Optimal Best Management Practices (BMPs) Placement Strategies - Application to Fei-Tsui Reservoir Watershed in Taiwan

The nonpoint source pollution control is in the beginning stage in Taiwan. Currently, the soil and water conservation law provides regulations that the land developer should retain the exceeding stormwater runoff and sediment due to any significant development in the watershed. Most of stormwater controls have been designed at the local, or on-site level, but not at the regional or watershed level in a comprehensive and systematic manner. The purpose of this study is to establish an optimization model for the optimal placement of structural Best Management Practices (BMPs) at the watershed scale. The complete model consists of two interacting components, i.e. an optimization model base on dynamic programming (DP) and a zero-dimensional reservoir water quality model. To search for the optimal placement strategy of BMPs system, a preliminary procedure is needed to find suitable sites for various BMPs construction in Fei-Tsui Reservoir watershed in northern Taiwan. The landuse type, terrain and land ownership are taken into consideration by using a geographic information system (GIS). In the optimization model, the objective function is to minimize the total construction cost of BMPs and constraints consider water quality standards for total phosphorus and suspended solid concentrations in the reservoir. Also, the zero-dimensional reservoir water quality model of Vollenweider type is embedded in the whole optimization framework to estimate the average pollutant concentrations after pollutants from nonpoint source pollution flow into Fei-Tsui Reservoir. Due to the advantages of DP, the most cost-effective BMPs placement strategies can be found in this study. The trade-off curves between the resulting optimal cost and benefit of water quality improvement can be found which provide the decision makers with clear and useful information for nonpoint pollution control and management at the watershed scale.