In California, a Race to Capture the Water Before It Escapes

PETALUMA, Calif.—Neil McIsaac has something many other dairy farmers here don’t: a storm-runoff capture system that can provide backup water for his herd when local reservoirs go dry, as they did last year.

Already, he and others involved in the project say it has proven its worth. It has captured 670,000 gallons so far this winter, enough to slake the thirst of his 700 cows for a month, Mr. McIsaac said.