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ARS Home » Southeast Area » Oxford, Mississippi » National Sedimentation Laboratory » Watershed Physical Processes Research » Research » Publications at this Location » Publication #186499
Title: DEVELOPMENT OF TMDL IMPLEMENTATION PLAN USING ANNAGNPS: A CASE STUDY

Author
item YUAN, YONGPING - UNIVERSITY OF MISSISSIPPI
item Bingner, Ronald - Ron
item THEURER, FRED - NRCS

Submitted to: Federal Interagency Sedimentation Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 4/4/2006
Publication Date: 4/4/2006
Citation: Yuan, Y., Bingner, R.L., Theurer, F. 2006. Development of TMDL implementation plan using ANNAGNPS: A case study. In: Proceedings of the 8th Federal Interagency Sedimentation Conference, April 2-6, 2006, Reno, Nevada. CDROM.

Interpretive Summary: The development of management practices used to reduce pollutants produced from agricultural fields entering stream systems is critical in improving overall watershed water quality. The evaluation of the effectiveness of conservation management practices is difficult because of the long-term data collection effort needed throughout a watershed system. In order to better assess conservation practices, computer simulation modeling tools have been developed to evaluate how much pollutants are produced and where they come from within watersheds. In addition, these tools serve as an aid in determining the most effective conservation practices that can be applied to minimize any downstream impacts on water quality. This study introduces the development of an implementation plan for Bayou LaFourche, one of the impaired sub-segments of Ouachita River Basin in the northern Louisiana. Bayou LaFourche is listed in the Modified Court Ordered 303(d) List for Louisiana as not fully supporting the designed use of propagation of fish and wildlife. The major causes for impairment cited in the 303(d) List is sediment and nutrients. The AnnAGNPS computer model was used to simulate amount of water and sediment generated from each user-specified computational area; thus, critical areas producing higher pollutants were identified. Then, AnnAGNPS was applied to simulate the impact of implementing alternative agricultural management options on high sediment producing areas. Through AnnAGNPS simulations, the impact of alternative agricultural management options for reducing non-point source pollution was ascertained. It was found that the best scenario would result in an 80 percent reduction in sediment loads at the watershed outlet.

Technical Abstract: Section 319 of the amended Federal Clear Water Act requires states to outline management plans for impaired water bodies to address non-point source pollution. When determining priority for conservation measures within a watershed for non-point source pollution control, models are valuable tools that can provide clues as to where potential sources of water pollution may be and which problems can most easily be corrected. The USDA Annualized Agricultural Non-Point Source Pollution model (AnnAGNPS) is such a model which has been developed to aid in the evaluation of watershed response to agricultural management practices. This paper presents the processes used for developing an implementation plan for Bayou LaFourche, one of the impaired sub-segments of Ouachita River Basin in the northern Louisiana. In this study, the AnnAGNPS model was used to simulate amount of water and sediment generated from each user-specified computational area and their contributions to the watershed outlet; AnnAGNPS was also applied to simulate the impact of alternative agricultural management options on the water quality. Through AnnAGNPS simulations, high sediment producing areas were identified and those areas should be the targeted areas for effective non-point source pollution control. The alternative agricultural management options for reducing non-point source pollution and their simulated impacts on water quality are also presented in the paper. Among all the alternative agricultural management options, scenario E would reduce sediment loads at the watershed outlet by 80 percent by converting 25 percent of the highest eroding cropland in the watershed to grassland.