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An Evaluation Framework for NPS TMDL Implementation
Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.orgCitation: Pp. 405-412 in Total Maximum Daily Load (TMDL) Environmental Regulations–II Proceedings of the 8-12 November 2003 Conference (Albuquerque, New Mexico USA), Publication Date 8 November 2003. .(doi:10.13031/2013.15588)
Authors: Author Thomas E. Davenport, Lyn Kirschner
Keywords: Adaptive management, TMDLs, NPS implementation plans, Evaluation, Indicators
A missing element in most approved TMDLs is an evaluation component. TMDLs identify the
point source and nonpoint source load reductions necessary to achieve water quality standards.
The point source load reductions are implemented and monitored through the NPDES Program.
The nonpoint source load reductions to be achieved are identified by pollutant source or
subwatershed. A water quality-based watershed plan that provides the implementation details
also needs to be developed to support the achievement of the necessary NPS reductions. The plan
identifies the Best Management Practices (BMPs) that will be supported, necessary information
and education activities, monitoring effort, implementation schedule, cost (administrative,
technical and financial incentives), and responsibilities. In order to ensure the necessary nonpoint
source load reductions are achieved, an adaptive management approach is recommended for
inclusion in the watershed management plan. The most defensible measure of the watershed
management efforts performance is a well-designed and implemented monitoring effort that
examines statistically the relationship between the projects activities and changes in water
quality. Monitoring during the nonpoint source implementation phase of a TMDL is done
primarily to ensure the management plan is correctly carried out. The monitoring results should
be able to check if assumptions about the direct, indirect and cumulative effects of management
activities on resources are valid. Thus, the monitoring effort is the key element in the adaptive
management of a watershed. There are five common designs utilized in watershed monitoring.
Each design relies on a different level and intensity of monitoring and answers different
questions at various levels of confidence. The watershed level monitoring effort enables the
implementing entity and the public to measure progress toward meeting pollutant load