The concentration of nitrate-nitrogen is shown in the following figure. The concentration expressed as milligrams/liter (mg/L) is the same as parts per million (ppm). The safe drinking water standard for public water supplies is 10 ppm (or 10 mg/L) of nitrate-nitrogen. Water quality is most severely affected in the Platte River Valley and in the Eastern Sandhills region. Preventing further water quality degradation or improving water quality requires careful irrigation management along with proper fertilizer management.