Mackay dam
Mackay
Mackay, a privately owned dam located in Idaho, was completed in 1918 and sits on the Big Lost River Sinks. This rockfill dam stands at a height of 75.2 feet with a storage capacity of 45,000 acre-feet and a surface area of 1,392 acres. With a drainage area of 788 square miles, the dam has a maximum discharge rate of 7,000 cubic feet per second.
Despite being classified as having a high hazard potential, Mackay is currently in fair condition following its last inspection in October 2019. The dam features an uncontrolled spillway and a slide (sluice gate) outlet gate. Its emergency action plan (EAP) status is not specified, and there have been no inundation maps prepared. The risk assessment for Mackay indicates a moderate risk level (3), suggesting a need for ongoing monitoring and risk management measures to ensure the safety and integrity of the structure.
For water resource and climate enthusiasts, Mackay presents an intriguing case study in dam infrastructure management and risk assessment. Its location in the scenic Custer County, Idaho, surrounded by the natural beauty of the Big Lost River Sinks, underscores the importance of balancing water resource development with environmental conservation and safety considerations. As discussions around climate change and water scarcity continue to evolve, understanding the condition and risk profile of dams like Mackay becomes increasingly vital for sustainable water management practices in the region.
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.
- 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.
- 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.
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, environmental 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.
Plan around the weather
Same NOAA / yr.no feed Snoflo's iOS app uses. Watch the precipitation column on the meteogram -- rain on the basin upstream typically lifts inflow 24-72 hours later.
Next 5 days, hour by hour
Temperature line with weather symbols on top, snow + rain accumulation as columns, humidity as a dotted line.
5-day forecast table
Every 3 hours, broken out across temperature, snow, rain, humidity, and wind. Each cell is colour-coded relative to the column min/max.
| Time | Condition | Temp (°F) | Snow (in) | Rain (in) | Humidity (%) | Wind (mps) | Wind dir |
|---|---|---|---|---|---|---|---|
| Loading detailed forecast… | |||||||
15-day temperature & precipitation
Daily temperatures, snow, and rain projected over the next two weeks.
Nearby streamflow gauges
USGS streamgauges around Mackay -- inflows here typically show up in storage 24-72 hours later.
| Streamgauge | Discharge | View |
|---|---|---|
| Big Lost River Bl Mackay Res Nr Mackay Id | 564 cfs | → |
| Big Lost River At Howell Ranch Nr Chilly Id | 742 cfs | → |
| Nf Big Lost River At Wild Horse Nr Chilly Id | 267 cfs | → |
| Little Lost River Bl Wet Creek Nr Howe Id | 121 cfs | → |
| Little Lost River Nr Howe Id | 114 cfs | → |
| Big Lost River Nr Arco Id | · | → |
Make a day of it
Boat launches, lakeside camping, fishing access, and other reservoirs near Mackay.
Campgrounds
- Mackay Reservoir Access Area - Ifg
- Joseph T. Fallini Campground
- Joe T. Fallini - Mackay Reservoir
- Joseph T. Fallini
- Mackay Tourist Park
- Loristica Group Campground
Track Mackay in the Snoflo app
Save this dam as a favorite and get the local NOAA / yr.no forecast plus regional flow context wherever you are.
About Mackay
Where does the data for Mackay come from?
Structural and regulatory data come from the U.S. Army Corps of Engineers' National Inventory of Dams (NID). Weather forecast comes from NOAA / yr.no -- the same feed Snoflo's iOS app uses.
How often is the report updated?
NID structural data refreshes annually as the Corps publishes updated assessments. The weather forecast refreshes throughout the day.
What does the High hazard rating mean?
The Corps of Engineers' hazard potential classification grades probable consequences if the dam fails: High = probable loss of human life; Significant = no probable loss of human life but possible economic loss / environmental damage; Low = no probable loss of human life, only minor economic / environmental losses. See the Dam Data Reference card above for the full definitions.
What's "% of normal"?
The current storage value compared to the historical average storage on this calendar day. 100% = right on average; values above 100% mean above-normal storage (wet year); values below mean below-normal (dry year or drought).
Can I get alerts when storage crosses a threshold?
Yes -- alerts are managed in the Snoflo iOS app. Favorite this dam, set a threshold, and you'll get a push the moment conditions cross.
Other water bodies near here
Snoflo-tracked reservoirs and dams within driving distance of Mackay.