Gammon dam
Gammon
Gammon, located in Johnson, Wyoming, is a privately owned irrigation dam on T. A. Creek completed in 1974. With a height of 24 feet and a length of 1120 feet, this earth dam serves the primary purposes of flood risk reduction and irrigation, providing a storage capacity of 86 acre-feet. Despite its low hazard potential, the dam's structural condition is assessed as poor, emphasizing the need for regular inspections and maintenance.
The dam features an uncontrolled spillway with a width of 30 feet and a maximum discharge capacity of 271 cubic feet per second. The surrounding area has a drainage area of 0.5 square miles, with a normal storage capacity of 46 acre-feet. The dam's poor condition assessment raises concerns about its long-term reliability and underscores the importance of risk management measures to ensure the safety of downstream communities and agricultural lands.
As a vital water resource infrastructure in Wyoming, Gammon serves as a critical component of the local irrigation system, highlighting the intersection of water management and climate resilience. With its outdated design and poor condition, the dam presents challenges that must be addressed through proactive monitoring, maintenance, and potential rehabilitation efforts to safeguard its functionality and mitigate potential risks to the surrounding ecosystem and community.
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 Gammon -- inflows here typically show up in storage 24-72 hours later.
| Streamgauge | Discharge | View |
|---|---|---|
| Clear Creek Near Buffalo | 116 cfs | → |
| Nf Powder River Below Pass Creek | 50 cfs | → |
| North Fork Powder River Near Hazelton | 3 cfs | → |
| Rock Creek Near Buffalo | 70 cfs | → |
| Piney Creek At Kearny | 113 cfs | → |
| South Piney Creek At Willow Park | 0 cfs | → |
Make a day of it
Boat launches, lakeside camping, fishing access, and other reservoirs near Gammon.
Campgrounds
- Canyon Campground
- Muddy Guard Cabin
- Crazy Woman Campground
- Pole Creek Cabin
- Lost Cabin Campground
- Lost Cabin
Fishing spots
- Tie Hack Reservoir
- Healy Lake
- Lake Desmet
- Veterans Cove Fishing Site
- Upper Paintrock Fishing Site
- Sheridan Fairgrounds Pond
More reservoirs
Track Gammon 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 Gammon
Where does the data for Gammon 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 Gammon.