SGMA Basin Boundary and Priority

The Sustainable Groundwater Management Act (SGMA) requires medium- and high-priority groundwater sub-basins to have a Groundwater Sustainability Agency (GSA) which executes a Groundwater Sustainability Plan (GSP) to bring their groundwater sub-basin into “sustainable yield.” Sustainable yield refers keeping the basin healthy by balancing groundwater withdrawals with a healthy level of groundwater in the sub-basin and larger groundwater basin. However, the sub-basin boundaries were only recently settled by the Department of Water Resources (DWR), and the official priorities of each sub-basin will not be approved until May or June of 2019. This article will assist you in understanding the timeline and what this means for planning your water strategy in the near future.

Basin Boundaries

Basin boundaries refer to the groundwater basin’s exterior borders. Groundwater basins are broken into smaller sub-basin numbers. For example, in Figure 1, you can see that Redding is in a basin that is broken in to several sub-basins. The number to the left of the decimal place: 5-006 identifies the groundwater basin; the number to the right of the decimal point identifies the sub-basin.

Basin Priority

Basin priorities categorize each sub-basin as very low, low, medium, or high priority. Priorities were initially based on an older program called California Statewide Groundwater Elevation Monitoring (CASGEM). The final SGMA prioritization process is set for completion in “Spring 2019” as shown in Figure 2.

CASGEM

CASGEM became law in 2009 as part of a comprehensive water package to improve water data collection for California’s groundwater. CASGEM resulted in identification of 515 groundwater basins and the opportunity for local agencies to act was groundwater monitoring entities. CASGEM laid the foundations for SGMA’s mandate for GSA’s within each specific basin and is part of DWR’s basin prioritization process.

SGMA Priority Points

SGMA required DWR to assess a groundwater basin’s priority to determine which basins needed a GSA to manage the basin back to a sustainable yield. DWR developed a point system that factors multiple groundwater related metrics resulting in a final priority score. Factors included:

  1. Population
  2. Rate of population growth
  3. Number of public supply wells
  4. Total number of wells
  5. Total irrigated acreage
  6. Degree to which persons overlying the basin rely on groundwater as their primary source of water
  7. Documented impacts on the groundwater within the basin, including overdraft, subsidence, saline intrusion, and other water quality degradation
  8. Any other information determined to be relevant by the department, including adverse impacts on local habitat and local streamflows, based on groundwater monitoring

Scores above 14 are required to have a GSA and eventually a GSP. While points were produced and coincide with the CASGEM basin boundaries, the priorities were last updated for 2016 to match the change in basin boundaries that occurred since 2014. The final basin prioritization points will undergo an opportunity for public comment this spring and should be finalized in “late spring.”

How does this impact water research?

The “Legacy Basin Priority” map layer in the AQUAOSO map displays priorities from 2016 that are currently used for SGMA planning purposes. We received multiple inquiries about the 2018 finalization and found it necessary to distinguish the 2016 priorities and the upcoming final priorities. We obtained additional information that we integrated into the our new “SGMA Basin” map layer, including the points awarded to each sub-basin by DWR to determine priority. We kept the “Legacy Basin Priority” layer because it is still a useful planning tool until DWR finalizes the 2018 priorities.

Next Steps

Take a look at the two layers. You can overlay them and see the pending status for a basin and what its 2016 priority indicated. There is a high likelihood that the priorities will stay the same, but a few may change from medium to high, or high to medium priorities. We will keep the map updated as information becomes available to provide you with a reliable SGMA planning tool.

As always, we are here to help and answer your questions. Contact us today!