Infographic: California Urban Water Conservation Standards

Cities must cut water use by 25 percent in 2015.

On May 5, in response to an executive order from Governor Jerry Brown (D), the State Water Resources Control Board adopted California’s first-ever mandatory water restrictions for urban areas. The state’s 411 urban water suppliers — those serving more than 3,000 connections — will be required, in total, to reduce water use by 25 percent between June 2015 and February 2016 compared to the same months in 2013-14.

The target of the regulation is lawn watering, which accounts for roughly half of residential water use in California. However, residential water use makes up only 13 percent of the state’s total freshwater withdrawals.

Cities with high per-capita water use will be asked to conserve more than those where water use is comparatively low.

The top map shows the level of conservation that is required for each of the cities covered by the regulation. The conservation tiers, which are based on residential water use per person during the summer of 2014, range from 8 percent (blue) to 36 percent (red). In other words, the redder cities are using more water per person per day (215-612 gallons) when compared to the bluer cities (0-64 gallons). Notice that big cities along the coast on the map tend to use less water per person because of cooler climates, higher urban density, and more rainfall, while inland cities tend to be hotter, drier, and more spread out with larger lawns that use more water.

But some cities have already made great water-conservation strides over the last two years. The middle map shows the gap between current levels of conservation and those required by the new rules. For example, a city in the 24 percent conservation tier (green-yellow in the top map) that has already cut water use by 10 percent must make only an additional 14 percent reduction (light blue in the middle map) before February 2016.

The bottom chart shows conservation by volume, sorted according to hydrologic region. Because it is home to more than half of California’s 39 million people, the South Coast hydrologic region, which includes Los Angeles and San Diego, will conserve the most gallons of water.

The Water Board will begin assessing compliance with the rules in July, looking both at month-to-month comparisons and aggregate water use over the nine-month period. In all, the cuts will save California close to 400 billion gallons of water.

Click the infographic below to learn more.

Brett Walton contributed reporting. Contact Brett Walton or by @waltonwater on Twitter.