USING IN-SITU AND SATELLITE-BASED OBSERVATIONS TO STUDY THE HIGH PLAINS AQUIFER IN KANSAS

Satellite and other remotely sensed products can provide high resolution, spatially continuous information about water resources. Combined with discrete in-situ measurements, they can provide insights that would not be possible using satellite or in-situ data alone. Here, GRACE-derived annual changes in TWS (ΔTWS) from NASA’s Jet Propulsion Laboratory (JPL) and Goddard Space Flight Center (GSFC) are compared to annual changes in saturated groundwater volumes (ΔGW) in the High Plains aquifer (HPA) and overlying alluvial aquifers in Kansas. Evaluation of linear trends suggests that ∆TWS is more closely related to ∆GW_alluvial than to ∆GW_HPA. Unlike alluvial aquifers, a thick vadose zone overlies the HPA. Changes in vadose zone water content (∆VZ) are estimated using GRACE products and shallow (0-2m) North American Land Data Assimilation System data. The estimates are similar in magnitude to ∆TWS, suggesting an unexpected dominance of ∆VZ given the quantity of groundwater extracted and declines in groundwater levels. Results indicate that even in regions with large, heavily used aquifers subject to substantial groundwater depletion, relatively small ΔVZ or well-constrained ΔVZ estimates may be needed in order for GRACE-derived estimates of ∆TWS to provide guidance for aquifer management. Other ongoing research is studying changes in HPA porosity using synthetic aperature radar (SAR) data from ESA Sentinel-1 combined with porosity estimates from core thin sections.