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<br />001577 <br /> <br />31. 3lb <br /> <br />WATER INFORMATION MANAGEMENT SYSTEM HANDBOOK <br /> <br />31.3 - Data Needs. Maintenance flow quantification requires some basic <br />hydrologic data. These include streamflow, channel geometry, and watershed <br />characteristics data. <br /> <br />It is neither practicable nor reasonable, however, to presume that <br />streamflow data is necessary on all channels administered by the USDA <br />Forest Service before such channels can be managed so as to secure a <br />favorable condition of water flows. Therefore, the procedure is designed <br />to achieve the favorable flow objective without the benefit of on-site data. <br /> <br />31.31 - Streamflow Data. Obtain data for as many streamflow gaging <br />stations as practical within the area to be quantified. In most cases, the <br />USDI Geological Survey will be the only available source of these data. <br /> <br />31.31a - Criteria. Streamflow data utilized in the analysis should meet <br />the followlng criteria: <br /> <br />1. Flow regimes described by gaging station data should be <br />representative of areas where maintenance flows will be calculated. <br /> <br />2. Data should consist of at least a representative 10 years of <br />record. <br /> <br />3. <br />should <br />gaging <br /> <br />Gaging stations used in the analysis <br />have less than 10 percent of the total <br />station diverted or regulated. <br /> <br />of unregulated watersheds <br />annual flow volume above the <br /> <br />4. Data sets utilized should, as much as practicable, represent long <br />term average conditions. <br /> <br />31.31b - Gaging Station Data. <br />each gagi ng stat ion. However, <br />items. <br /> <br />The following data should be obtained for <br />not all methods require all listed data <br /> <br />1. Log-Pearson type III flood frequency analysis for the period of <br />record. <br /> <br />2. Log-Pearson type III low flow frequency analyses for 1- , 3- , <br />7- , 14- , 30- , and 90-day low flows. <br /> <br />3. Selected basin charact~ristics [such as mean basin elevation, and <br />drainage area]. <br /> <br />4. Flow duration data of daily mean discharges for periOd of record. <br /> <br />5. Mean annual discharge. <br /> <br />If. no. ) <br />8/2r;/87 <br />