National Water-Quality Assessment (NAWQA) Program - High Plains Regional Groundwater (HPGW) Study

Unsaturated-Zone Study - Ogallala Formation, southern High Plains

Boreholes were drilled at one site in Chase County, Nebraska, at which rangeland was the dominant land use, and at two sites in Yuma County, Colorado and Perkins County, Nebraksa, at which irrigated agriculture was the dominant land use. Sediment cuttings and cores were collected during drilling for the analysis of physical properties (particle size, bulk density, porosity, gravimetric and volumetric water contents, and matric potentials) and chemical concentrations (tritium, chloride, nitrate, and six pesticides and two pesticide degradates). The boreholes were instrumented with monitoring wells and pressure transducers to measure ground-water elevations, advanced tensiometers (AT's) and heat-dissipation probes (HDP's) to measure soil-water matric potentials, suction lysimeters were installed in the unsaturated zone to collect soil-water samples, and ground-water samples were collected from the monitoring wells. Soil water collected in 2003 was analyzed for chloride, nitrate, and atrazine. Groundwater collected in 2002 - 2003 was analyzed for tritium, chloride, nitrate, and 47 pesticides and pesticide degradates. Water potentials and profiles of tritium, chloride, nitrate, and pesticide concentrations were used to evaluate water movement through thick unsaturated zones overlying the central High Plains aquifer.

Publication available at: Storage and transit time of chemicals in thick unsaturated zones under rangeland and irrigated cropland, High Plains, United States, Water Resources Research , Vol 42

Figure 1

Shows the location of the wells.
Shows the location of the wells.

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