Managed aquifer recharge through off‐season irrigation in agricultural regions

Abstract

Options for increasing reservoir storage in developed regions are limited and prohibitively expensive. Projected increases in demand call for new long‐term water storage to help sustain agriculture, municipalities, industry, and ecological services. Managed aquifer recharge (MAR) is becoming an integral component of water resources around the world. However, MAR faces challenges, including infrastructure costs, difficulty in enhancing recharge, water quality issues, and lack of available water supplies. Here we examine, through simulation modeling of a hypothetical agricultural subbasin in the western U.S., the potential of agricultural managed aquifer recharge (Ag‐MAR) via canal seepage and off‐season field irrigation. Weather phenomenon in many regions around the world exhibit decadal and other multiyear cycles of extreme precipitation. An ongoing challenge is to develop approaches to store greater amounts of water during these events. Simulations presented herein incorporate Ag‐MAR programs and demonstrate that there is potential to enhance regional recharge by 7–13%, increase crop consumptive use by 9–12%, and increase natural vegetation consumption by 20–30%, where larger relative increases occur for lower aquifer hydraulic conductivity and higher specific yield values. Annual increases in groundwater levels were 7 m, and sustained levels following several years of drought were greater than 2 m. Results demonstrate that Ag‐MAR has great potential to enhance long‐term sustainability of water resources in agricultural basins.

Increasing Groundwater Availability and Seasonal Base Flow Through Agricultural Managed Aquifer Recharge in an Irrigated Basin

“…Irrespective of the diversion amount for groundwater recharge considered in our simulations, about 34% of the recharged water remained in groundwater storage and about 66% returned to streams as base flow, indicating that Ag‐MAR has the potential to stabilize and locally recover aquifer levels while increasing streamflow during summer low flow periods and the amount of groundwater available for irrigation. Similar groundwater storage gains were found by Niswonger et al () (e.g., 26–29% depending on aquifer hydraulic conductivity) for large‐scale Ag‐MAR simulations in the Carson Valley, NV and Ghasemizade et al () for the eastern San Joaquin Valley, CA. Other large‐scale MAR modeling studies have seen lower gains in groundwater storage (e.g., Ronayne et al, ; Scherberg et al, ); however, most studies observed similar clear benefits of recharge for groundwater‐dependent ecosystems and instream flows.…”

“…Feedback mechanisms between recharge and crop water consumption, crop ET, and water consumption by natural vegetation from elevated soil moisture and groundwater levels could not be estimated in this study because the model does not support simulation of recharge through the root and unsaturated zone. Although such processes are important for enhancing ecosystem services of groundwater‐dependent ecosystems (Bolund & Hunhammar, ; Dillon et al, ; Eamus & Froend, ; Fisher, ), Niswonger et al (), Wu et al (), and Ghasemizade et al () showed that the effect of recharge on crop water consumption and crop ET is modest (e.g., 3–6% increase in crop water consumption over the simulation period; Niswonger et al, ), but the increase in ET by natural vegetation can be significant (e.g., 20–30%; Niswonger et al, ) depending on soil moisture content.…”

Modeling managed aquifer recharge processes in a highly heterogeneous, semi-confined aquifer system

“…There is interest in expanding use of MAR in CA, both to offset overdraft and to hedge against future decreases in snowpack-water storage and changes in the timing and volume of surface-water availability. Established MAR projects commonly use dedicated infiltration basins located over locally coarse-texture geological deposits to increase recharge, but increasingly, MAR on agricultural fields during nongrowing seasons (Ag-MAR) has been proposed as an alternative to infiltration basins (Dahlke et al 2018;Harter and Dahlke 2014;Niswonger et al 2017). Studies have noted that even during periods of water scarcity, wet-season high-magnitude streamflows (HMF) can often provide ample unmanaged surface water for MAR during nongrowing seasons in CA (Beganskas and Fisher 2017;Kocis and Dahlke 2017) and elsewhere (Chinnasamy et al 2018).…”

Adapting to Variable Water Supply in the Truckee-Carson River System, Western USA

“…To date, these adaptation measures focus on alternative water management strategies to enhance supply and include: reoperating federally managed Truckee River reservoirs to enhance surface water storage under earlier snowmelt regimes [96], constructing a reservoir in the Carson River headwaters to store snowmelt for downstream agricultural irrigation [97], and exploring managed aquifer recharge in the Carson Valley through off-season/winter irrigation in agricultural areas [98].…”