1. Who operates the gates?
The Illinois Department of Natural Resources Office of Water Resources operates the gates at Stratton and Algonquin Dams.
2. How are the gates operated?
Gates are opened to achieve a specified flow per the operation guide (Operations of Stratton and Algonquin Dams, Fox River in Lake and McHenry Counties). Flows for gate operations are determined using:
a. inflows to the Chain of Lakes as monitored at the stream gages at Fox River near New Munster, Wisconsin and Nippersink Creek near Spring Grove
b. stage of Fox Lake; and
c. predicted peak inflows to Chain based on hydrologic modeling from observed precipitation.
Regional impacts are assessed and minor adjustments are made to the gates if there are regional benefits and these adjustments will not cause flooding downstream or upstream.
3. How was the operation guide developed?
The operation guide criteria for operating the gates were developed with the Illinois State Water Survey. The ISWS developed the hydrologic model. The hydrologic model was calibrated and was utilized with the hydraulic model, Full Equations (FEQ). The hydraulic model was calibrated then verified by the U.S. Geological Survey by making flow measurements and taking water surface elevations during a high water event. These models were used to investigate 10 alternative gate operation scenarios including the use of the proposed hinged crest gates and analyze winter drawdown. The analysis was based on historic storm events. After verifying the benefits of the proposed hinged crest gates, the ISWS developed the refined operation flow chart utilizing predicted peak inflows. This analysis included the hinged crest gates even though the gates were not in place at the time of the analysis.
4. What are the operation objectives?
Operation objectives are to:
a. maintain a recreational pool,
b. utilize available storage in the Chain of Lakes to minimize regional flooding,
c. maintain minimum flows for water supply and aquatic habitat, and
d. limit flows during ice jam periods
5. Why is there flooding after the installation of the new hinged crest gates?
When the hinged crest gates were studied, the analysis showed that the gates would reduce flooding but not eliminate flooding. The reduction in peak water surface elevations and flooding justified the economics for construction of the gates.
6. What is the maximum impact that gate operations can have on water levels upstream and downstream?
The ISWS study of alternative operation scenarios showed during the historic storms the use of the hinged crest gates would have reduced peak water surfaces from the Chain of Lakes to Fox River in Johnsburg by 0.1' to 0.5' from conditions without the hinged crest gate. At Stratton Dam the hinged crest gates reduce water surfaces 0.1' to 1.0' for these historic flood events. The hinged crest gate at Algonquin Dam reduces peak water surface elevations immediately upstream of the dam 0.3' to 1.0' for the historic storms. The benefits of the Algonquin hinged crest diminish as you move further upstream of Algonquin Dam.
The capacity of Fox River controls flows during extremely large events when the gates are opened fully. During lesser high flow events, the storage in the Chain of Lakes can be utilized to contain the flows to the banks of the Fox River without flooding occurring on the Chain of Lakes.
7. Why are the gates not opened before the rain falls?
.The ISWS analysis does not recommended using predicted rainfall. Rainfall, especially in the Wisconsin portion of the watershed, takes 1 to 6 days before the runoff enters the Chain of Lakes. Therefore, adequate time exists to open the gates using the recorded rainfall. The Quantitative Precipitation Forecast (QPF), prepared by the NWS, typically over-estimates watershed average rainfall. The largest problem with using the QPF occurs if gates are raised to increase flows above bankfull, i.e. flooding occurs downstream of Stratton Dam based on predicted rainfall. If the predicted rainfall does not occur, unnecessary flooding would have occurred.
However, the impacts of predicted rainfall are analyzed. Minor changes to gate settings that may be beneficial if the predicted rainfall occurs may be made if these changes will not induce or increase flooding on residences downstream. The gates will not be opened fully unless flooding throughout the entire Fox River and Chain of Lakes is anticipated.
8. Does IDNR communicate with my local emergency management officials during storm events?
.The County Emergency Managers and Stormwater Managers are contacted with daily updates of gate settings and flow at Stratton and Algonquin Dams during high flow events. The National Weather Service predictions for flows and potential qualitative impacts for the Fox River and Chain of Lakes in Illinois are discussed. This information is available late morning after decisions for gate operations are made.
9. How do I find out what the forecasted peak stages are on the Chain of Lakes?
The National Weather Service forecasts river stages and peak stages at stream gage locations. On the Fox River, these predictions occur at the Fox River near New Munster, Wisconsin and Fox River at Algonquin, Illinois. No forecasts are made for the Chain of Lakes.
10. Why are they boating on the Chain of Lakes while my house on the Fox River or Chain of Lakes is flooding?
.The Chain of Lakes and Fox River reaches do not always flood at the same time, therefore flood conditions may exist in the Fox River when the lakes are open. Flooding levels on the lakes and Fox River occur at different flows.
The Illinois Department of Natural Resources can designate a body of water a Restricted Boating Area when conditions make navigation of a body of water significantly dangerous to the public. Title 17 Illinois Administrative Code Section 2030.80 describes the procedure for enacting and rescinding a Restricted Boating Area. The determination to enact and rescind a boating restriction is made on a case by case basis. This determination is made based on the totality of circumstances. Section 2030.15 (c) specifies that restricting boating for the purposes of protecting property is prohibited. The Office of Law Enforcement administers Restricted Boating Areas.
11. How are no-wake boating restrictions implemented?
Waterway Agency has the authority to enact no-wake boating restrictions during high water events. Chapter 5 of the FWA ordinance specifies the water stages when these restrictions can be enacted. The Illinois Department of Natural Resources does not have the authority to implement no-wake restrictions.
12. How much flood storage is there in the Chain of Lakes?
From normal summer pool to when flooding begins there is 10,400 acre-feet of storage in the Chain of Lakes. From winter pool to when flooding begins there is 22, 200 acre-feet of storage. There is not enough storage to prevent flooding for extremely large events.
13. What were the flood benefits of the Wilmot Dam?
The dam at Wilmot, Wisconsin on the Fox River was removed in 1992. The hydraulic drop at the dam was only three feet. The dam acted like run of the river dam during high flow events. Minimal storage was provided upstream of the dam. No flood benefits were seen from the small dam.
14. Why is there a winter drawdown?
Winter drawdown lowers the Chain of Lakes 1.5' to increase the storage by 10,000 acre-feet, almost doubling the storage. Drawdown begins on November 1 and is targeted to be complete by December 1. This storage is used as warm weather melts the snow and spring rainfall causes higher flows. The Chain of Lakes rises in the spring when the flows increase.
15. Why are flows from Stratton Dam restricted in winter?
To prevent ice jam flooding on the Fox River, flows at Stratton Dam are limited to 1000 cfs after 60 degree freezing days are reached. When an ice jam occurs, flooding occurs at approximately 1/3 of the flow when flooding would occur on the open river. Limiting flows may require the use of the storage created by winter drawdown.
16. Why are the ice booms not being used?
Two ice booms were constructed and utilized in Carpentersville and East Dundee. The booms were considered a pilot project and were operated by the IDNR/OWR for 10 years. Kane County and the Villages of East Dundee and West Dundee were asked to take over the operation and maintenance of the ice booms. These local government agencies would not assume these responsibilities.
