Human activities may contribute to the eutrophication of surface waters by
providing nutrients to aquatic ecosystems. Phosphorus is frequently identified as a
nutrient that is limiting to most aquatic ecosystems under natural conditions. Sources of
phosphorus contributing to eutrophic conditions often include nonpoint sources that are
dispersed across the landscape....
Fish assemblage structure was determined along a longitudinal
gradient for three drainages in the upper John Day basin: Middle
Fork, South Fork, and upper Mainstem proper. One or two tributaries
in each drainage were included. Where possible, sites were paired:
those with good versus those with poor riparian habitat. Detrended...
While resource managers often rely on feedback from recreation users on which to base long-term decisions, displacement (when users dissatisfied with crowding or resource impacts move on to more remote sites) and product shift (users respond to increased densities by changing their definition of the recreation experience) are viewed as...
This study used contingent valuation techniques to estimate the willingness of central Oregon Irrigators to donate a portion of their water rights to increase Deschutes River flow. This study was different from previous contingent valuation studies in that it used water rights as the payment vehicles instead of dollars -...
This report presents results of an investigation of water and streambed-sediment quality in selected tributaries of the South Umpqua River. Concentrations of inorganic constituents in water (major and minor ions, nutrients, and trace elements) and streambed sediment (primarily trace elements), along with standard field parameters, are tabulated for samples collected...
The Tualatin Basin landscape has undergone extensive change since the initiation of Euro-American settlement, with important consequences for basin hydrology and water quality. Changes that include the isolation of the Tualatin River from its floodplain areas, losses of important wetlands and riparian areas, and urbanization associated with population growth in...
This report presents estimates of land uses, concentrating on agricultural land in the Tualatin drainage basin. Acreage in different crop groups and agricultural water use and distribution in the watershed were estimated. The total amounts of nitrogen and phosphate applied to agricultural land and the average loading of nutrients per...
The Tualatin River Basin in Washington County, Oregon, is a complex area with highly developed agricultural, forestry, industrial, commercial, and residential activities. Population has grown in the past thirty years from fifty to over 270 thousand. Accompanying this population growth have been the associated increases in transportation, construction, and recreational...