Subsurface flow in a southern Illinois fragipan soil

In an eight-year study of precipitation and water-yield relationships on the Lake Glendale Watershed, Boggess et al (1965) suggested that the nature of the underlying fragipan soil had a significant effect on the flow characteristics of the drainage. The outflow hydrographs were characterized by sustained recession legs, indicating a substantial amount of detained or delayed flow. The authors stated, "Water yield was composed of both surface (overland) and subsurface flow. ...subsurface flow was a major contributor to total yield, due both to the presence of the slowly permeable fragipan and the relatively low moisture storage capacities of the soil profiles." Subsurface flow was believed to be largely made up of downslope seepage along the top of the fragipan, since a perched water table formed there during prolonged periods of wet weather. No attempt was made in their study to determine the relative amounts of surface and subsurface f low. Research reported in this paper was directed toward determining the contribution of each of these flow components in the total water yield from the Grantsburg soiIs.U.S. Department of the InteriorU.S. Geological SurveyOpe

Impacts of land use conversion on bankfull discharge and mass wasting

Abstract Mass wasting and channel incision are widespread in the Nemadji River watershed of eastern Minnesota and northwestern Wisconsin. While much of this is a natural response to glacial rebound, sediment coring and tree ring data suggest that land use has also influenced these erosional processes. We characterized land use, inventoried mass wasting, surveyed stream channels and collected discharge data along segments of five streams in the Nemadji River watershed. Due to natural relief in this region, wetlands and agricultural lands are concentrated in the flatter terrain of the uplands of the Nemadji watershed, while forestland (coniferous or deciduous) is concentrated in the deeply incised (50-200% slope) stream valleys. Bankfull discharge was higher where forests had been converted from coniferous to deciduous forests and where there were fewer wetlands. Mass wasting increased exponentially with bankfull flows. While mass wasting was not correlated with forest type conversion and agricultural land use, it was negatively dependent upon wetland extent in headwater areas. Interactions between the spatial distribution of land use and terrain obfuscate any clear cause-and-effect relationships between land use, hydrology and fluvial processes. Published by Elsevier Ltd