Integrated watershed management modeling: Generic optimization model applied to the Ipswich River Basin

A generic integrated watershed management optimization model was developed to efficiently screen a broad range of technical, economic, and policy management options within a watershed system framework and select the optimal combination of management strategies and associated water allocations for designing a sustainable watershed management plan at least cost. The watershed management model integrates both natural and human elements of a watershed system including the management of ground and surface water sources, water treatment and distribution systems, human demands, wastewater treatment and collection systems, water reuse facilities, nonpotable water distribution infrastructure, aquifer storage and recharge facilities, storm water, and land use. The model was formulated as a linear program and applied to the upper Ipswich River Basin in Massachusetts. Our results demonstrate the merits of integrated watershed management by showing (1) the relative efficacy and economic efficiency of undervalued or underutilized management options such as incentive pricing; (2) the value of management strategies that serve several functions such as the benefits of increased infiltration for meeting both storm water and water supply management objectives; and (3) that both human and environmental water needs can be met by simultaneously implementing multiple diverse management tools, which in this case study led to achieving 70% of the recommended in-stream flow with only 25% decrease in net benefits.