Andreasen Lower Reservoir Report

Last Updated: December 6, 2025

Located in Thatcher, Idaho, the Andreasen Lower dam plays a crucial role in irrigation, serving as a key water resource for the region since its completion in 1960.


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Summary

With a height of 33.1 feet and a hydraulic height of 29.3 feet, the dam holds a storage capacity of 100 acre-feet, providing water for agricultural purposes in the area. The dam is primarily constructed with earth and stone materials, supported by rock and soil foundations, making it a vital infrastructure for water management in the region.

State regulated and inspected by the Idaho Department of Water Resources, Andreasen Lower dam is deemed to have a significant hazard potential, although its condition assessment as of August 2017 was satisfactory. The dam has a spillway type of uncontrolled with a maximum discharge capacity of 12 cubic feet per second, ensuring proper water flow management during peak times. Despite facing a moderate risk level, the dam continues to meet guidelines for operation and maintenance, highlighting its importance in ensuring water security for the surrounding community.

With its location in Franklin County, Idaho, Andreasen Lower dam stands as a testament to effective water resource management, providing essential irrigation water for agricultural activities in the region. As a privately owned structure, the dam undergoes regular inspections and maintenance, ensuring its structural integrity and fulfilling its primary purpose of supporting the local farming community. As climate change impacts water availability, the Andreasen Lower dam remains a vital infrastructure for sustainable water resource management in the area, playing a crucial role in maintaining the region's agricultural productivity and water security.

Year Completed

1960

Dam Length

720

Dam Height

33.1

River Or Stream

ROCKY CANYON CREEK COTTONWOOD CREEK

Surface Area

10

Hydraulic Height

29.3

Drainage Area

0.8

Nid Storage

100

Outlet Gates

None

Hazard Potential

Significant

Foundations

Rock, Soil

Nid Height

33
       
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.