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Table 1: RSRA indicator variables and the reasons for including them in the protocol. <br />CATEGORY AND <br />JUSTIFICATION FOR INCLUSION IN THE RSRA ASSESSMENT <br />VARIABLE <br />Dense algal growth may indicate nutrient enrichment and other types of pollution which may <br />Algal <br />Water Quality: <br />result in decreased dissolved oxygen in the water column and affect invertebrates and the ability <br />growth <br />of fish to spawn. <br />Channel <br />Water Quality: Solar exposure affects stream temperature and productivity. Decreased streambank vegetation <br />shading and solar cover, increased channel width, and reduced stream depth increases exposure, raises water <br />exposure temperatures and impacts aquatic life. Native trout usually require cool stream temperatures. <br />Channels that are deeply downcut or incised result in a reduced frequency of overbank flooding <br />Hydrogeomorphology: <br />into the adjacent flood plain during peak runoff or stream flows. The absence of flooding lowers <br />Floodplain connection <br />water tables, reduces nutrient availability in the floodplain, decreases plant germination, growth <br />and inundation <br />and survivorship, and may lead to the loss of riparian vegetation and the invasion of upland <br />frequency <br />species. <br />Steep and unstable vertical banks dominate many southwestern streams, limiting the physical <br />Hydrogeomorphology: <br />dynamics of aquatic ecosystems and increasing erosion and sediment loads through sloughing off <br />Vertical bank stability <br />of soils during high flow events. Steep banks may limit wildlife access to water. <br />Hydrogeomorphology: Fish and aquatic invertebrate diversity and population health is related to habitat diversity. <br />Hydraulic habitat Features such as oxbows, side channels, sand bars, gravel/cobble bars, riffles, and pools can <br />diversity provide habitat for different species or for the different life stages of a single species. <br />Hydrogeomorphology: Riparian soils reflect existing stream flow dynamics (e.g., flooding), management practices, and <br />Riparian area soil vegetation. It affects potential vegetation dynamics and species composition, as well as wildlife <br />integrity habitat distribution and quality. <br />Beavers are keystone species in riparian systems because they modify geomorphology and <br />Hydrogeomorphology: <br />vegetation, and reduce variance in water flows and the frequency of floods. Beaver dams and <br />Beaver activity <br />adjacent wet meadows provide important fish and plant nursery habitat. <br />Fish/Aquatic Habitat Fish and most aquatic invertebrates require perennial or constant flows to survive. Streams that <br />Loss of <br />Qualifier: were originally perennial but are now ephemeral no longer provide habitat for these species unless <br />perennial flows there are refuges that never dry out (e.g., permanent pools). <br />Fish use pools, with reduced current velocity and deep water, to rest, feed and hide from predators. <br />Pool <br />Fish/Aquatic Habitat: Many species use gravel-bottomed riffles to lay their eggs. The number, size, distribution, and <br />distribution quality of pools, and pool to riffle ratios indicate the quality of fish habitat. 1:1 pools to riffle <br />ratios are generally considered to be optimum. <br />Underbank cover is an important component of good fish habitat, used for resting and protection <br />Fish/Aquatic Habitat: <br />from predators. A number of aquatic invertebrates also use these areas. Underbank cover usually <br />Underbank cover <br />occurs with vigorous vegetative riparian growth, dense root masses, and stable soil conditions. <br />Low levels of gravel and boulder embeddedness on the channel bottom increase benthic <br />productivity and fish production. The filling of interstitial spaces between rocks with silt, sand, <br />Fish/Aquatic Habitat: <br />and organic material reduces habitat suitability for feeding, nursery cover, and spawning (egg to <br />Cobble embeddedness <br />fry survival) by limiting space and macroinvertebrate production. Increased embeddedness often <br />reflects increased sediment loads and altered water flow patterns. <br />The density and composition of aquatic invertebrates are strong indicators of stream health, <br />Fish/Aquatic Habitat: <br />including temperature stresses, oxygen levels, nutrients, pollutants, and sediment loads. Larvae <br />Diversity of aquatic <br />and adult macroinvertebrates provide critical food for fish and other invertebrate and vertebrate <br />invertebrates <br />species in stream-riparian ecosystems. <br />13 <br />