WASHINGTON — The Trump administration is poised to roll back Clean Water Act protections on millions of acres of waterways and wetlands, including up to two-thirds of California’s inland streams, following through on a promise to agriculture interests and real estate developers to rewrite an Obama-era rule limiting pollution.

The administration’s plan for a vastly scaled-down Clean Water Rule is expected to be released as soon as Tuesday. Officials said nearly two years ago that they had begun the process of reversing the rule President Obama put in place, and internal talking points laying out its case were disclosed late last week by the environmental media outlet E&E News.

The talking points signal that the Environmental Protection Agency intends to strip federal protections from many of the nation’s wetlands and streams that do not flow year-round. The administration has not challenged the accuracy of the talking points.

“The previous administration’s 2015 rule wasn’t about water quality,” the draft talking points said. “It was about power — power in the hands of the federal government over farmers, developers and landowners.”

At stake are billions of dollars in potential development rights, the quality of drinking water for tens of millions of Americans and rules that affect farming in much of the country, as well as wildlife habitat for most of the nation’s migratory birds and many other species.

Under the administration’s plan, the Clean Water Act’s protections would no longer apply to most seasonal ponds, wetlands and streams, including those that form major parts of drinking-water systems and fisheries throughout the nation, particularly in the arid West.

As many as 1 in 3 Americans drink water derived in part from seasonal streams that may no longer get protections, according to scientific studies the Obama-era EPA relied on in writing the original rule.

In California, where many significant stretches of fresh water dry up in the summer, as much as 66% of the state’s freshwater streams could lose federal protection. The waters would continue to have protection under state law, but few states are in position to replace the regulatory systems currently run by federal officials.

“These protections have been around for 50 years,” said Jessica Kao, who until this year was the EPA’s lead Clean Water Act enforcement attorney in the Southwest. “It’s not that easy for a state to just step in and take it over. You need to build up expertise and devote significant resources to it.”

Trump administration officials reject the federal data that show as many as 66% of the freshwater streams in California — and 81% in the arid Southwest overall — could lose Clean Water Act protection, saying the Obama EPA lacked enough specifics to back up that estimate.

“The premise … is wrong,” EPA spokesman John Konkus said an email. “The previous administration did not have enough information to accurately or responsibly quantify changes in federally regulated waters. That means there are no data to support the 80% estimate.”

The Trump administration’s plan would preserve protections for some seasonal streams that regulators would classify as “perennial and intermittent tributaries to traditional navigable waters.” Protections would also be preserved for wetlands adjacent to navigable waters.

Administration officials have declined to specify how many streams fall into the “intermittent” category.

The EPA and the Army Corps of Engineers share authority over development that affects lakes and rivers used in interstate commerce. But because pollution flows downstream, the government also has taken jurisdiction over nonnavigable waters that connect to those.

The issue that has generated battles through four consecutive administrations involves how far upstream the government’s reach can extend.

Environmentalists have pushed to extend protections to seasonal waters, seeing them as key resources for healthy ecosystems. Agricultural and real estate interests have pushed back hard, complaining of intrusions by heavy-handed bureaucrats.

Farmers have argued the Obama-era rules could force them to get costly and cumbersome permits just to dig a drainage ditch. Developers warned the new restrictions could needlessly complicate home building.

They are joined by mining and oil companies seeking to limit the reach of environmental rules that hold the firms accountable for industrial activities disrupting streams and wetlands.

In a federal court brief filed in June in North Dakota, a large coalition of industry groups argued they risked “crushing fines and possible criminal penalties” for failing to get permits to discharge pollutants into waters that were never meant to protected by the Clean Water Act.

Under Obama, the EPA found many of those fears exaggerated. The agency concluded that the protections it put in place would actually create a net economic benefit for the nation of as much as $550 million a year.

“You can’t protect the larger bodies of water unless you protect the smaller ones that flow into them,” said Ken Kopocis, who was the chief EPA water official under Obama. “You end up with a situation where you can pollute or destroy smaller streams and bodies, and it will eventually impact the larger ones.”

All of the historic federal water cleanups have involved repairing damage that was done to intermittent streams flowing into a major navigable river or lake, he said.

Because of conflicting court rulings, the Obama rules have been in effect in only part of the country. Federal courts covering 22 states, including the West Coast, New England, the mid-Atlantic and parts of the upper Midwest, have allowed the rules to go into effect.

In those states, mostly controlled by Democrats, state governments have generally supported the Obama-era rules.

Courts covering most of the South, the Great Plains and the Rocky Mountain states have put the rules on hold in response to suits brought by developers, farm groups and conservative states that have sought to overturn the Obama rules.

In those states, regulators have provided Clean Water Action protections to seasonal streams and wetlands on a case-by-case basis.

Those legal battles came nearly a decade after the Supreme Court waded into the issue, with the justices split on what waters warrant Clean Water Act protections. A deciding opinion by former Justice Anthony M. Kennedy created a path for the Obama administration to apply its rules to seasonal streams and wetlands.

Environmental groups warn the new Trump rules would restrict the EPA from any enforcement, leaving the job entirely to the states and giving some of the most crucial bodies of water the least amount of protection they have had in decades.

“It is hard to overstate the impact of this,” said Blan Holman, managing attorney at the Southern Environmental Law Center, an advocacy group.

“This would be taking a sledgehammer to the Clean Water Act and rolling things back to a place we haven’t been since it was passed. It is a huge threat to water quality across the country, and especially in the West.”

evan.halper@latimes.com