Mann Creek Reservoir Report

Last Updated: December 14, 2025

Mann Creek, also known as Spangler, is a federally owned irrigation structure located in Weiser, Idaho.


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Summary

Managed by the Bureau of Reclamation, this earth dam was completed in 1966 and serves the primary purpose of irrigation. With a height of 148 feet and a storage capacity of 15,372 acre-feet, Mann Creek plays a crucial role in water management in the region.

The dam, with a spillway width of 69 feet, has a maximum discharge capacity of 3,885 cubic feet per second, ensuring efficient water release during peak flow periods. Although categorized as having a high hazard potential, the overall risk assessment for Mann Creek is moderate. Despite the lack of available condition assessment data, the structure undergoes regular inspections by the Bureau of Reclamation to ensure its safety and functionality for the surrounding community.

Located in the Walla Walla District, Mann Creek is a key component of the local water infrastructure, providing essential irrigation water for agricultural activities in the area. As a climate and water resource enthusiast, exploring the details of Mann Creek offers valuable insights into the management and regulation of water resources in Idaho, highlighting the importance of sustainable water practices for the future.

Year Completed

1966

Dam Length

1176

Dam Height

148

River Or Stream

MANN CREEK

Primary Dam Type

Earth

Surface Area

283

Hydraulic Height

132

Drainage Area

56

Nid Storage

15372

Structural Height

148

Hazard Potential

High

Foundations

Rock

Nid Height

148
       
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.