DOMESTIC WELL WATER-QUALITY IN RURAL NEBRASKA - FOCUS ON NITRATE-NITROGEN, PESTICIDES, AND COLIFORM BACTERIA

For this statewide assessment. 1808 wells were sampled and a data base compiled that included water-quality data (NO3-N, pesticides, colifor m bacteria) and site-specific data collected at each location. Domesti c, rural water quality in Nebraska varies substantially from one groun d water region to another and is a function of well characteristics, d istances to potential contamination sources, and hydrogeologic and sit e characteristics. The percentage of wells exceeding the 10 ppm MCL fo r NO3-N ranged from 3 to 39 percent, depending on the ground water reg ion. This large range of values indicates the inadequacy of stating th at an average of 19 percent of domestic wells in Nebraska are contamin ated by nitrates. This statistic does not describe the nature, extent, and variability of the contamination problem. Depending on the ground water region, the degree of nitrate contamination in rural domestic d rinking water wells has remained generally unchanged or has only sligh tly increased since the last statewide assessment conducted from 1985 to 1989. Bacterial contamination has either remained the same or has d ecreased. The percentage of wells affected by bacteria ranged from 8 t o 26 percent, depending on the ground water region. Statewide, about 7 0 wells, or 4 percent of the wells sampled, had detectable pesticide l evels, of which atrazine was the most common. Eighty-two percent of th e detections were in the Platte River Valley or in the South Central P lains, both of which are characterized by heavily irrigated corn and a statistical association between nitrate and atrazine contamination. T o improve the quality of domestic drinking water will require a combin ation of activities, including the application of best management prac tices specific to a ground water region and individual action at rural households, such as conducting sanitary surveys of existing wells bef ore installing new wells.