Comprehensive Management and Modeling of Water Quantities: Utilizing an Existing Watershed Model for Comprehensive Water Management and Planning, and Optimal Design of Outlet Control Structures for Ecological Detention Ponds

Abstract

This dissertation research has three primary objectives. Firstly, this work examines the use of a statistical flow methodology for characterizing ecologically important stream flows, the Indicators of Hydrologic Alteration (IHA), as a means to evaluate hydrologic model performance. Typically, IHA has been used to identify the extent of human impacts on a stream's hydrology and to set management goals to restore the stream ecology. In this work, the use of the seven "extreme low flow" statistics of IHA is extended to the evaluation of the performance of a hydrologic simulation model under low flow conditions. Specifically, this work uses the IHA framework to evaluate the accuracy of the Chesapeake Bay Program Phase 5 (CBP5) watershed model during low flow events on a regional scale that is relevant to many water supply planners and managers. Because the CBP5 model's primary focus is predicting the Bay's water quality, the measures used to calibrate the CBP5 model focused primarily on the calibration of the entire hydrological record and had only secondary emphasis on specific flow regimes, ecodifference in a receiving stream can be calculated using the outflow hydrograph from a detention pond hydrologic simulator. First, a design approach-using a hydrologic model, detention pond model, and the ecodifference metric-is used to design a series of flow controls in a detention pond outlet control structure that reduces the ecological impact to the stream caused by development, while meeting current design regulations.Then, a simulation-optimization strategy that incorporates a genetic algorithm with the design approach is introduced to design an outlet control structure that best minimizes the ecological impact to the stream. For a case study site, optimized designs have demonstrated that improvements in ecological flows can be achieved while meeting design regulations. By introducing this approach for eco-detention ponds, and then ! iv! demonstrating its performance, this work has potential to impact stormwater management design practice.