Johnson Dam Reservoir Report
Nearby: Cranston Brothers Dam Wunschel Dam
Last Updated: January 11, 2026
Johnson Dam, located in Ida Grove, Iowa, was completed in 1996 by the USDA NRCS and serves multiple purposes including fire protection and as a small fish pond.
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Summary
The dam is of earth type construction with a height of 28 feet and a length of 265 feet, providing a storage capacity of 20 acre-feet and covering a surface area of 1 acre. It is situated on the TR- MAPLE RIVER and is owned by a private entity.
The dam has a low hazard potential and a moderate risk assessment rating. It has not been inspected or assessed for condition, and there is no Emergency Action Plan in place. Despite its small size and limited capacity, Johnson Dam plays a vital role in water resource management in the area, serving as a source of water for fire protection and supporting local biodiversity through its function as a fish pond. Enthusiasts of water resources and climate will find this structure intriguing for its design and multi-functional use in a rural setting.
Year Completed |
1996 |
Dam Length |
265 |
Dam Height |
28 |
River Or Stream |
TR- MAPLE RIVER |
Primary Dam Type |
Earth |
Surface Area |
1 |
Drainage Area |
0.07 |
Nid Storage |
20 |
Hazard Potential |
Low |
Foundations |
Soil |
Nid Height |
28 |
Seasonal Comparison
Weather Forecast
Nearby Streamflow Levels
Little Sioux River At Correctionville
|
327cfs |
North Raccoon River Near Sac City
|
312cfs |
Maple River At Mapleton
|
323cfs |
Little Sioux River At Linn Grove
|
257cfs |
West Fork Ditch At Hornick
|
80cfs |
Little Sioux River Near Turin
|
1040cfs |
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.
Johnson Dam