| Abstract: | ABSTRACT: Protecting surface water quality in watersheds undergoing demographic change requires both the management of existing threats and planning to address potential future stresses arising from changing land use. Many reservoirs and threatened waterbodies are located in areas undergoing rapid population growth, and increases in density of residential and commercial land use, accompanied by increased amount of impervious surface area, can result in increased pollutant loading and degradation of water quality. Effective planning to address potential threats, including zoning and growth management, requires analytical tools to predict and compare the impacts of different management options. The focus of this paper is not on developing demographic projections, but rather the translation of such projections into changes in land use which form the basis for assessment of future watershed loads. Land use change can be forecast at a variety of spatial and temporal scales. A semi-lumped, GIS-based, transition matrix approach is recommended as consistent with the level of complexity achievable in most watershed models. Practical aspects of forecasting future land use for watershed assessment are discussed. Several recent reservoir water supply projection studies are used to demonstrate a general framework for simulating changes in land use and resulting impacts on water quality. In addition to providing a technical basis for selecting optimal management alternatives, such a tool is invaluable for demonstrating to different stakeholder groups the trade-offs among management alternatives, both in terms of water quality and future land use patterns within the watershed. |
