The Sustainable Groundwater Management Act (SGMA) requires Groundwater Sustainability Agencies (GSAs) to submit Groundwater Sustainability Plans (GSPs) that include mandatory sections discussing how the GSA intends to bring the underlying groundwater basin into sustainable yield. For the agricultural sector, some of the biggest questions surrounding groundwater regulation are answered by the GSP including:

  • What is the sustainable yield for the basin?
  • Will there be restrictions to groundwater pumping for agricultural purposes? If so, what are those restrictions?
  • Are there land use impacts due to overdraft?
  • Are there groundwater quality concerns in the basin?
  • Are there new fees?

While each GSP is designed and implemented at the local GSA level, there are requirements from the State regarding mandatory sections to include in the GSP. This guide is designed to assist you in understanding what might be included in each relevant section and what that means for agricultural lenders, investors, appraisers, and other professionals in the ag community. You will be prepared to review GSPs relevant to your portfolio or your client’s properties.

The Introduction and Plan Area

The beginning of the GSP should include a discussion of the legal authority and cost associated with implementing a GSP. The cost section may be important to review because it could signal one-time or recurring fees related to the creation and implementation of the GSP. Some GSAs will also discuss grant funding received for technical assistance from the Department of Water Resources (DWR).

Another important part of the introduction that the GSP should include is how the GSA is organized. GSAs may be part of a group of GSAs or contain sub-areas within the GSA boundaries called Management Areas that may have different fees, restrictions, or benefits that are discussed later in the GSP.

Plan Area

The Plan Area and Basin Setting are designed as an overview of the important geographic and hydrological elements of a basin. The Plan Area is focused on the political boundaries and the Basin Setting on the hydrologic data. The Plan Area is important for agricultural community members primarily because it discusses further the multiple political jurisdictions that may exist within a GSA, the area the GSP covers, and current land use designations, such as land designated for agriculture. Below is an example of a GSA that has jurisdiction in multiple counties.


Understanding the area covered includes whether or not there is an area covered under a groundwater adjudication. A groundwater adjudication is a court supervised settlement for all stakeholders within the adjudicated area, a specific basin, which sets out the rules the parties to the settlement agree to. If a property is within an adjudicated basin, the property owner should refer to the settlement documents and contact the appointed watermaster regarding groundwater rules, which may be different than those contained in the GSP. Below is a map showing adjudications in the southern part of California.

GSP Sections - Plan Area and Basin Setting

Other Jurisdictions

GSAs do not exist in a political vacuum. There are still multiple other government agencies with various mandates and jurisdictional boundaries within the GSP Plan Area. The below image depicts a GSA that has boundaries in two different counties.

GSP Sections - Plan Area and Basin Setting

Federal, State, County, municipal and special district boundaries are discussed as part of the Plan Area. Putting the GSP in context of other governmental regulations assists stakeholders in understanding their responsibilities. For example, water quality regulations come from federal, state, and regional governmental entities. However, a GSP must also address impacts to water quality within the framework of existing law. AQUAOSO provides political boundary information on the GIS map allowing you to see the various jurisdictions impacting a property.

Water Plans and Monitoring

Another important Plan Area topic is a description of water monitoring. A GSP should list regional water plans, Agricultural Water Management Plans, Urban Water Management Plans, and other water plans that are part of the Plan Area. Additionally, monitoring programs implemented by federal, state, and local entities belong in this section. Understanding the monitoring programs already in existence provides added context for potential additional groundwater monitoring requirements as part of the GSP.

Conjunctive Use Programs

If a water district or other governmental agency participates or administers a conjunctive use program, that should be included in the Plan Area portion of the GSP. Conjunctive use policies encourage the use of surface water when available to reduce groundwater pumping and increase groundwater recharge. This is essential information when analyzing how to use surface water to support basin health through groundwater recharge programs. Conjunctive use programs may also identify use of recycled wastewater and stormwater.

Land Use

Land use in the Plan Area looks at existing general plans and other land use plans that list crops, agricultural land acreages, urban acreages, and other land use statistics. Understanding the typical types of crops and how much of a basin’s overlying land is dedicated to agricultural use can assist in estimating impacts to the community and key stakeholders. For example, if a basin is made up of primarily agricultural land and that land is largely permanent crops, the impacts of reduced groundwater pumping may be more severe than in a more urban, less permanent cropped basin. Additionally, this section would cover permitting processes, such as well permits, that agencies other than the GSA have authority over.

Basin Setting

Basin setting refers to hydrogeological models, current and historical groundwater conditions, water budget information, and whether there are designated management areas within the basin boundaries. The following items highlight key points to pull from the Basin Setting section.


Hydraulic conductivity of soils is used for pinpointing soils with higher permeability and infiltration rates, meaning the path from surface water to groundwater is easier to travel and more closely interconnected. This could also indicate areas suitable for groundwater recharge activities. Many of the GSPs will likely use the Soil Agricultural Groundwater Banking Index (SAGBI) to assist in determining crucial areas for recharge. AQUAOSO includes SAGBI as a GIS layer as part of our research tool to better assist customers in locating potential recharge opportunities.

GSP Sections - Plan Area and Basin Setting

AQUAOSO Map showing SAGBI Layer for California

Clay Layer

Indication of weather large deposits of clay, like the Corcoran Clay layer, may present issues with groundwater quality, perched aquifers, and groundwater supply depending on the depth and thickness of the clay layer. Many GSAs will treat the upper and lower aquifers, with the clay layer in-between, as separate for sustainable yield goals. AQUAOSO provides two Corcoran Clay GIS layers, depth and thickness, to better assist customers with identifying potential issues resulting from the clay layer.

GSP Sections - Plan Area and Basin Setting

AQUAOSO Map Showing Corcoran Clay Depth and Thickness

Surface Water Sources: Local and Imported Supplies

Local and imported water supplies. Important for understanding additional sources of water potentially available to a parcel within the basin. AQUAOSO also provides information on surface water sources for water districts allowing you to read and view on our GIS map for comparison purposes.

Current and Historical Groundwater Conditions

GSPs include historical groundwater data based on past studies and reports. GSPs will update every five years and evolve as groundwater monitoring continues to increase in frequency. Below are some key points to pull out of the Groundwater Conditions section of a GSP.

Groundwater Elevation

Groundwater elevation provides evidence of groundwater extraction, difficulty of extraction, and an indicator of potential overdraft issues. Also, if there are different parts of the aquifer, such as lower and upper, that have different characteristics, this section will account for those elevations separately. AQUAOSO provides publicly available groundwater depth data in an easy-to-view GIS map layer allowing a glimpse into recent groundwater depth readings for your area of interest.

GSP Sections - Plan Area and Basin Setting - Groundwater Elevation

AQUAOSO Map Showing Groundwater Depth

Groundwater Hydrographs

Hydrographs can illustrate trends in groundwater depth over long periods of time. The GSP will provide those graphs and explain the trends in more detail. A trend in declining groundwater levels indicates a net loss of groundwater for the basin which may lead to subsidence, expensive groundwater extraction, and a likelihood of stricter restrictions on future pumping.

Groundwater Storage

The groundwater storage section of the GSP provides insight into the total amount of groundwater stored in a subbasin and the specific yield estimates. Specific yield assists in understanding the actual porosity, or how much space is available for the water to infiltrate, of a subbasin. Additionally, the change in groundwater storage is mentioned in a GSP. The change in storage indicates whether or not there is a consistent decline in groundwater in the subbasin. Knowing there is a consistent decline indicates a higher likelihood of groundwater pumping restrictions to ensure the subbasin reaches sustainable yield. Owning a property in an area with consistent decline in groundwater storage may present problems in relying on groundwater as a source of water for crops.

Water Quality

The amount of groundwater is important, but equally as important is the quality of the available groundwater. Contaminants such as nitrate and arsenic, as well as water salinity, can impact crop yields and soil health. The GSP will look at whether the specific contaminants analyzed, such as nitrate, exceeds the Maximum Contaminant Load (MCL) over a defined period of time. Such analysis is useful in understanding the water quality trends for the basin and planning appropriate measures to protect land and crops from high levels of contamination.

Land Subsidence

GSPs will also comment on land subsidence within a basin. GSPs will likely rely on various past subsidence studies showing historical trends in subsidence. Subsidence impacts groundwater quality, drainage, infrastructure, and other important agricultural assets. State and Federal government programs are analyzing subsidence with greater detail and more recent data should be forthcoming over the next few years.

Water Budget Information

The GSP water budget section will explain the methodology used to determine the water budget and then present the results. Water budget components are largely dictated by regulation. [Insert Image of Accounting Center and GSP Regs]. Interesting information coming from the water budget analysis includes groundwater extraction by water use sectors, inflows and outflows based on local surface water sources and canals, and impacts on changes to water storage.  Finally, the water budget section of the GSP will describe whether overdraft conditions are present.

Subbasin Sustainable Yield

GSP Regulations require the water budget to quantify the sustainable yield for the subbasin. Sustainable yield is defined as “the maximum quantity of water, calculated over a base period representative of long-term conditions in the subbasin and including any temporary surplus, that can be withdrawn annually from a groundwater supply without causing an undesirable result” (CWC Section 10721(w)). The sustainable yield will be a basis for groundwater pumping restrictions, fees, and other GSA rules governing a subbasin. The GSP will also cover available water and programs for groundwater recharge which can assist with mitigating impacts resulting from groundwater pumping.

Management Areas

Within a GSA, there may be certain areas that require specific management practices due to political or environmental reasons. These management areas typically report back to the GSA and abide by the GSP. Potential differences in fees and severity of pumping restrictions may depend on which management area a property is located within.

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