Integrated watershed management modeling: Optimal decision making for natural and human components

Complex interactions among components of a watershed system necessitate the evaluation of management options within a watershed framework in order to realize the full impact of management decisions. A generic optimization model was developed to evaluate a broad range of technical, economic and policy management options within a watershed context. With continued development and urbanization, human impact on the hydrology of a watershed can be significant such that it not only impacts but dominates the system. Therefore, the model integrates natural and human elements of a watershed system. Since water demands consist of concurrent requirements for both water quantity and quality, the model was developed considering both the flow and the concentration of constituents to evaluate the full impact of management decisions. The initial application of the model to the upper Ipswich River Basin in Massachusetts is a linear programming formulation where quantity is considered in management decisions. A future version will include a nonlinear solution to the combined consideration of the quantity and quality impacts of various decisions.; Initial results demonstrate the relative efficacy of undervalued management options. The results also document the merits of integrated water resources management by demonstrating the value of management strategies that serve several integrated functions. For example, increased infiltration benefits both stormwater and water supply management. The model also successfully reveals that the apparent economic inefficiency of demand management occurs when consumptive demand is reduced and the pricing of wastewater services is based on water demand rather than actual wastewater flows.; "When one tugs at a single thing in nature, he finds it attached to the rest of the world." John Muir (1838--1914)...