About Your Groundwater Basin

The Department of Water Resources identifies 515 alluvial groundwater basins in California.  Alluvial basins are formed by sediment deposited over time by streams, rivers and wetlands.  Of these 515 basins the Department has identified 127 basins or sub-basins as high or medium priority based upon human reliance for irrigation, industrial or domestic uses.  Those 127 basins were singled out by the Sustainable Groundwater Management Act of 2014 (SGMA) as the focus of state required groundwater management.

Do you live in one of these high or medium priority basins? The Department maintains an interactive Groundwater Management Tool. To use it, simply check the boxes for the information you’re interested in – in this case, check the box next to “CASGEM Groundwater Basin Prioritization.” The map will then highlight the 515 groundwater basins, color-coded according to priority.

This map can also be used to identify whether your basin already has an existing groundwater management plan. This is not the plan required by SGMA, but a pre-existing plan.  Simply check the box next to “Groundwater Management Plans” and then click on that part of the map where your basin or the one you’re interested in are located.

High and medium priority basins

If you live in or are working in a high or medium priority basin, that basin has until June 1, 2017 to establish a “Groundwater Sustainability Agency (GSA).”  Many entities have already filed a notice with the Department to be named their local GSA.  The Department has yet another map where you can find that information if it has been submitted.  Simply enter the name of the community or county for which you’re interested in finding GSA information.

It’s important to note that a GSA does NOT have to cover an entire groundwater basin, and in some areas of the state, basins will be represented by multiple GSAs.  In other basins, the Department has not yet received a notice of formation, so no information is posted.
If a GSA is not formed, the county is considered the responsible body for overseeing groundwater.

Low and Very Low Priority Basins

The majority of groundwater basins in the state are NOT part of SGMA. There are many reasons for this.  The 2009 law (SBX7 6) that established the prioritization process (CASGEM or California Statewide Groundwater Elevation Monitoring) included criteria for prioritizing the basins according to how heavily they are relied upon for municipal or irrigation purposes.  SGMA added a layer to that review to require the department to include “adverse impacts on local habitat and local streamflows.”  Now that prioritization doesn’t just depend upon human reliance on groundwater, some of the low and very low priority basins could be elevated in priority.  The Department is required to consider this in their update of their Groundwater Plan, Bulletin 118, which is due to be updated no later than January 1, 2017, and every three years thereafter.

Not a Groundwater Basin?

Are you missing from this list altogether?  That’s not unusual.  Because the Department only counts “alluvial” aquifers, it misses other sources of underground water.  This is a particular problem for residents in mountainous areas of the state that rely upon volcanic or other fractured rock formations for their water supply.  If you’re interested in having your water source counted as a groundwater aquifer, you should consider contacting the Department during their triennial update of their groundwater plan, known as “Bulletin 118 update.” The next update will be prepared in the second half of 2016, for adoption on or before January 1, 2017. T o find out more about this process, visit the Bulletin 118 webpage.