The lake is a man-made reservoir, completed in 1953 by the U. S. Army Corps of Engineers. The Corps built earthen dams across the north and south forks of the Kern River to create the Isabella Reservoir. At a surface area of 11,200 acres, it is Kern County’s largest body of water. Originally designed for water storage for agricultural users in the Bakersfield area, the lake is also the favorite site of recreational enthusiasts for fishing, water skiing, camping and other outdoor activities.
In recent years, endangered species issues and dam integrity problems have required that Isabella Reservoir levels be kept at about two-thirds of capacity.
One of the problems surrounding the Main Dam involves an inadequate spillway. Because the Main Dam was designed under 1950s-era standards, the spillway does not meet current standards. A newly designed spillway is slated to be completed by 2017.
Earthquake safety is another issue at Isabella Reservoir. The original engineers on the project knew there was a fault line beneath the Auxiliary Dam, but believed it was inactive. Engineers now consider that fault active and the Auxiliary Dam has a potential for failure, in the event of a large earthquake. Repairs for this are also expected to be completed by 2017.
Because Isabella Reservoir is now maintained at lower levels, managing Kern River water supplies is challenging. Several agricultural districts normally store water in the reservoir in the spring, then draw on that water later in the year for irrigation needs. Now these districts sometimes have to take Kern River water in the spring – often when other water supplies are more plentiful such as State Water Project (SWP) water.