Shaw Twins Upper Reservoir Report

Last Updated: December 15, 2025

Shaw Twins Upper is a private irrigation dam located in Valley, Idaho, along the unnamed stream of Lake Fork Creek.


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Summary

Built in 1930, this concrete dam stands at a height of 17 feet and has a storage capacity of 188 acre-feet. With a fair condition assessment and low hazard potential, Shaw Twins Upper plays a crucial role in providing water resources for agricultural purposes in the region.

Despite its modest size, the dam is regulated by the Idaho Department of Water Resources, ensuring that it meets state inspection and enforcement standards. The dam features an uncontrolled spillway and slide gates for water release, with a maximum discharge capacity of 48 cubic feet per second. The surrounding area covers 20 acres, serving a drainage area of 0.1 square miles and contributing to the overall water management system in the region.

Overall, Shaw Twins Upper serves as a reliable infrastructure for irrigation purposes in Valley, Idaho, maintaining a moderate risk assessment level. With a history dating back to the early 20th century, this dam continues to support the local agricultural community while adhering to state regulations and inspection protocols to ensure its safe and efficient operation in the face of changing climate conditions.

Year Completed

1930

Dam Length

75

Dam Height

17

River Or Stream

UNNAMED STREAM LAKE FORK CREEK

Surface Area

20

Hydraulic Height

15

Drainage Area

0.1

Nid Storage

188

Outlet Gates

Slide (sluice gate)

Hazard Potential

Low

Foundations

Rock, Soil

Nid Height

17
       
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.