1-6 Enhancing Aquifer Storage through Managed Aquifer Recharge and Conjunctive Use in the Southwestern US

Session: Advances in Managed Aquifer Recharge

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Abstract:

In this study, we utilize Gravity Recovery and Climate Experiment (GRACE) satellite data, along with complementary analysis, to identify hotspots of groundwater depletion in the southwest US. We also evaluate the potential of conjunctive use of surface water and groundwater, as well as managed aquifer recharge (MAR), to improve water availability in response to floods and droughts. Data from the southwestern United States provide informative examples of managing climate extremes that can be deployed in many other regions to improve water resources management.

Results indicate a cumulative net groundwater depletion in the Lower Colorado River Basin of approximately 60 cubic kilometers (km³) since the 1940s, primarily in the areas near Phoenix, Pinal, and Tucson, Arizona. This depletion has resulted in the formation of significant subsurface groundwater storage space, creating opportunities for conjunctive use. Transfers of Colorado River water to central Arizona through the Central Arizona Project (CAP) have facilitated the conjunctive use of surface water and groundwater, resulting in a total increase of about 18 km³ of in-lieu recharge and approximately 6 km³ of MAR in Active Management Areas from 1989 - 2019. Projected declines in Colorado River water, however, may reduce the availability of future surface water supplies for managing droughts.

In the California Central Valley, water managers have adapted to climate extremes with surface water transfers from north to south allowing for the conjunctive use of surface water and groundwater supplies. During wet years, surface water can meet as much as 70% of supply, while during dry years groundwater can account for up to 60% of supply. Historically, MAR contributed a total of around 12 km³ from 1962 - 2019, and its implementation is expanding, including long-term MAR using spreading basins and more recently agricultural MAR or flood-MAR, especially in the southern Central Valley. Despite these water management efforts, the Central Valley has followed a similar trajectory to Arizona with an estimated cumulative loss of approximately 160 km³ of groundwater storage from predevelopment to 2019. The expansion of conjunctive use and MAR is expected to continue as part of the movement towards more sustainable groundwater management linked to the California Sustainable Groundwater Management Act.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-8275

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