Program is designed to assess the status of and trends in the quality of the Nation's water resources, and to gain a better understanding of the natural and human factors that affect water quality. Where more than one analysis was available for a well, this document refers to the mean concentration as the nitrate concentration for the well. Land use is the greatest influence over nitrate concentration.
Nitrate concentration is related in general to fertilizer and water usage .
Nitrate in drinking water is a health issue in parts of the Central Columbia Plateau. Land use practices are the dominant influence over the distribution and concentration of nitrate in ground water. Nitrogen fertilizers applied to fields are the primary source of nitrate in shallow ground water. Nitrogen fertilizers not used by crops can be carried to the underlying aquifer by water percolating through the soil. In the arid Central Columbia Plateau, irrigation water carries nitrate into shallow ground water.