Total maximum daily load, or TMDL, is defined by the U.S. Environmental Protection Agency as the calculation of the maximum amount of a pollutant allowed to enter a waterbody. By establishing TMDLs, states and localities can improve water quality by setting pollution limits. Originally stemming from the 1972 Clean Water Act, TMDL development and implementation has grown more complex over the past five decades. Because TMDLs have a narrow focus between pollutant loads and modeling, this, along with limited involvement by various parties, has hampered implementation. A disconnect has developed between critical parties in the water quality field and their understanding of the challenges associated with TMDL development. To get a better sense of the perceived problems, the ASCE Environmental & Water Resources Institute’s TMDL Analysis and Modeling Task Committee surveyed administrators, policymakers, environmental managers, and researchers or modelers.
In their paper “Rethinking TMDLs: Perspective Based on Community Survey,” authors Saurav Kumar, Sanaz Imen, Ebrahim Ahmadisharaf, Raquel Neri Barranco, Sumon Hossain Rabby, John J. Ramirez-Avila, Vamsi Sridharan, Craig Lott, Rosanna La Plante, Harry X. Zhang, and Nigel W. T. Quinn outline the survey and its findings. Their paper investigates the views of the survey respondents, identifying current limitations and proposing potential advancements in TMDL development and water quality modeling to inform more effective decision-making processes. Their findings suggest a desire for TMDL development to evolve to address the increasing complexity and variability of modern environmental challenges. Learn more about the methods, results, and limitations of the study, which will ensure TMDLs continue to help with maintaining water quality, in the Journal of Environmental Engineering at https://ascelibrary.org/doi/10.1061/JOEEDU.EEENG-8104. The abstract is below.
Abstract
The study investigated the perspectives of professionals involved in total maximum daily load development. A survey instrument was developed to understand the challenges and advancements necessary to enhance water quality management. This survey explored various dimensions of TMDL development, including identifying impaired waterbodies, water quality modeling, implementation, postimplementation assessment, and stakeholder engagement. Thirty-seven professionals involved in TMDL development took the survey. The results indicated a consensus on the need to reassess existing methodologies, particularly in the postimplementation phase, with a strong emphasis on the importance of sufficient funding for data collection. Limited resources, computational challenges, and a lack of trust in advanced models were identified as barriers to advancing water quality modeling. The participants also recognized the urgency of incorporating more validation data, especially through conventional monitoring and remote sensing, to enhance water quality modeling efforts. Although including social systems in modeling was considered crucial, it was not universally prioritized. This study developed a survey instrument to capture the evolving perspectives of stakeholders involved in TMDL processes. The survey’s structure provides a framework that can be improved and adapted for ongoing assessment and improvement. A continuous feedback mechanism, such as the one provided by the survey, is essential for ensuring that TMDL practices remain responsive to emerging challenges and are better equipped to manage water quality in an increasingly complex landscape.
Explore the findings in more detail in the ASCE Library: https://ascelibrary.org/doi/10.1061/JOEEDU.EEENG-8104.
