Mcnab Dam dam
Mcnab Dam
Mcnab Dam, located in Valley, Montana, is a gravity dam with a hydraulic height of 33 feet and a structural height of 39 feet. Built in 2003 by the Bureau of Land Management, the dam has a storage capacity of 172.25 acre-feet and covers a surface area of 10.6 acres. With a controlled spillway type, the dam has a spillway width of 2 feet and is classified as having a low hazard potential.
Despite its low hazard potential, the condition assessment of Mcnab Dam is considered unsatisfactory, signaling potential risks that need to be addressed. The last inspection date was in August 2016, with an inspection frequency of every 5 years. The dam's risk assessment is classified as very high, highlighting the importance of implementing risk management measures to ensure the safety and integrity of the structure.
As an important water resource in Montana, Mcnab Dam serves as a vital infrastructure for water storage and management. With its unique design and construction by the Bureau of Land Management, the dam plays a crucial role in regulating water flow and providing flood control measures in the region. Climate and water resource enthusiasts can appreciate the significance of Mcnab Dam in sustaining the local ecosystem and supporting water-related activities in the area.
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 Mcnab Dam -- inflows here typically show up in storage 24-72 hours later.
| Streamgauge | Discharge | View |
|---|---|---|
| Beaver Creek Near Hinsdale Mt | 31 cfs | → |
| Milk River At Juneberg Bridge Nr Saco Mt | 178 cfs | → |
| Beaver Cr Bl Guston Coulee Nr Saco Mt | 67 cfs | → |
| Milk River At Tampico Mt | 47 cfs | → |
| Milk River At Malta Mt | 31 cfs | → |
| Milk River At Nashua Mt | 57 cfs | → |
Make a day of it
Boat launches, lakeside camping, fishing access, and other reservoirs near Mcnab Dam.
Track Mcnab Dam 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 Mcnab Dam
Where does the data for Mcnab Dam 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 Low 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.