Water Quality in Our Nation’s Streams and Groundwater

The U.S. Environmental Protection Agency (EPA) consistently ranks nutrients as one of the top three causes of degradation in U.S. streams and rivers. Nutrients can occur naturally in water, but elevated concentrations usually originate from man-made sources such as artificial fertilizers, manure, wastewater effluent, and atmospheric deposition from power plants. These nutrients can cause human illness and negative impacts on aquatic life. The findings of the NAWQA study, which analyzed nitrate, ammonia, total nitrogen, orthophosphate, and total phosphorus, are particularly important to consider in developing effective policies and actions to reduce pollution – so as to protect drinking water sources and control nutrient loadings to estuaries – as well as in developing nutrient criteria.

On September 24, 2010, the Environmental and Energy Study Institute (EESI), Water Environment Federation (WEF), Office of Senator Benjamin Cardin (D-MD), and Office of Senator George Voinovich (R-OH) held a briefing on nutrient conditions in the nation’s waters, their significance to human and aquatic health, and trends in conditions over time. The briefing released new information from the U.S. Geological Survey (USGS) National Water Quality Assessment Program (NAWQA). Speakers explained where, how, and when nutrients enter streams and ground water, how these factors and their impacts vary by region, and how much progress the nation has made in reducing excessive nutrient levels after decades of work by federal, state, and local governments.

This briefing was held in cooperation with the USGS Office of Water Quality and its National Water-Quality Assessment (NAWQA) Program.

• Phosphorous and nitrogen levels are above recommended maximum contaminant levels (MCLs) primarily because of non-point sources like agriculture and storm drainage, though there have been improvements in water quality by reducing contamination from point sources.
• Nutrient concentrations in streams are highest in urban watersheds, and in agricultural areas in the Northeast, Midwest, and Northwest.
• In streams draining agriculture and urban water sheds, all five nutrients studied — nitrate, ammonia, total nitrogen, orthophosphate, and total phosphorous — exceeded background concentrations at more than 90 percent of the 190 streams sampled.
• Subsurface tile drains deliver nitrogen from agriculture areas directly into streams, and are one of the highest contributors to nitrogen contamination. If drains are present, three times the amount of nitrogen is introduced into streams than in agriculture areas without these drains.
• Nutrient over-enrichment is one of the top five causes of impairments to streams in Ohio.
• Nitrate in groundwater exceeded background concentrations of 64 percent of the shallow wells sampled.
• In public supply wells, nitrate concentrations are low; however, levels are expected to increase as nutrient contamination from monitoring and private wells move into the public supply.
• There is extensive contamination of fresh water sources above recommended MCLs across the United States, and in most fresh water sources, contamination levels are increasing.
• To combat contamination issues, criteria must be established for acceptable nutrient levels using samples across a wide biological conditions gradient.
• EPA recognizes that we know a great deal about nutrient concentrations in fresh water, but the general population needs to take simple, common-sense steps to address the problem, and use regulations that are already in place.