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<br />e <br /> <br />e <br /> <br />Ie <br /> <br />PREFACE <br /> <br />This report presents guidelines and procedures for hydrologic <br />investigations of "ungaged" watersheds, that is, watersheds for which <br />available streamflow data are insufficient for making dependable <br />discharge-frequency estimates by statistical procedures. Data availability <br />may vary from the extreme of none at all to situations where some <br />discharge-frequency data can be used with a hydrologic model to extend the <br />aischarge-frequency curve to estimate less-frequent events. The hydrologic <br />model can also be used to develop discharge-frequency relationships at <br />ungaged locations in the basin, <br /> <br />The procedures presented center on computer program HEC-l, a <br />general-purpose watershed-modeling program package developed at the <br />Hydrologic Engineering Center (HEC) of the U,S, Army Corps of Engineers. The <br />analysis techniques, developed at HEC, have been used in a number of studies <br />of ungaged watersheds, Examples from three studies are used herein to <br />illustrate use of the procedures, <br /> <br />This report discusses general approaches to frequency analyses for <br />ungaged watersheds, effects of the extent of data availability on choice of <br />approach, and regionalization of hydrologic parameters, Hypothetical <br />rainfall data are often the only rainfall data available for a study, so <br />methods for use of this type of data are presented. The use of HEC-l for <br />watershed modeling is described, and techniques are given in detail for the <br />estimation and calibration of HEC-l model parameters. <br /> <br />xi <br />