A portion of the 5-foot-diameter pipeline broke into three sections, according to DWR spokesman Eric Alvarez. The situation was discovered Dec. 22.
The spur line transports water from Lake Del Valle to communities in Alameda and Santa Clara counties. It was being pressed into extra service during the state's ongoing project to enlarge and improve the South Bay Aqueduct, the main means of water delivery in the region.
DWR engineers believe the breakage is the result of water, either from recent rainstorms or from a small leak in the pipeline, saturating the earth beneath the pipe that supports its weight.
Residents should not see any effect in their water supply, according to Alvarez, and DWR engineers are putting alternative water sources in place.
"The immediate supply they are already rectifying from the San Luis Reservoir," he said.
Repair of the spur is expected to take at least two months, but the aqueduct enlargement project is scheduled to be completed Jan. 11, restoring the region's main water delivery source.
Crews are still assessing the total damage and planning the specifics of the repairs, according to the DWR.
The break occurred in a portion of the water line on a hillside just above the Wente Vineyards. Water flooded a vineyard and parking lot at the facility, according to the DWR.