From the sprinkler to satellite: Combining fixed and mobile cosmic-ray neutron probes for realtime multiscale monitoring of soil moisture in agricultural systems

Abstract:

Approximately 40% of global food production comes from irrigated agriculture. With the increasing demand for food even greater pressures will be placed on water resources within these systems. In this work we aimed to characterize the spatial and temporal patterns of soil moisture at various scales by combining fixed and roving cosmic-ray neutron probes at four study sites across an East-West precipitation gradient overtopping the High Plains Aquifer (HPA). Each of the four study sites consisted of coarse scale mapping of the entire ~12 by 12 km domain and detailed mapping of 1 quarter section (0.8 by 0.8 km) agricultural field. By using a simplistic data merging technique we are able to produce a statistical daily soil moisture product at a variety of key spatial scales in support of irrigation water management technology: the individual sprinkler (~10² m²) for variable rate irrigation, the individual pie slice (~10³ m²) for variable speed irrigation, and the quarter section (0.64 km²) for uniform rate irrigation. In addition, we are able to provide a daily soil moisture product over the 144 km² study area at a variety of key remote sensing scales 1, 9, and 144 km². These products can be used to support SMAP/SMOS through calibration, validation, and value addition by statistical downscaling. Future work could include larger scale monitoring in support of GRACE total water storage calculations in the HPA or other key groundwater resource locations by incorporating existing COSMOS sites or establishment of new networks.