Isom Reservoir Report
Nearby: Powers Stock Paterson Lake
Last Updated: December 5, 2025
Isom, also known as Austin, is a privately owned irrigation dam located in Granger, Wyoming.
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Summary
Built in 1976, this earth dam stands at a height of 20 feet with a hydraulic height of 15 feet and a length of 1790 feet. It serves multiple purposes including irrigation, fire protection, stock, and small fish pond management. The dam has a storage capacity of 3635 acre-feet and covers a surface area of 268 acres, drawing water from the Austin Wash and TR Black Rock Drw rivers.
Despite being classified as having a low hazard potential, Isom has a moderate risk assessment rating. It is regulated by the state of Wyoming and falls under the jurisdiction of the State Engineer's Office. The dam's spillway type is uncontrolled with a width of 10 feet, and it features a single slide (sluice gate) outlet gate. While the dam has undergone inspections in the past, its condition assessment is currently listed as "Not Rated," with the last inspection conducted in October 2009.
For water resource and climate enthusiasts, Isom presents an intriguing case study of a privately owned irrigation structure in Wyoming. Its design and construction details, along with its multiple purposes and risk assessment, offer valuable insights into the management and regulation of water resources in the region. Further research and monitoring of Isom's condition and performance could provide valuable data for understanding the intersection of water infrastructure, climate resilience, and regulatory processes in the area.
Year Completed |
1976 |
Dam Length |
1790 |
Dam Height |
20 |
River Or Stream |
AUSTIN WASH, TR BLACK ROCK DRW |
Primary Dam Type |
Earth |
Surface Area |
268 |
Hydraulic Height |
15 |
Drainage Area |
9.2 |
Nid Storage |
3635 |
Structural Height |
20 |
Outlet Gates |
Slide (sluice gate) - 1 |
Hazard Potential |
Low |
Foundations |
Soil |
Nid Height |
20 |
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.
Isom