The Bay Delta Conservation Plan staff on their website have admitted to the fact that the water destined for the peripheral tunnels could be used for fracking.
The site says that Fracking presumably would be an “industrial” use of water, a "beneficial" use of project water.
Here's the BDCP's question and answer about fracking:
Will water pumped from the Delta be used for fracking in the Central Valley?
"The California Department of Water Resources does not regulate the uses to which State Water Project supply is put.
State constitutional restrictions require the reasonable and beneficial use of water, and state laws require that water pumped from the Delta be put to stipulated beneficial uses. Beneficial uses include agricultural, municipal, and industrial consumptive uses; power production; and in-stream uses including fish protection flows. Fracking presumably would be an “industrial” use of water.
The state Department of Conservation is currently working on fracking regulations and rules passed by the Legislature have been sent to the governor. Through the rule-making process, the state will better understand how much water is actually used for fracking in California. Voluntary reporting indicates that the use of water for fracking is minimal. The Department of Conservation estimates that statewide, about 270 acre-feet of water per year is used for hydraulic fracture stimulation activities. For comparison’s sake, roughly 5.2 million acre-feet of water a year have been diverted from the Delta, on average, over the last 20 years by the federal and state water projects for farms and cities.
The State Water Resources Control Board could modify water permits to balance and protect beneficial uses of water. If the Legislature declared fracking to be unreasonable, it would potentially trigger the State Water Resources Control Board to revise water right permits in such a way as to restrict Delta water from being used for fracking.