SAN FRANCISCO (AP) — In California, few issues are as divisive as water. It pits North against South, fisherman versus farmer.

With cycles of drought, dwindling groundwater and a future marked by a changing climate and a thirsty, booming population, no other resource is as imperiled in the Golden State.

Yet many Californians turn on their taps knowing little about the complicated systems and politics involved in the delivery and whisking away of the precious resource at their homes.

Access to data about groundwater levels, pollutants and who owns the rights to siphon water from rivers and aquifers is available through government websites, but the information is often obscured by outdated or ineffective technology.

Now a group of self-described “nature nerds” made up of database experts, academics and conservationists are trying to bring meaning to the state’s mass of water data. The effort is called The New California Water Atlas, and will use interactive maps powered by government data that are currently publicly available, but hard to synthesize.

“The records are so convoluted ... nobody can use them,” said Huey Johnson, who served as natural resources director under Gov. Jerry Brown from 1978-1982. “You can’t manage what you don’t know.”

The group posted its first effort earlier this year: a map comprised of 50,000 records that shows who owns water rights, and where. The atlas will grow and change over the years as new information becomes available.

The map is a heavily dotted California landscape, with each dot’s size representing the amount of water each right-holder is allowed to take. If California’s watershed was a huge glass of water, the map shows who holds the rights to dip in their straws.

The atlas team is also building maps that depict water levels in California’s aquifers over the past 30 years. Another map will use crowdsourcing — data provided by people connected online — to show how the price of water varies from region to region.

“We want people to understand the California water system as a whole, both natural and man-made systems,” said Laci Videmsky, the atlas’ 35-year-old project director. “It’s an owners’ manual of sorts.”

The people are building the new atlas on the modern principle that free and open access to government data will create a more informed citizenry, and better policy.

But the techno-savvy map builders were inspired by the work of a previous generation, who tried to do the same thing with more rudimentary tools.

Johnson, now 80, helped build the state’s first public water atlas in 1979 along with Stuart Brand of the Whole Earth Catalog. While a product of a different time, the first California Water Atlas was based on the same principle: that people deserved to know who controlled the water.

Now, Johnson funding the project through his Resource Renewal Institute and providing historical context for the new project, which is benefiting from collaboration of multiple generations of Californians who bring different skills and knowledge to the effort. So far about $70,000 has been spent getting the website and first map up and running, and its future will rely greatly on continued donations and volunteers.

“Our millennial generation is fairly ignorant about the great California water system we are about to inherit, but we have a plan to solve this problem,” Chacha Sikes, 38, another new atlas group member, wrote in the journal Boom published by the University of California.

“We believe by sharing information about our natural resources more openly and understandably, we can make smarter choices with water and heal the devastation caused by previous generations.”

Scholars who study California’s water supply say an interactive atlas could be helpful for homeowners, farmers and others by providing a foundation of quality information to everyone in a way they can understand it.

“Government agencies have done a good job of collecting a bunch of data, but have done a horrible job of making it useful,” Jay Lund, director of the University of California, Davis’ Institute on Watershed Sciences.

“I’m excited to see the possibilities for more of a modern and open way of developing this kind of resource that everyone can gain from,” Lund said.

State water officials have been slow to embrace the effort, saying they were worried it might present the data inaccurately.

But after some mistrust in the early stages from both sides, the State Water Resources Control Board worked with Videmsky to deliver and vet the first dump of government data to ensure that what the atlas was receiving was complete.

“To the extent that a tool like this engages the public, and informs them about the competing demands on our resources ... I think this kind of tool is a good thing,” said Amanda Montgomery of the water board.