Exploring the human influence on surface water availability in the contiguous United States

Abstract

Finding which factors control the spatial variability of surface runoff is fundamental for assessing regional surface water availability. These controlling factors drive the water balance and vary from physio-climatic catchment attributes to anthropogenic activities. A few studies evaluated these factors in the Contiguous United States on catchments with non-human influence (Abatzoglou & Ficklin, 2017). Yet, a comprehensive analysis of the human influence on surface water availability is still missing.Here, we employed a parametric Budyko-based framework to assess the long-term runoff sensitivity in the last 30 years of 502 catchments in the Contiguous United States. We linked the Budyko-based framework's landscape parameter with an extensive set of 50 climatic, topographic, anthropogenic, and soil factors that were previously found influential on partitioning precipitation into evapotranspiration and runoff. The catchments belong to the GAGES-II database (Falcone, 2010) and have been grouped in reference and human-impacted basins (urban and agricultural) using the most updated land cover data of 2019. A stepwise multiple linear regression model is developed to find the most significant factors in the partitioning depending on the most extensive human activity on the basin and assess their interactions. Also, we analyzed how anthropogenic activities (e.g., irrigated agriculture, urban settlements) alter the effect of climate variables.Preliminary results suggest that cultivated land is the second most important factor in explaining runoff variability in agricultural basins, and urban settlements increase the runoff in catchments with a high interannual variability of precipitation. ReferencesAbatzoglou, J. T., & Ficklin, D. L. (2017). Climatic and physiographic controls of spatial variability in surface water balance over the contiguous United States using the Budyko relationship. Water Resources Research, 53(9), 7630–7643. https://doi.org/10.1002/2017WR020843Falcone, J. A., Carlisle, D. M., Wolock, D. M., & Meador, M. R. (2010). GAGES: A stream gage database for evaluating natural and altered flow conditions in the conterminous United States. Ecology, 91(2), 621–621. https://doi.org/10.1890/09-0889.