Evaluating the risks of groundwater extraction in an agricultural landscape under different climate projections

Authors: ACERO TRIANA, JUAN - University Of Illinois; CHU, MARIA - University Of Illinois; GUZMAN, JORGE - University Of Illinois; Moriasi, Daniel; STEINER, JEAN - Kansas State University

Submitted to: Water
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/31/2020
Publication Date: 2/2/2020
Citation: Acero Triana, J., Chu, M.L., Guzman, J., Moriasi, D.N., Steiner, J.L. 2020. Evaluating the risks of groundwater extraction in an agricultural landscape under different climate projections. Water. 12(2):400. https://doi.org/10.3390/w12020400.
DOI: https://doi.org/10.3390/w12020400

Interpretive Summary: Rainwater harvesting and implementation of more efficient irrigation systems are two practices commonly used to mitigate declining patterns in groundwater resources for major aquifers in the US and around the world. In order to utilize these mitigation practices, it is essential for farmers and water resource managers to understand the interaction of surface and groundwater resources and their responses to land management and varying climatic conditions. The goals of this study were to: 1) evaluate the impacts of current land management under the most severe projections of future climate; and 2) quantify the potential mitigation effects of three conservation scenarios on water resources in the Fort Cobb Reservoir Experimental Watershed (FCREW) in western Oklahoma. The linked Soil and Water Assessment Tool and Modular Three-Dimensional Finite-Difference Groundwater Flow (SWATmf) model was used to simulate the impacts of using a more efficient irrigation system and the conversion of 50% and 75% of the FCREW cropland area to rangelands under projected climate scenarios. Results showed that by the end of the century the projected most severe future climate could reduce surface water by 18% and lower the groundwater elevations between 99% and 120% in the western part of the FCREW, if the current water extraction level is maintained. Results further indicated that if the proposed conservation practices are implemented, the groundwater elevations would recover in 7 to 10 years after implementation. Use of an efficient irrigation system that reduced 50% of current irrigation water application led to the fastest recovery of the groundwater elevations. The results of this study contribute to the Conservation Effects Assessment Project (CEAP) that seeks to quantify the environmental benefits of conservation practices.

Technical Abstract: Groundwater resources worldwide are being depleted at alarming rates since 1960 to support agriculture, industry, and domestic water demand. Water-harvesting and the implementation of reduced application or more efficient irrigation technologies were identified as two of the most efficient practices to mitigate the declining patterns on groundwater resources. However, prior to implementing these practices, understanding how groundwater interacts with surface water and responds to natural and anthropogenic stressors is crucial. Integrated modeling tools that are able to exchange fluxes in both domains are needed to assess how conservation practices will affect our water resources under different projected climate and land use scenarios. This study aimed to evaluate the most likely impacts of current land management practices under the most severe projections of future climate (RCP8.5) and quantify the potential mitigation effects of three conservation scenarios on the water resources of the Fort Cobb Reservoir Experimental Watershed (FCREW) in western Oklahoma. The semi-coupled SWAT-MODFLOW (SWATmf) model was used to simulate the hydrologic responses of the FCREW to a 50% reduction in the irrigation depths and the transition of 50% and 75% of croplands to rangelands under 32 distinct climate projections. Results showed that future climate can drive a reduction in the streamflow (-18%) and an increase to the depth of the water table (99-120%) in the western part of the FCREW by the end of the century. The Fort Cobb Reservoir was expected to reduce its release after the mid-2060s to maintain its current target level. All the scenarios, aimed at decreasing groundwater extractions or implementing conservation measures, signaled a full recovery response in the groundwater levels 7-10 years after the year the conservation practices were implemented. The 50% reduction in the irrigation depths was found to elicit faster hydrologic systemic responses than the two that implemented conservation measures, which contravene tradition and would imply cessation of agricultural activities. This study can enable stakeholders to formulate timely adaptation and mitigating strategy to adopt to land-use changes.