Evaluation of Nitrate Content of Ground Water in Hall County, Nebraskaa

Abstract

ABSTRACTNitrate concentrations in ground water are low, less than 10 mg/l, in most parts of Hall County. Water from 46 percent of the sampled wells had nitrate concentrations greater than 10 mg/l, and 13 percent had greater than 45 mg/l. Sharp contrasts in concentrations occurring within short distances are common. Seasonal changes and a progressive increase of nitrate concentrations have occurred in some observed wells. Concentrations decrease with increasing well depth and well penetration below the water table. Nitrate in ground water is stratified where the concentration is high. Highest concentrations are found at or near the water table in the vicinity of sampled wells located close to a potential nitrate source. Potential sources of nitrate in the ground water of Hall County are fertilizers, feedlots, septic‐tank effluents, seepage from the Wood River, precipitation, and soil fertility. Whereas seepage from the Wood River contributes nitrate to ground water adjacent to the stream, seepage from the Platte River dilutes the nitrate content of ground water. The hydraulic conductivity of the unsaturated zone is an important factor in controlling nitrate content of ground water.