Practical Saturated Thickness: a More Realistic Measure of Groundwater Availability in Heterogeneous Aquifers

Ground-water availability from the High Plains aquifer in Southwest Kansas Ground-water Management District 3 (GMD 3) is declining as it is elsewhere in the western part of the state (Figure 1). Water-use density, defined as the annual amount of water pumped from the aquifer per unit of land area, is high over much of the District and greatly exceeds annual recharge (McMahon et al., 2003). Subsurface data indicate that the thickness, composition, and properties of the aquifer are highly variable. These factors argue for a tailored approach to manage the remaining supplies in the aquifer. A key element in determining the best method to subdivide the High Plains aquifer into smaller units for management purposes is the geospatial distribution of permeable, water-yielding zones. One approach to characterizing the distribution of permeable zones within the High Plains aquifer is to mine the information contained in the thousands of drillers’ logs of test holes and production wells drilled for water supply in GMD 3. The sheer abundance of these logs makes them an attractive source of information even though many geologists and hydrogeologists downplay their value.