BASS LAKE DAM HISTORY/INFO
BASS LAKE IS ALSO KNOWN AS CRANE VALLEY RESERVOIR
The original dam was built in 1896 and enlarged in 1910. The Sugar Pine Railroad used to cross the dam, bringing logging to Fresno. The Dam is actually two parts both basically earth (Hydraulic Fill). The long side, the one you see from most angles of the lake has no spillway. There is a water tower which allows for the regulated outflow to the generator and stream.
The other side is around to the East. It is where the spillway is located. The spillway is specially designed to allow high levels of water to flow down stream without damaging the dam.
The spillway has 2 moveable gates to regulate outflow. The height of the Spillway to the top of the gates is about 11.5 ft. The top of the gate is 3376.4 ft elevation.
Here you see the steel tracks for the removable boards. The boards slide into a track and hold water back. They are installed after April 1st and remove November 1st. They can not be removed when holding back water. Typically no water goes through the spillway since it cannot be used to generate power. The spillway provides emergency protection to the dam. All outflow is regulated through the power station.
The Boards and the Gates are closed in this picure taken with the lake filling and only 3" of water pushing against the boards.
Take a Hike!
The Dam is accessible from the public boat ramp on the South East side of the Lake from Road 222. You can walk across the long dam, follow the paved road a little further and you will see the Spillway. If you follow the paved road for 10 minutes you will meet Road 274 and see Browns Ditch, or reverse the path and start at browns Ditch.
Along side the Falls are trails on both sides. They will take you up the creek to where Road 274 crosses. The trails go up at least another mile. Beware of poison oak. Be in shape because it is a steep climb. Have fun.
Water Sources
Most of the rain and snow melt, run into the lake through the Falls located at the North West end. North Shore Road (rd 432) crosses over this creek called 'North Willow Creek' This creek is also the source of drinking water for the Pines Track & Falls Tracks
Another major source is Browns Ditch. This slue was added to increase the inflow when the dam was enlarged in 1910. The slue is located at the North Eastern side of the Lake. You can see Browns Ditch on Road 274 & Central Camp. Water fills the slue at a maximum rate of 75 cu/ft/sec from Browns Creek and South Willow Creek along with several other unnamed creeks.
Many smaller streams also feed water to the lake.
Willow Cove - Pines Creek
Lake Shore Cove - Salter Creek
Recreation Point - Slide Creek
The Crane Valley Power House, at Bass Lake has a 900 KW Generator, installed in 1919. This is one of 5 generators on the San Joaquin River system producing about 28 MW's of power.
The power House as seen from the top of the dam. Water is diverted to either the creek or to another slue taking it to other generators. Water is always released into the creek to maintain the down stream habitat.
Dam Operation and Description
The Lake is Owned by PG&E and regulated by government agencies. PG&E operates the lake under a Federal License which sets the conditions for maintaining the lake's water level and outflow needs. Considerations are made for the following uses:
Flood Control & Lake Level
This needs are obvious. As summer ends the lake level is lowered to 50% of capacity to about -23 ft. Regulations require the Lake to be lowered to 50% by November 1st. The Bass Lake Homeowners Association and other community interest lobbies PG&E to request a waiver of the rules delaying the draw down. This waiver is granted if a number of conditions exist to assure the lake is lowered to required levels. PG&E also schedules a maintenance outage to service all the power stations and slues in the system. This outage usually occurs in July & August so the ability to draw down the lake is limited to providing water to downstream habitat. Over the past few years the lake level has been kept high enough to keep docks floating through Labor Day.
Drink Water Supply
The Lake provides limited drinking water to the PG&E Camp site area behind Millers Landing. Bass Lake Water District draws water from the stream feeding the falls. Other homes and tracks obtain well water.
Down Stream Habitat
It is not possible to cut all water out flow down stream without damaging the habitat. Water supports fishing and wild life. It is not wasted however since down stream dams also generate power. Water flows into the central valley and is used for drinking and agriculture.
Power Generation
Crane Valley Powerhouse, sited immediately below Bass Lake Dam generates 900 KW of power through its turbine and after the water is discharged from the powerhouse, it continues through four more down stream powerhouses generating about 28 MW for the system. From the top of the dam you can see the powerhouse and the water moving down stream. Power is generated when ever the lake is drawn down for any reason. Sometimes energy needs out weigh the recreational needs to keep the lake full.
Recreational Use
The Lake brings thousand of people to the area and make a significant contribution the the area's economy. The government and PG&E do there best to maintain the lake's condition including keeping the water level high enough during the summer.