A Study of Nonpoint Source Groundwater Contamination in the Vicinity of Superior, Nebraska:
A Groundwater Management Area Report
The Nebraska Department of Environmental Control (DEC) undertook a study in 1988 to determine if nonpoint source (NPS) contamination is occurring in the vicinity of Superior, Nebraska. If so, designation of a Special Protection Area (SPA) would help the local Natural Resources Districts (NRDS) manage the problem.
The study area consists of an agricultural (both irrigated and non-irrigated) area underlain by fine-grained loess sediments in the uplands and coarser alluvial sediments in the drainages, especially the Republican River Valley. Irrigation is practiced primarily in the Republican Valley and the southeast and northeast corners of the study area, as these portions have aquifers sufficient to yield water to high capacity wells. The aquifer in the remainder of the study area is sufficient only for low yield domestic and stock wells.
100 samples obtained in the spring and summer of 1988 were analyzed for a variety of parameters. Nitrate-nitrogen (NO3-N) contents of these samples were highest in the south-central and southeast portions of the study area. These areas exhibited widespread, homogeneous levels of NO3-N often exceeding 10 mg/I, even after point sources were eliminated. In addition, several irrigation and municipal wells contained residues of atrazine, a common corn and sorghum herbicide.
In view of the above information, it is concluded that NPS ground water contamination is occurring in a portion of the study area. It is recommended that an SPA be declared in this region to help the local NRDs manage the problem. Boundaries for the SPA are suggested, but could be adjusted after consultation with the NRDs or after a public hearing.