The quality of our nation's waters: Nutrients in the nation's streams and groundwater, 1992-2004

• DOI: 10.3133/cir1350
• Publication Date: 2018-08-15T18:47:28Z
• Authors: Neil Dubrovsky; Karen R. Burow; Gregory M. Clark; JoAnn M. Gronberg; Pixie A. Hamilton; Kerie J. Hitt; David S. Mueller; Mark D. Munn; Bernard T. Nolan; Larry Puckett; Michael G. Rupert; Terry M. Short; Norman E. Spahr; Lori A. Sprague; William G. Wilber

National Findings and Their ImplicationsAlthough the use of artificial fertilizer has supported increasing food production to meet needs a growing population, increases in nutrient loadings from agricultural and, lesser extent, urban sources have resulted concentrations many streams parts aquifers that exceed standards for protection human health (or) aquatic life, often by large margins.Do NAWQA findings substantiate national concerns health?National Water-Quality Assessment (NAWQA) indicate groundwater basins with significant or development are substantially greater than naturally occurring "background" levels. For example, median total nitrogen phosphorus about 6 times background also routinely were 2 10 regional criteria recommended U.S. Environmental Protection Agency (USEPA) protect life. Such differences magnitude suggest reductions nutrients, as well land management strategies reduce transport nutrients streams, needed draining areas development.Nitrate above Federal drinking-water standard—or Maximum Contaminant Level (MCL)—of milligrams per liter (mg/L, nitrogen) relatively uncommon samples used drinking water deep aquifers; MCL is exceeded, however, more 20 percent shallow (less 100 feet below table) domestic wells areas. This finding raises rural where supply may warn future contamination deeper pumped public‑supply wells.Are levels decreasing?A decadal assessment trends 1993 2003 shows minimal changes those majority studied across Nation, upward downward at sites changes. These underscore need inputs would streams. Upward evident among all uses, including only minimally affected development, which suggests additional some our Nation's most pristine warrants consideration.The nitrate 495 increased significantly 3.2 3.4 mg/L (6 percent) during same period, proportion 16 21 percent. Nitrate likely increase next decade elevated moves downward. The potential requires attention because these commonly public supply, restoration costly difficult.Long-term consistent monitoring improved accounting sources, tracking modeling climatic landscape will be essential distinguishing concentrations, understanding causes trends, accurately effectiveness implemented manage nutrients.