Aquifer — a geologic formation(s) that is water bearing; a geological formation or structure that stores and/or transmits water, such as to wells and springs. Use of the term is usually restricted to those water-bearing formations capable of yielding water in sufficient quantity to constitute a usable supply for people’s needs.

Aquifer (confined) — soil or rock below the land surface that is saturated with water. There are layers of impermeable material both above and below it, and it is under pressure so that when the aquifer is penetrated by a well, the water will rise above the top of the aquifer.

Aquifer (unconfined) — an aquifer whose upper water surface (water table) is at atmospheric pressure, and thus is able to rise and fall.

Aquitard — a geologic formation or stratum that lies adjacent to an aquifer and that allows only a small amount of liquid to pass.

Artificial recharge — a process where water is put back into groundwater storage from surface-water supplies such as irrigation, or induced infiltration from streams or wells.

De minimis extractor – a person who extracts, for domestic purposes, two acre-feet or less per year.

Department of Water Resources (DWR) – State agency that oversees the implementation of SGMA.

Diversion canal — a waterway used to divert water from its natural course.

Drainage basin — the land area where precipitation runs off into streams, rivers, lakes, and reservoirs. It is a land feature that can be identified by tracing a line along the highest elevations between two areas on a map, often a ridge. Large drainage basins, like the area that drains into the Mississippi River, contain thousands of smaller drainage basins. Also called a “watershed.”

Drawdown — a lowering of the groundwater surface caused by pumping.

Evapotranspiration — the process by which water is transferred from the land to the atmosphere by evaporation from the soil and other surfaces and by transpiration from plants.

Groundwater — (1) water that flows or seeps downward and saturates soil or rock, supplying springs and wells. The upper surface of the saturate zone is called the water table. (2) Water stored underground in rock crevices and in the pores of geologic materials that make up the Earth’s crust.

Groundwater, confined — groundwater under pressure significantly greater than atmospheric, with its upper limit the bottom of a bed with hydraulic conductivity distinctly lower than that of the material in which the confined water occurs.

Groundwater recharge — inflow of water to a groundwater reservoir from the surface. Infiltration of precipitation and its movement to the water table is one form of natural recharge. Also, the volume of water added by this process.

Groundwater Sustainability Agency (GSA) – one or more local agencies that implement SGMA. The Santa Margarita Groundwater Agency (SMGWA) is the GSA for the Santa Margarita Basin.

Groundwater Sustainability Plan – a plan of a groundwater sustainability agency proposed or adopted pursuant to SGMA.

Groundwater, unconfined — water in an aquifer that has a water table that is exposed to the atmosphere.

Groundwater management plan — identifies actions necessary to contribute to an effective water resources management framework. It is intended to provide planned and coordinated monitoring, operation and administration of groundwater basins with the goal of long-term groundwater resource sustainability.

Injection well — an injection well is used to place fluid underground into porous geologic formations. These underground formations may range from deep sandstone or limestone to a shallow soil layer. Injected fluids may include water, wastewater, brine (salt water) or water mixed with chemicals.

In-lieu use – the use of surface water by persons that could otherwise extract groundwater in order to leave groundwater in the basin.

Monitoring well — a well designed and installed to obtain representative groundwater quality samples and hydrogeologic information. Deep and shallow monitoring wells provide controlled access for sampling groundwater near an agricultural waste storage or treatment facility to detect seepage and monitor groundwater quality.

Overdraft — overdraft occurs when, over a period of years, more water is pumped from a groundwater basin than is replaced from all sources – such as rainfall, irrigation water, streams fed by mountain runoff and intentional recharge. While many of its individual aquifers are not overdrafted, California as a whole uses more groundwater than is replaced.

Private pumpers — groundwater users operating their own wells outside of any water agency.

Recharge — water added to an aquifer. For instance, rainfall that seeps into the ground.

Sustainable Groundwater Management Act (SMGA) — the SGMA provides a framework for sustainable management of groundwater supplies by local authorities. Recognizing that groundwater is most effectively managed at the local level, the SGMA empowers local agencies to achieve sustainability within 20 years. The SGMA establishes minimum standards for sustainable groundwater management, improves coordination between land use and groundwater planning, provides state technical assistance, protects water rights, and creates a mechanism for state intervention if a local agency is not managing its groundwater sustainability.

Surface water — water that is on the Earth’s surface, such as in a stream, river, lake or reservoir.

Undesirable result – under SGMA, one or more of the following effects caused by groundwater conditions occurring throughout the basin:

• chronic lowering of groundwater levels

• significant and unreasonable reduction of groundwater storage

• significant and unreasonable seawater intrusion

• significant and unreasonable degraded water quality

• significant and unreasonable land subsidence

• depletions of interconnected surface water 

Water table — the top of the water surface in the saturated part of an aquifer.

Water year — the water year is Oct. 1 to Sept. 30.

Water use — water that is used for a specific purpose, such as for domestic use, irrigation or industrial processing. Water use pertains to human’s interaction with and influence on the hydrologic cycle and includes elements such as water withdrawal from surface and groundwater sources, water delivery to homes and businesses, consumptive use of water, water released from wastewater treatment plants, water returned to the environment, as well as instream uses, such as using water to produce hydroelectric power.

Watershed — the land area that drains water to a particular stream, river or lake. It is a land feature that can be identified by tracing a line along the highest elevations between two areas on a map, often a ridge. Large watersheds, like the Mississippi River Basin, contain thousands of smaller watersheds.

Well Owner Representative – director on the Santa Margarita Groundwater Agency Board who represents private pumpers.