A Rapid Method for Analyzing Well Log Records in Preparation for Water Resource Mapping

The needs of subregional and local entities for water resource management are immediate, and required information is not forthcoming in a timely and relatively inexpensive manner. The following method allows one to use all available well record data to produce baseline hydrogeologic unit maps using geographic information system querying and mapping techniques. Subjective borehole and geophysical strata descriptions are converted to objective equivalent numerical values by establishing the average hydraulic conductivity of the combined soils making up the stratum of interest. These hydraulic conductivity values are then used to assign each stratum to a hydrogeologic unit based on typical ranges of hydraulic conductivity for aquifers, aquitards and aquicludes. The resulting data are queried and mapped to provide a preliminary description of a shallow aquifer system composed of unconsolidated materials. This method can be used to provide information to make initial estimates of the configuration of the shallow aquifer system and to plan for groundwater sustainability. Two examples of maps for an area in northeastern Illinois that were prepared using the resulting database are presented.