The Chapter 12, “Modeling for Total Maximum Daily Load (TMDL) Implementation,” in the ASCE Manual of Practice 150, “TMDL Development and Implementation: Models, Methods, and Resources,” written by the ASCE-EWRI TMDL Analysis and Modeling Task Committee, discusses state-of-the-practice on uses of models in TMDL implementation planning, and reviewed six watershed models found in implementation planning of TMDLs by stakeholders. The Committee is currently expanding the work as follows.

The six models reviewed will be further reviewed along with other models such as, USEPA’s Green Infrastructure (GI) Modeling Toolkit along with existing best management practice (BMP) and low impact development (LID) simulation models, L-Grld model aimed at designing GI with stakeholder engagement, decision support tools for stormwater management, and other watershed and receiving waterbody models (e.g., IRIC simulating flow and morphodynamics in rivers) that may advance TMDL implementation state-of-the-practice. Uses of these modeling tools, which may have barriers and challenges (e.g., data limitations), will be addressed. Non-traditional approaches with more realistic and cost-effective implementation will be looked-into, along with broadening the scope of TMDL to combine with other similar efforts and avoiding conflicts.

Designing the implementation measures before going into the ground is a crucial step and will be addressed including selection of BMPs (e.g., from single, multiple, or using existing), engaging stakeholders, managing multiple co-benefits and diverse costs, subjective preferences, and unintended consequences. Emerging technologies (e.g., remote sensing) will be further looked-into from the perspective of evaluating efficacy of the implementation measures in the long run.

A progress on the above work will be presented and feedback from the audience will be encouraged.