The Total Maximum Daily Load (TMDL) Analysis and Modeling Task Committee of the American Society of Civil Engineers (ASCE) Environmental and Water Resources Institute (EWRI) was formed to address concerns over the current practices of analysis and modeling in TMDL development and implementation in terms of analysis technique and model selection, data requirement, calibration, validation, uncertainty reporting, margin of safety, etc. The committee reviewed the current practices of analysis and modeling in TMDL and documented an assessment of those in a book “Total Maximum Daily Load Analysis and Modeling: Assessment of the Practice,” published by ASCE in 2017. The committee expanded the report chapters into peer-reviewed journal articles for a special collection of the Journal of Hydrologic Engineering during 2018-2019 to support an ASCE manual of practice (MOP) on TMDL analysis and modeling with sound scientific basis and details, reviewed and accepted by the peers. Based on these publications, the Committee has completed writing a draft Manual of Practice on TMDL Analysis and Modeling with the following 12 chapters addressing various key topics on the subject.

CHAPTER 1 – Introduction

CHAPTER 2 – Watershed Models

CHAPTER 3 – Receiving Water Quality Models

CHAPTER 4 – Integrated Modeling Systems and Linked Models

CHAPTER 5 – Simple Models and Methods

CHAPTER 6 – Critical Condition Modeling and Analysis

CHAPTER 7 – Model Data, Geographical Information Systems and Remote Sensing

CHAPTER 8 – Model Calibration and Validation

CHAPTER 9 – Model Uncertainty Analysis and Margin of Safety

CHAPTER 10 – USEPA TMDL Report Archive and Report Search Tool

CHAPTER 11 – TMDL Analysis and Modeling Methodology: Model Selections

CHAPTER 12 – Modeling for TMDL Implementation

An overview of the Task Committee and the Manual of Practice will be presented along with some details on Chapter 2 – Watershed Models, in which 14 prevalent watershed models were selected and reviewed for their suitability and capability for TMDL development and implementation. The watershed models are: AGNPS/AnnAGNPS, ANSWERS2000, DWSM, GSSHA, GWLF, HEC-HMS, HSPF, KINEROS, LSPC, MIKE SHE, SWAT, SWMM, WAM, and WARMF.