SURFACE WATER SUPPLY ISSUES AND AVAILABILITY FOR THE FOX RIVER WATERSHED IN NORTHEASTERN ILLINOIS

Surface waters are often used as water supply sources where local groundwater sources are limited or when a community's water use outgrows the available supply. Whereas the Great Lakes provide water for many communities bordering the lakes, other communities that are relatively distant from the lakes or located just outside of the Great Lakes watershed may need to turn to streams or inland lakes for water supply. This presentation focuses on the existing and potential public water supply use of flows in the Fox River, a tributary to the Illinois River. The Fox River watershed, located on the western margins of the Chicago metropolitan area, is a region that is expected to see its population and water use grow by as much as 100% over the next 40 years. As groundwater use in the Fox River watershed continues to increase, the amount of effluent discharged to the river originating from groundwater also is increasing, producing elevated low flows in the river. Although Illinois requires a protected instream flow for the Fox River, future increases in the river's low flow quantity resulting from upstream effluents may be considered available for potential downstream water supply withdraws. The withdrawal of river water is thus, in effect, a form of water reuse. A considerable portion of upstream effluents in the Fox River originate from communities near its headwaters in Waukesha County, Wisconsin. If communities in the Waukesha region are successful in efforts to obtain Lake Michigan water for their water supply, they would be required to discharge their effluents to Lake Michigan instead of the Fox River, thus reducing the potential available surface water supply to Illinois communities. This presentation examines the various factors that will affect the future low flows and water supply availability in the Fox River, including the strong relationship to groundwater use within the watershed and the fate of Waukesha's water supply, potential climate change impacts, and river water quality concerns.