Agnes Lake dam
Agnes Lake
Agnes Lake, located in Beaverhead, Montana, is a privately owned dam on Agnes Creek that serves primarily for irrigation purposes. Completed in 1928, this earth dam stands at a height of 13 feet with a hydraulic height of 9 feet and a length of 174 feet. With a storage capacity of 1900 acre-feet, it is a crucial water resource in the region, holding a normal storage level of 790 acre-feet.
Despite its age, Agnes Lake Dam is in a condition that has not been officially rated, posing a high hazard potential due to its uncontrolled spillway and outlet gates. The risk assessment for this structure is considered moderate, with an inspection frequency of once a year. While the emergency action plan status and risk management measures are unclear, the dam remains under state regulation and jurisdiction, ensuring that it meets necessary safety standards.
Water resource and climate enthusiasts interested in the history and current status of Agnes Lake Dam will find it intriguing to explore the complexities of this irrigation infrastructure in Montana. As a key component of water management in the area, the dam's design and operation, along with its high hazard potential and moderate risk assessment, highlight the importance of ongoing monitoring and evaluation to ensure the safety and reliability of this vital water resource for the community.
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 Agnes Lake -- inflows here typically show up in storage 24-72 hours later.
| Streamgauge | Discharge | View |
|---|---|---|
| Big Hole River Near Melrose Mt | 2,080 cfs | → |
| Big Hole River At Maiden Rock Nr Divide Mt | 1,980 cfs | → |
| Big Hole River Near Glen Mt | 2,250 cfs | → |
| Beaverhead River Near Twin Bridges Mt | 193 cfs | → |
| Beaverhead River At Dillon Mt | 130 cfs | → |
| Ruby River Near Twin Bridges Mt | 371 cfs | → |
About Agnes Lake
Where does the data for Agnes 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 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 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.