Investigating the Impact of River Regulation on Groundwater Supplies in the Western US
Reclamation has a long history of ensuring water supplies are available in the western US for irrigation and power generation. Throughout its history, seepage from Reclamation's canals, reservoirs, and irrigated lands have been actively recharging local aquifers. In some cases, this seepage has resulted in benefits being accrued by non-Reclamation water users through increased recharge to groundwater, wetlands, and drain return systems. In addition, in some cases this seepage has resulted in losses due to localized flooding. With the growing concern of water availability in many of the western states, it is important to understand the extent of Reclamation's impact on both surface and groundwater supplies by answering the question, what is the impact that river regulation has on groundwater supplies in the western U.S.? By fully understanding the relationship between Reclamation's projects and local aquifer systems, more comprehensive solutions to water availability problems can be developed, and a more thorough economic analysis of Reclamation projects can be completed.
Need and Benefit
Reclamation has improved western US water supplies by storing water in surface reservoirs and releasing it for irrigation and power needs. It can be argued that the western US can sustain population is due to the benefits that Reclamation's projects have had on water supplies. The seepage from Reclamation's delivery and storage facilities has had both positive and negative impacts on groundwater supplies. Elevated groundwater levels can reduce economic costs to groundwater pumpers and provide drain returns to surface irrigators within Reclamation projects. In addition, elevated groundwater levels can create wetlands, but they can also flood developed areas, negatively impacting home owners. Return flows to drains, creeks, and streams caused by elevated groundwater levels can provide cool water to spawning sections of streams.
Changes made to Reclamation's operations and infrastructure can have impacts on groundwater supplies. More and more, Reclamation decision makers are being asked to include total system effects into the decision making process. By understanding the relationship between Reclamation's projects and local aquifers, decision makers can make more informed decisions related to operations, water supplies, and infrastructure.
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Independent Peer Review
The following documents were reviewed by qualified Bureau of Reclamation employees. The findings were determined to be achieved using valid means.
Investigating the Impact of River Regulation on Groundwater Supplies in the Western U.S. (interim, PDF,
By Dr. John Tracy
Report completed on May 21, 2015