sions GSA-owned recharge ponds and ASR facilities coupled with financial incentives, studies, and environmental approval for landowners to implement similar projects. The GSA and its water users dedicated over 470,000 acre-feet (AF) of water to recharge projects during the 2023 historically wet and 2024 above normal water years, which directly increased groundwater levels, groundwater in storage, and contributed to elastic rebound of the land surface in large areas of the GSA. Demand reduction strategies have centered around groundwater pumping management and changes to land use policy. The GSA’s Groundwater Allocation Program, which began implementation in 2020, includes a 10-year phased implementation schedule, mandatory well registration, and real-time metering of all non-de minimis groundwater extractions to align groundwater extraction with the Subbasin’s sustainable yield. The Targeted Pumping Reduction Program enables the GSA to incentivize landowners to reduce groundwater pumping near hydraulically impaired portions of the SLC depending on water level and subsidence conditions. Land repurposing is also being used to reduce groundwater demand in areas with subsidence risk. Through direct land acquisition, 5,349 irrigable acres near the SLC have been retired, with additional large-scale agricultural land repurposing pursued through the Valley Clean Infrastructure Plan and the Multi-Benefit Land Repurposing Program. Subsidence management in the Westside Subbasin remains an active, ongoing effort. Westlands Water District continues to invest substantial resources for sustainable groundwater management and adapt its strategy in the most at-risk areas, illustrating how targeted implementation can support groundwater sustainability while protecting critical infrastructure. Kaweah Subbasin The Kaweah Subbasin (Figure 1) illustrates how SGMA implementation can become especially complex in areas where subsidence, overdraft, and competing groundwater demands must all be managed at once. The Subbasin is managed through close coordination by three GSAs—East
Kaweah, Greater Kaweah, and Mid-Kaweah. Although the Subbasin has relatively limited exposure to the major canalconveyance risks seen elsewhere in the State, preventing flooding caused by differential subsidence remains a concern, particularly after the historically wet 2023 water year. The Kaweah Subbasin’s subsidence management approach relies on targeted demand management, MAR, and regional coordination to reduce overdraft and limit subsidence. East Kaweah and Mid-Kaweah GSAs have implemented strict allocations that effectively eliminate overdraft, aligning allowable pumping with native and sustainable yield since 2022, while Greater Kaweah GSA has scheduled ramp-down reductions of groundwater overdraft. The GSAs are considering aquifer-specific monitoring, management actions, and policies to better manage lower-aquifer pumping where it presents the greatest subsidence risk. While conceptually appealing, a by-aquifer allocation framework is difficult to implement in practice. Key constraints include significant data gaps in active well location and depths, construction, and perforation information, the widespread use of composite wells across multiple aquifers, and the coarse spatial resolution of available datasets used to delineate the Corcoran Clay and other compressible clay units. Adding further complexity, municipal reliance on lower-aquifer pumping can create localized subsidence that is not readily addressed through traditional agricultural allocation frameworks, and restrictions on deeper pumping may inadvertently shift demand to upper aquifers, increasing risks to shallow domestic wells. To manage these competing challenges, the GSAs are prioritizing improved well data collection through registration programs and a comprehensive well inventory exercise, as well as instituting policies such as Mid-Kaweah’s requirement linking registration to access to future groundwater allocations above the native yield. The GSAs are using both MAR and demand management to increase groundwater supplies and reduce overdraft in areas affected by subsidence. To date, most recharge projects have relied on surface recharge basins. However, these projects often provide limited direct benefit to the lower aquifer beneath the Corcoran Clay, where subsidence is generally understood article continues on next page
Hydro Visions
2026 Summer Issue
13