The U.S. Geological Survey began the National Water Quality Assessment Program (NAWQA) in 1991. Goals of the program are to describe the status of and trends in the quality of a large representative part of the nation's surface and groundwater resources and to provide a sound scientific understanding of the primary natural and human factors affecting the quality of these resources. The principal deign of the NAWQA program is based on study unit investiga- tions of hydrologic systems that include parts of most major river basins and aquifer systems in the Great Plains. All or part of 18 study units that are up to 40,000 sq mi in size cover the Great Plains.
The Central Nebraska Basins study unit is typical of the study units in the Great Plains. Production agriculture is the primary economic base and a major factor in policy decisions. This area is dominated by large contiguous areas of cropland in the Platte River valley, in contrast to large areas of grassland in the Sandhills. The Platte River alluvium serves as the source for most of the public water supply and a major source of irrigation water. Public water supplies rely on induced recharge of Platte River water to the alluvium to sustain supplies. In addition to water supplies, streams and wetlands serve as aquatic habitat for typical prairie species and include critical habi- tat for endangered species in the middle reach of the Platte River.
Water quality is an important consideration in this area because of the extensive use of agricultural chemicals. Increased concentration of nitrate in groundwater and large concentrations of pesticides in the Platte River threaten public supply wells in the alluvium. The critical habitat reaches of the Platte River and other wetland areas are also vulnerable to water quality degradation from agricultural chemicals. The NAWQA study in central Nebraska will provide essential information to address these water quality issues. Water quality samples have been collected at 9 fixed sites on the Platte River and selected tributaries to determine concentrations of pesticides and nutrients. Sampling schedules have been designed to document spring runoff when concentrations of pesticides are the largest. Low-flow samples have been collected at about 30 selected sites to determine baseline concentrations of pesticides and nutrients. Groundwater sampling wells have been drilled at multiple depths at selected locations in the alluvium to determine the sources and three-dimensional movement of pesticides and nutrients, particularly nitrate, in the alluvium of the Platte River valley. Ecological information is being collected at the 9 fixed sites and at about 30 wetland sites to determine the biological and aquatic habitat characteristics of this study area, particularly those aquatic habitats critical to threatened species.
Interpretive analysis of the field information is focused on the water supply and aquatic and riparian habitat issues in the study unit. Results are communicated through traditional reports, magazines, and journals. In addition, meetings are held with a liaison committee whose membership includes local and special interest organizations, and state and federal agencies. The liaison committee generally meets twice a year to assist in planning activities, review and comment on interim results, and facilitate communication of results. Implications of NAWQA results will influence water policy and water quality management in the central Nebraska study unit. Similar activities and results from other study units will collectively contribute to more informed water policy for the Great Plains.
Huntzinger, Thomas, 1995, Water quality assessment in the Great Plains--Assurance of a sustainable future [abs.]: Planning for a sustainable future--The case of the North American Great Plains, Lincoln, Nebr., 1995, Proceedings, p. 169-171.