NITROGEN AND PHOSPHORUS IN WATER AS RELATED TO ENVIRONMENTAL SETTING IN NEBRASKA

Spatial distributions of nitrogen and phosphorus in water were related to environmental setting as part of a regional water-quality assessme nt of the Central Nebraska Basins. The environmental settings (Sandhil ls, Loess Hills, Glaciated Area, and Platte Valley) were characterized by different concentrations of nitrogen and phosphorus in ground wate r and stream water. Statistically significant differences in nitrate c oncentrations in both ground-water and stream-water samples were relat ed to regional distributions of cropland and rangeland. Nitrate concen trations were larger, especially in shallow ground water, in environme ntal settings dominated by cropland and associated fertilizer use than in settings dominated by rangeland. Similarly, total-nitrogen and nit rate concentrations were relatively large in selected streams draining primarily cropland. Comparative concentrations of phosphorus in strea m water on the basis of environmental setting were similar to those of nitrogen, although the largest phosphorus concentrations probably rel ate to wastewater discharge into small streams. Nitrogen and phosphoru s concentrations in much of the Platte River apparently reflected the quality of water entering the study unit from upstream and limited bas e-flow contributions from within the Platte Valley itself.