Extended and extreme periods of drought driven by climate change have placed a high demand on groundwater resources in the western United States. Despite a water windfall this year, consecutive years of drought have led to declining groundwater levels in the west.
Many stakeholders are looking to groundwater recharge as an effective strategy to replenish water supplies. Simply put, agricultural groundwater recharge is the practice of taking water when it is available, putting it on farm, and allowing it to percolate down to the aquifer. In fact, the recently released ‘California Water Plan Update’ 2023 draft highlights the need and intention to fast-track groundwater recharge projects and maximize stormwater capture by investing in and incentivizing groundwater recharge projects.
Summer 2023 was the driest on record across parts of Arizona, New Mexico and Oregon, yet the wettest on record across much of Southern California and parts of the Rocky Mountains in Colorado and Wyoming. The influx of rainfall in the southern U.S. was mostly due to Tropical Storm Hillary, the first intact tropical cyclone to make landfall in California in decades.
As we enter into fall, climatologists are predicting with high certainty El Niño/Southern Oscillation (ENSO) conditions to maintain, through January to March 2024. The Climate Predictions Center (CPC) anticipates ENSO will encourage more rainfall during this late winter period, especially in Southern and Central California, along the coast of California, as well as in Arizona and New Mexico, although a wetter-than-average winter is not always guaranteed. What we can expect to see are more intense atmospheric rivers due to maintained warmer than average near shore ocean temperatures. Which begs the question, where will all this water go?
Recent Public Policy Institute of California (PPIC) reports found that, among the available options to expand water supply, the least expensive options include capturing more local run off via groundwater recharge and reoperation of reservoirs to expand the joint storage potential of surface and groundwater storage. Additionally, according to California Department of Water Resources (DWR), California’s 515 groundwater basins can hold between 850 million and 1.3billion acre-feet of water, 8-12 times more than the combined 50 million acre-feet of storage for California’s major reservoirs.
Groundwater recharge, in conjunction with improved trading rules and water infrastructure, could lower the cost of adapting to reduced water availability via the Sustainable Groundwater Management Act (SGMA), climate change, and environmental flows. However, major roadblocks slow the adoption of this practice, especially for those managing agricultural lands. There is consensus among water districts, policy makers, environmentalists, and groundwater sustainability agencies (GSAs) that infrastructure, policy, and research are in great need of development.
Groundwater recharge project participants will require advanced preparation, infrastructure, and access to funding to facilitate project development and management. Growers will need assurances in instances of incidental take, advanced permits, and options to mitigate risk. Streamlining the process will necessitate clarity on under what conditions water can become available for groundwater recharge and additional research quantifying flow levels to accommodate critical wildlife habitats and capacity for crops to tolerate increased soil moisture.
Groundwater recharge presents land managers with the opportunity to capture excess waterflow in areas where conditions permit, as we saw this past season. Growers must be considered in conversations about how they can be included in groundwater recharge opportunities and what is an equitable next step for those outside of the ideal conditions. With expected increased rainfall in late winter 2024, we must consider what should be the future of our water security.