Gann Lake Dam Reservoir Report
Last Updated: December 6, 2025
Gann Lake Dam, located in Johnson County, Missouri, is a private earth dam constructed in 1972 by the USDA NRCS for the primary purpose of recreation.
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Summary
The dam stands at a height of 43 feet and spans a length of 650 feet, with a storage capacity of 275 acre-feet and a surface area of 15 acres. The dam regulates the flow of a tributary to the Little Blackwater Creek, providing a serene environment for water resource and climate enthusiasts to enjoy various recreational activities.
Despite being classified as having a low hazard potential and a satisfactory condition assessment, Gann Lake Dam is subject to state regulation, permitting, inspection, and enforcement to ensure its safety and compliance with regulatory standards. The dam has an uncontrolled spillway with a width of 3 feet and a maximum discharge capacity of 98 cubic feet per second. The last inspection date was in September 2015, with a scheduled inspection frequency of 5 years to assess any potential risks and maintenance needs.
With its scenic location and moderate risk assessment rating, Gann Lake Dam serves as a vital water resource and recreational attraction in the area. While it may not be as prominent as other dams, its role in managing water flow and providing a habitat for diverse flora and fauna make it a noteworthy destination for those interested in water resource management and climate preservation efforts.
Year Completed |
1972 |
Dam Length |
650 |
Dam Height |
43 |
River Or Stream |
TRIB. TO LITTLE BLACKWATER CR |
Surface Area |
15 |
Drainage Area |
240 |
Nid Storage |
275 |
Structural Height |
43 |
Outlet Gates |
None |
Hazard Potential |
Low |
Foundations |
Soil |
Nid Height |
43 |
Seasonal Comparison
Weather Forecast
Nearby Streamflow Levels
Dam Data Reference
Condition Assessment
SatisfactoryNo 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
HighDams 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.
Gann Lake Dam