Quantifying Groundwater Resources in Alluvial Aquifers Using GIS

Many alluvial aquifers are becoming more important water resources as water supplies become stressed from population, pollution and politics.  Not only are alluvial aquifers often good sources of water, but the application of bank infiltration through alluvium can provide effective pretreatment for surface water supplies. However, alluvial aquifers are extremely complex, varying across almost the entire gamut of transmissivity values as both texture and thickness change dramatically. In addition, most alluvial deposits contain unconfined aquifers where water level fluctuations affect transmissivity values. Because this variability is spatial in nature, GIS is a valuable tool for data management and quantitative assessment. Therefore, GIS was used in this study to quantify the groundwater potential for the Brazos River alluvium aquifer. The Brazos alluvium aquifer is an important minor aquifer in central Texas that has the potential to meet water needs for the region. GIS was used to develop a quantitative database for the Brazos floodplain alluvium, determine the volume of groundwater contained in the alluvium, and identify the areas with the most potential for groundwater production and bank infiltration. Most data were available from the Texas Natural Resources Information System and the Texas Water Development Board, then supplemented by regional and local studies.  GIS also provided the ability to utilize detailed data for selected areas and extrapolate it into a regional context. Perhaps a more important contribution to alluvial water management than the final report is the creation of a GIS data base with the flexibility to continually incorporate new information.