GEOLOGIC CONTROL ON DENVER BASIN AQUIFERS

The water yield charactertistics of the Denver Basin bedrock aquifers are controlled by the depositional environments and subsequent diagenetic phenomenon associated with the accumulation of fluvial and paludal sedimentary rocks in the Denver Basin. A regional subdivision of the aquifers into administrative units forms the present framework for administering the groundwater resources of the basin. These aquifer units can be divided into a series of unconformity-bounded sequences that permit enhanced genetic models to be proposed. By better understanding the paleo-landscapes responsible for the accumulation of the sedimentary rocks the aquifer geometries and heterogeneities can be better understood and predictive insight obtained. Large-scale fans and distinctive fluvial systems have been identified in the Denver Basin sediments by use of outcrop studies and electric log analyses. A particularly well-defined lobe of coarse arkosic debris is defined in northern Douglas County. A series of multi-storied channels sandstone bodies make up the Arapahoe aquifer in this area. Map patterns suggest sediment dispersal by a long-lived major river system draining the early Front Range. Aquifer performance is tied directly to these environments of deposition and studies are in progress to predict the spatial performance of the designated aquifer units.