The Delaware River provides about 60 percent of the water consumed by Philadelphians. It is also a source of water to New York City's system.
Some media outlets erroneously reported that Philadelphia had intervened in the lawsuit after an advocacy group issued a news release Oct. 13 saying the city had joined the legal action.
But the Council resolution, though politically symbolic, carries no legal force. The mayor's office determines the city's legal strategy, and it appears to be taking a noncombative approach to the emotional shale-gas drilling debate.
"Although the city has not joined as a friend of the court, we are taking an active role with state and federal regulators to ensure the protection of the Delaware River watershed," Nutter's spokesman, Mark McDonald, wrote in an e-mail after the vote.
Iris Marie Bloom, the director of Protecting Our Waters, the group that lobbied City Council to pass the resolution, said she expected Council to file papers supporting the lawsuit.
"Regardless of the disappointing lack of direct assistance from the Nutter administration, Council will file the brief on behalf of the city, which is fantastic," she said.
A spokeswoman for Councilman Curtis Jones Jr., a sponsor of the resolution, did not respond to a request for comment.
The Water Department is at odds with activists who say drilling poses an immediate environmental threat to the city's water supplies.
"We're looking at this and trying to figure out rationally what it is we're looking for here, and certainly not the end of the Marcellus shale drilling," Neukrug said last week.
"We're just looking for good regulations and to see that drilling happens - and this term's being used a little bit too much - but it's done smart."
The Water Department's position, which Neukrug's team spelled out in 2010 when Council first adopted an anti-drilling stance, is that shale gas is only one of several development issues that could affect the upper Delaware in the coming decades.
Activists focus on the threat of spills from drilling and hydraulic fracturing, which tend to be localized.
While Water Department planners say they are concerned about accidents 180 miles upstream from the city's water intakes, they worry mostly about chronic degradation in the largely forested upper Delaware region caused by development.
"We're talking about what does this area look like 50 years from now, 100 years from now?" Neukrug said. "Is it a suburb of New York City? Are there new roads and restaurants and gas stations? Are there a lot of drilling rigs? What is the ultimate use of this land?"
He said the region needs a commission to look at all land-management issues "to create a master plan for the next 100 years."
Maya K. van Rossum, the head of the Delaware Riverkeeper Network, said the city's noninvolvement in the lawsuits "would be a huge disappointment, a huge loss for Philadelphia and its future."
Van Rossum's organization is leading a charge to try to persuade the DRBC to block drilling in the Delaware Basin until a full environmental analysis is completed.
New York's attorney general sued the Army Corps of Engineers and other federal agencies in May seeking to block drilling, and environmental groups sued those agencies and the DRBC in August.
No commercial drilling has taken place in the Delaware basin while the commission has been drafting new regulations that are stricter than those imposed by the Pennsylvania Department of Environmental Protection.
The DRBC is scheduled to vote Nov. 21 on proposed regulations.
If they are approved, a ban on drilling in the Delaware watershed would be lifted, at least in Pennsylvania. New York has a statewide ban on hydraulic fracturing but is considering relaxing the restrictions.
Statewide polls of Pennsylvanians have generally shown conditional support for Marcellus drilling. A Quinnipiac University poll in September found voters say, 62 percent to 30 percent, that the economic benefits of shale gas outweigh environmental concerns.
Patrick Creighton, a spokesman for the Marcellus Shale Coalition, an industry trade association, derided Philadelphia's Council for opposing shale development so far from the city limits.
"It's unfortunate that the Philadelphia City Council continues to pass political resolutions that are short on facts and science and do little to further a constructive conversation related to responsible Marcellus development," he said.
Contact staff writer Andrew Maykuth at 215-854-2947, email@example.com, or @Maykuth on Twitter.
Inquirer staff writer Miriam Hill contributed to this article.