Groundwater is essential to life in the West, but many western aquifers are declining faster than they can be recharged naturally. Artificial groundwater recharge is one vital tool that can help address this challenge.
Artificial groundwater recharge
Artificial recharge directs excess surface water or recycled wastewater into aquifers through injection wells or by spreading water on the surface to increase soil infiltration and percolation to the aquifer. The recharged water can then be withdrawn during droughts or periods of high demand. Storing water underground has several advantages compared to reservoirs: the water does not evaporate and it can be more easily protected from contamination. On the other hand, the costs of recharge technology and methods may not be economically feasible in some situations, particularly in areas where raw water costs are low. Consequently, the feasibility of a recharge project will depend on climate, water demands, soil conditions, economics, and other factors that vary across the West.
Artificial recharge examples
Artificial recharge is most commonly used to store or bank excess water for future use. The Arizona Water Banking Authority, for example, oversees a program that stores unused portions of the state’s Colorado River apportionment underground for future use in times of shortage. Arizona Water Banking Authority, What Is Recharge? http://www.azwaterbank.gov. In Utah, the Jordan Valley Water Conservancy District takes a slightly different approach, treating and injecting surface water supplies in the winter and spring when water demands are low for use during the summer when demands are high. Utah Division of Water Resources, Conjunctive Management of Surface and Groundwater, 62 (July 2005), https://water.utah.gov/OtherReports/CMReport/CMReport1bCC.pdf.
An increasing number of projects are leaving water in the aquifer to relieve overdrafting or address other issues. One can be found in Los Angeles, where reclaimed water is injected into the ground to create a freshwater mound. The mound then acts as a barrier between the fresh water supplies in the aquifer and intruding sea water that could make the aquifer unsuitable for most users if left unchecked. U.S. Geological Survey, California Water Science Center, Aquifer Storage and Recovery (Jan. 5, 2012), https://ca.water.usgs.gov/misc/asr.
The law and artificial recharge
State laws and policies govern artificial recharge. Although these laws vary, there are some common themes. First, most states require a permit, usually issued by a state agency or a regional entity. Second, permitting authorities generally consider impacts to other water rights and whether a recharge project will degrade groundwater quality. Third, some states require rechargers to show that they have control or dominion over the recharged water.
There are differences as well. Some states have comprehensive statutes specific to artificial recharge, while others address recharge through their general groundwater permitting regimes. In addition, most western states regulate groundwater under the prior appropriation doctrine, but some states assign different rights to groundwater and surface water. Moreover, while the public owns groundwater in most states, landowners in Oklahoma and Texas own the groundwater beneath their land. These considerations can impact who has rights to pump groundwater, including recharged water.
Artificial recharge in the High Plains aquifer system
Aquifers do not respect state boundaries, and groundwater pumping in one state can affect groundwater and surface supplies in another. This concern is particularly pronounced in the High Plains aquifer system, which includes the famed Ogallala aquifer and is a critical water source for parts of Colorado, Kansas, Nebraska, New Mexico, Oklahoma, South Dakota, Texas, and Wyoming. Because the Ogallala aquifer has little natural recharge, water levels have steadily declined since irrigation began in the 1940s, with some parts of Kansas, New Mexico, Oklahoma, and Texas seeing declines of 100 feet, raising questions about the aquifer’s future. U.S. Geological Survey, High Plains Regional Ground-Water Study (Aug. 2000), https://pubs.usgs.gov/fs/2000/0091/report.pdf.
Artificial recharge is one of the tools stakeholders in the region are considering to address declining aquifer levels. For example, the city of Wichita is recharging water from the Little Arkansas River into the Equus Beds aquifer at the eastern edge of the High Plains aquifer system, recharging about 8,600 acre-feet as of July 2016, or about 15 percent of the total Wichita draws in a year. Richard Banks, Saving the Ogallala: How to Reverse Its Decline, MyFarmLife.com, https://myfarmlife.com/features/saving-the-ogallala-how-to-reverse-its-decline. In Texas, however, efforts to recharge the Ogallala with water from playa lakes have encountered water quality challenges due in part to legal constraints that prohibit water quality degradation in aquifers. O. Templar and L. Urban, Conjunctive Use of Water on the Texas High Plains, 106 J. of Contemporary Water Research and Education 102, 105 (1997), http://www.ucowr.org/files/Achieved_Journal_Issues/V106_A13Conjunctive%20Use%20of%20Water%20on%20the%20Texas%20High%20Plains.pdf.
Artificial recharge projects that involve interstate aquifers present unique considerations and opportunities. Because some compacts may be construed to govern groundwater pumping, a careful review of potentially applicable compacts may be necessary before investing in an artificial recharge project. Conversely, a lack of clarity over rights to an interstate aquifer may create a disincentive to artificial recharge. In such cases, states may need to renegotiate existing surface water compacts or enter into new compacts to clearly define how water imported into the system by artificial recharge will factor into the apportionment scheme, including how artificial recharge can be used for compliance purposes. Finally, the power of the U.S. Supreme Court to require a state to disgorge profits relating to water must be factored into the analysis and negotiation of compacts, as evidenced by the Court’s 2015 decision requiring Nebraska to disgorge $1.8 million to Kansas for pumping excess groundwater in violation of the Republican River Compact. Kansas v. Nebraska, 135 S. Ct. 1042 (2015).