US EPA

3349654 

Journal Article 

Factors affecting the response of small watersheds to precipitation in humid areas 

Hewlett, JD; Hibbert, AR 

1967 

Pergamon Press 

New York, NY 

Forest Hydrology 

11 

275-290 

English 

Customary separation of stream hydrographs into overland flow, interflow and base flow has little meaning when applied to most small watersheds. A revised description of runoff processes in forested headwaters relates quick rises in streamflow to variable source areas and subsurface translatory flow, or the rapid displacement of stored water by new rain. Because this makes the classification of hydrograph components difficult, if not impossible, a numerical rating system, the response factor, was developed from precipitation and streamflow records for use in classifying the hydrologic response of small watersheds in humid areas. A simple uniform hydrograph separation method was necessary to make inter-watershed and inter-regional comparison of response meaningful. Long-term hydrograph records from fifteen forested watersheds in eastern United States were separated into quick and delayed flow by computer and ranked according to mean precipitation, quick flow, and the response factors quick flow/precipitation and quick flow/total water yield. Similar data from nine agricultural watersheds allowed comparison of response among twenty-four small basins, systematically revealing important relationships not usually noted. The over-riding prevalence of subsurface flow was indicated and exceptions were pinpointed. Possibilities and advantages of mapping small watersheds or stream networks by a universal response factor were discussed. 

forest hydrology; hydrological flowpaths; variable source area; hydrology; stream network; intermittent streams; classification 

Hull, HW 

International Syposium on Forest Hydrology 

University Park, PA 

August 29 - September 10, 1965