Corn sweat: A qualitative and hydrologic analysis of a high resolution evapotranspiration model in Iowa

Evapotranspiration (ET) is the movement of water from the ground to the air by either evaporation off of the soil/water surface or through transpiration from growing crops. ET is one component used to understand and help predict streamflow and flooding in rivers. By knowing how much water has left the soil, we can tell the soil’s ability to hold water when it rains and further predict when flooding will occur. However, it is extremely expensive to directly measure ET and other available sources of ET do not accurately estimate ET. In addition, these sources of ET either do not cover a large enough area or they do not collect measurements in a timely manner. To solve this data gap, we propose an ET product that uses weather data to calculate ET at fine spatial and temporal resolutions using the Penman-Monteith equation.

To test whether our ET product performed well, we first did an area analysis over Iowa to see if we could capture daily and seasonal changes in ET. Additionally, we compared our ET product to other satellite and climate-based products. To learn whether high resolution ET data impacted streamflow modeling, we ran the Iowa Flood Center’s Hillslope-Link Model with our ET product to see if streamflow forecasts more closely match observations. We found that our ET product performed better than other sources of ET, but when used in the flood model, we could not determine whether better ET data resulted in better forecasts.