Koskella Reservoir Report

Nearby: Eld Yanke

Last Updated: December 18, 2025

Koskella is a privately owned irrigation dam located in Valley, Idaho, along an unnamed stream north of the North Fork Payette River.


°F

°F

mph

Wind

%

Humidity

Summary

Built in 1947, this earth and stone dam stands at a height of 24 feet and has a hydraulic height of 20.7 feet. With a storage capacity of 74 acre-feet and a drainage area of 0.4 square miles, Koskella serves the primary purpose of irrigation in the region.

Despite its age, Koskella has been regularly inspected and maintained by the Idaho Department of Water Resources, with the last inspection conducted in November 2016. The dam has been assessed to be in fair condition with a low hazard potential. The spillway, which is uncontrolled, has a width of 10 feet to manage a maximum discharge of 55 cubic feet per second. The risk assessment for Koskella indicates a moderate risk level, with appropriate risk management measures in place to ensure the safety and integrity of the structure.

Overall, Koskella is a crucial water resource infrastructure in Idaho, providing irrigation water for agricultural activities in the region. With its moderate risk level and fair condition, ongoing monitoring and maintenance efforts are essential to ensure the continued functionality and safety of this important dam in the face of changing climate conditions and water resource demands.

Year Completed

1947

Dam Length

310

Dam Height

24

River Or Stream

UNNAMED STREAM NORTH FORK PAYETTE RIVER

Surface Area

12

Hydraulic Height

20.7

Drainage Area

0.4

Nid Storage

74

Hazard Potential

Low

Foundations

Rock, Soil

Nid Height

24
       
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.