Lake Mills dam
Lake Mills
Lake Mills, also known as Rock Lake, is a picturesque reservoir located in Jefferson County, Wisconsin. Owned and regulated by the local government, this gravity dam was completed in 1865 for the primary purpose of recreation. With a height of 17.2 feet and a storage capacity of 28,330 acre-feet, the dam sits on Rock Creek and covers a surface area of 1,371 acres.
Despite its age, Lake Mills remains in satisfactory condition with a high hazard potential due to its location and structural specifications. Regular inspections are conducted by the Wisconsin Department of Natural Resources, with the last assessment taking place in October 2019. The dam has a controlled spillway and a maximum discharge of 115 cubic feet per second, serving as a vital resource for the community while also posing a very high risk in the event of a failure.
In recent years, Lake Mills has undergone modifications in 1962 and 2016 to ensure its continued safety and functionality. With its scenic surroundings and recreational opportunities, this reservoir serves as a key feature in the region's water resource management efforts, attracting enthusiasts interested in both water conservation and climate resilience.
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 Lake Mills -- inflows here typically show up in storage 24-72 hours later.
| Streamgauge | Discharge | View |
|---|---|---|
| Crawfish River At Milford | 624 cfs | → |
| Rock River At Robert Street At Fort Atkinson | 2,260 cfs | → |
| Rock River At Watertown | 1,050 cfs | → |
| Bark River Near Rome | 116 cfs | → |
| Yahara River At Forton St. Bridge At Stoughton | 227 cfs | → |
| Yahara River At Mc Farland | 132 cfs | → |
Make a day of it
Boat launches, lakeside camping, fishing access, and other reservoirs near Lake Mills.
Boat launches
- Rock Lake -- Mill Pond Rock Lake Access
- Rock Lake -- Sandy Beach Launch
- Rock Lake -- Ferry Park Landing Access
- Rock Lake -- Elm Point Rock Lake Access
- Rock Lake -- North End Launch Park Lane Rd
- Rock Creek -- Access South Of Rock Lake
Campgrounds
- Sandhill Station
- Jellystone Campground
- Astico County Park Campground
- Hidden Valley Rv Resort
- Babcock County Park Campground
- Harnischefeger Park
Fishing spots
Paddle runs
More reservoirs
Track Lake Mills 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 Lake Mills
Where does the data for Lake Mills 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 Lake Mills.