MICROWAVE REMOTE-SENSING OF SOIL-MOISTURE FOR ESTIMATION OF PROFILE SOIL PROPERTY

Multi-temporal microwave remotely-sensed soil moisture has been utiliz ed for the estimation of profile soil property, viz. the soil hydrauli c conductivity. Passive microwave remote sensing was employed to colle ct daily soil moisture data across the Little Washita watershed, Oklah oma, during 10-18 June 1992. The ESTAR (Electronically Steered Thin Ar ray Radiometer) instrument operating at L-band was flown on a NASA C-1 30 aircraft. Brightness temperature (TB) data collected at a ground re solution of 200m were employed to derive spatial distribution of surfa ce soil moisture. Analysis of spatial and temporal soil moisture infor mation in conjunction with soils data revealed a direct relation betwe en changes in soil moisture and soil texture. A geographical informati on system (GIS) based analysis suggested that 2-days initial drainage of soil, measured from remote sensing, was related to an important soi l hydraulic property viz. the saturated hydraulic conductivity (K-sat) . A hydrologic modelling methodology was developed for estimation of K -sat of surface and sub-surface soil layers. Specifically, soil hydrau lic parameters were optimized to obtain a good match between model est imated and field measured soil moisture profiles. Relations between 2- days soil moisture change and K-sat of 0-5 cm, 0-30 cm and 0-60 cm dep ths yielded correlations of 0.78, 0.82 and 0.71, respectively. These r esults are comparable to the findings of previous studies involving la boratory-controlled experiments and numerical simulations, and support their extension to the field conditions of the Little Washita watersh ed. These findings have potential applications of microwave remote sen sing to obtain 2-days of soil moisture and then to quickly estimate th e spatial distribution of K-sat over large areas.