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<br />Sampling schedule <br /> <br /> <br />Initially, samples should be collected biannually. in early spring before upper basin runoff and <br /> <br /> <br />in fall after the summer thunderstorm season. This level of sampling intensity is a compromise <br /> <br /> <br />between monthly or quarterly sampling and annual sampling. Biannual sampling should be <br /> <br /> <br />adequate to provide sufficient information on taxonomic composition and abundance to evaluate <br /> <br /> <br />trends in invertebrate community responses to varying annual hydrologic regimes. The times <br /> <br /> <br />recommended for sampling represent two stable hydrologic periods. <br /> <br />Field methods <br />Sampling locations <br />Sampling reaches and potential sampling locations should be delineated on a set of office and <br /> <br />a set of field maps. Actual locations selected to be sampled each trip should be shown on both <br /> <br /> <br />sets of maps. The exact location of each sampling location should be determined in the field using <br /> <br /> <br />a portable global positioning system (GPS) unit. <br /> <br />Zoobenthos and organic matter <br /> <br />Zoobenthos and benthic organic matter should be collected using the most appropriate <br />sampling device for each habitat (Table 4). Both quantitative and qualitative zoobenthos samples <br />should be collected. Quantitative,samples should be used to evaluate changes in abundance of the <br />most common taxa. Methods may change as the study gets underway. however. based on <br />experience on these rivers, habitats should initially be sampled using the devices listed in Table 3. <br />Riffies and ~ble bars should be sampled using a Hess net witti a closed top. Main c~el and <br /> <br />7 <br />