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<br />e <br /> <br />\-. <br /> <br />I <br /> <br />e <br /> <br />e <br /> <br />parameters. In general, the model should be calibrated using measured flows <br />to ensure its proper formulation. <br /> <br />To permit basin mDdel1ng by a distributed-parameter approach, computer <br />program HEC-l contains kinematic-wave routing procedures for computing <br />subbasin outflow hydrographs and routing hydrographs through stream reacheS <br />(Hydrologic Engineering Center, 1980). These kinematic wave routing options <br />provide an alternative to the unit hydrograph method for determining direct <br />runoff. They also provide a streamflow routing technique which can be used <br />in place of the Muskigum, modified-PUIs, and other methods available in HEC-l. <br /> <br />A description of the kinematic-wave routing techniques available in <br />HEC-l is given in Chapter 7. Procedures for computing flow hydrDgraphs are <br />presented. The development of frequency estimates for this approach is in <br />general the same as when the unit hydrograph approach is used, once the <br />hydro graphs have been determined for various rainfall frequencies, <br /> <br />2,2 Regional Analysis of Watershed Characteristics <br /> <br />It is sometimes possible to transfer information from watersheds for <br />which data are available to nearby ungaged watersheds within a given region, <br />if they have very similar hydrological characteristics. If unit hydrograph <br />and loss rate parameters can be related to basin characteristics, then a <br />rainfall-runoff model such as HEC-l can be used to estimate discharge <br />information, <br /> <br />If a regional approach is used, care should be taken to select basins <br />that are indeed similar in hydrological characteristics. Thus, the basins <br />should have similar geological characteristics, tDpography, land uses, <br />vegetative cover, and agricultural practices. The basins should be of the <br />same general size, and the rainfall distribution and malJ1itude, as well as <br />the factors affecting loss rates, should be generally the same. <br /> <br />7 <br />