RESOLVING PRACTICAL PROBLEMS IN USING A SOIL-WATER MASS BALANCE MODEL TO ESTIMATE THE SPATIAL DISTRIBUTION OF RECHARGE

We used two versions of a model that uses GIS-based input data of soil properties, land cover, digital elevation model (DEM) along with meteorological data to estimate recharge in a drainage basin in central New York. The model routes water across the land surface based on the DEM while computing evapotranspiration and infiltration. The model is relatively easy to use, but obtaining and preparing input data can be challenging and frustrating. For example, soil survey data vary in quality and completeness, particularly for hydrologic information that is used as model input. Land cover data are often out of date or unavailable at a detailed scale. Accurate local daily meteorological data may be unavailable, requiring the use of data from distant stations that may not reflect local conditions.

We have encountered all of these situations in our modeling, and have resolved them in different ways. For instance, soil hydrologic information can be estimated from soil textural descriptions and other narrative information about the soil series. Land cover data can be translated from records kept by assessor's offices or determined from aerial photos from agricultural agencies. Local daily meteorological data are recorded by other entities than weather stations, but finding them can be challenging. While the input data was not always easy to obtain, the results of our model runs provided usable estimates of the spatial variability of recharge in our study area.