O'Farrell Dam No. 2 dam
O'Farrell Dam No. 2
O'Farrell Dam No. 2, located on the TR-N. Fork Whetstone River in Grant, South Dakota, is a privately owned structure designed by KONECHNE ENG. The dam, completed in 2006, stands at 20 feet tall and spans a length of 400 feet, providing a storage capacity of 65 acre-feet. With a low hazard potential and a moderate risk assessment, the dam is regulated by the South Dakota Department of Environment and Natural Resources (DENR) and undergoes state inspections, permitting, and enforcement.
Despite its relatively low hazard potential, O'Farrell Dam No. 2 plays a crucial role in water resource management and climate adaptation in the region. The dam's uncontrolled spillway, with a width of 150 feet, helps regulate the flow of the TR-N. Fork Whetstone River, reducing the risk of flooding and ensuring a stable water supply for nearby communities and agricultural activities. The dam's earth construction and soil foundation contribute to its structural integrity and operational efficiency, making it a key component in the local water infrastructure.
As a part of the Omaha District of the U.S. Army Corps of Engineers, O'Farrell Dam No. 2 serves as a testament to collaborative efforts between private owners and government agencies in ensuring the safety and sustainability of water resources. With its capacity to store 65 acre-feet of water and a normal storage level of 32 acre-feet, the dam plays a vital role in managing water supply during dry periods and mitigating potential risks during heavy rainfall events. Its presence highlights the importance of proactive dam management and the need for continued monitoring and maintenance to safeguard water resources and adapt to changing climate 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 O'Farrell Dam No. 2 -- inflows here typically show up in storage 24-72 hours later.
| Streamgauge | Discharge | View |
|---|---|---|
| Big Sioux River Nr Florence Sd | 7 cfs | → |
| Little Minnesota River Near Peever | 53 cfs | → |
| Whetstone River Near Big Stone City | 63 cfs | → |
| Big Sioux R Near Watertown Sd | 25 cfs | → |
| Minnesota River At Ortonville | 84 cfs | → |
| Big Sioux R At Watertown Sd | 29 cfs | → |
Make a day of it
Boat launches, lakeside camping, fishing access, and other reservoirs near O'Farrell Dam No. 2.
Boat launches
- Roberts County
- Mn 27 4906, Traverse County
- Mn 27 4924, Traverse County
- Rocky Point Big Stone City
- North Lake Drive 298, Watertown
- 63 Watertown
Track O'Farrell Dam No. 2 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 O'Farrell Dam No. 2
Where does the data for O'Farrell Dam No. 2 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 O'Farrell Dam No. 2.