Altnow Reservoir Reservoir Report
Nearby: Cottonwood (Drewsey) Stallard Dam
Last Updated: December 13, 2025
Altnow Reservoir, located in Harney County, Oregon, is a privately owned irrigation reservoir designed by M.A.
°F
°F
mph
Wind
%
Humidity
Summary
Palmer & Sons and completed in 1908. The reservoir has a dam height of 20 feet and a storage capacity of 122 acre-feet, with a surface area of 16.1 acres and a drainage area of 0.77 square miles. Its primary purpose is irrigation, drawing water from Warm Spring Creek to support agricultural activities in the surrounding area.
Despite its age, Altnow Reservoir has a low hazard potential and is not currently rated for its condition. The reservoir features a slide gate outlet structure and has a maximum discharge capacity of 183.94 cubic feet per second. The reservoir is state regulated by the Oregon Water Resources Department, with permitting, inspection, and enforcement measures in place to ensure its safe operation. While the last inspection date was in 2009, the reservoir is subject to regular inspections every six years.
Altnow Reservoir plays a vital role in supporting local agriculture in the Drewsey area, providing a reliable water source for irrigation purposes. With its earth dam construction and historical significance dating back over a century, the reservoir stands as a testament to the ingenuity and resourcefulness of early water management practices in Oregon. As water resource and climate enthusiasts, Altnow Reservoir serves as a reminder of the essential role that well-maintained reservoirs play in sustaining agricultural livelihoods and ecosystem health in arid regions.
Year Completed |
1908 |
Dam Length |
720 |
Dam Height |
20 |
River Or Stream |
WARM SPRING CREEK |
Primary Dam Type |
Earth |
Surface Area |
16.1 |
Hydraulic Height |
15 |
Drainage Area |
0.77 |
Nid Storage |
122 |
Structural Height |
23 |
Outlet Gates |
Slide (sluice gate) |
Hazard Potential |
Low |
Nid Height |
23 |
Seasonal Comparison
Weather Forecast
Nearby Streamflow Levels
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.
Altnow Reservoir
Malheur Nf
North Fork Malheur River