Nutrient enrichment and criteria
 
Nutrient enrichment and criteria
Nuisance plant growth is noted in streams across                the nation because of elevated concentrations of nutrients. In fact,                concentrations of phosphorus exceeded the USEPA desired goal for                phosphorus for preventing nuisance plant growth in streams (0.1                parts per million) in about 75 percent of agricultural and urban                streams sampled by the NAWQA Program. It is difficult and premature,                however, to attempt a national summary of the effects of eutrophication                because methodologies are limited for deriving criteria based only                on nutrient concentrations. In recognition of these limitations,                USEPA, in collaboration with USGS and other federal agencies, and                state agencies, is developing a strategy to evaluate aquatic plant                growth and to develop an understanding of stream nutrient dynamics,                stream habitat (including shading and temperature), turbidity, and                algal-growth processes.
We will work with states and tribes to develop a                methodology for deriving criteria, as well as developing criteria                where data are available, for nitrogen and phosphorus runoff for                lakes, rivers, and estuaries by the year 2000. We intend to develop                such criteria on a regional basis using scientifically defensible                data and analysis of nutrients, such as those available from the                USGS. We will assist states and tribes in adopting numerical nutrient                criteria as water-quality standards by the end of 2003 (Robert Cantilli,                Nutrients Criteria Coordinator, USEPA, U.S.                Geological Survey Circular 1225 , 1999).
NAWQA also works with individual states on nutrient standards and                criteria.
State of Louisiana�USGS works with the Louisiana Department                of Environmental Quality to develop nutrient criteria using NAWQA                information on chlorophyll a in the Acadian-Pontchartrain Basins.                According to Louisiana Department officials, "The largest, most                consistent source of chlorophyll a data for Louisiana comes from                NAWQA sites.�
State of Texas�NAWQA data for nutrients collected in the                Trinity River Basin are used by the Trinity River Authority to develop                nutrient criteria for streams.
Factors affecting nutrient enrichment
NAWQA information is used to assess factors affecting                eutrophication, both regionally and locally.
Mississippi River Basin and the Gulf of Mexico� NAWQA scientists                participate in a multi-agency effort, coordinated by the White House                Committee on Environmental Natural Resources (CENR), to assess nutrient                enrichment, eutrophication, and the effects of hypoxia (low oxygen                conditions) in the Gulf of Mexico. Specifically, NAWQA is modeling                sources and transport of nutrients using a spatially referenced                computer model throughout the Mississippi River watershed. The model                tracks the sources (including point sources, fertilizer, livestock                wastes, nonagricultural land, and atmospheric deposition) and movement                of nutrients in individual stream reaches across the watershed.                The effort has demonstrated key roles that hydrology and natural                processes play in the transport of nutrients to, and eutrophication                in, the Gulf of Mexico. Specifically, closer proximity of nitrogen                sources to large streams and rivers increases the transport of nutrients                to the Gulf. This is because nitrogen is not removed as readily                in the large streams and rivers by natural processes as in the smaller                tributaries and is, therefore, much more likely to reach a coastal                area if it originates close to a larger river. As a result, some                watersheds in the Mississippi River Basin are much more significant                contributors of nitrogen to the Gulf of Mexico than others, despite                similar nitrogen sources or similar distances from the Gulf.
State of North Carolina�NAWQA findings are used by the North                Carolina Department of Environment and Natural Resources to help                control excessive nutrients and resulting algal blooms, fish kills,                and Pfiesteria incidents in the Neuse and Tar-Pamlico Rivers. For                example, the findings led to the implementation of buffers in the                Neuse River, which proved to effectively reduce nutrient runoff                to the surface water. In addition, NAWQA research on the role of                organic matter in streambed sediment in removing nitrate from ground                water in some areas of the Coastal Plain has allowed the State to                prioritize its efforts in streams where elevated nitrate is not                as easily removed under natural conditions.
The St. Croix National Scenic Riverway (NSR) was established                in 1968 under the National Wild and Scenic Rivers Act. In the early                1990�s continued development and usage of the St. Croix River concerned                water resource managers about the impact on water quality. Research                from the NAWQA Program provided evidence that nutrient loading from                the tributaries was increasing the rate of eutrophication in Lake                St. Croix, a sink of the St. Croix River Basin. In response to these                threats, a cooperative agreement was signed in 1993 by the National                Park Service, the Minnesota Department of Natural Resources, the                Wisconsin Department of Natural Resources, and the Minnesota Pollution                Control Agency. To date, the partnership that was formed (St. Croix                Basin Water Resources Planning Team) has relied heavily on data                from NAWQA to implement a protection strategy for the St. Croix                River (Pam Davis, Coordinator, St. Croix Basin Water Resource                Planning Team, March 2001).