Influence of Wetlands on Streamflow in Illinois

by Misganaw Demissie, Illinois State Water Survey, Champaign, United States,
Abdul Khan, Illinois State Water Survey, Champaign, United States,
Radwan Al-Mubarak, Illinois State Water Survey, Champaign, United States,



Document Type: Proceeding Paper

Part of: Hydraulic Engineering

Abstract: Streamflow records from 30 gaging stations in Illinois were analyzed to assess the influence of wetlands on streamflow. The objective of this research was to determine if streamflow parameters of streams draining watersheds with varying percentage of wetland areas were related to percentage of wetlands in the watersheds. The parameters analyzed included peakflow to average precipitation ratio, peakflow to peak precipitation ratio, peakflow to total precipitation ratio, and floodflow volume to total precipitation ratio. The results show that the ratios, in general, decrease with increasing percentage of wetlands in the watershed. The relation is most pronounced for peakflow to average precipitation ratio and least conclusive for floodflow volume to total precipitation ratio. On a regional basis, the ratios decrease appreciably with increasing percentage of wetlands for central and northern Illinois, and increase slightly for southern Illinois. Seasonal analysis of the data indicates that for the peakflow ratios, the most definitive relationship is for fall while for floodflow volume ratio, the most noticeable relationship is for summer. Analysis of low-flow parameters indicates that low flows generally increase with increasing percentage of wetlands.

Subject Headings: Wetlands (fresh water) | Streamflow | Watersheds | Precipitation | Water flow | Parameters (statistics) | Floods | Low flow | North America | Illinois | United States

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