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USEPA REGION 10 REGIONAL ENVIRONMENTAL MONITORING AND ASSESSMENT PROGRAM: DISCHARGE
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The USEPA designed and implemented the Environmental Assessment Program (EMAP) to determine the current status, extent, changes, and trends in indicators of the condition of the Nations ecological resources on regional and national scales with known confidence. USEPA Region 10s Regional Environmental Monitoring and Assessment Program (REMAP) adapted EMAP procedures for inland surface waters for use at the regional level. The REMAP is a cooperative program between USEPA Region 10, the Washington Department of Ecology, and the Oregon Department of Environmental Quality. Sample sites were selected with a randomized, systematic design using Region 10s Reach File 3 as the basis of the stream population. The sample population was restricted to wadeable streams represented by the blue- line stream network on USGS 1:100,00 maps. In 1994, 60 sites were sampled in the Coast Range Ecoregion (30 sites per state) and 15 sites were sampled in the Yakima River Basin. The study was repeated in 1995. In 1996, only Oregon conducted sampling; 30 sites in the Coast Range Ecoregion. Instantaneous discharge was measured as a component of the physical habitat assessment. Several different methods of discharge measurement were used. The standard Velocity-Area Method was used in streams sufficiently large to use the electromagnetic or impeller-type water velocity meter. Water depth and velocity were measured at 15 to 20 equally-spaced intervals at one optimally chosen cross-section. In very small streams, discharge was measured by either using a portable weir or timing the filling of a calibrated bucket. Alternatively, the cross- sectional depth profile and time for a floating object to move through a measured length were measured. Total discharge was calculated in cubic feet/second. Data sets for other components of the physical habitat assessment are available for this study, as well as other related data sets (e.g., fish, water chemistry), and can be linked with this data set.