Hydrogeology of Aquifers
The major objectives of the Upper Arkansas River Corridor Study were to document the fate and effects of contaminated Arkansas River flows on the aquifers in the river valley and to clearly determine the links among decreased flow in the Arkansas River, increased levels of water contamination in the aquifers, and lowered ground-water tables. In order to achieve these objectives, an understanding of the spatial characteristics of the aquifers was necessary. In particular, knowledge of the distribution of low-permeability clay layers and high-permeability sands and gravels was needed for the High Plains and alluvial aquifers in the river corridor. This information would allow a better determination of the factors controlling movement of the saline Arkansas River water within the alluvial aquifer, from the alluvium to the underlying High Plains aquifer, and within the High Plains aquifer. The data were also needed as input for conceptual and numerical models of ground-water flow in the corridor. Therefore, the design of the study included investigation of existing data and collection of new data on the hydrogeology of the aquifers.
The existing data included lithologic logs from KGS and USGS publications and water-well driller's logs, and published values and maps of aquifer parameters such as hydraulic conductivity and specific yield for the unconsolidated sediments in the river corridor. Thousands of water-well driller's logs were examined and those with the best data records were selected for further use. New data included lithologic and geophysical logs and aquifer tests in multi-level wells drilled during the study at selected locations along the river corridor. The lithologic data were used to prepare a series of cross sections that visually display both continuous and heterogeneous strata in the alluvial and High Plains aquifers. The report for this investigation on the lithology of the alluvial and High Plains aquifers that includes images of these cross sections is in this web section (Lithologic Characterization of Unconsolidated Deposits along the Arkansas River Corridor in Southwest Kansas).
The main aquifers of the Arkansas River corridor are the alluvial aquifer and the High Plains aquifer. The alluvial deposits of the Arkansas River valley include recent alluvium underlying the floodplain that is about 2- to 4-miles wide from Hamilton County to Ford County. A trough of alluvial deposits underlies the dune sand south of the Arkansas River in Hamilton County and southwest Kearny County. The High Plains aquifer underlies most of the study area east of the Bear Creek fault zone that crosses under the river valley in south-central Kearny County. The northern part of the Crooked Creek-Fowler Fault crosses the river valley in eastern Ford County. The High Plains aquifer thins on the east side of the fault. Most of the bedrock underlying the High Plains aquifer or surface loess in the study area is either Upper Cretaceous shales and chalks or Lower Cretaceous shales and sandstones. The Lower Cretaceous bedrock includes the Dakota aquifer from which ground water can be produced from sandstone units. Extensive information on the hydrogeology of the Dakota aquifer can be found in the KGS web site.