Zemba Reservoir Report

Last Updated: December 5, 2025

Zemba, located in Farson, Wyoming, is a privately-owned earth dam completed in 1915 primarily for irrigation purposes.


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Summary

The dam stands at a height of 16 feet with a hydraulic height of 11 feet and a length of 320 feet. It has a storage capacity of 124 acre-feet, with a normal storage level of 87 acre-feet, serving the Long Draw & Granite Gulch rivers and streams in Sublette County. Despite its age, the dam has a low hazard potential but is assessed to be in poor condition, last inspected in August 2017.

Managed by the Wyoming State Engineer's Office, Zemba features an uncontrolled spillway with a width of 10 feet and a single outlet valve. Its condition assessment indicates a need for maintenance and potential risk management measures to ensure its continued safety and functionality. While it has not been modified in recent years and its inundation maps and emergency action plan status are unclear, Zemba remains a critical water resource infrastructure in the region, supporting agricultural activities and water management in the area.

With its moderate risk level and limited associated structures, Zemba represents a historic yet essential part of the water management system in Wyoming. As climate change impacts continue to affect water resources, ensuring the safety and reliability of dams like Zemba becomes increasingly important for sustainable water management practices and adaptation strategies in the face of changing environmental conditions.

Year Completed

1915

Dam Length

320

Dam Height

16

River Or Stream

LONG DRAW & GRANITE GULCH

Primary Dam Type

Earth

Surface Area

18

Hydraulic Height

11

Nid Storage

124

Structural Height

16

Outlet Gates

Valve - 1

Hazard Potential

Low

Foundations

Soil

Nid Height

16
       
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.