Submitted to: Encyclopedia of Life Sciences
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/28/2003
Publication Date: 12/20/2003
Citation: Sharpley, A.N., Krogstad, T., Mcdowell, R., Kleinman, P.J. 2003. Phosphorus transport in riverine systems. Encyclopedia For Life Sciences. p. 1-6. Interpretive Summary: The loss of phosphorus in agricultural runoff has been linked to an increased risk of surface water eutrophication. However, this risk can be changed when stream sediments modify phosphorus inputs to streams by various uptake and release processes. Thus, successful watershed management to minimize phosphorus loss requires consideration of not only phosphorus inputs, but also the fate of these inputs in fresh water systems, such as streams and rivers. Research described in this report shows that several interdependent riverine processes influence the amounts and forms of P transported from edge-of-field agricultural sources to the point of impact (i.e., river, lake, reservoir, and estuary). These processes will, thus, be critical in defining agricultural source management and in determining eutrophic response. Without information on the direction and magnitude of change in P transport in river systems, the degree to which agricultural Best Management Practices will remediate against impairment of receiving waters cannot be fully determined.
Technical Abstract: The role of phosphorus (P) inputs in accelerating eutrophication of freshwaters is well documented. The total load of P to a river can broadly be divided into point source inputs, typically dominated by sewage treatment effluents, and diffuse sources, often dominated by agriculture. There is a general increase in P transport in the order of rivers draining forested - native ecosystems, intensively managed agriculture, and urban settings. Point sources enter the river more continually through the year than do non-point sources, which are subject to large seasonal variation, typically as a function of overland flow. Changes in the forms and amounts of P during transport in streams and rivers can greatly influence the eventual impact of P loss on the degree of eutrophic response of receiving waters. These changes are mediated by physical (sediment deposition and resuspension and flow regimes), abiotic (P sorption and desorption), and biotic (microbial and plant uptake) processes.