If you thought California’s water wars were bitter, just wait until you see our water data wars. Digital tools have expanded the ability of governments, companies and nonprofits to measure the uses of California water in detail, and thus build more water-efficient products, boost water conservation, and replace expensive and inefficient infrastructure. But the abundance of water data effectively makes every piece of land and every drop of water in California the subject of measurement – and conflict. The data also exposes the fragmentation and deficiencies of California’s system of water management.