Spatio-temporal linkages between hydrologic and ecologic dimensions of watersheds play a critical role in conservation policies. Habitat potential is influenced by variation along longitudinal and lateral gradients and land use disturbance. An assessment of these influences provides critical information for protecting watershed ecosystems and in making spatially explicit, conservation decisions. We use an ecohydrologic approach that focuses on interface between hydrological and ecological processes. This study focuses on changes in watershed habitat potentials along lateral (riparian), and longitudinal (stream order) dimensions and disturbance (land use). The habitat potentials were evaluated for amphibians, reptiles, mammals, and birds in the Westfield River Watershed of Massachusetts using geographic information systems and multivariate analysis. We use a polynomial model to study nonlinear effects using robust regression. Various spatial policies were modeled and evaluated for influence on species diversity. All habitat potentials showed a strong influence along spatial dimensions and disturbance. The habitat potential for all vertebrate groups studied decreased as the distance from the riparian zone increased. Headwaters and lower order subwatersheds had higher levels of species diversity compared to higher order subwatersheds. It was observed that locations with the least disturbance also had higher habitat potential. The study identifies three policy criteria that could be used to identify critical areas within a watershed to conserve habitat suitable for various species through management and restoration activities. A spatially variable policy that is based on stream order, riparian distance, and land use can be used to maximize watershed ecological benefits. Wider riparian zones with variable widths, protection of headwaters and lower order subwatersheds, and minimizing disturbance in riparian and headwater areas can be used in watershed policy. These management objectives could be achieved using targeted economic incentives, best management practices, zoning laws, and educational programs using a watershed perspective.

Impact of climate change and land use on watershed runoff involves multiattribute ecohydrologic interactions. This information is critical to development of comprehensive storm water management policies. Watersheds in the continental United States have diverse temperatures and precipitation regimes and varying hydrogeomorphic features that influence runoff. This study investigates watershed-scale runoff using statistical modeling for storm water policy optimization. Multivariate statistical modeling show that vegetative activity, annual evaporation, precipitation, temperature, and soil moisture significantly influenced watershed runoff. Soil moisture has a strong influence on runoff with each percent increase causing 5% increase in runoff. Nonlinear modeling with quadratic and interaction effects shows a significant interaction between soil moisture and other climatic variables in influencing annual runoff patterns. Changes in climate affect ecohydrologic characters by altering available soil moisture, evaporation, precipitation patterns, and runoff. Optimization of green infrastructure design can be a successful management tool for runoff with an understanding that changes to multiple attributes in ecohydrologic variables affect runoff. Multi-attribute-based green infrastructure and incentive policies can result in comprehensive storm water policies that incorporate climatic and ecohydrologic conditions of watershed systems.

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A watershed-based assessment is used to assess the effect of urbanization on vertebrate habitat potential in Westfield River Watershed in Massachusetts, USA. A spatial analysis is used to develop urban indicators and habitat potential for each subbasin in the watershed. It is observed that threshold effect of urbanization on habitat potential of vertebrates is at 10 to 12 percent impervious cover. Amphibian habitat is influenced by available open space and land use disturbance in the watershed. The reptile habitat is sensitive to impervious coverage and land use disturbance, and decreased with fragmentation. The habitat for birds is influenced by land use disturbance, human population densities, size of forest patch, and open space in the watershed. Mammal habitat is influenced by human population density, land use disturbance, and fragmentation. A watershed-based assessment is useful to identify critical areas of high urban influence. Threshold values and nature of interactions between urbanization and habitat are assessed and used in policy recommendations. Policies and practices that minimize effects of urbanization in the watershed include impervious taxes, zoning policies, and open space protection. The need for provision of education and information on the relationship between urbanization and habitat potential is emphasized for sustainable use of watershed resources.

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