Hornet Creek Upper South Reservoir Report

Last Updated: December 13, 2025

Hornet Creek Upper South is a privately-owned irrigation dam located in Washington County, Idaho, completed in 1913.


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Summary

The dam, built primarily for irrigation purposes, stands at a height of 19.3 feet and has a hydraulic height of 15.3 feet. With a storage capacity of 265 acre-feet and a drainage area of 0.6 square miles, the dam serves as a crucial water resource for the surrounding area.

Although the dam's condition was assessed as fair during the last inspection in August 2017, it is classified as having a significant hazard potential. The risk assessment has categorized it as high (2), indicating the need for appropriate risk management measures. Despite the challenges posed by its condition and hazard potential, the dam continues to play a vital role in water resource management in the region, highlighting the importance of addressing maintenance and safety concerns to ensure its continued functionality for irrigation and water supply purposes.

With its historical significance and role in supporting agricultural activities, Hornet Creek Upper South serves as a reminder of the intricate relationship between water resources, climate, and human development. As climate change poses new challenges to water management, maintaining the integrity and safety of structures like this dam becomes increasingly important in ensuring sustainable water access for both current and future generations.

Year Completed

1913

Dam Length

400

Dam Height

19.3

River Or Stream

HORNET CREEK WEISER RIVER

Surface Area

32

Hydraulic Height

15.3

Drainage Area

0.6

Nid Storage

265

Outlet Gates

None

Hazard Potential

Significant

Foundations

Rock, Soil

Nid Height

19
       
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.