AN INTERPRETATION OF METHODOLOGIES FOR INDIRECT MEASUREMENT OF SOIL-WATER CONTENT

Using a new technique referred to as the triangle method, surface soil water content and fractional vegetation cover were derived from surfa ce radiant temperature measurements and normalized difference vegetati on index (NDVI). Application of the technique is made with reference t o NS001 multispectral scanner measurements made by a C-130 aircraft ov er the Mahantango Watershed in Pennsylvania. The derived surface soil water content values were compared with those obtained from the Push B room Microwave Radiometer (PBMR) aboard the same aircraft and with in- situ ground measurements, A large disparity was found to exist between all three measurements, suggesting that the surface becomes decoupled from the deeper substrate in regions of rapid drying, where large ver tical gradients in soil water content may exist near the surface.