Modeling the surface water and groundwater budgets of the US using MODFLOW-OWHM

• Published in: Advances in water resources 2020-09, Vol.143, p.103682, Article 103682
• Main Authors: Alattar, Mustafa H., Troy, Tara J., Russo, Tess A., Boyce, Scott E.
• Format: Article
• Language: English
• Subjects: Climate variability; Evapotranspiration; MODFLOW-OWHM; Streamflow; Surface-groundwater interactions; Water budgets
• ISSN: 0309-1708; 1872-9657
• DOI: 10.1016/j.advwatres.2020.103682

•A generalized, calibrated set-up of the USGS MODFLOW-One World Hydrologic Model across CONUS is presented that includes human impacts.•The model reasonably simulates the spatial patterns of hydrologic fluxes across the model domain, with the largest errors occurring in regions with heterogeneous topography.•Water budget analysis highlights the variability in precipitation, recharge, and streamflow with evapotranspiration demonstrating the least interannual variability. Assessments of groundwater and surface water budgets at a large scale, such as the contiguous United States, often separately analyze the complex dynamics linking the surface and subsurface categories of water resources. These dynamics include recharge and groundwater contributions to streamflow. The time-varying simulation of these complex hydrologic dynamics, across large spatial and temporal scales, remains a scientific challenge due to the complexity of the processes and data availability. In this study, groundwater fluxes and surface hydrologic processes are simulated across the contiguous US for 1950-2010. The simulation estimates the monthly water budget components, such as groundwater recharge, surface runoff, and evapotranspiration; streamflow in major rivers is routed while accounting for groundwater exchange. Human impacts are included through groundwater pumping, and climate variability is included, including variability in precipitation, temperature and potential evapotranspiration. The simulated groundwater level and river discharge have strong correlation with USGS observation wells and streamflow gages, with R2 values of 0.992 and 0.946, respectively. The simulated evapotranspiration is compared with three other published estimation methods, showing that it is able to capture the magnitude and seasonality of evapotranspiration over the Mississippi River basin. As such, the model is able to reasonably simulate the surface and groundwater budgets over the US, allowing for questions of the relative importance of climate and human impacts to be explored in the future.