Conjunctive water management to sustain agricultural economic returns and a shallow aquifer at the landscape level

Abstract

Irrigated farming regions around the world face the problem of groundwater scarcity. We examine the economic effectiveness of conjunctive water management with on-farm reservoirs and tail-water recovery to address this scarcity in the Lower Mississippi River Region of Arkansas, United States. A landscape level economic model is used because groundwater use by one producer affects the groundwater available for other producers. The present value of farm net returns over 30 years on the agricultural landscape depends on the crop mix, reservoir adoption, and the groundwater depletion that are optimal using a spatial-dynamic programming problem. We find that reservoirs should be built when the depth to the aquifer exceeds 18.3 m (60 ft), and the average share of productive land in a reservoir should be about 2%. Rice (Oryza sativa) intensive areas use reservoirs to replace groundwater with reservoir surface water when the depth to groundwater increases. Soybean (Glycine max) intensive areas use reservoirs sparingly to support shallow groundwater pumping depths, but groundwater remains the primary source of irrigation.