Conservation Agriculture's Effect on Groundwater: A HYDRUS 1D Study

Abstract

Conventional farming has historically focused on high-volume groundwater extraction for irrigation and the broad application of chemicals to boost crop yield and productivity. This intensive reliance on irrigation water to grow food has contributed to over-consumption and contamination of groundwater resources in aquifers in agricultural regions. However, conservation farming practices, such as replacing high water demand crops like corn with cereal grains and using crop water use-based irrigation, have the potential to mitigate groundwater depletion and contamination by improving efficiency in groundwater use. Therefore, I used the Hydrus 1D model with R Statistical Software to analyze how various crop rotation and irrigation management practices influence water inputs, crop water use, and deep percolation using representative values for soil, climate, and crop systems for a hypothetical study site in Hall County, Nebraska, which extracts its irrigation water exclusively from the Ogallala Aquifer. Four scenarios were then simulated and compared to assess how these agricultural management practices impact groundwater, assuming conservation and recharge will improve where water use efficiency, as mediated by soil improvements derived from those practices, increases. Irrigation inputs and deep percolation outputs were used as proxies for groundwater conservation and groundwater recharge, respectively. Soybean-wheat-corn-soybean (SWCS) rotation reduced irrigation inputs and consumptive water losses from evapotranspiration and runoff while increasing non-consumptive water losses to deep percolation compared to a soybean-corn-soybean-corn rotation (SCSC) over four years. Irrigation scheduling based on crop water use reduced irrigation inputs and runoff losses while increasing soil water losses and deep percolation. Keeping irrigation volume stable but increasing application frequency with lower intensity decreased consumptive losses to runoff and re-routed those savings to deep percolation. These results suggest that conservation practices can enhance groundwater recharge and reduce aquifer withdrawals, contributing to the long-term sustainability of aquifers like the Ogallala Aquifer.