Mcmahon dam
Mcmahon
Mcmahon is a private earth dam located in Snelling, California, along Maxwell Creek. Built in 1957, this dam serves primarily for water supply, with a storage capacity of 520 acre-feet. It stands at a height of 52 feet and has a hydraulic height of 42 feet, making it a crucial structure for irrigation and water supply in the area.
Managed by the California Department of Water Resources, Mcmahon is regulated, permitted, inspected, and enforced by state agencies to ensure its safety and compliance with regulations. Despite its low hazard potential, the dam is regularly assessed and deemed to be in satisfactory condition. The last inspection in August 2019 confirmed its structural integrity, making it a reliable resource for water management and climate resilience in Mariposa County.
With its strategic location and vital role in water supply, Mcmahon represents a valuable asset for the community and the environment. As a key structure along Maxwell Creek, this dam not only provides essential water resources but also contributes to the overall sustainability and resilience of the region. Its satisfactory condition and low hazard potential underscore the importance of proper maintenance and monitoring to ensure its continued functionality and safety for years to come.
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 Mcmahon -- inflows here typically show up in storage 24-72 hours later.
| Streamgauge | Discharge | View |
|---|---|---|
| Big C Ab Whites Gulch Nr Groveland Ca | 1 cfs | → |
| Turlock Cn Nr La Grange Ca | 890 cfs | → |
| Tuolumne R Bl Lagrange Dam Nr Lagrange Ca | 184 cfs | → |
| Modesto Cn Nr La Grange Ca | 1,140 cfs | → |
| Tuolumne R Bl Early Intake Nr Mather Ca | 1,270 cfs | → |
| Cherry C Bl Dion R Holm Ph | 791 cfs | → |
Make a day of it
Boat launches, lakeside camping, fishing access, and other reservoirs near Mcmahon.
Boat launches
- Merals Pool Put-In
- Forest Route 1n10 Tuolumne County
- Forest Route 1n04, Groveland
- Glory Hole Road 6503, Angels Camp
Campgrounds
- Horseshoe Bend Rec Area
- Barrett Cove Rec Area
- Bagby Rec Area
- Mcclure Point Rec Area
- Pines Group Campground
- The Pines
Fishing spots
Paddle runs
- Clavey River From Cottonwood Road To Confluence With Tuolumne
- Confluence With Middle Fork Tuolumne River To Confluence With Tuolumne River
- Clavey River From 3n01 To Cottonwood Road
- Clavey River At Confluence Of Bell And Lily Creeks To 3n01
- Headwaters Near The Tuolumne And Mariposa County Lines To Western Boundary Of Yosemite National Park
- Confluence With North Fork And Middle Fork Stanislaus To Clark Flat
More reservoirs
Track Mcmahon 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 Mcmahon
Where does the data for Mcmahon 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 Mcmahon.