Little Sister Lake Dam Reservoir Report

Last Updated: December 21, 2025

Little Sister Lake Dam, located in Maple Mills, Illinois, is a public utility structure designed by Frank Gaweda in 1965 with a primary purpose of recreation.


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Summary

The earth dam stands at 38 feet high and stretches 380 feet in length, creating a reservoir with a storage capacity of 221 acre-feet. Situated on Little Sister Creek, the dam serves as a popular spot for outdoor activities such as fishing, boating, and hiking, offering a serene escape for water resource and climate enthusiasts.

Managed by the Illinois Department of Natural Resources (IDNR), the dam has a low hazard potential and a moderate risk assessment rating. With uncontrolled spillways and outlets, the structure poses minimal threat to surrounding areas but is subject to regular state inspections to ensure its safe operation. Despite limited condition assessment data, the dam continues to provide valuable recreational opportunities while contributing to the local ecosystem and water resources in Fulton County.

As part of the Rock Island District, Little Sister Lake Dam exemplifies the harmonious relationship between water management and public recreation. With its serene location and well-maintained facilities, the dam stands as a testament to sustainable infrastructure development and responsible stewardship of water resources. For enthusiasts interested in the intersection of water management and climate resilience, this structure offers a fascinating case study in balancing human recreation with ecological conservation.

Year Completed

1965

Dam Length

380

Dam Height

38

River Or Stream

LITTLE SISTER CREEK

Primary Dam Type

Earth

Surface Area

36

Nid Storage

221

Outlet Gates

Uncontrolled

Hazard Potential

Low

Foundations

Unlisted/Unknown

Nid Height

38
       
Seasonal Comparison

Weather Forecast

Dam Data Reference

Condition Assessment

Satisfactory
No existing or potential dam safety deficiencies are recognized. Acceptable performance is expected under all loading conditions (static, hydrologic, seismic) in accordance with the minimum applicable state or federal regulatory criteria or tolerable risk guidelines.
Fair
No existing dam safety deficiencies are recognized for normal operating conditions. Rare or extreme hydrologic and/or seismic events may result in a dam safety deficiency. Risk may be in the range to take further action. Note: Rare or extreme event is defined by the regulatory agency based on their minimum
Poor A dam safety deficiency is recognized for normal operating conditions which may realistically occur. Remedial action is necessary. POOR may also be used when uncertainties exist as to critical analysis parameters which identify a potential dam safety deficiency. Investigations and studies are necessary.
Unsatisfactory
A dam safety deficiency is recognized that requires immediate or emergency remedial action for problem resolution.
Not Rated
The dam has not been inspected, is not under state or federal jurisdiction, or has been inspected but, for whatever reason, has not been rated.
Not Available
Dams for which the condition assessment is restricted to approved government users.

Hazard Potential Classification

High
Dams assigned the high hazard potential classification are those where failure or mis-operation will probably cause loss of human life.
Significant
Dams assigned the significant hazard potential classification are those dams where failure or mis-operation results in no probable loss of human life but can cause economic loss, environment damage, disruption of lifeline facilities, or impact other concerns. Significant hazard potential classification dams are often located in predominantly rural or agricultural areas but could be in areas with population and significant infrastructure.
Low
Dams assigned the low hazard potential classification are those where failure or mis-operation results in no probable loss of human life and low economic and/or environmental losses. Losses are principally limited to the owner's property.
Undetermined
Dams for which a downstream hazard potential has not been designated or is not provided.
Not Available
Dams for which the downstream hazard potential is restricted to approved government users.