Milles Lake Dam dam
Milles Lake Dam
Milles Lake Dam in Twisp, Washington, stands as a vital structure for fish and wildlife conservation and irrigation purposes. Completed in 1950, this earth dam boasts a hydraulic height of 13 feet and a structural height of 11 feet, providing a crucial 24-acre-feet of storage capacity for the surrounding area. Situated on the Unnamed Tributary of the Twisp River, the dam serves as a key feature within the Okanogan County landscape, regulated and inspected by the Washington Department of Ecology to ensure its safety and functionality.
With a Hazard Potential rated as High and a Condition Assessment deemed Satisfactory during the last inspection in June 2021, Milles Lake Dam remains a significant contributor to the region's water resource management. Its location in the Congressional District 04 of Washington underlines its importance within the state's infrastructure. As a state-regulated and state-permitted dam, it plays a crucial role in maintaining the ecological balance of the area, serving as a lifeline for the local fish and wildlife populations while also supporting agricultural activities through irrigation provisions. The dam's capacity to store 20 acre-feet of water under normal conditions highlights its essential role in sustaining the surrounding environment.
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 Milles Lake Dam -- inflows here typically show up in storage 24-72 hours later.
| Streamgauge | Discharge | View |
|---|---|---|
| Twisp River Near Twisp | 801 cfs | → |
| Methow River At Twisp | 3,590 cfs | → |
| Methow River At Winthrop | 2,870 cfs | → |
| Chewuch River At Winthrop | 914 cfs | → |
| Methow River Above Goat Creek Near Mazama | 1,400 cfs | → |
| Okanogan River At Malott | 4,980 cfs | → |
Make a day of it
Boat launches, lakeside camping, fishing access, and other reservoirs near Milles Lake Dam.
Boat launches
- Conconully Road Conconully
- Okanogan County
- Sinlahekin Road 100-144, Okanogan
- Green Lake Road 50-374, Okanogan
- Sinlahekin Road, Okanogan
Campgrounds
- Tent Camping
- Campbell Lake - Wdfw
- Pearrygin Lake State Park
- Blackpine Lake
- Black Pine Lake Campground
- Cougar Lake Campground
Paddle runs
- Private Land Boundary To Okanogan Nf Boundary
- Lake Chelan-Sawtooth Wilderness Boundary To Okanogan Nf Boundary
- Confluence Of South Fork Wolf Creek To Lake Chelan-Sawtooth Wilderness Boundary
- Lake Chelan-Sawtooth Wilderness Boundary To Private Land Boundary Near Lime Creek In Se1/4 Of Sec 18, T33n, R20e
- Pasayten Wilderness Boundary To Okanogan Nf Boundary
Track Milles Lake 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 Milles Lake Dam
Where does the data for Milles Lake 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 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 Milles Lake Dam.