Jefferts Dam dam
Jefferts Dam
Located in San Juan, Washington, the Jefferts Dam stands as a crucial water resource structure for irrigation and recreation purposes. Completed in 1988, this earth-type dam boasts a hydraulic height of 15 feet and a structural height of 12 feet, with a storage capacity of 52 acre-feet. Situated on the Tr-San Juan Channel, the dam covers a surface area of 5 acres and serves a drainage area of 0.06 square miles.
Owned privately, the Jefferts Dam is regulated and permitted by the Washington Department of Ecology, ensuring its compliance with state laws and regulations. With a low hazard potential and a condition assessment of "Not Rated," this dam plays a significant role in water management and conservation efforts in the region. Despite its modest size, the dam has a maximum discharge capacity of 100 cubic feet per second, providing a vital water source for the surrounding agricultural lands.
Managed by the Seattle District of the US Army Corps of Engineers, the Jefferts Dam maintains a strong operational record, with regular inspections and enforcement procedures in place. With its strategic location and purposeful design, this dam serves as a testament to the importance of sustainable water resource management in the face of changing climate patterns and growing water demands.
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 Jefferts Dam -- inflows here typically show up in storage 24-72 hours later.
| Streamgauge | Discharge | View |
|---|---|---|
| Nooksack River At Ferndale | 3,120 cfs | → |
| Samish River Near Burlington | 117 cfs | → |
| Olsen Creek Near Bellingham | 2 cfs | → |
| Carpenter Creek At N Shore Drive Nr Bellingham | 1 cfs | → |
| Skagit River Near Mount Vernon | 18,300 cfs | → |
| Brannian Creek At S Bay Dr Nr Wickersham | 2 cfs | → |
Make a day of it
Boat launches, lakeside camping, fishing access, and other reservoirs near Jefferts Dam.
Boat launches
- Dock Road 98, San Juan County
- Cayou Quay Marina
- Odlin Park Road 177-199, Lopez Island
- Hummel Lake Road 674, Lopez Island
- San Juan County
- Saint John's Road San Juan County
Campgrounds
- Spencer Spit State Park Campground
- Cascadia Marine Trail Campsite
- Moran State Park Campground
- Fox Cove Camp
- Snoring Bay Camp
- Shallow Bay South
Paddle runs
- Fish Hatchery To Confluence With South Fork Nooksack River
- Sleepy Hollow Creek To Olympic Nf Boundary
- Usfs Road 2870 Bridge To Confluence With Dungeness River
- Olympic Nf/Olympic Np Boundary To Usfs Road 2870 Bridge
- Nooksack Falls Power Plant To Fish Hatchery Near Kendall, Wa
- 1.4 Miles Upstream From Confluence With Elwha River To Confluence With Elwha River
Track Jefferts Dam 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 Jefferts Dam
Where does the data for Jefferts Dam 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 Jefferts Dam.