Preston Forebay dam
Preston Forebay
Preston Forebay is a historic hydroelectric facility located in Ione, California, owned by a public utility. Built in 1892, this offstream dam stands at a height of 40 feet and has a storage capacity of 30 acre-feet. The primary purposes of the dam include flood risk reduction, hydroelectric power generation, and irrigation, making it a vital water resource for the region.
Managed by the California Department of Water Resources (DWR), Preston Forebay is regulated, permitted, inspected, and enforced by state agencies to ensure its safety and functionality. With a low hazard potential and a satisfactory condition assessment, the dam provides reliable water storage and power generation while maintaining minimal risk to surrounding communities. The dam's historical significance, combined with its modern regulatory oversight, makes it a valuable asset in managing water resources and climate challenges in Amador County.
As part of the San Francisco District, Preston Forebay plays a crucial role in the local water infrastructure, contributing to the overall resilience of the region. With a strong emphasis on safety and regulatory compliance, this dam serves as a testament to the intersection of traditional hydroelectric technology and modern water management practices. For water resource and climate enthusiasts, Preston Forebay offers a fascinating glimpse into the history and evolution of water infrastructure in California.
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 Preston Forebay -- inflows here typically show up in storage 24-72 hours later.
| Streamgauge | Discharge | View |
|---|---|---|
| Cosumnes R A Michigan Bar Ca | 168 cfs | → |
| Deer C Nr Cameron Park Ca | 8 cfs | → |
| Laguna C Nr Elk Grove Ca | 1 cfs | → |
| American R A Fair Oaks Ca | 1,920 cfs | → |
| Morrison C Nr Sacramento Ca | 11 cfs | → |
| Arcade C Nr Del Paso Heights Ca | · | → |
Make a day of it
Boat launches, lakeside camping, fishing access, and other reservoirs near Preston Forebay.
Boat launches
- Willow Creek Boat Ramp
- Jedediah Smith Memorial Trail, Gold River
- Lake Natoma Northern Boat Ramp
- Green Valley Road 661, El Dorado Hills
- Pennsylvania Avenue 3885, Fair Oaks
- Harrington Way 950, Carmichael
Campgrounds
- Rancho Seco Rec Area
- Oak Knoll - New Hogan Lake
- Acorn - New Hogan Lake
- Acorn Campground
- Indian Grinding Rock Campground
- Indian Grinding Rock State Park
Fishing spots
Paddle runs
More reservoirs
Track Preston Forebay 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 Preston Forebay
Where does the data for Preston Forebay 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 Preston Forebay.