Overnight Reservoir dam
Overnight Reservoir
Overnight Reservoir, located in Beaverhead, Montana, is a privately owned irrigation reservoir completed in 1920. With a dam height of 17 feet and a storage capacity of 88 acre-feet, this earth dam serves the primary purpose of providing water for irrigation in the region. Situated along the TR-CAVE GULCH river or stream, this reservoir plays a crucial role in supporting agricultural activities in the area.
Managed by the Montana Department of Natural Resources and Conservation (DNRC), Overnight Reservoir has a low hazard potential and is currently rated as "Not Rated" in terms of condition assessment. Although details on inspection frequency and emergency preparedness are not provided, the reservoir remains a key water resource infrastructure in the region. With its strategic location in the Walla Walla District and close proximity to GLEN city, Overnight Reservoir continues to contribute to water security and support sustainable agriculture practices in the area.
While the exact dimensions of the reservoir's spillway, surface area, and maximum discharge are not specified, Overnight Reservoir stands as a vital component of water resource management in Beaverhead County. As water resource and climate enthusiasts, the details of this reservoir highlight the importance of maintaining and monitoring such infrastructure to ensure sustainable water supply and irrigation for agricultural activities 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 Overnight Reservoir -- inflows here typically show up in storage 24-72 hours later.
| Streamgauge | Discharge | View |
|---|---|---|
| Beaverhead River At Dillon Mt | 116 cfs | → |
| Big Hole River Near Glen Mt | 1,590 cfs | → |
| Beaverhead River Near Twin Bridges Mt | 102 cfs | → |
| Big Hole River Near Melrose Mt | 1,630 cfs | → |
| Beaverhead River At Barretts Mt | 521 cfs | → |
| Ruby River Near Twin Bridges Mt | 31 cfs | → |
Make a day of it
Boat launches, lakeside camping, fishing access, and other reservoirs near Overnight Reservoir.
Boat launches
- S-324 155, Beaverhead County
- S-324 84-256, Beaverhead County
- Maiden Rock Boat Ramp
- Divide Bridge Boat Ramp
Campgrounds
- Birch Creek Cabin
- Glen Fas
- Notch Bottom Fas
- Dinner Station Campground And Picnic Area
- Barretts Park - Usbr
- Brownes Bridge Fas
Fishing spots
Track Overnight Reservoir 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 Overnight Reservoir
Where does the data for Overnight Reservoir 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.
Other water bodies near here
Snoflo-tracked reservoirs and dams within driving distance of Overnight Reservoir.