Modeling agro-hydrological surface-subsurface processes in a semi-arid, intensively irrigated river basin

Authors: ABBAS, SALAM - Colorado State University; BAILEY, RYAN - Colorado State University; Arnold, Jeffrey; White, Michael; MIRCHI, ALI - Oklahoma State University

Submitted to: Journal of Hydrology: Regional Studies
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/7/2025
Publication Date: 2/1/2025
Citation: Abbas, S.A., Bailey, R.T., Arnold, J.G., White, M.J., Mirchi, A. 2025. Modeling agro-hydrological surface-subsurface processes in a semi-arid, intensively irrigated river basin. Journal of Hydrology: Regional Studies. 57. Article 102188. https://doi.org/10.1016/j.ejrh.2025.102188.
DOI: https://doi.org/10.1016/j.ejrh.2025.102188

Interpretive Summary: This study examines how irrigation systems in large river basins, like the Lower Arkansas River Basin in Colorado, affect water movements and storage. Using the process-based SWAT+ model, the study quantifies these hydrological fluxes, testing its accuracy against actual river flow and groundwater levels. The model performs well. Key findings show that of the basins 308 mm annual rainfall, 2% is used for surface water irrigation, and 2% contributes to groundwater recharge. The study identifies crucial factors influencing hydrology in the basin, such as soil characteristics and plant water uptake. This model may help predict the effects of climatic changes and water management strategies on these fluxes, aiding in better resource planning.

Technical Abstract: The process of implementing irrigation in large river basins often results in significant changes in hydrologic pathways and fluxes, such as canal seepage, runoff, recharge, pumping, and groundwater-river exchange. The objective of this study is to quantify the hydrologic fluxes in a highly irrigated river basin and investigate the controls on these fluxes, using the Lower Arkansas River Basin (LARB) (64,000 km2) in Colorado, USA as a demonstration case. We use the SWAT+ watershed model, enhanced with the new groundwater module gwflow, canal seepage, and irrigation application driven by daily canal diversions and groundwater pumping. The model is tested against streamflow and groundwater head, showing good performance along the Arkansas River and the alluvial corridor. On average, precipitation in the basin is 380 mm/yr, of which 2% (10 mm/yr) becomes recharge and 2% is irrigation (80% surface water irrigation). Water yield is 18 mm/yr (5%), principally surface runoff and net groundwater discharge. Canal seepage is only 0.2% of precipitation. Irrigation fluxes, canal and plant ET are highest in the downstream regions. Sensitivity analysis reveals the controlling watershed features on streamflow, groundwater head, and hydrologic fluxes for each region. Main parameters include streambed conductivity, plant uptake factors, snowmelt factors, aquifer properties, soil available water capacity, and soil percolation coefficient, with each parameter ranked by influence for each region within the basin. The calibrated models can be used to explore the impact of changes in climate, irrigation practices, and general water management schemes.