GW Resource Category Definitions

Background – Introductory information to SGMA or groundwater; information where someone who has limited knowledge can get background understanding

Groundwater 101 – Basic facts about groundwater Including climate science material

Understanding SGMA  – Deeper explanation of SMGA and its framework

Ecosystem Preservation – Environmental preservation including pollution issues, local fauna, and instream flow

Surface Water Interactions and Groundwater Recharge  – Stormwater water capture; aquifer recharge, including Managed Aquifer Recharge (MAR) and Recharge Net Metering (RNM)

Water Allocation  – Groundwater markets and trading; Water rights administration

Data/Monitoring Systems – Navigating water data and climate science projections; building and using relevant groundwater models

Community Engagement – How stakeholders can engage with GSPs; environmental justice considerations

Water Quality – Including issues related to fracking

GSP Best Practices – Interested parties can see what’s been done; including “Measuring Objectives category”



Acre-Foot – The volume of water required to cover one acre of land (43,560 square feet) to a depth of one foot. Equal to 325,851 gallons or 1,233 cubic meters

Adsorbed – “Stuck” to the edges of sediments.

Aquifer – A saturated underground layer of water-bearing permeable rock or unconsolidated materials (gravel, sand, silt, permeable rock or unconsolidated materials (gravel, sand, silt, or clay) from which groundwater can be extracted using a well.

Artesian – Condition in which a confined aquifer is under pressure such that the static level within a cased borehole that rises above an impermeable (confining) layer (e.g., peat layer) or in which water discharges to the surface from an unlined borehole.

Base-flow stream – A perennial stream supported by ground-water discharge during periods of low or no precipitation or snowmelt.

Basin – An aquifer or system of aquifers that has reasonably well-defined boundaries

Best available science – The use of sufficient and credible information and data, specific to the decision being made and the time frame available for making that decision, that is consistent with scientific and engineering professional standards of practice.

BMP – Best Management Practices.

Bog – A peat-accumulating wetland that has no significant in-flows or outflows and supports acidophilic mosses, particularly Sphagnum. In general, bogs are supported by precipitation.

Boundary condition – Description of the flows at the edges of the area analyzed by a model.

Bryophytes – Nonvascular land plants (mosses, liverworts, and hornworts) that have tissues and enclosed reproductive systems but lack vascular tissue that circulates liquids. They neither have flowers nor produce seeds because they reproduce via spores.

Carolina Bay – Elliptical depressions or shallow basins that occur throughout the Southeastern United States Coastal Plain. Their hydrology is dominated by precipitation inputs and evapotranspiration losses, and they range from nearly permanently inundated to frequently dry.

Cave – A natural underground space formed by various geologic processes. Caves are common in karst terrain and areas of psuedokarst.

CEC – Contaminants of Emerging Concern

Cienega – Usually a wet, marshy area at the foot of a mountain, in a canyon, or on the edge of a grassland where groundwater reaches the surface. Often, a cienega does not drain into a stream but instead evaporates. Also called helocrene.

Cone of depression – A lowering of the water table when ground- water is pumped from a well, especially in the immediate circle around the pumping area.

Crenobiontic – Organisms that live only in springs.

Critically overdrafted basin – A groundwater basin in which the continuation of present practices of withdrawing water would likely result in significant negative environmental, social, or economic impacts.

CSO – Combined sewer overflow

Data gap – A lack of information that significantly affects the understanding of the basin setting or evaluation of the efficacy of plan implementation, and could limit the ability to assess whether a basin is being sustainably managed.

Dissolved – In liquid form; part of the groundwater.

Diversion recoverable loss – Canal leakage.

DWR – Department of Water Resources. They oversee SGMA implementation.

EJ – Environmental Justice

EPA – U.S. Environmental Protection Agency

ESJ – Eastern San Joaquin

Evapotranspiration – The quantity of water released by plants, retained in plant tissues, and evaporated from plant tissues and surrounding soil surfaces.

Exposure spring – Groundwater is exposed at the land surface but does not have surface inflow or outflow. Exposure springs occur in karst (sinkholes) and psuedokarst (lava flows) but could form in other types of vertical conduits into an aquifer.

Fen – In general, wetlands that develop where a relatively constant supply of groundwater to the plant rooting zone maintains saturated conditions most of the time and the water chemistry reflects the mineralogy of the surrounding and underlying soils and geological materials.

Fibric – Organic soil material that contains 3/4 or more recognizable fibers (after rubbing between fingers) of undecomposed plant remains. Bulk density is usually very low and water-holding capacity very high. Also referred to as peat.

Forb – Herbaceous flowering plant that is not a graminoid.

Fountain spring – Cool, artesian springs that are forced above the land surface by artesian or gas pressure.

GAC – Groundwater Advisory Committee

Geyser – Geothermal springs that emerge explosively and usually erratically. A geyser is a hot spring characterized by intermittent discharges of water that are ejected turbulently by a vapor phase.

GIS – Geographic Information System

Graminoid – True grasses (Poaceae) or grass-like plants, such as sedges (Cyperaceae) or rushes (Juncaceae).

Groundwater – All water below the ground surface, including water in the saturated and unsaturated zones.

Groundwater recharge – Augmentation of groundwater by natural or artificial means.

Groundwater-dependent ecosystems (GDEs) – Communities of plants, animals, and other organisms whose extent and life processes are dependent on access to or discharge of ground-water.

GSA – Groundwater Sustainability Agency. The local agency or agencies with water supply, water management or land use responsibilities in a basin that chooses to implement SGMA.

GSI – Green stormwater infrastructure

GSP – Groundwater Sustainability Plan. Defined by legislation.

GSWG – Groundwater Sustainability Work Group

GWA – Groundwater Authority

Gushet – Discrete sources of flow pouring from cliff faces. Gushets typically emerge from perched, unconfined aquifers, often with dissolution enhancement along fractures, exhibit thin sheets of water flowing over rock faces.

Hanging garden or wet wall  – Springs that emerge along geologic contacts or fractures and seep, drip, or pour onto underlying walls. Hanging gardens in the Southwestern United States typically emerge from perched, unconfined aquifers in Aeolian sandstone units.

Helocrene  – Low-gradient springs and/or wetlands; often indistinct or multiple sources of groundwater. Also called wet meadows or cienegas.

Hemic – Organic soil material at an intermediate degree of decomposition that contains 1/6 to 3/4 recognizable fibers (after rubbing between fingers) of undecomposed plant remains. Bulk density is usually very low and water-holding capacity very high. Also referred to as mucky peat.

Herbaceous – A plant that has leaves and stems that die down to the ground at the end of the growing season. They have no persistent woody stems.

High-oxygen and low-oxygen – Conditions that reflect how much oxygen is dissolved into groundwater. High-oxygen conditions are sometimes called “aerated”, while low-oxygen (~1% or lower dissolved oxygen) is called “reduced”.

Hillslope – Springs and/or wetlands on a hillslope (generally 20- to 60-degree slope), often with indistinct or multiple sources of groundwater.

Histic epipedon – An 8- to 16-inch layer at or near the surface of a mineral hydric soil that is saturated with water for 30 consecutive days or more in most years and contains a minimum of 20 percent organic matter when no clay is present or a minimum of 30 percent organic matter when clay content is 60 percent or greater. Soils with histic epipedons are inundated or saturated for sufficient periods to greatly retard aerobic decomposition of the organic surface and are considered to be hydric soils.

Histosol – Histosols (organic soils) develop under conditions of nearly continuous saturation and/or inundation. All histosols are hydric soils except folists, which are freely drained soils occurring on dry slopes where excess litter accumulates over bedrock. Organic hydric soils are commonly known as peats and mucks.

Hydrogeologic conceptual model – A description of the geologic and hydrologic framework governing the occurrence of groundwater and its flow through and across the boundaries of a basin and the general groundwater conditions in a basin or subbasin.

Hydrologic model –  A conceptual representation of part of the water cycle that uses three-dimensional information that is geographically specific

Hypocrene  – A buried spring where flow does not reach the surface. This term is common to the Southwestern United States. Elsewhere, these features may be equivalent to shallow groundwater areas, including fens.

Hyporheic zone – Area of a stream bed and bank where surface and ground waters mix. A similar area, the hypolentic zone, exists in lakes and ponds.

Inflow – Water that moves into a basin

Insurgence – The point of inflow for surface water into subsurface conduits in karst areas.

Jurisdictional wetlands – Those areas that are inundated or saturated by surface or ground water (hydrology) at a frequency and duration sufficient to support and that, under normal circumstances, do support a prevalence of vegetation (hydrophytes) typically adapted for life in saturated soil conditions (hydric soils). Wetlands generally include swamps, marshes, bogs, and similar areas.

Karst – A terrain or type of topography generally underlain by soluble rocks, such as limestone, gypsum, and dolomite, in which the topography is chiefly formed by dissolving the rock; karst is characterized by sinkholes, depressions, caves, and underground drainage. Psuedokarst is an area of depressions, caves, and internal drainage that result from volcanic activity.

Land subsidence –  Lowering or sinking of the land surface due to a number of factors, including the overdraft of a groundwater basin over the long term or a decline in groundwater levels year by year

Limnocrene  – Groundwater emerges in one or more pools.

Marsh – A frequently or continually inundated wetland characterized by emergent herbaceous vegetation adapted to saturated soil conditions.

Measurable objectives –  Specific measures used to determine whether the GSA of a basin is successful in achieving its sustain- ability goal and avoiding undesirable results

Mineralized mounds – Springs that emerge from (usually carbonate) precipitate mounds.

Minerogenous – See minerotrophic peatlands.

Minerotrophic peatlands – Peatlands that receive water that has passed through mineral soil. Also called minerogenous hydrological systems.

Minimum thresholds – Numeric values used to define undesirable results. The minimum threshold is the lowest level of the metric that should not be crossed, regardless of fluctuations in dry and wet years

MS4 – Municipal separate storm sewer system

Muck – Organic soil material in which a significant part of the original plant parts are recognizable and a significant part is not. Also referred to as hemic material.

Mucky peat – Organic soil material in which the original plant parts are not recognizable. Contains more mineral matter and is usually darker in color than peat. Also referred to as sapric material.

Naturally occurring – Present within the rocks that make up the aquifer; not due to human activity.

NPDES – National Pollutant Discharge Elimination System

NSQD – National Stormwater Quality Database

Ombrogenous – Peatland with inflow from precipitation only. Also called ombrotrophic.

Organic soil – Organic soils (histosols) develop under conditions of nearly continuous saturation and/or inundation. All organic soils are hydric soils except folists, which are freely drained soils occurring on dry slopes where excess litter accumulates over bedrock. Organic hydric soils are commonly known as peats and mucks.

Outflow – Water that leaves a basin

Overdraft – A situation that occurs when more water is pumped from a groundwater basin than is replaced from all sources, not measured annually but rather over a period of years

Peat – Organic soil material that is undecomposed or weakly decomposed. The plant remains are distinct and identifiable.

Peatland – A generic term for any wetland that accumulates partially decayed plant matter (peat).

pH – A measure of the acidity of the water. Groundwater pH is generally between 6.5 and 8.5. Water with lower pH is more acidic, while higher pH indicates alkaline (basic) conditions.

Phreatophyte – Plant whose roots generally extend downward to the water table and customarily feed on the capillary fringe. Phreatophytes are common in riparian habitats. Term literally means “well” plant or water-loving plant.

Piezometer – Small-diameter well open at a point or over a short length in the aquifer to allow measurement of hydraulic head at that location.

Planning horizon – The length of time into the future that is accounted for in a particular plan

Plume – A body of one fluid moving through another, often used to refer to the presence of contaminated water in—or its migration into—an aquifer

Pocosin – Peat-accumulating, nonriparian freshwater wetland, generally dominated by evergreen shrubs and trees and found on the Southeastern Coastal Plain of the United States. The term comes from the Algonquin word for “swamp on a hill.”

Principal aquifers – Aquifers or aquifer systems that store, transmit, and yield significant or economic quantities of groundwater to wells, springs, or surface water systems.

Proprietary software – Software that is owned by an individual or company and usually has major restrictions on its use by other people

Public domain, open-source software – Software that is in the public domain and usually is freely available for anyone’s use

Qualified map – A geologic map of a scale no smaller than 1:250,000 that is published by the U. S. Geological Survey or the California Geological Survey, or is a map published as part of a geologic investigation conducted by a state or federal agency, or is a geologic map prepared and signed by a Professional Geologist that is acceptable to the Department.

Recharge – The practice of increasing the amount of water flowing into a groundwater basin

Recharge area – The area that supplies water to an aquifer in a groundwater basin.

Redoximorphic features – Features formed by the reduction, translocation, and/or oxidation of iron and manganese oxides; used to identify hydric soils.

Rheocrene – Flowing springs that emerge directly into one or more stream channels.

Riparian – Pertaining to the bank of a body of flowing water; the land adjacent to a river or stream that is, at least periodically, influenced by flooding. Riparian sometimes is used to indicate the banks of lakes and ponds subject to period inundation by wave action or flooding.

SA – Situation Assessment

Safe yield –  The maximum quantity of water that can be withdrawn from a groundwater basin at a given time without overdraft

Saltwater/seawater intrusion –  The movement of saltwater into freshwater aquifers, which can lead to contamination of drinking water sources and other consequences

Sapric – Organic soil material that contains less than one out of six recognizable fibers (after rubbing between fingers) of undecomposed plant remains. Bulk density is usually very low, and water-holding capacity very high. Also referred to as muck.

Scenario-based planning – An approach that examines management options under a range of possible future conditions in order to develop solutions that would work well across the range

Seep – A discharge of water that oozes out of the soil or rock over a certain area without distinct trickles or rivulets.

SGMA – Sustainable Groundwater Management Act

Specific conductance – A measure of an aqueous solution’s ability to carry an electrical current (also called electrical conductance or conductivity).

Spring – A place where groundwater flows naturally from the earth into a body of surface water or onto the land surface.

Spring brook – Runout channel from a spring, which may become a stream at some distance from the spring source.

Spring source – The location where the spring emerges from the ground onto the land surface. Also referred to as the spring orifice.

String and flark microtopography – Slow groundwater movement through broad, gently sloped peatlands forms a series of linear hummock ridges called strings, separated by parallel hollows known as flarks. Strings and flarks are arranged perpendicularly to the flow of water through the peatland and can form a regular pattern of parallel ridges and hollows or an intricate, braided or branching (anastomosing) pattern.

Surface water – Water that is on Earth’s surface in rivers, lakes, reservoirs, or oceans

Sustainability goal – The objective of operating a basin within its sustainable yield

Sustainable yield – The maximum quantity of water that can be withdrawn annually from a groundwater supply without causing an undesirable result

Swamp – Wetland dominated by trees or shrubs.

Technical study – A geologic or hydrologic report prepared and published by a state or federal agency, or a study published in a peer-reviewed scientific journal, or a report prepared and signed by a Professional Geologist or by a Professional Engineer.

TMDL – Total Maximum Daily Load.

Uncertainty – A lack of understanding of the basin setting that significantly affects an Agency’s ability to develop sustainable management criteria and appropriate projects and management actions in a Plan, or to evaluate the efficacy of Plan implementation, and therefore may limit the ability to assess whether a basin is being sustainably managed.

Undesirable result – One of six groundwater conditions that must be avoided in order to comply with the Sustainable Groundwater Management Act: significant and unreasonable reduction of groundwater storage, significant and of groundwater levels, significant and unreasonable seawater intrusion, significant and unreasonable degraded water quality, significant and unreasonable land subsidence, and significant and unreasonable depletions of interconnected surface water unreasonable lowering.

Upland – Land that is not influenced by a consistent source of surface water or groundwater and, therefore, does not support wetland vegetation or hydric soil development as would a wetland or riparian area.

Vulnerability analysis – The process of identifying, quantifying, and prioritizing (or ranking) the potential threats to people, infrastructure, and other assets within a system.

Water budget – An accounting of the total groundwater and surface water entering and leaving a basin including the changes in the amount of water stored.

Water source type – The source from which water is derived to meet the applied beneficial uses, including groundwater, recycled water, reused water, and surface water sources identified as Central Valley Project, the State Water Project, the Colorado River Project, local supplies, and local imported supplies.

Water use sector – Categories of water demand based on the general land uses to which the water is applied, including urban, industrial, agricultural, managed wetlands, managed recharge, and native vegetation.

Wet meadow – Area that is saturated with water for much of the year but does not have standing water, except for brief periods, during the growing season.

Wetland – lands that are transitional between terrestrial and aquatic systems where the water table is usually at or near the surface or the land is covered by shallow water.