ARS | Publication request: Determination of root-zone water storage in a desert woodland using a two-layer moisture balance model

Submitted to: Meeting Proceedings
Publication Type: Proceedings/Symposium
Publication Acceptance Date: November 15, 2007
Publication Date: N/A

Interpretive Summary: The water content of the land surface is an important environmental variable in agriculture and hydrology. Because of the impracticality of measuring by hand soil moisture over large areas, scientists have developed a number of remote-sensing methods for estimating the water content of surface soils. However, remote-sensing methods generally measure the moisture content of only the top few centimeters of soil. The amount of water contained in the deeper soil can be calculated from these surface measurements if a mathematical model exists that relates the surface layer moisture to the water stored in the deeper soil. In this work, we developed and tested a new mathematical model that included for the first time the effects of shallow groundwater on near-surface soil moisture. Good agreement was found between model predictions and measured field data, and it was concluded that the new model may be useful in future remote sensing studies. This work will be of interest to researchers and others working on procedures for mapping soil moisture.

Technical Abstract: Root-zone water storage (RWS) is a fundamental component of the soil-plant-atmosphere continuum. In the lower reaches of arid river basins in inland China, low water recharge and hence low RWS have been associated with a series of ecological and environmental problems. Developing an improved understanding of RWS, as well as methods for estimating RWS, will permit improved water management and help achieve sustainable development in these arid basins. In this study, the temporal variation of RWS under the natural undershrub Sophora alopecuroides (S. alopecurorides) was examined at an experimental site located in the Ejina basin of northwest China. RWS was modeled using a two-layer soil moisture balance model comprising a shallow surface layer (0-10 cm) and a root-zone layer. Model simulations were found to be in very good agreement with experimental data. Possible future applications include regional RWS assessments in Northwestern China in which the model surface layer is correlated with remote-sensing measurements of surface moisture content.