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Title: Importance of Wetlands to Streamflow Generation
Author: Verry, E. S.; Kolka, R. K.
Publication: In: Renard, Kenneth G.;et al., eds. 1st Interagency Conference on Research in the Watersheds; 2003 October 27-30; Benson, AZ. [City, State]: US Department of Agriculture, Agricultural Research Service: 126-132
Key Words: source of streamflow, peatlands, uplands, subsurface flow, interflow, hydrograph separation
Abstract: Hewlett (1961) proposed the variable-source-area concept of streamflow origin in the mountains of North Carolina suggesting streamflow was produced from water leaving saturated areas near the channel. Dunne and Black confirmed this concept on the Sleepers River watershed in Vermont (1970). Areas near the river were saturated by subsurface or interflow from adjacent upland slopes. In turn, these saturated areas fed water directly to the channel. In the northern Lake States, wetlands and lakes make up 10 to 35% of the basin. These flat landscape components are surrounded by relatively steep (10-15% slope) glacial moraine uplands. We investigated the importance of wetlands to streamflow production on watershed two at the Marcell Experimental Forest in north central Minnesota. A hydrograph seperation technique for the entire watershed yielded hydrographs for water both from the upland alone and from the wetland alone. Additionally, selected direct measurements of upland runoff and watershed streamflow confirmed the timing of hydrograph peaks for the separated watershed components. The wetland produced 50 to 70% of the annual streamflow even though the wetland comprised only l/3" of the basin. Storm peaks from the wetland were 5 to 10 times higher than storm peaks from the upland and occurred about 1 hour before upland runoff peaked. Saturated wetlands (and lake surfaces) are the primary source of streamflow in these glacial landscapes.
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