Johnson No. 1 Reservoir Report
Nearby: Paddy No. 1 Paddy No. 2
Last Updated: December 6, 2025
Johnson No.
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Summary
1 is a private irrigation dam located in Niobrara, Wyoming, along the Hancock Draw river. Built in 1916, this Earth dam stands at 30 feet high and spans 460 feet in length, providing essential water storage for agricultural purposes. Despite its age, the dam has a low hazard potential but is in poor condition, highlighting the need for maintenance and upkeep to ensure its continued functionality.
With a normal storage capacity of 239 acre-feet and a maximum storage of 333 acre-feet, Johnson No. 1 plays a crucial role in supporting local irrigation needs. The dam features an uncontrolled spillway with a width of 50 feet and two other controlled outlet gates. However, its last inspection in May 2017 revealed a poor condition assessment, indicating the importance of regular maintenance and risk management to prevent potential failures and protect downstream areas.
While Johnson No. 1 is not currently considered a high-risk structure, its moderate risk assessment serves as a reminder of the ongoing challenges faced by aging infrastructure in the face of changing climate conditions. As water resources and climate enthusiasts, it is essential to prioritize the maintenance and management of dams like Johnson No. 1 to ensure the resilience and sustainability of our water systems for future generations.
Year Completed |
1916 |
Dam Length |
460 |
Dam Height |
30 |
River Or Stream |
HANCOCK DRAW |
Primary Dam Type |
Earth |
Surface Area |
40 |
Hydraulic Height |
25 |
Nid Storage |
333 |
Structural Height |
30 |
Outlet Gates |
Other Controlled - 2 |
Hazard Potential |
Low |
Foundations |
Soil |
Nid Height |
30 |
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.
Johnson No. 1