Challenges of watershed implementation plans: Joe's bayou watershed

Authors: Moriasi, Daniel; BOYDSTUN, J - ASABE

Submitted to: Conference on Watershed Management to Meet Emerging TMDL Environmental Regulations
Publication Type: Proceedings
Publication Acceptance Date: 2/15/2007
Publication Date: 3/10/2007
Citation: Moriasi, D.N., Boydstun, J.R. 2007. Challenges of watershed implementation plans: Joe's bayou watershed. In: Proceedings of the Fourth Conference on Watershed Management to Meet Emerging TMDL Environmental Regulations, March 10-14, 2007, San Antonio, Texas. p.408-413.

Interpretive Summary: A watershed implementation plan is a written strategy and work plan used to achieve water resource goals. This study presents Joe’s Bayou watershed implementation plan as an example and some of the challenges encountered in developing that plan. Joe’s Bayou watershed is located in the Ouachita River Basin, Louisiana and covers a drainage area of about 173 square kilometers. This watershed is listed as impaired for dissolved oxygen (DO) and nutrients. The TMDL report recommends 89% reduction of total non-point source loading to meet the DO standard of 5 mg/L. The main goal of this study was to identify the sources of pollution and recommend best management practices and strategies to reduce pollutant levels. Land use types in Joe’s Bayou include cultivated agriculture (72%), pasture-idle (16%), forestry (7%), and miscellaneous (5%). Based on limited data collected in 1999 and 2005, there was no conclusive evidence to conclude that the watershed is impaired due to DO and nutrients. Possible reasons for this contradictory deduction include: 1) load reduction calculation is based on conservative critical condition and 2) a margin of safety to account for TMDL uncertainty, which may be unrealistic. Joe’s Bayou is also listed as impaired for total suspended solids (TSS), turbidity, and selected pesticides by EPA. The 1999 TSS and turbidity data analysis and a study completed by EPA in 2001 show that these impairments could have greater effects on water quality in Joe’s Bayou than the dissolved oxygen. However, the solution to the TSS and turbidity impairment may be somewhat related to that of DO impairment. Since pollution from agriculture was suspected of contributing to low DO, a high priority should be given to reducing NPS loading from farm fields using practices such as conservation tillage, crop nutrient management, pest management, and conservation buffers. These practices need to be implemented with a concerted effort by stakeholders within the watershed. The greatest need to improve Joe’s Bayou watershed implementation plan is the collection of long-term land use and management records, water quality and quantity data, and climatic information. These data will in turn be used for model the best management practices (BMPs) scenario simulations to determine the most effective agricultural BMPs and sections of the watershed where BMP placement would have the greatest impact.

Technical Abstract: Joe’s Bayou watershed is located in the Ouachita River Basin, Louisiana and covers a drainage area of about 173 square kilometers. This watershed is listed on the §303(d) List for Louisiana as impaired for dissolved oxygen (DO) and nutrients. The TMDL report recommends a reduction of 89% of total non-point source loading to meet the DO standard of 5 mg/L. The main goal of this study was to identify the sources of pollution and recommend best management practices and strategies to reduce pollutant levels. Land use types in Joe’s Bayou include cultivated agriculture (72%), pasture-idle (16%), forestry (7%), and miscellaneous (5%). Based on limited data collected in 1999 and 2005, there was no overwhelming evidence to conclude that the watershed is impaired due to DO and nutrients. Possible reasons for this contradictory deduction include: 1) load reduction calculation is based on conservative critical condition and 2) a margin of safety to account for TMDL uncertainty, which may be unrealistic. Joe’s Bayou is also listed on the §303(d) List for Louisiana as impaired for total suspended solids (TSS), turbidity, and selected pesticides by EPA. The 1999 TSS and turbidity data analysis and a study completed by EPA in 2001 show that these impairments could have greater effects on water quality in Joe’s Bayou than the dissolved oxygen. However, the solution to the TSS and turbidity impairment may be somewhat related to that of DO impairment. Since pollution from agriculture was suspected of contributing to low DO, a high priority should be given to reducing NPS loading from farm fields. Consequently, agricultural best management practices (BMPS) found in Volume 6 of the State of Louisiana Water Quality Management Plan need to be implemented with a concerted effort by stakeholders within the watershed. Some of the challenges that need to be addressed include insufficient data needed for modeling.