Los Angeles Mayor Eric Garcetti’s office unveiled a sweeping city sustainability plan Wednesday that seeks to reduce the amount of imported water used by Angelenos, improve air quality levels and reduce greenhouse emissions over the next two decades.

The 105-page “Sustainable City Plan” sets out dozens of major environmental yardsticks for Los Angeles to reach by 2025 and 2035.

Matt Petersen, Garcetti’s top adviser on sustainability issues, said the plan addresses the “economic and equality” issues expected to face a city grappling with rising temperatures and denser living conditions in coming years.

By 2035, the city could have an additional half a million residents, Petersen said.

“How do we have a city where people thrive, rather than just be accommodated?” Petersen said. “That means we have to help the environment, we have a robust economy and we create an equal opportunity for every Angeleno.”

The 20-year plan comes amid new focus on climate change at City Hall and follows Garcetti’s 2013 appointment to President Obama’s Task Force on Climate Preparedness and Resilience.

Several other large cities, including New York, Chicago and San Jose, have released sustainability plans in recent years.

The plan also comes amid the ongoing California drought, which gives Los Angeles a “particular urgency,” said Garcetti, who asked Angelenos to conserve water.

“Shave in the sink, take that shorter shower, think about replacing that grass,” Garcetti said at a news conference for the new sustainability plan.

In one of the plan’s more ambitious goals, Los Angeles would source 50 percent of its water locally by 2035 by turning to recycling, stormwater capture and other conservation methods. The Los Angeles Department of Water and Power currently gets about 85 percent of its water from outside sources.

“That’s transformative,” said Mark Gold, a director at UCLA’s Institute of the Environment and Sustainability, of the proposed water benchmark.

The plan also seeks to have “zero days” when air pollution reaches unhealthy levels by 2025. The city saw 14 days last year when levels reached unhealthy thresholds, Petersen said.

Some of the proposals listed are already being enacted. Garcetti has already committed to creating 20,000 green jobs by 2017; under the plan, that number would grow to 150,000 by 2035.

In another goal, 75 percent of Angelenos would live within a half mile of a park or open space by 2035. By 2017, 56 percent of residents will do so, according to the report.

David Pettit, attorney for the Natural Resources Defense Council, expressed disappointment over the plan’s goal of increasing the percentage of port-related goods movement trips that use zero emissions technology to 25 percent by 2035.

His group wants all trips to have zero emissions, and that should happen “a lot sooner than 2035,” Pettit said.

The plan’s goal of requiring all farmers markets in Los Angeles to accept EBT (electronic benefit transfer, commonly referred to as food stamps) drew praise from James Haydu, executive director of the Sustainable Economic Enterprises of Los Angeles, which operates eight farmers markets.

Haydu said he applauds Garcetti’s efforts to “level the playing field when it comes to fresh food access for all Angelenos, no matter where they live and no matter what their income is.”

If re-elected in 2017, Garcetti would be termed out after the 2022 election, so the report’s goals could be changed by the next City Hall administration.

Other yardsticks could also change, depending on what federal or state laws pass in the coming years, Petersen said.

He said his office will release updates periodically on the plan.

“But we’re not going to re-write the report every four years,” Petersen said.