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Evaluation of Sediment Transport Models and Comparative Application of Two Watershed Models

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EPA/600/R-03/139 September 2003 Evaluation of Sediment Transport Models and Comparative Application of Two Watershed Models By Latif Kalin Oak Ridge Institute for Science and Education Cincinnati, Ohio 45268 and Mohammed M. Hantush National Risk Management Research Laboratory Office of Research and Development U.S. Environmental Protection Agency Cincinnati, Ohio 45268 National Risk Management Research Laboratory Office of Research and Development U.S. Environmental Protection Agency Cincinnati, Ohio 45268 Notice The U.S. Environmental Protection Agency through its Office of Research and Development funded the research described here. It has been subjected to the Agency’s peer and administrative review and has been approved for publication as an EPA document. This research was supported in part by an appointment to the Post Doctoral Research Program at the National Risk Management Research Laboratory, administered by the Oak Ridge Institute for Science and Education through Interagency Agreement No DW89939836 between the U.S. Department of Energy and the U.S. Environmental Protection Agency. Mention of trade names or commercial products does not constitute endorsement or recommendation for use. Foreword The U.S. Environmental Protection Agency (EPA) is charged by Congress with protecting the Nation’s land, air, and water resources. Under a mandate of national environmental laws, the Agency strives to formulate and implement actions leading to a compatible balance between human activities and the ability of natural systems to support and nurture life. To meet this mandate, EPA’s research program is providing data and technical support for solving environmental problems today and building a science knowledge base necessary to manage our ecological resources wisely, understand how pollutants affect our health, and prevent or reduce environmental risks in the future. The National Risk Management Research Laboratory (NRMRL) is the Agency’s center for investigation of technological and management approaches for preventing and reducing risks from pollution that threaten human health and the environment. The focus of the Laboratory’s research program is on methods and their cost-effectiveness for prevention and control of pollution to air, land, water, and subsurface resources; protection of water quality in public water systems; remediation of contaminated sites, sediments and ground water; prevention and control of indoor air pollution; and restoration of ecosystems. NRMRL collaborates with both public and private sector partners to foster technologies that reduce the cost of compliance and to anticipate emerging problems. NRMRL’s research provides solutions to environmental problems by: developing and promoting technologies that protect and improve the environment; advancing scientific and engineering information to support regulatory and policy decisions; and providing the technical support and information transfer to ensure implementation of environmental regulations and strategies at the national, state, and community levels. This publication has been produced as part of the Laboratory’s strategic long-term research plan. It is published and made available by EPA’s Office of Research and Development to assist the user community and to link researchers with their clients. Lee A. Mulkey, Acting Director National Risk Management Research Laboratory iii Abstract Suspended solids and sediments are regarded as the two leading pollutants of nation’s streams and waterbodies. They serve as carriers for various pesticides, radioactive materials and nutrients. Section 303(d) of the 1972 Clean Water Act requires states, territories, and authorized tribes to identify and list impaired waters every two years and to develop Total Maximum Daily Loads (TMDLs) for pollutants in these waters. Mathematical models are widely accepted, effective and powerful tools for TMDL development, and evaluating performances of Best Management Practices (BMP). The rapid pace of computer technology has been a milestone for mathematical models in hydrology, hydrodynamics and recently water quality. The high demand on computer models resulted in development of many models and placed a new burden on model users, that is model selection. The selection of the right model under certain constraints requires a comprehensive knowledge of the capabilities and features of available models. This report provides an overview and evaluation of sediment models and compares two distributed, watershed scale models by application to an experimental watershed. A probabilistic, risk-based mathematical optimization framework is presented and proposed as a strategy for solving the TMDL-BMP problem involving multiple stressors in feature endeavors. Future modeling efforts may benefit from exploring the use of system analysis approaches to obtain cost-effective, optimal load reductions using BMPs. The report is comprised of two parts. The first part evaluates and summarizes some of the key features of the most widely cited watershed scale, hydrodynamic and water quality models with the emphasis on TMDLs and BMPs. Reviewed models were selected based on minimum criteria. Water quality models, specifically those that can simulate nutrients in the environment are also considered since transport and fate of sediments and nutrients are intimately related phenomena. Among the reviewed loading models SWAT and AGNPS offer the most BMP alternatives at agricultural watersheds. For urban areas SWMM, and for mixed land uses, i.e. rural and urban, HSPF are identified as the most suitable loading models. These models need to be used with hydrodynamic and water quality models for a complete TMDL analysis and BMP development. BASINS and MIKE-SHE are comprehensive watershed-water quality modeling systems, with varying degrees of complexity. WMS offers a tractable watershed-modeling platform if fully developed can be used for sediment TMDLs allocation. Available and potential model linkages between loading, hydrodynamic and water quality models are also discussed. It is observed that most physically based models are incapable for a complete BMP assessment. As a future need in modeling, enhancement of such models to simulate more BMPs is recommended along with development of more linkages between loading and hydrodynamic/water quality models. The second part of the report evaluates, by application to an experimental watershed, two promising distributed watershed-scale sediment models in detail: KINEROS-2 and GSSHA. Sensitivity of KINEROS­ 2 to model parameters was evaluated within a probabilistic framework using Monte Carlo simulations to identify key model parameters for calibration. It was shown that the order of parameter sensitivities changes with the quantity of interest (peak flow, total sediment yield, etc.). The calibration/verification procedure performed over KINEROS-2 has shown that the Manning’s roughness and soil erosion parameters show systematic seasonal variations. Both models were calibrated and verified and the results clearly highlight the challenges modelers face when applying complex, distributed watershed models. The results are discussed and compared. They highlight the importance for numerical application of different watershed models to gauged watersheds as means for models evaluation. Future efforts aiming at the evaluation of hydrologic and water quality models should migrate from qualitative analysis to actual comparative applications to real case studies. iv Contents Foreword ....................................................................................................................................................... iii Abstract ..........................................................................................................................................................iv Figures ............................................................................................................................................................vi Tables ........................................................................................................................................................... vii 1 Introduction............................................................................................................................................1 1.1 Overview............................................................................................................................................1 1.2 Total Maximum Daily Loading (TMDL)...........................................................................................3 1.3 Mathematical Models.........................................................................................................................3 1.3.1 Brief History of Sediment Modeling ..................................................................................4 1.4 Risk Management Watershed Modeling ............................................................................................4 2 Model Classifications.............................................................................................................................8 3 Model Evaluation Criteria....................................................................................................................10 3.1 Screening Criteria ............................................................................................................................10 3.2 Evaluation Criteria ...........................................................................................................................10
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