The Trump administration is moving to weaken the so-called Waters of the U.S. rule, which protects wetlands and other waterways from development. California plans its own regulations to fill the gap, but progress is slow.

California officials are poised to seize control over a major arena of federal regulation in response to Trump administration rollbacks: the management and protection of wetlands.

Wetlands are vital features on the landscape. Basically low spots in a watershed, when they fill with water they provide important habitat for birds, fish and other species. Wetlands also help control floods and recharge groundwater, and they filter the water we drink. On the other hand, being generally flat and maligned as “swamps,” they are popular places to pave and build.

As a result, wetlands have nearly disappeared across the western United States. That has given rise to the controversial policy known as the Waters of the U.S. rule, or WOTUS. The rule is an effort, first, to define wetlands, which turns out to be monumentally difficult. And second, to regulate development in and around wetlands.

One of President Donald Trump’s first acts upon taking office in 2017 was to direct the Environmental Protection Agency to rescind and rewrite the WOTUS rule. The rule had been comprehensively updated in 2015 by the Obama administration, after years of analysis and public review. But Trump viewed it as overly broad. In January, the EPA fulfilled his promise by suspending the rule.

California decided to take action in response. Since 1993, it has been state law to avoid ongoing wetland losses – a so-called “no net loss” policy. So the California State Water Resources Control Board (SWRCB) began preparing its own rules, which would put the state in full control of wetland protection.

If passed later this year, it could become the first move by a state to seize a broad arena of regulatory power for itself in response to Trump’s regulatory rollbacks.

“Our update will advance the ball and add clarity without giving up any authority that’s important to protect wetlands,” said Felicia Marcus, chair of the SWRCB and a former EPA regional administrator during the Clinton administration. “That’s what we’re working on.”

The WOTUS rule has been around – under various names and iterations – as a component of the Clean Water Act, which was first adopted by Congress in 1972.

The overarching goal is to prevent pollution and erosion that harms water quality for people and wildlife. Building in wetlands and other water bodies, including the dredging needed to maintain harbors, often causes pollution by eliminating natural filtration and stirring up contaminated sediment.

The rules have been jointly enforced by the EPA and the U.S. Army Corps of Engineers. They also apply to tidal waters, seasonal streams, ponds, lakes, playas, meadows, mudflats and any waters considered “navigable” or important to industry or commerce. As a result, how the rule is interpreted and applied has huge implications for the environment and the economy.

For decades, this interpretation had been left intentionally vague, both to provide regulatory flexibility and to avoid controversy.

“There’s been confusion over the scope of WOTUS since 2001,” said Holly Doremus, a professor of environmental law at the University of California, Berkeley.

That was the year the U.S. Supreme Court ruled that the EPA and the Army Corps had been applying the law too broadly, and that some waters not connected to traditionally navigable waterways should not be regulated. A clear definition of regulated waterways had to be made.

A second Supreme Court ruling in 2006 made things more confusing: a divided court held that waters with a “significant nexus” to something navigable could be regulated. This led to the 2015 WOTUS rule adopted by the Obama administration.

The court’s definitions left a lot of room for interpretation. As a result, the Obama administration drew a large regulatory circle after a years-long effort to analyze the issue. Now the Trump administration wants to draw it much smaller.

“The core of that problem is that wetlands are not necessarily water and they’re not necessarily dry land. It’s hard for the public to understand,” Doremus said. “If you or I went out and stood somewhere and looked around, we wouldn’t necessarily know whether a place should be a wetland or not. It does take a technical expert examination.”

California’s “no net loss” wetlands policy arose from a 1993 proclamation by then governor Pete Wilson. The proclamation also declared that the state must work to increase wetland acreage over time. Although it has remained state policy ever since, the policy has not been fulfilled.

There is no formal state program to monitor wetland acreage, but evidence suggests total acreage has declined since 1993. The state has lost at least 91 percent of its historic wetlands, according to the U.S. Geological Survey.

“This federal rollback is a big threat,” said Rachel Zwillinger, water policy adviser at Defenders of Wildlife. “We have continued to lose wetlands. And there are losses occurring that are completely outside the permitting process, which is really problematic.”

California actually began drafting its own wetlands rule in 2004, partly to fulfill the “no net loss” policy and to provide more regulatory certainty. It went through several revisions but was never completed. The effort took on more urgency with Trump’s election in 2016.

California’s authority to regulate wetlands on its own arises from the general legal principles of statehood, Doremus said: states can adopt any regulations that promote the public welfare.

In addition, California has established the legal basis to protect all its waters in the Porter-Cologne Water Quality Control Act. The law, adopted in 1969, gives the state authority to enforce water quality in wetlands.

California’s new regulations would seek to protect wetlands and other waterways as “waters of the state.” Officially described as “dredge and fill” regulations, the rules would govern any activities that disturb wetlands and other surface waters.

A starting point for the rules is simply defining a wetland. A key difference from federal regulations is that the state’s proposal does not require the presence of vegetation to declare that a water body is a wetland. The state rules require water to be present long enough for anaerobic (absence of oxygen) conditions to exist in the upper soil surface of the water body.

Another goal is to streamline the process of obtaining a permit, for example, to dredge a harbor, or pave a parking lot in an area that may or may not be a wetland. Currently, due to the absence of clear state regulations, the permit process can vary quite a bit in different regions of the state.

“We won’t make it crystal clear, but we will make it way more clear than it is and give some degree of comfort to both the environmental community and the developer community,” said the SWRCB’s Marcus. “We’re trying to create enough clarity for good government while protecting precious wetlands.”

Even though California is moving to adopt its own regulatory program, losing an active federal presence will be challenging. One reason is that the Army Corps plays a big role in identifying and mapping waterways that should be protected under the WOTUS rule – a process known as delineation. If federal changes eliminate or substantially shrink this role, the state’s workload is likely to increase substantially whether or not it adopts its own regulations.

The Trump administration’s moves so far have been followed by more court actions and more uncertainty. The latest development came on Aug. 16, when a federal judge in South Carolina issued an injunction against the administration’s February order suspending WOTUS. But the order only applies in 26 states not covered by stays issued in two previous court rulings.

In the West, this means the Obama-era WOTUS rules are again in force in California, Oregon, Washington and Texas, but not in Alaska, Colorado, Idaho, Montana, Wyoming, Utah, Nevada, Arizona and New Mexico.

Because of the state water board’s delays, another pressure has come to bear: Gov. Jerry Brown’s term ends this year. Even assuming another Democrat replaces him, the transition to a new administration will be disruptive.

In addition, Marcus’ own term as chair of the water board ends in January.

“We’ve been really disappointed the state board has not yet finalized the policy,” Zwillinger said. “It’s been a decade in the making. And with the new, urgent threat at the federal level, we’d like to see it get across the finish line in this [state] administration.”

Marcus could not say when the water board might adopt the new rules. The board has already held many days of public hearings and workshops on the draft policy. But more deliberations will be required before adoption, and none have been scheduled yet.

“Because it’s so contentious, we’re trying to get it right,” Marcus said.