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United States Department of Agriculture

Agricultural Research Service

Title: The Importance and Role of Watersheds in the Transport of Nitrogen.

Authors
item Sauer, Thomas
item Alexander, Richard - USGS
item Brahana, John - UNIVERSITY OF ARKANSAS
item Smith, Richard - USGS

Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: July 11, 2001
Publication Date: December 9, 2001
Citation: SAUER, T.J., ALEXANDER, R.B., BRAHANA, J.V., SMITH, R.A. THE IMPORTANCE AND ROLE OF WATERSHEDS IN THE TRANSPORT OF NITROGEN. FOLLETT,R.F., HATFIELD, J.L., EDITORS. ELSEVIER SCIENCE PUBLISHERS, THE NETHERLANDS. NITROGEN IN THE ENVIRONMENT: SOURCES, PROBLEMS, AND MANAGEMENT. BOOK CHAPTER. 2001. P. 147-181.

Interpretive Summary: A watershed is an area of land where all the surface water eventually flows to one stream, river, or lake. Nutrients, especially nitrogen and phosphorus, are some of the most common pollutants of surface water. When lakes and streams have high amounts of nutrients in them, there is often excessive growth of algae and weeds, which can cause fish kills and limit recreational uses of these waters. Many studies have been conducted to measure nutrient movement in watersheds including where the sources of nutrients are and how they reach the stream or lake. This chapter summarizes information from watershed studies of nitrogen movement. Nitrogen transport is complicated because different land uses like agriculture and urban have different sources of nitrogen and different pathways for the water that transports nitrogen. Watersheds that have more fertilizer and manure applied to the soil tend to have more nitrogen moving downstream to the outlet. The results of this research can be used by land managers to help understand the processes of nitrogen movement in the environment and how land use and climate affects the amount of nitrogen that is transported.

Technical Abstract: A recent report to Congress indicated that nutrients, primarily nitrogen (N) and phosphorus (P), contributed to the impairment of 30% or 135,000 km of the nation's impaired rivers and streams, 44% of the impaired lakes, and 23% of the impaired estuaries. The movement of N in the terrestrial environment is intimately related to the movement of water. Water in the form of precipitation, flowing across the soil surface as runoff, and percolating through soil layers to ground water can be a significant carrier of organic and inorganic N constituents. The relative importance of these transport mechanisms is a complex function of N sources and transformations, hydrologic processes, climate patterns, and land use. While some elements of the N cycle can be studied in the laboratory under controlled experimental conditions, many can be studied in a meaningful way only in the natural and culturally affected environments of watersheds. The strengths of watershed-scale evaluations include easily definable hydrologic boundaries, identification of N sources with respect to water flow patterns, and a convenient, integral measure of water-quality response at a single point (the basin outlet). The objective of this chapter is to synthesize current understanding of the major processes and controls affecting N transport in watersheds. The scope is limited to technical issues of flow and chemistry of fixed (i.e. biologically reactive) organic and inorganic N forms in watersheds.

Last Modified: 8/21/2014
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