Fox River Status Update
March 6, 2014
Inflows to the Chain of Lakes are estimated to be near 450 cfs as the stream gages at Fox River near New Munster, Wisconsin and Nippersink Creek near Spring Grove appear to be effected by ice. The Chain of Lake stage is 2.5 feet at Fox Lake which is winter pool elevation. Winter pool lowers the Chain of Lakes 18” below summer pool levels and creates 10,000 acre-feet of storage for snow melt and spring precipitation. Outflows from Stratton Dam are 350 cfs with a tailwater stage of 2.3 feet. Flows at Algonquin Dam are 700 cfs which is below normal for early March. The pool at Algonquin Dam is at stage of 1.5’ which is 3 ½” below optimum summer pool.
At Stratton Dam, 18” of snow was measured March 3rd with a snow water equivalent of 3.2”.
The National Weather Service (NWS) is predicting above freezing day time temperatures with below freezing temperatures for most of the next week. The snow will begin melting during the day and re-freeze at night. The amount of runoff released from the snow melt is estimated to be minimal over the weekend. The NWS does not have a river forecast issued for the Fox River at New Munster, WI or Algonquin Dam tailwater because they are not anticipating flooding over the weekend.
If most of the snow would melt over this next week without additional rain, inflows to the Chain of Lakes could reach 3200 cfs around March 13 or 14. Inflows of 3200 cfs would equate to bank full conditions on the Fox River and Chain of Lakes. Snow melt without additional rain is the best possible scenario. Any additional rainfall with the snow melt will raise the flood potential.
The NWS presented their early spring Hydrologic Outlook. These comments are my interpretation of what was said. With the deep levels of frost in the ground and high snow water equivalent in the snow, northern Illinois and southern Wisconsin have increased risk of significant flooding. It is anticipated that the spring flooding will be delayed 2 to 3 weeks later than normal, i.e. April. The potential for flooding will linger after the snow melt as the frozen ground will inhibit infiltration.
We will continue to monitor rainfall and river levels. The gates at Stratton Dam are opened to try to keep the Chain of Lakes at winter pool levels. Future updates will be provided as conditions warrant.
Rita M. Lee, P.E., CFM
IDNR Office of Water Resources
1 Natural Resources Way
Springfield, IL 62702