April 1, 2014, was to be the day that mandatory water rationing would begin in Marin County's largest water district, following a 2013 that "proved to be the driest year in 135 years," according to General Manager Krishna Kumar.

[caption id="attachment_89510" align="alignright" width="350"] Rainfall remains lower than historic average for the Marin Municipal Water District (image credit: Krishna Kumar)[/caption]

In a region heavily dependent on rainwater runoff, officials at the Marin Municipal Water District were starting to draw comparisons to the most intense drought in recent memory, a two-year period from 1976 to 1977. The region had seen no rain since December of 2012, and planned to ratchet up its mandated rationing if those conditions were to continue.

"2013 started even worse than '76, '77," said Mr. Kumar, speaking as part of the water panel during North Bay Business Journal's Impact Marin conference March 13.

That all changed when a "special package" -- a massive rain storm -- broke through a long-lived high-pressure system off the western United States to dump 20 inches of rain on Mt. Tamalpais from Feb. 6--8. Continuing rains boosted half-full reservoirs to around 75 percent of total capacity as of mid-March, allowing Marin Municipal Water District officials and their 185,000 customers to breathe a sigh of relief.

"That's how lucky we were this time," Mr. Kumar said. "But we can't expect these 'special packages' to arrive each time."

It is a near-miss scenario that has played out throughout the state in recent years, obscuring what panelists said is an ongoing need to augment current infrastructure with measures that acknowledge the ongoing risk of drought in California.

"Droughts occur, and they will occur again," said J. Dietrich Stroeh, a partner at CSW/Stuber-Stroeh Engineering Group who served as general manager of the district during the mid-1970s drought. "We should be doing more and more planning, but when it rains, we don't plan for more water."

Unlike water districts in Central and Southern California that rely on water piped from distant regions, the North Bay benefits from a system that hinges largely on regional watersheds able to collect and store enough rainwater for local use in a typical year.

Yet that storage capacity -- around 29.9 million gallons across seven reservoirs for the Marin Municipal Water District -- is not limitless. Without rain, those reservoirs are only sufficient for about two years, Mr. Kumar said.

"We went from our reservoirs being 100 percent full to, in 14 months, a serious conversation about mandatory rationing," Mr. Kumar said.

Much of the state's reservoir construction came in response to historic droughts in the early 1900s, giving the state greater resiliency in dry years and supporting growth over the next century, Mr. Stroeh noted.

Yet California may have gotten off easy during that that five-year drought, and even the drought of the mid 1970s, he said. Research points to a regional drought that lasted as long as 50 years around the year 1150 and other droughts after that lasting a quarter-century.

The time may well have come again for new infrastructure, with measures that include greater utilization of treated wastewater for irrigation, facilities to desalinate ocean water for potable use and new pipelines to supply water from other areas in an emergency. All of those measures are currently under consideration in Marin, Mr. Kumar said.

That work may come with costs for ratepayers. But given how costs escalate for even close-spigoted water users during a drought, boosting that infrastructure could pay off in the long run, panelists said.

The North Marin Water District, serving 20,000 customers in Novato and some unincorporated areas, has ramped up its supply of recycled water for irrigation to large commercial customers, said Chief Engineer Drew McIntyre. Major participants include Valley Memorial Cemetery and Fireman's Fund Insurance. The approach preserves more potable water for drinking.

"We've had a major expansion of our recycled water customers," Mr. McIntyre said. "Three years ago, we had two. I'm happy to report, this year we have close to 50."

The North Marin district did not see the same boost from the recent rains, lacking the benefit of runoff from Mt. Tamalpais. Storage accounts for around 20 percent of its customer supply. The remainder is purchased from Sonoma County Water Agency.

The situation highlights the dynamic nature of rainfall across the North Bay and beyond, as well as the benefit of regional cooperation.

"Most water agencies are very provincial -- they don't want to work with each other," Mr. Stroeh said. "We're pretty good in the North Bay. The state needs to come up with a plan to operate as one water agency."