Google Earth Engine Evaporation Flux (EEFlux): A New Operational Tool for Mapping Root Zone Soil Water Content and Water Storage Capacity.

Previous and current work by us and other investigators has demonstrated that a simple soil water balance model is a powerful tool for the characterization of root zone soil moisture dynamics. However, the success of this method depends on a correct estimation of the soil water storage capacity also known as total available water. We have developed and published a method to estimate the soil water storage capacity at 30 m spatial resolution from evapotranspiration (ET) maps acquired from Landsat imagery by implementing the remote sensing algorithm Mapping EvapoTranspiration at high Resolution with Internalized Calibration (METRIC). This method does not require a soil or vegetation map of the study region and, therefore, can be applied wherever clear sky Landsat images are available. A big hurdle to its widespread application by soil scientists was the need to know how to apply METRIC for the generation of the ET map. The 2016 launch of the Google Earth Engine Evaporation Flux (EEFlux) has removed this obstacle so that the soil water storage capacity no longer needs to be the least known parameter of soil water balance models. We will present examples how to use EEFlux ET maps for soil mapping and the regional estimation of root zone soil water content, evapotranspiration and groundwater recharge.