Glossary of Terms

An acre-foot is a unit of volume equal to 325,851 gallons or the volume of water required to cover one acre to a depth of one foot.

An aqueduct is a water conveyance or transportation structure, such as a channel, that transports water from one place to another. The Tri-Valley is supplied State Water Project water (and other imported or non-local water) via the South Bay Aqueduct through our regional wholesaler, Zone 7 Water Agency.

An aquifer is an underground layer of rock, gravel, sand, and/or silt that contains groundwater. Also known as a groundwater basin.

The California Aqueduct is the primary conveyance facility of the State Water Project. It extends from the southern side of the Sacramento-San Joaquin Delta to Riverside County.

Climate change is the significant change in long-term weather patterns, including changes in temperature and precipitation. Climate change is expected to increase the intensity and frequency of extreme weather events such as floods, heat waves, and droughts - which impact Zone 7’s flood control infrastructure and water supply.

Conveyance is the process of moving something from one place to another. Infrastructure such as pipes and channels are used for water conveyance.

A dam is a structure that restricts or stops the flow of water, usually along a river or stream. Dams can be used to create a reservoir to store water for water supply. Dams are often used for hydroelectric power generation.

Department of Water Resources - DWR is a department under the California Natural Resources Agency that manages California's water resources, systems, and infrastructure, including the State Water Project.

Desalination is the process of removing salts and minerals from salt water. The Tri-Valley water partners are exploring desalination through the Bay Area Regional Desalination Project in which brackish water (less salty than seawater) from the Delta is used as a source of water supply.

A drought occurs when there is a lack of water and is usually caused by a prolonged period of dry weather lasting multiple years.

Groundwater is water that is found underground in the spaces between soil, sand, gravel, and rocks. It supplements the Tri-Valley’s surface water supplies. The Livermore Valley Groundwater Basin lies beneath most of the Tri-Valley and is an important source of groundwater to the Tri-Valley.

Groundwater banks are created to allow water agencies to store excess supplies during wet years in aquifers for later use during droughts and emergencies. Zone 7 uses groundwater banks operated by Semitropic Water Storage District and Cawelo Water District in Kern County. Water from these banks are recovered, when needed, to supplement other sources of water supplies.

Imported water refers to water that is captured in a non-local watershed and is conveyed to us for local use. Our largest source of imported water comes from the State Water Project and travels through the Delta.

Local water refers to water that is captured from our local Arroyo Valle watershed and is stored in Lake Del Valle. Local water from Lake Del Valle becomes available for use after it has been stored for 30 days. Before or during major storm events, DWR may also release local water from Lake Del Valle for immediate use by Zone 7.

Non-potable reuse refers to using recycled water for non-drinking water purposes, such as outdoor irrigation.

Potable reuse is the use of recycled water for drinking water purposes. Wastewater goes through an advanced purification process to ensure it meets the stricter standards for drinking water quality.

Potable water is water suitable for drinking.

This term is often used interchangeably with ‘recycled water’. It is wastewater that has been treated to standards suitable for non-potable or non-drinking water uses.

This term is often used to refer to wastewater that has been treated to standards suitable for non-potable or non-drinking water uses, like irrigation. However, it may also refer to the general reuse of wastewater, including potable use.

A natural or, more commonly, constructed storage facility for surface water supply. Reservoirs can be formed by building a dam on a river; however, they can also be “off-stream”, which means they do not block a river or stream. Lake Del Valle and Lake Oroville are vital reservoirs to the Tri-Valley. Zone 7 is considering investments in new or expanded reservoirs.

The Delta is formed by the merging of the Sacramento River flowing south and the San Joaquin River flowing north, in the area just south of Sacramento. It is a very important environmental and water supply resource for the State of California. It serves as the hub of California’s two largest surface water delivery projects, the State Water Project and the federal Central Valley Project, providing drinking water supply to 29 million Californians and irrigation water for large portions of California’s farms.

Sustainable Groundwater Management Act - This legislation was passed in 2014 to help protect the groundwater resources of the State of California. SGMA requires the formation of Groundwater Sustainability Agencies or GSAs for groundwater basins that need to be protected. Zone 7 is the GSA for the local groundwater basin.

The Sierra Nevada is a mountain range in between the Central Valley of California and the Great Basin. Imported water’s journey to the Tri-Valley starts at the peaks of the Sierra Nevada.

Snowpack is the accumulation of packed snow that usually melts during the warmer months. The Sierra Nevada snowpack is critical for California as it serves as a type of reservoir, ultimately providing about 30% of the state’s fresh water supply in an average year. California’s snowpack is typically the deepest on April 1.

The South Bay Aqueduct conveys State Water Project water from the Delta--and other sources of imported water--to the Tri-Valley and other South Bay Aqueduct Contractors. It is the northernmost branch of the California Aqueduct.

Surface water is water that is located above ground. Examples include lakes, rivers, wetlands, and oceans.

State Water Contractors - The SWC is a non-profit organization of 29 water agencies that receive water from the SWP, working to protect the environment and water supplies. Zone 7 is the Tri-Valley area’s water wholesaler and local member of the SWC.

State Water Project - The SWP is owned and operated by DWR and it delivers water to 27 million Californians, 750,000 acres of farmland, and businesses throughout the state. The SWP is the nation’s largest state-owned water and power generator and user-financed water system. Water is received by 29 long-term State Water Project contractors who distribute it to farms, homes, and industry. SWP contractors pay for the cost of the SWP through property taxes, water rates, and connection fees.

The Tri-Valley area is made up of three valleys in the East Bay region of California’s Bay Area. The three valleys are Amador Valley, San Ramon Valley and Livermore Valley. Tri-Valley Water includes the cities of Livermore, Pleasanton, Dublin, and Dougherty Valley.

A water year is a 12-month time period that starts October 1 of a given year and ends September 30 of the following year. The water year is designated by the calendar year in which it ends. For example, October 1, 1999 to September 30, 2000 would constitute the 2000 water year.