Oneal Lake Reservoir Report
Nearby: Billingsley #3 Billingsley #2
Last Updated: December 28, 2025
Oneal Lake is a privately owned reservoir located in Yavapai, Arizona, with a primary purpose of irrigation.
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Summary
Built in 1894, the earth dam stands at a height of 9.7 meters and has a length of 560 meters, providing a storage capacity of 88.9 acre-feet. The reservoir covers a surface area of 13.4 acres and is regulated by the Arizona Department of Water Resources, with state permitting, inspection, and enforcement in place to ensure its safety and compliance.
Despite being classified as having a low hazard potential, Oneal Lake is considered to have a moderate risk level, with a risk assessment rating of 3. The spillway type is uncontrolled with a width of 23 meters, and the dam is designated as a buttress earth structure. The last inspection of the reservoir was conducted in May 2020, with a scheduled inspection frequency of every 5 years. While the condition assessment is currently not rated, the reservoir is under state jurisdiction and meets regulatory guidelines for operation and management.
Water resource and climate enthusiasts may find Oneal Lake to be an intriguing case study in irrigation infrastructure, showcasing historical engineering practices and the ongoing efforts to maintain dam safety and compliance with state regulations. The reservoir's location in a picturesque setting in Yavapai, Arizona, provides a unique opportunity to explore the intersection of water management, environmental stewardship, and sustainable agriculture in the arid southwestern United States. With its rich history dating back to the late 19th century, Oneal Lake serves as a vital water source for agricultural activities in the region, highlighting the importance of responsible water resource management in the face of changing climate conditions.
Year Completed |
1894 |
Dam Length |
560 |
Dam Height |
9.7 |
River Or Stream |
UNKNOWN |
Primary Dam Type |
Earth |
Surface Area |
13.4 |
Nid Storage |
88.9 |
Hazard Potential |
Low |
Foundations |
Unlisted/Unknown |
Nid Height |
10 |
Seasonal Comparison
Weather Forecast
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.
Oneal Lake