MAPPING GROUNDWATER USE WITH SATELLITE SENSOR FUSION AND MACHINE LEARNING (Invited Presentation)

Changes in groundwater storage due to excessive withdrawals threatens food, water and energy security. Globally, groundwater withdrawals are one of the primary drivers creating changes in storage. However, very few regions of the world monitor groundwater withdrawals at the local scale necessary to implement sustainable management solutions. Multiple satellite sensors are sensitive to different elements of groundwater flux, yet integrating these sensors to predict withdrawals is a challenge due to a lack of water use data, and complexities in the theory relating sensor measurement to withdrawals. Machine learning methods have been shown to be effective in relating earth science observations to various processes and are a promising technique for improving our ability to model and monitor groundwater systems. Here, we present a machine learning framework for integrating multiple satellite sensors and derivative data products related to water use. Using primarily data from Landsat, Sentinel-1, GRACE, GRACE-FO, and MODIS, as well as products derived from sensors on these satellites, we are able to estimate groundwater withdrawals at the local (1-5 km resolution) scale. The satellite products measure different components of the water balance at resolutions ranging from 10 m to 100s of km, and are integrated using data driven algorithms including random forests and neural networks. We are currently implementing these models in portions of three regional aquifer systems: the Mississippi Alluvial Aquifer in Mississippi, Arkansas, Missouri, and Louisiana; the High Plains Aquifer, in Kansas; and the Basin and Range Aquifer System, in Arizona. Complexity in irrigation practices and the aquifer itself results in varying model quality with r² ranging from 0.5 to 0.9 across these study areas. Ultimately, we plan to extend these withdrawal estimates to the conterminous United States, producing high resolution, annual estimates of groundwater use.