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United States Department of Agriculture

Agricultural Research Service


item Bryant, Ross
item Thoma, David
item Moran, Mary
item Holifield Collins, Chandra
item Goodrich, David - Dave
item Keefer, Timothy - Tim
item Paige, V.
item Williams, D.
item Skirvin, Susan

Submitted to: First Interagency Conference on Research in the Watersheds
Publication Type: Proceedings
Publication Acceptance Date: 8/1/2003
Publication Date: 9/1/2003
Citation: Proc. 1st Interagency Conf. on Research in the Watersheds, Oct. 27-30, 2003, Benson,AZ., pp. 528-523.

Interpretive Summary: Resource managers need information about soil moisture status to make land use decisions regarding cross-country mobility, irrigation scheduling, pest management, fire behavior, biomass production and soil erosion. However, soil moisture is difficult and time consuming to measure over large areas by taking and analyzing soil samples on the ground. Remote sensing has advantages for monitoring surface soil moisture by measuring large areas in a timely and efficient manner. This project demonstrated that reflectance, thermal and radar measurements can all be used to measure soil moisture. But reflectance and thermal measurements cannot easily be applied to different soil types and only measure the first few millimeters of soil. However, radar offers the potential for directly measuring soil moisture, can measure all types of soil, and measures moisture to depths of several centimeters. The ability of radar to measure soil moisture of many types of soil makes it potentially very useful in many regions, thus greatly extending the monitoring capability and information available for resource management decision making.

Technical Abstract: Remote sensing techniques for monitoring soil moisture were tested by comparing hyperspectral reflectance and spectral indexes; surface temperature (Ts) and thermal indexes; and normalized radar backscatter to soil moisture. A laboratory study indicated that hyperspectral reflectance and Ts were sensitive to surface soil moisture (r2 range from 0.72 to 0.96). However, Ts was the only optical measurement that appeared insensitive to soil type. An index derived from differences between measurements of dry and wet soils ('-index) was presented and tested on the optical data as well as on data collected from two radar field studies at the United States Department of Agriculture ' Agricultural Research Service (USDA-ARS) Walnut Gulch Experimental Watershed (WGEW). Using the '-index, radar backscatter measured by different satellite sensors was merged into a single relationship with surface soil moisture. Furthermore, the radar '-index may be physically related to surface soil moisture such that field-based empirical relationships may be unnecessary in sparsely vegetated environments.

Last Modified: 10/19/2017
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