Evans Konnowac Dam Reservoir Report
Nearby: Roy Farms Irrigation Pond Gamache Dam
Last Updated: December 15, 2025
Evans Konnowac Dam, located in Yakima, Washington, is a privately owned offstream dam primarily used for irrigation purposes.
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Summary
Completed in 1990, this earth dam stands at a structural height of 33 feet and has a storage capacity of 28 acre-feet, with a normal storage level of 21 acre-feet. The dam covers a surface area of 2.3 acres and serves a drainage area of 0.05 square miles.
Despite its important role in supporting agricultural activities in the region, the dam has been assessed to have a high hazard potential and poor condition. The last inspection in April 2015 revealed the need for maintenance and improvements to ensure the safety and integrity of the structure. The dam is regulated by the Washington Department of Ecology, with state permitting, inspection, and enforcement in place.
As an essential water resource in the area, the Evans Konnowac Dam plays a crucial role in providing irrigation water to support farming activities. However, the dam's poor condition and high hazard potential highlight the need for ongoing monitoring and maintenance to mitigate any risks and ensure its continued functionality in the face of changing climate patterns and water resource demands.
Year Completed |
1990 |
Dam Length |
320 |
River Or Stream |
offstream |
Primary Dam Type |
Earth |
Surface Area |
2.3 |
Hydraulic Height |
33 |
Drainage Area |
0.05 |
Nid Storage |
28 |
Structural Height |
33 |
Hazard Potential |
High |
Foundations |
Soil |
Nid Height |
33 |
Seasonal Comparison
Weather Forecast
Nearby Streamflow Levels
Yakima River Above Ahtanum Creek At Union Gap
|
14200cfs |
Ahtanum Creek At Union Gap
|
197cfs |
Granger Drain At Granger
|
13cfs |
Yakima River At Umtanum
|
6380cfs |
Columbia River Below Priest Rapids Dam
|
124000cfs |
Toppenish Creek Near Fort Simcoe
|
57cfs |
Dam Data Reference
Condition Assessment
SatisfactoryNo 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
HighDams 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.
Evans Konnowac Dam