Page Banner

United States Department of Agriculture

Agricultural Research Service

Title: Remote Sensing and Estimation of Root Zone Water Content

Authors
item Starks, Patrick
item Jackson, Thomas -

Submitted to: International Association of Hydrological Science
Publication Type: Proceedings
Publication Acceptance Date: January 7, 2000
Publication Date: N/A

Interpretive Summary: Knowledge of the spatial variation of soil water content over large land areas is needed by researchers in the agricultural, meteorological and hydrological sciences as well as by water resources managers. It has been demonstrated that passive microwave remote sensing can provide estimates of near-surface (0-5 cm layer) volumetric water content. Moreover, remote sensing is the only technique that can provide soil water content estimate over large regions. However, surface soil water content estimates need to be linked to that in the remainder of the root zone to be useful. A simple, two layer soil water budget model, which links surface water content to that in the total root zone, was evaluated for implementation into regional remote sensing studies of soil water content variations. Field measurements and remotely sensed estimates of near-surface volumetric water content were used separately to initialize the model. The model was run for a month time period at four rangeland study sites. Model output o root zone volumetric water content compared well to measured values at all study sites for both model initialization scenarios. Modeled near-surface volumetric water content diverged more from measured values when remotely sensed data were used to initialize the model than when field measurements were used. The model performed well overall, and its simplicity makes it suitable for implementation into remote sensing studies of spatial and temporal variations of soil water content over large regions.

Technical Abstract: It has been demonstrated that remote sensing can provide estimates of near- surface (0-5 cm layer) volumetric water content. However, these near- surface estimates need to be linked to the remainder of the root zone (approximately the 0-1000 cm layer in this study) to be useful to water resources managers and researchers in the hydrological and agricultural sciences. A simple, two layer soil water budget model, which links the near-surface to the total root zone layer, was evaluated for use in remote sensing studies of volumetric soil water content in rangeland settings of central and south central Oklahoma. Field measurements and remotely sensed estimates of near-surface volumetric water content were used separately to initialize the model. The model was run for a month time period at four rangeland study sites. Model output of root zone volumetric water content compared well to measured values at all study sites for both model initialization scenarios. Modeled near-surface volumetric water content diverged more from measured values when remotely sensed data were used to initialize the model than when field measurements were used. The model performed well overall, and its simplicity makes it suitable for implementation into remote sensing studies of spatial and temporal dynamics of soil water content over large regions.

Last Modified: 10/21/2014
Footer Content Back to Top of Page