"Validation and application of the Soil Moisture Active Passive Satellite Mission in Texas"
Dr. Todd Caldwell
Bureau of Economic Geology
The 2011 drought in Texas resulted in a total water storage deficit of over 60 km3, nearly 50 million acre-feet, with soil moisture accounting for 20-100% of this loss. Such data from the NASA's Gravity Recovery and Climate Experiment require land surface models (LSM) to partition the water balance between soil, surface, and groundwater storage. Clearly, these models are difficult to validate on many levels. Now, we are poised to receive globally mapped soil moisture at unprecedented accuracy, resolution, and coverage following the successful launch of NASA’s Soil Moisture Active Passive (SMAP) satellite. Using a combined passive L-band radiometer and active L-band radar, soil moisture to 5 cm depth is retrieved at 3, 9 and 36km spatial resolutions every few days. The primary SMAP mission objectives is a soil moisture product with an unbiased error <0.04 m3 m-3 to ground-based networks. However, few such monitoring networks exist at the scale appropriate to validate SMAP, or any other LSM or remote sensing product. In response to this need, we built the Texas Soil Moisture Observation Network (TxSON): an intensively monitored watershed (1300 km2) located on the Edwards Plateau along the Pedernales River. TxSON consists of over 40 monitoring stations nested within the Equal-Area Scalable Earth Grid with replicated soil moisture sensors installed at 5, 10, 20 and 50 cm depths. This presentation will highlight the SMAP mission, its products and applications, and the on-ground activities related to large-scale soil moisture validation efforts. I will also present several of our applications to flood mitigation and groundwater recharge. My goal with this talk is to show you the power of soil moisture on terrestrial hydrology, even if it is just scratching the surface.