Submitted by Rupak Thapaliya on Tue, 2009-04-21 11:45
In an order issued last week, FERC approved a new flow schedule for the Cresta reach of the North Fork Feather River. Coalition members California Sportfishing Protection Alliance (CSPA) and American Whitewater (AW) were instrumental in achieving the improved flows in the river.
While the new flow regime was designed largely to be more protective of Foothill Yellow-Legged Frogs, it will also provide additional opportunities for whitewater recreation.
Journal of the American Water Resources Association
We evaluated the impact of land cover on fish assemblages by examining relationships between stream hydrology, physicochemistry, and instream habitat and their association with fish responses in streams draining 18 watersheds of the Lower Piedmont of western Georgia. Several important relationships between land use and physicochemical, hydrological, and habitat parameters were observed, particularly higher frequency of spate flows, water temperatures, and lower dissolved oxygen (DO) with percentage impervious surface (IS) cover, higher habitat quality with percentage forest cover, and elevated suspended solid concentrations with percentage pasture cover. Fish assemblages were largely explained by physicochemical and hydrological rather than habitat variables. Specifically, fish species diversity, richness, and biotic integrity were lower in streams that received high frequency of spate flows. Also, overall fish assemblage structure as determined by nonmetric multidimensional scaling was best described by total dissolved solids (TDS) and DO, with high TDS and low DO streams containing sunfish-based assemblages and low TDS and high DO streams containing minnow-based assemblages. Our results suggest that altered hydrological and physicochemical conditions, induced largely by IS, may be a strong determinant of fish assemblage structure in these lowland streams and allow for a more mechanistic understanding of how land use ultimately affects these systems.
Brian S. Helms, Jon E. Schoonover, and Jack W. Feminella
We propose a hierarchical system of classifying stream habitats based on three increasingly fine descriptions of the morphological and hydraulic properties of channel geomorphic units. We define channel geomorphic units as areas of relatively homogeneous depth and flow that are bounded by sharp gradients in both depth and flow. Differences among these units provide a natural basis for habitat classification that is independent of spatial scale. At the most general level of resolution, we divide channel units into fast- and slow-water categories that approximately correspond to the commonly used terms "riffle" and "pool." Within the fast-water category, we identify two subcategories of habitats, those that are highly turbulent (falls, cascades, chutes, rapids and riffles) and those with low turbulence (sheets and runs). Slow-water habitats include pools formed by channel scour (eddy pools, trench pools, midchannel pools, convergence pools, lateral scour pools and plunge pools) and those formed behind dams. Dammed pools include those obstructed by debris dams, beaver dams, landslides and abandoned channels. We consider backwaters as a type of dammed pool. Fishes and other stream organisms distinguish among these habitats at one or more levels of hierarchy. Habitats defined in this way represent an important habitat templet on which patterns of biological diversity and production form. We believe that a hierarchical system of classification will facilitate understanding of biotic-habitat relationships in streams and lead to more effective methods of evaluating the effects of environmental change on stream ecosystems. Refining the criteria by which habitats are distinguished, quantifying how different species use different habitats, and integrating the ways biota respond to habitat variation should facilitate We believe that a hierarchical system of classification will facilitate understanding of biotic-habitat relationships in streams and lead to more effective methods of evaluating the effects of environmental change on stream ecosystems. Refining the criteria by which habitats are distinguished, quantifying how different species use different habitats, and integrating the ways biota respond to habitat variation should facilitate the emergence of a theory of stream habitat organization.
Hawkins, Charles, Kershner, Jeffery, Bisson, Peter
We evaluated sampling variability of stream habitat sampling methods used by the USDA Forest Service and the USDI Bureau of Land Management monitoring program for the upper Columbia River Basin. Three separate studies were conducted to describe the variability of individual measurement techniques, variability between crews, and temporal variation throughout the summer sampling season. We quantified the variability between crews and through time, and described the percent of the total variability attributed between crew and seasonal variability. We then estimated the number of samples needed to detect change between managed and reference sites. Differences among streams accounted for a larger share of the total variability than did differences among observers. Stream variability was greater than 80 percent of the total variability for 12 of the 16 variables measured. This is somewhat surprising given the similarities between the study streams. Observer variability was minimal for stream habitat methods describing reach, streambank, and cross-section variables. Conversely, variability was higher for pool, large woody debris, and substrate variables. Seasonal variation was minimal for stream channel variables with the exception of substrate particle sizes. Sample sizes derived from both observer and stream variability (type I error 0.1, type II error 0.9, minimum detectable change 10 percent) ranged from 10 to 3,502 sites to detect changes between two populations. We believe that these estimates represent an unambiguous and powerful way to display the consequences of variability to scientists and managers.