Agricultural irrigation effects on hydrological processes in the northern high plains simulated by the coupled SWAT-MODFLOW system

Authors: DANGOL, S. - University Of Maryland; Zhang, Xuesong; LANG, XIN-ZHONG - George Mason University; MIRALLES-WILHELM, F. - Nature Conservancy

Submitted to: Water
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/14/2022
Publication Date: 6/16/2022
Citation: Dangol, S., Zhang, X., Lang, X., Miralles-Wilhelm, F. 2022. Agricultural irrigation effects on hydrological processes in the northern high plains simulated by the coupled SWAT-MODFLOW system. Water. 14(12):1938. https://doi.org/10.3390/w14121938.
DOI: https://doi.org/10.3390/w14121938

Interpretive Summary: Aquifer overdraft in the grain-growing region in the High Plains of the United States causes groundwater depletion. The High Plains states face challenges to adopt more sustainable approaches to conserve groundwater while maintaining or increasing productivity. We developed a watershed model to quantify the water budgets of the Northern High Plains with an area of 347,000 km2 and apply the model to understand how historical groundwater-based irrigation practices influenced the water cycle for the period 1982-2008. We found that, while irrigation improves crop productivity by nearly 26.5% for corn and 32.4% for soybeans, it significantly altered the water cycle in the Northern High Plains. For example, historical irrigation practices increased surface runoff by 14.1% and caused a decline in groundwater level and groundwater discharge to rivers by 11.3-137% in different parts of the Northern High Plains. Our findings suggest that designing sustainable irrigation practices to enhance crop productivity must consider both regional landscape characteristics and downstream aquatic consequences. The model we developed holds promise to provide scientific support for future efforts aimed at sustainable use of groundwater in the Northern High Plains.

Technical Abstract: Groundwater use for irrigation is widespread and has a major influence on local water resources worldwide. This study examined the effects of groundwater irrigation on the water cycle in the Northern High Plains (NHP) using the coupled SWAT-MODFLOW model simulations during 1982-2008. The auto-irrigation scheduling based on plant water stress from SWAT (Auto-Irr) generally outperforms the prescription of irrigation well-pumping rates by MODFLOW in simulating evapotranspiration, groundwater irrigation volume, groundwater level, and streamflow at multiple stations across the NHP. Using the Auto-Irr scheme, irrigation produces a large recharge in the north-central Sand Hills landscapes and along the Elkhorn and Platte rivers. On average in the entire NHP, irrigation increases surface runoff, evapotranspiration, soil moisture and groundwater recharge by 14.11%, 1.85%, 1.95% and 1.41%, respectively. Irrigation also declines groundwater levels and reduces aquifer discharge by 11.30-136.52%. The latter is important to streamflow except for the South Platte River where river seepage is dominant. Thus, irrigation significantly alters the regional hydrology with large variations across the NHP. On the other hand, irrigation improves crop water productivity by nearly 26.5% for corn and 32.4% for soybean. Therefore, designing sustainable irrigation practices to enhance crop productivity must consider both regional landscape characteristics and downstream aquatic consequences.