Nelsonville dam
Nelsonville
Nelsonville, located in Portage, Wisconsin, is home to a hydroelectric dam on the Tomorrow River. This historic dam, completed in 1855, serves multiple purposes including hydroelectric power generation and recreation. With a gravity dam type and a height of 14 feet, the Nelsonville dam has a low hazard potential and is classified as having a very high risk due to its age and structural condition, which has not been rated.
The dam has a storage capacity of 180 acre-feet and a drainage area of 69 square miles, with a maximum discharge of 1685 cubic feet per second. Despite its age, the Nelsonville dam is still in operation and is regulated by the Wisconsin Department of Natural Resources (WIDNR), which oversees its permitting, inspection, and enforcement. The dam's condition is currently not rated, and it has a 10-year inspection frequency to ensure its safety and functionality.
Water resource and climate enthusiasts will be intrigued by the historical significance and operational capabilities of the Nelsonville dam. Its location on the Tomorrow River, combined with its hydroelectric power generation and recreational uses, make it a key structure in the region. However, the dam's age and risk assessment highlight the importance of ongoing monitoring and maintenance to ensure its safety and efficiency in the face of changing environmental conditions.
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 Nelsonville -- inflows here typically show up in storage 24-72 hours later.
| Streamgauge | Discharge | View |
|---|---|---|
| Tomorrow River Near Nelsonville | 53 cfs | → |
| Waupaca River Near Waupaca | 431 cfs | → |
| Little Wolf River At Royalton | -999,999 cfs | → |
| Wisconsin River At Wisconsin Rapids | 6,450 cfs | → |
| Wolf River At New London | 2,460 cfs | → |
| Tenmile Creek Near Nekoosa | 153 cfs | → |
Make a day of it
Boat launches, lakeside camping, fishing access, and other reservoirs near Nelsonville.
Boat launches
- Meyers Lake -- Access
- Lake Emily -- Access - Lake Dr
- Lake Emily -- Access Nr Edgewater Dr
- Rinehart Lake -- Access
- Tomorrow River -- Access
- Sunset Lake -- Access
Track Nelsonville 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 Nelsonville
Where does the data for Nelsonville 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 Nelsonville.