A measurement of water equaling 325,900 gallons & enough to fill a football field, or one acre, to a depth of one foot.

agricultural runoff:

Water applied to an agricultural field, not evaporated, absorbed into the ground or utilized by the crop, transferred back into the water system for in-stream and downstream use.


A naturally occurring underground geologic formation that can store a significant amount of water.

area of origin:

A surface water source where water precipitates and runs off.

CALFED Bay-Delta Program:

A cooperative effort among the public, state and federal agencies with management and regulatory responsibility in the Bay-Delta system. It was formed in 1994 as part of the Bay-Delta Accord to address the water management and environmental problems associated with the Bay-Delta system, including ecosystem restoration, water quality, water use efficiency and levee system integrity. The mission of the CALFED Bay-Delta Program is to develop a long-term, comprehensive plan that will restore ecological health and improve water management for beneficial uses of the Bay-Delta system.

Central Valley Project (CVP):

The federal water storage and transportation system in California, providing 20 percent of delivered water in the state.

Central Valley Project Improvement Act (CVPIA):

Legislation enacted in 1992 that provided for substantial changes in CVP operations with emphasis on the protection, restoration and enhancement of fish and wildlife and their habitats. The CVPIA dedicated 800,000 acre-feet of project yield to fish and wildlife purposes, provided for anadromous fish restoration and created a restoration fund financed by water and power users.

conjunctive use:

The practice of using both groundwater and surface water.

developed water supply:

The water available for agricultural, municipal, industrial, and environmental uses, not including the water that evaporates, flows directly into the ocean, or is naturally diverted to other uses.

Endangered Species Act (ESA):

Approved in 1973, the federal Endangered Species Act is intended to protect and promote the recovery of animals and plants that are in danger of becoming extinct due to human activities. The ESA gives the Secretary of the Interior (Director of the Fish and Wildlife Service) the responsibility for determining whether to place an animal or plant on the federal list of endangered and threatened species.


Water that is stored naturally or artificially in the ground, usually in aquifers. Some stores of groundwater are naturally and regularly replenished, while others are depletable sources of water, not easily and quickly recharged.

irrigation efficiency:

The determination of water lost to evaporation and runoff from an irrigated field. Irrigation efficiency is derived from the ratio of the average depth of water seeped and stored at the root zone to the average depth of water applied to the field.

nonpoint source pollution:

Pollution that is carried in runoff water from widely dispersed land areas, such as fields, forests or urban areas.

off-stream storage:

A form of water storage where a dam is constructed in a dry or seasonal wash � not on a free-flowing river.


The amount of water from the yearly total extraction from the aquifer that is not replaced by natural or artificial recharge.


to trickle or seep through a permeable substance.

point source pollution:

Pollution that is discharged from a discernible, confined and discrete conveyance, such as a pipe, ditch or channel, tunnel, conduit, well container, concentrated animal feeding operation or vessel.


The natural or artificial process of replenishing the groundwater.

Regional Water Quality Control Board (RWQCB):

There are nine regional boards to develop and enforce water quality objectives and implementation plans to protect the beneficial uses of the State’s waters � recognizing local differences in climate, topography, geology and hydrology. RWQCBs develop “basin plans” for their hydrologic areas, govern requirements and issue waste discharge permits, take enforcement action against violators and monitor water quality.

State Water Resources Control Board (SWRCB):

Created by the legislature in 1967 to ensure the highest reasonable quality for waters of California, while allocating those waters to achieve the optimum balance of beneficial uses. The SWRCB has joint authority of water allocation and water quality protection.


Total Maximum Daily Load is a written plan that describes how a waterway of a reduced quality will meet federal water quality standards. Section 303(d) of the federal Clean Water Act requires states to develop TMDLs for impaired water bodies that do not meet the established water quality standards.

waste discharge waivers and permits:

The California Water Code allows RWQCBs to issue waivers, instead of permits, to dischargers when the boards find it in the public interest to do so. Over the years, all nine RWQCBs have adopted waivers for certain types of dischargers, including the return of agricultural irrigation water to surface streams and rivers. In 1999, Senate Bill 390 amended the California Water Code to rescind all waivers by the end of 2002, expect those that the RWQCBs decided to readopt under new stricter guidelines.


The area of land that catches rain and snow and drains or seeps into a marsh, stream, river, lake or groundwater. Specifically, the term watershed describes an area of land that drains downslope to the lowest point. The water moves through a network of drainage pathways, both underground and on the surface. Generally, these pathways converge into streams and rivers, which become progressively larger as the water moves on downstream. No matter where you are, you’re in a watershed!

water transfers:

Transactions between a water supplier, agreeing to transfer a volume of water, and the recipient of the water, under mutually acceptable terms, including the volume of water, the price paid, the time period and the condition of water for transfer.

For additional water terminology, go to Water Words at the State Water Resources Control Board’s website.