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Saturated thickness and thickness change over time are important parameters used to model and manage the High Plains aquifer. Insight into how these parameters are being used for High Plains aquifer management can be found through HiPLAIN ( http://www. hiplain .org/ ). Calculation of these parameters is made possible because of depth to water measurements taken annually in irrigation and other types of water wells and the driller’s and geophysical logs of the thousands of wells that have been drilled in the region. These data are readily available over the Internet from HiPLAIN or the Kansas Geological Survey directly (KGS, http://www. kgs . ku . edu / ) through the WIZARD, Water Well Completion Records, Oil and Gas, and other derivative databases. These large databases represent the collected field observations and experiences of science practitioners (well drillers and field technicians) and thus present opportunities for learning, 3-D visualization, and skill development, especially the ability to use geographic information systems (GIS) to analyze geospatial data sets from diverse sources. Using the WIZARD database, students can directly import data into spreadsheet programs to (1) calculate the water-table elevation at each well measured and (2) create hydrographs showing trends in depth to water at a particular well and determine rates of water-level decline or rise, if there are sufficient historical data. The driller’s logs in the Water Well Completion Records database and the geophysical logs in the Oil and Gas database must be interpreted to delineate the depth to the base of the High Plains aquifer from surface. Alternatively, a depth to bedrock database derived from driller’s and geophysical log interpretation has recently been completed and is on-line at the KGS web site, if working with the driller’s logs is not of interest. Land-surface elevation is generally not reported on these forms, but can be determined from a digital elevation model using GIS procedures. Depending on its local relief, the elevation of the base of the High Plains aquifer data can be contoured manually or automatically using a GIS geostatistics package. Saturated thickness and thickness change can then be calculated using one of several GIS procedures to subtract the bedrock surface from the water-table surface elevation. Abstract Kansas Ogallala/High Plains Aquifer Hydrostratigraphy The High Plains aquifer consists of Pliocene and Quaternary unconsolidated to partly consolidated alluvial, lacustrine, and eolian deposits. Lithologically, the aquifer consists of gravel, sand, silt, and clay in proportions that are highly variable across the western Kansas region. Caliche and silcrete dominated horizons are prominent. In southwest Kansas, lacustrine limestones and marls occur in the lower part of the section. All of these lithotypes occur as discontinuous layers of highly variable lateral extent. Driller’s logs of boreholes to install water wells were analyzed to characterize the distribution of lithologies within the Ogallala aquifer in two small study areas of northwest Kansas. Each study area was approximately 324 mi 2 . The histograms to the left and the scatterplots below illustrate the aquifer’s highly variable lithologic make-up. Coarse Fraction Thickness = Aggregate Sand + Aggregate Sand & Gravel Thickness Thickness Caliche & cemented layer occurrence, upper half vs. lower half in the two study areas Calculation of Saturated Thickness Depth to bedrock from surface estimated using gamma-ray & driller’s logs Depth to the water table from surface estimated from depth to water measurements taken during annual surveys of water wells Land surface elevation estimated from digital elevation models Land Surface Elevation (2000 feet) Water Table Elevation (1950’) Bedrock Elevation (1800’) Water Table Elev. – Bedrock Elev. = Saturated Thickness (150’) Calculation Algorithm High Plains Aquifer Information and Databases: Large Data Sets for Earth Science and GIS Learning and Skill Development P. Allen Macfarlane, B.B. Wilson, and M.A. Townsend Kansas Geological Survey, University of Kansas, 1930 Constant Ave., Lawrence Kansas 66047
