Allen Lake dam
Allen Lake
Allen Lake, located in Boulder, Colorado, is a privately-owned reservoir with a primary purpose of irrigation. Built in 1928, the earth dam stands at 24 feet high and spans 1525 feet in length, providing a maximum storage capacity of 865 acre-feet. The reservoir covers a surface area of 36 acres and is fed by Left Hand Creek-OS, with a significant hazard potential due to its uncontrolled spillway and satisfactory condition assessment.
The dam at Allen Lake is regulated by the Colorado Division of Water Resources, with state permitting, inspection, and enforcement in place to ensure its safety and compliance. The dam is equipped with a slide (sluice gate) outlet gate and has a moderate risk assessment rating. The surrounding area is under the jurisdiction of Longmont city and falls within the congressional district of Joe Neguse (D). Water resource and climate enthusiasts can appreciate the historical significance and functional importance of Allen Lake in sustaining agricultural activities and providing water for various purposes in the region.
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 Allen Lake -- inflows here typically show up in storage 24-72 hours later.
| Streamgauge | Discharge | View |
|---|---|---|
| Left Hand Creek Near Boulder | 36 cfs | → |
| St. Vrain Creek At Lyons | 89 cfs | → |
| Left Hand Creek At Hover Road Near Longmont | 1 cfs | → |
| Boulder Cr At North 75th St Nr Boulder | 37 cfs | → |
| Fourmile Creek At Orodell | 2 cfs | → |
| Boulder Creek Near Orodell | 63 cfs | → |
Make a day of it
Boat launches, lakeside camping, fishing access, and other reservoirs near Allen Lake.
Boat launches
- Lagerman Trail Boulder County
- Miramonte Road Boulder County
- Standley Lake Trail Westminster
- Ralston Creek Trail Arvada
- West 69th Avenue 4700, Westminster
- Boat Ramp Larimer County
Campgrounds
- Meadow Park
- Boulder County Fairground
- Glacier View Ranch
- Peaceful Valley
- Peaceful Valley Campground
- Camp Dick Campground
Fishing spots
- South Saint Vrain Fishing Site #4
- South Saint Vrain Fishing Site #2
- South Saint Vrain Fishing Site #5
- Lagerman Reservoir
- Boulder Reservoir
- Coot Lake
Track Allen Lake 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 Allen Lake
Where does the data for Allen Lake 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 Significant 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 Allen Lake.