Johnstown dam
Johnstown
Johnstown, located in Weld County, Colorado, is home to a critical water resource infrastructure known as the Johnstown Dam. Completed in 1953, this earth dam on the Big Thompson River-OS serves as a vital water supply source for the region, with a storage capacity of 350 acre-feet and a surface area of 34 acres. Despite its importance, the dam's condition assessment in 2020 deemed it unsatisfactory, with a high hazard potential, indicating the need for significant maintenance and upgrades to ensure the safety of the surrounding community.
The Johnstown Dam, standing at 16 feet in height and stretching over 5737 feet in length, plays a crucial role in water management and supply for the area. However, its high risk assessment of 2 (on a scale of 1-5) underscores the urgency of addressing its structural integrity and hazard potential. With state regulation and inspection in place, efforts must be intensified to improve the dam's condition and reduce the risk to downstream communities in case of a potential failure.
As water resource and climate enthusiasts, the situation at the Johnstown Dam highlights the importance of proactive maintenance and risk management for critical infrastructure in the face of changing environmental conditions. It serves as a reminder of the ongoing challenges faced in safeguarding our water resources and infrastructure against potential threats, underscoring the need for continued monitoring, investment, and community engagement to ensure resilience in the face of a changing climate.
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 Johnstown -- inflows here typically show up in storage 24-72 hours later.
| Streamgauge | Discharge | View |
|---|---|---|
| Big Thompson River At Loveland | 82 cfs | → |
| St. Vrain Creek At Mouth | 89 cfs | → |
| Big Thompson River At Mouth | 33 cfs | → |
| St Vrain Cr Blw Boulder Cr At Hwy 119 Nr Longmont | 59 cfs | → |
| St. Vrain Creek Below Longmont | -999,999 cfs | → |
| Boulder Creek At Mouth | 9 cfs | → |
Make a day of it
Boat launches, lakeside camping, fishing access, and other reservoirs near Johnstown.
Boat launches
- Boat Ramp Larimer County
- Lagerman Trail Boulder County
- Filter Plant River Access Point (Put-In)
- Brighton
- Adams County
- Bridges River Access Point (Take-Out)
Campgrounds
- Missile Site Park
- Boyd Lake State Park
- Union Reservoir
- St. Vrain State Park
- Carter Lake - South Side Campgrounds
- Carter Lake - North Side Campgrounds
Fishing spots
Track Johnstown 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 Johnstown
Where does the data for Johnstown 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 Johnstown.