lower level by atmospheric pressure, forcing it up the short leg while the weight of water in the longer leg causes continuous downward flow.

Slide gate - A steel gate that upon opening or closing slides on its bearings in edge guide slots.

Snowpack - The annual accumulation of snow in mountain areas.

Spillway - Section of a dam designed to permit water to pass over its crest; a weir or channel taking overflow from the dam; serves as a safety channel to prevent erosion of the dam.

Spinning reserves - Available capacity of generating facilities synchronized to the interconnected electric system where it can be called upon for immediate use in response to system problems or sudden load changes.

Spoil - Dirt or rock which has been removed from its original location.

Standby reserves - Unused capacity in an electric system in machines that are not in operation but that are available for immediate use if required.

State Water Project contractors - Agencies that have long-term contracts for water entitlements from the State Water Project.

Static head - A fixed, nonvarying positive pressure at a given point in a liquid system, normally expressed in feet of water.
Stilling pool - A pool located below a spillway, gate, or valve into which the discharge dissipates energy to avoid downstream channel degradation.

Stoplog - A steel or concrete beam that fits into a groove between walls or piers to prevent the flow of water.
Stream gaging - A process of determining the rate of flow, or the discharge, of streams.

Structural height - When referred to dam sites, it is the distance between the lowest point in the excavated foundation and the top of the dam.

Sump - A pit or pool for draining, collecting, or storing water.

Supply capability (SWP) - The amount of water available for delivery to State Water Contractors. SWP delivery capabilities analysis takes into account storage levels at the beginning of the water year (October to October), target storage levels at the end of the water year (including need for emergency reservoir storage and releases sufficient to protect Delta water quality), the probability of various levels of rainfall over the remainder of the water year, the operational capacity of SWP facilities, and federal and state operational mandates to protect the Bay-Delta estuary.

Surface water - Water on the earth's surface exposed to the atmosphere, e.g., rivers, lakes, streams, oceans, ponds, reservoirs, etc.

Surge - Sudden changes of current or voltage, or of hydraulic pressure. t

Surge tank - A standpipe or storage reservoir at the downstream end of a closed feeder pipe allowing upsurge and downsurge to take place thus reducing sudden variations in pressure within determined design parameters.

Switchyard - An area where an electrical current, produced by a generating unit, is altered so that it can be transmitted to another location, or where it can be received and altered so that it can be used by pumping units.

T

Tailrace - The channel into which water is discharged after passing through the turbines.

Tailwater - Water that accumulates in depth downstream from any hydraulic structure.

Test pit - Put dug for geologic investigation or inspection and testing of earthwork placement.

Toe - The point of intersection between the upstream or downstream face of the dam and natural ground, for example, the upstream or downstream toe of a dam.

Topography - Physical shape of the ground surface.

Transformer - An electrical device which by electromagnetic induction transforms electric energy from one or more circuits to one or more other circuits at the same frequency, usually with changed values of voltage and current.

Transition zone (semipervious zone) - A substantial part of the cross section of an embankment dam comprising material whose grading is of intermediate size between that of an impervious zone and that of a permeable zone.

Transmission - The transporting or conveying of electric energy in bulk to a convenient point at which it is subdivided for delivery to the distribution system. Also used to indicate the conveying of electric energy over any or all of the paths from source to point of use.

Trashracks - Structural members so arranged in a waterway to prevent trash and objects from entering a conduit, channel, or a plant intake.

Tributary - A stream that flows into a larger stream or other body of water.

Trunion - A pin or pivot attached to a pier or dam face for rotating a radial gate.

Turbine - A device which produces power by diverting water through blades of a rotating wheel which turns a shaft to drive generators.

Turnout - A branch in the canal for diverting water to a specific destination; where water is diverted to users.

U

Underchute - A drainage culvert passing local drainage under a canal.

Unwatering - As opposed to dewatering, unwatering is the interception and removal of groundwater outside of excavations and the removal of ponded or flowing surface water from within excavations; to remove or drain off water.

Upstream face - The inclined surface of the dam that is in contact with the reservoir.

V

Valve - A device to regulate or stop the flow of water or gas in a pipe.

Velocity - Rate of flow of water expressed in feet per second or miles per hour.

Volt (V) - The unit of measurement of electromotive force. It is equivalent to the force required to produce a current on 1 ampere through a resistance of 1 ohm.

Voltage (E) - Electrical pressure, i.e. the force which causes current to flow through an electrical conductor. The greatest effective difference of potential between any two conductors of a circuit.

Volt-ampere (VA) - A unit of apparent power in an ac circuit containing reactance. It is equal to the potential in volts multiplied by the current in amperes, without taking phase into consideration.

Vortex - A revolving mass of water (whirlpool) in which the streamlines are concentric circles and in which the total head is the same. Water rotating about an axis.

W

Water hammer - Any rapid increase of pressure in a pipeline caused by stopping the flow suddenly. Surge tanks are used to counter water hammers.

Watermaster - An employee of a water department who distributes available water supply at the request of water right holders and collects hydrographic (changes in water flows or elevation of water level with respect to time) data.

Water quality - A term used to describe the chemical, physical, and biologic characteristics of water with respect to its suitability for a particular use.

Water right - A legally protected right, granted by law, to take possession of water occurring in a water supply and to divert the water and put it to beneficial uses.

Watershed - The area or region drained by a reservoir, river, stream, etc.; drainage basin.

Water table - The surface of underground, gravity-controlled water.

Water year - The 12-month period, usually October 1 through September 30 over which yearly hydrologic data is averaged. The water year is designated by the calendar year in which it ends and which includes nine of the 12 months. For example, the year ending September 30, 1989 is called the 1989 Water Year.

Watt - Basic unit of electrical power produced at one time. One watt equals one joule per second.

Wetlands - Lands including swamps. marshes, bogs, and similar areas such as wet meadows, river overflows, mud flats, and natural ponds. An area characterized by periodic inundation or saturation, hydric soils, and vegetation adapted for life in saturated soil conditions.

Wheeling service - An electric operation wherein transmission facilities of one system are used to transmit power of another system; can also refer to the use of conveyance facilities of one system used to transport water to another system.