Sunnyside Mp 59.29 Reservoir Reservoir Report
Last Updated: December 15, 2025
Located in Prosser, Washington, the Sunnyside Mp 59.29 Reservoir is a vital water resource managed by the Washington Dept of Ecology.
°F
°F
mph
Wind
%
Humidity
Summary
Built in 2005 by CH2MHill, this earth dam reservoir serves primarily for irrigation purposes, with a storage capacity of 400 acre-feet. The reservoir covers an area of 21 acres and has a drainage area of 0.03 square miles, drawing water from the Spring Cr Wasteway - Offstream.
With a structural height of 41 feet and a hydraulic height of 44 feet, the Sunnyside Mp 59.29 Reservoir has a high hazard potential but is currently assessed to be in fair condition. The reservoir undergoes inspections every 5 years, with the last assessment conducted in October 2021. Despite its age, the dam continues to meet regulatory standards and serves as a critical component of the region's water management infrastructure, ensuring a reliable water supply for agricultural purposes in Benton County, Washington.
Year Completed |
2005 |
Dam Length |
3800 |
River Or Stream |
Spring Cr Wasteway - Offstream |
Primary Dam Type |
Earth |
Surface Area |
21 |
Hydraulic Height |
44 |
Drainage Area |
0.03 |
Nid Storage |
400 |
Structural Height |
41 |
Hazard Potential |
High |
Foundations |
Rock, Soil |
Nid Height |
44 |
Seasonal Comparison
Weather Forecast
Nearby Streamflow Levels
Yakima River At Kiona
|
23800cfs |
Yakima River At Mabton
|
28900cfs |
Granger Drain At Granger
|
13cfs |
Columbia River Below Priest Rapids Dam
|
124000cfs |
Umatilla River Near Umatilla
|
516cfs |
Crab Creek Near Beverly
|
158cfs |
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.
Sunnyside Mp 59.29 Reservoir