Carlton Lake #1 Reservoir Report

Last Updated: December 5, 2025

Carlton Lake #1, located in Missoula, Montana, is a private irrigation reservoir constructed in 1899 by the USDA NRCS.


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Summary

The dam, classified as an Earth type, stands at a height of 22 feet and stretches 420 feet in length, with a storage capacity of 450 acre-feet. Situated on Carlton Creek, the reservoir covers an area of 40 acres and serves the primary purpose of irrigation for the surrounding agricultural lands.

With a significant hazard potential and a moderate risk assessment level, Carlton Lake #1 is regulated by the Montana Department of Natural Resources Conservation (DNRC) and undergoes regular state inspections and enforcement measures. The spillway, classified as uncontrolled, is 28 feet wide, providing a vital safety feature for managing water levels during periods of high discharge. Despite its age, the dam's condition assessment remains unrated, prompting the need for ongoing monitoring and risk management measures to ensure its structural integrity and the safety of downstream communities.

As a historical irrigation structure, Carlton Lake #1 represents a key component of the local water resource infrastructure, playing a crucial role in supporting agricultural activities in the region. With its location in the picturesque city of Lolo and its association with the scenic Carlton Creek, the reservoir stands as a testament to the engineering ingenuity of its time, while also highlighting the importance of sustainable water management practices in the face of changing climate conditions.

Year Completed

1899

Dam Length

420

Dam Height

22

River Or Stream

CARLTON CREEK

Primary Dam Type

Earth

Surface Area

40

Hydraulic Height

22

Drainage Area

1

Nid Storage

450

Structural Height

22

Hazard Potential

Significant

Nid Height

22
       
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.