Study of water use in the Central Sands of Wisconsin at high spatiotemporal resolution

The Central Sands region, located in Central Wisconsin, is a mosaic of cropland, managed grasslands and scattered woodlots of pine, oak, and aspen. Water issues have loomed over the region for years, but concerns heightened in 2012 when drought conditions spurred massive increases in groundwater pumping, used chiefly for supporting irrigated agriculture.   However, the amounts of groundwater pumped for irrigation, applied to fields, and consumptively used (i.e. through evapotranspiration, or ET) is somewhat uncertain. This study aims to provide spatially detailed ET information on a daily basis from 2010 to 2014 to facilitate groundwater resource management at this region. The ET mapping procedure used in this study combines a multi-scale surface energy balance algorithm (the Atmosphere-Land Exchange Inverse Model; ALEXI) with a data fusion methodology (the Spatial and Temporal Adaptive Reflectance Fusion Model; STARFM). Remotely sensed land surface temperature derived from various thermal imaging sensors over a range of different spatial and temporal resolutions drive a multi-scale surface energy balance algorithm. The system outputs high spatiotemporal ET map timeseries at daily timesteps and 30-m spatial resolution – capable of resolving water use dynamics at sub-field spatial scales.  The 5-year geospatial dataset was used to provide an accounting of water use by crop type and land-use/water management class, and to study differences in water use in drought versus non-drought years. Working collaboratively with researchers in Wisconsin, these consumptive use estimates will be used to evaluate impacts of irrigated agriculture on ground and surface water supplies within the Central Sands.