Drought conditions have prompted the building of a 750-foot wide rock barrier to prevent saltwater intrusion into the Sacramento-San Joaquin River Delta.

The California Department of Water Resources constructed the temporary barrier with 110,000 cubic yards of rock off West False River in Contra Costa County. Principal engineer Jacob McQuirk said that without the barrier, saltwater would endanger freshwater supplies in the Delta and water exports to the south.

“Every tidal cycle, that saltwater slowly propagates into the interior Delta,” he said. “Really, the beneficial uses of the interior Delta, they include agricultural supply, also interior municipal supplies.”