Big Lake Dam
Big Lake
Big Lake, located in Missoula, Montana, is a significant earth dam constructed in 1915 primarily for water supply purposes. The dam stands at a height of 30 feet and has a storage capacity of 621 acre-feet, with a normal storage capacity of 143 acre-feet. The reservoir covers a surface area of 38 acres and drains a 4.1 square mile watershed, with a maximum discharge of 95 cubic feet per second.
Managed by the local government and regulated by the Montana Department of Natural Resources and Conservation (DNRC), Big Lake is classified as having a significant hazard potential and a moderate risk level. The dam features an uncontrolled spillway with a width of 25 feet and outlet gates that are also uncontrolled. The last inspection of the dam was conducted in August 2017, with its condition currently rated as "Not Rated" in terms of assessment.
Water resource and climate enthusiasts will find Big Lake an intriguing structure due to its historical significance, design, and operational details. Situated in a picturesque location in the Seattle District, the dam serves as a vital resource for water supply in the region. With its unique features and regulatory oversight, Big Lake presents an opportunity for further exploration and study in the realm of water resource management and climate resilience.
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 Big Lake -- inflows here typically show up in storage 24-72 hours later.
| Streamgauge | Discharge | View |
|---|---|---|
| South Fork Jocko River Near Arlee Mt | 61 cfs | → |
| Clark Fork Above Missoula Mt | 2,710 cfs | → |
| Blackfoot River Near Bonner Mt | 1,410 cfs | → |
| Clark Fork Below Missoula Mt | 3,970 cfs | → |
| Clark Fork At Turah Bridge Nr Bonner Mt | 1,280 cfs | → |
| Bitterroot River Near Missoula Mt | 1,320 cfs | → |
Make a day of it
Boat launches, lakeside camping, fishing access, and other reservoirs near Big Lake.
Boat launches
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Campgrounds
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Fishing spots
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River runs
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More reservoirs
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About Big Lake
Where does the data for Big Lake 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 Significant 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 below 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.
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.