|Magette, William - UN.COLLEGE,DUBLIN IRELAND|
Submitted to: Water Resources Research
Publication Type: Proceedings
Publication Acceptance Date: October 20, 2001
Publication Date: March 10, 2001
Citation: HUBBARD, R.K., MAGETTE, W.L., SHERIDAN, J.M. APPLICATION OF A WATERSHED SCALE RANKING SCHEME FOR EVALUATING IMPACTS OF AFOS ON WATER QUALITY. WATER RESOURCES RESEARCH. p. 682-685. 2001. Interpretive Summary: Contamination of soils, surface water, and ground waters from animal wastes is an environmental concern. Intensive animal operations can result in high nitrogen (N) or phosphorus (P) loading rates to soils and waters. A framework is needed for evaluating specific soils, landscapes, farming systems, and their management for potential loss and delivery of nutrients from animal feeding operations (AFOs) to water bodies. A ranking system designed by Magette which estimates potential nutrient loss hazard was evaluated for potential P loss from two subwatersheds of the Shannon River in Ireland. The Magette scheme includes factors and weights for 1) Nutrient Usage, 2) Condition of Receiving Waters, 3) Ratio of Land to Water, 4) Farmyard Conditions, 5) Nutrient Application Rates, 6) Nutrient Application Times, 7) Soil Test P, 8) Overland Flow Distance, and 9) Runoff Risk. Results from the ranking were compared with water quality. The ranking system was found to correctly match potential P losses with what actually occurred. The Magette P ranking scheme is currently being tested with data from the Little River Watershed (LRW) located in the Coastal Plain of southeast Georgia. Two subwatersheds with differing land use and intensities of animal feeding operations are being compared. The concepts and information from this research are important to scientists and land managers responsible for practices which ultimately impact on soil and water quality.
Technical Abstract: Nonpoint sources of nitrogen (N) and phosphorus (P) leaving the agricultural landscape can cause eutrophication of surface water with associated degradation of water quality. Land use managers need tools to assist in making informed land use decisions and prescribing management practices to minimize potential N and P losses to water resources. A ranking scheme including both management practices and hydrologic and landscape properties was devised by Magette for both farm and watershed scale use. The scheme includes factors and weights for (1) Nutrient Usage, 2) Condition of Receiving Waters, 3) Ratio of Land to Water, 4) Farmyard Conditions, 5) Nutrient Application Rates, 6) Nutrient Application Times, 7) Soil Test P, 8) Overland Flow Distance, and 9) Runoff Risk. This paper presents the concepts involved in applying multi-parameter assessments to the landscape and using the assessment results to provide additional land management information relative to animal feeding operations (AFOs). The assessments proposed are intended to be a first step toward providing an objective basis by which to make environmental decisions about land management, both at the field and watershed level. The paper also presents results of using the ranking system to compare two different watershed subareas having different intensities of AFOs and compares the ranking system results with observed water quality measurements.