Significance of surface water in the terrestrial water budget: A case study in the Prairie Coteau using GRACE, GLDAS, Landsat, and groundwater well data

The terrestrial water budgets of the Prairie Coteau (PC; 38,000 km ²) and Northern Glaciated Plains (NGP; 66,000 km²) regions of South Dakota, USA were characterized using a combination of in situ observations of groundwater and surface water, remote sensing estimates of terrestrial water storage changes from the Gravity Recovery and Climate Experiment (GRACE) and surface water changes from Landsat, and modeled changes in soil moisture, snow water equivalent, and total canopy water storage. In response to increased wetness in 2010 and 2011 over the region, prevalent surface water bodies accounted for a significant fraction of the terrestrial water budget of the PC, whereas the NGP, an area with sparse surface water, exhibited a greater increase in groundwater storage concomitant with enhanced seasonal variability. Over the study period from 2003 to 2011, GRACE-based estimates of terrestrial water storage agreed well with combined groundwater, soil moisture, snow water equivalent, and total canopy water storage over the NGP, as surface water is not a significant component in this area. However, closure was improved over the PC if surface water changes were included in the water budget. Key Points Individual components of terrestrial water storage were quantified. Surface water is a significant contributor to the terrestrial water budget. Future investigations would be aided by continuous monitoring of surface water.