Cox Hollow Number Two dam
Cox Hollow Number Two
Cox Hollow Number Two, also known as Twin Valley Lake at Governor Dodge State Park in Wisconsin, is a state-owned recreational dam on Mill Creek. Built in 1965 by the USDA NRCS, this earth dam stands at a height of 55 feet and has a hydraulic height of 37 feet, providing a storage capacity of 5,370 acre-feet. With a surface area of 152 acres and a drainage area of 13.9 square miles, the dam serves the primary purpose of recreation.
Despite its age, Cox Hollow Number Two is in fair condition with a high hazard potential, prompting regular inspections by the Wisconsin Department of Natural Resources. The dam's spillway is controlled with a width of 5 feet, and it has a maximum discharge capacity of 606 cubic feet per second. The risk assessment for the dam is categorized as very high, emphasizing the need for continued monitoring and maintenance to ensure public safety and water resource protection in the surrounding area.
For water resource and climate enthusiasts, Cox Hollow Number Two offers a fascinating glimpse into the intersection of human infrastructure and natural ecosystems. This recreational dam not only provides opportunities for outdoor activities but also serves as a vital component of the local watershed, contributing to flood control and water storage. As we continue to navigate the challenges of climate change, understanding and maintaining dams like Cox Hollow Number Two will be crucial in safeguarding our water resources for future generations.
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 Cox Hollow Number Two -- inflows here typically show up in storage 24-72 hours later.
| Streamgauge | Discharge | View |
|---|---|---|
| Black Earth Creek At Black Earth | 51 cfs | → |
| East Br Pecatonica River Near Blanchardville | 183 cfs | → |
| Wisconsin River At Muscoda | 10,400 cfs | → |
| Brewery Creek-Upstream Site-At Cross Plains | 2 cfs | → |
| Pecatonica River At Darlington | 242 cfs | → |
| Badger Mill Creek At Verona | 11 cfs | → |
Make a day of it
Boat launches, lakeside camping, fishing access, and other reservoirs near Cox Hollow Number Two.
Boat launches
- Twin Valley Lake Boat Ramp
- Cox Hollow Lake -- Access
- Mill Creek At Mill Rd
- Wisconsin River -- Pecks Landing
- Sneed Creek At High Point Rd
- Trout Creek - Birch Lake -- Access
Campgrounds
- Twin Valley Campground
- Governor Dodge State Park
- Governor Dodge State Park Campground
- Tower Hill State Park Campground
- Tower Hill State Park
- Blackhawk Lake Rec Area - Highland
Track Cox Hollow Number Two 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 Cox Hollow Number Two
Where does the data for Cox Hollow Number Two 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 Cox Hollow Number Two.