A lawyer for Columbia University said Tuesday that a demand from the Trump administration for dramatic changes in student discipline had merely sped up policies the university had already been planning to enforce.

In a March 13 letter, the Trump administration said the university had failed to stop “antisemitic violence and harassment,” adding that policy changes would have to be made before the government would discuss resuming $400 million in canceled grants and contracts. Last week, the school complied with most of the government’s requests, regulating masks on campus and empowering a team of security officers to make arrests.

The lawyer’s assertion that Columbia had been planning the changes all along came during a hearing in Federal District Court in Manhattan over a request by a group of anonymous Columbia and Barnard College students that a judge bar school officials from handing over confidential disciplinary records to a congressional committee that has asked for them.

Both Columbia and the committee have contended that the students have not shown a sufficient legal basis for such an order. The judge, Arun Subramanian, made no ruling Tuesday.

The arguments in court stemmed from a request by the House Committee on Education and Workforce for disciplinary records related to several incidents, including the occupation of a university hall last spring by pro-Palestinian demonstrators, a protest of a class taught by former Secretary of State Hillary Clinton, and an art exhibition the committee said had “promoted terrorism.”

Seven anonymous students and Mahmoud Khalil, a former student and legal permanent resident who helped lead protests last year and whom the Trump administration is trying to deport, sued to keep the records private. The lawsuit said that to fully comply, Columbia would have to turn over private files of hundreds of students, faculty and staff members.

Their lawyers have argued that the House committee was trying to coerce the university into becoming the government’s proxy to chill speech critical of Israel and to suppress association, actions that the First Amendment would prohibit the government from taking.

Marshall Miller, a lawyer for Columbia, denied in court on Tuesday that the university was being coerced, saying that it was voluntarily responding to government requests.

At one point, Judge Subramanian asked Mr. Miller whether Columbia would have announced new rules last Friday without a suggestion from the executive branch that money was at stake.

“It’s a hypothetical,” Mr. Miller said.

“I don’t think it’s a hypothetical,” Judge Subramanian replied.

Mr. Miller then conferred briefly with colleagues before saying that although the new policies had been developed over many months, the Trump administration’s demand affected their “precise timing.”

Ester R. Fuchs, a Columbia professor who is the co-chair of the university’s antisemitism task force, said last week that “a lot of these are things we needed to get done and were getting done, but now we’ve gotten done more quickly.”

The provisions the school adopted were made public in an unsigned statement that many faculty members greeted with dismay, seeing an unprecedented level of deference to the Trump administration.

Among other things, Columbia banned face masks on campus for the purpose of concealing identity during disruptions and said it would adopt a formal definition of antisemitism.

The university also said it would appoint a senior vice provost to oversee the Middle Eastern, South Asian and African Studies Department, which the Trump administration had said should be placed into receivership.

Lawyers for the students said their clients could suffer harm if their disciplinary information was handed over to lawmakers allied with the Trump administration. The lawyers wrote in court papers that after Columbia provided such information to the government last year, “members of Congress or their staffers posted students’ private information on social media sites and identified students and faculty on the public record during congressional hearings,” resulting in harassment.

Mr. Miller said on Tuesday that Columbia had “anonymized” information provided to the committee.

A lawyer for the students, Amy Greer, said that students who had participated in pro-Palestinian demonstrations were “some of the most surveilled people in our country right now,” adding that several private organizations had worked to target students for their speech.

Even if Columbia removed names from information it gave the committee, the inclusion of physical descriptions and details of activity at specific times and places meant “somebody is going to recognize them,” Ms. Greer added.

Earlier in the hearing Judge Subramanian had asked a lawyer for the House committee what lawmakers might do with the student disciplinary records.

The lawyer, Todd Tatelman, replied that the identities of students might in “certain circumstances” be relevant.

“There is no intent to publicize student names?” Judge Subramanian asked.

Mr. Tatelman replied that he knew of no such plans. The judge asked next whether the committee would turn over the names of students to any “administrative agency.”

Mr. Tatelman replied that it would not be “a typical action.”

“But you cannot rule it out?” the judge asked.

“At this point,” Mr. Tatelman replied, “I cannot rule anything out.”

During his U.S. Senate confirmation hearing to become the No. 2 official at the Justice Department, Todd Blanche suggested that he had no direct knowledge of the decision to abandon a criminal corruption case against the mayor of New York City.

But in a draft letter unsealed on Tuesday, the interim U.S. attorney in Manhattan wrote that a top department official, Emil Bove III, had suggested otherwise before ordering her to seek the case’s dismissal.

The U.S. attorney, Danielle R. Sassoon, wrote that when she suggested that department officials await Mr. Blanche’s Senate confirmation so he could play a role in the decision, Mr. Bove informed her that Mr. Blanche was “on the same page,” and that “there was no need to wait.” The draft was written by Ms. Sassoon earlier this year, as she fought for the case’s survival.

The draft letter was among a cache of communications, including emails and texts, submitted under seal to a judge, Dale E. Ho, by Mr. Bove and Mr. Blanche, after his confirmation, to support their argument for dismissal of the corruption indictment against the mayor, Eric Adams. Judge Ho has yet to rule.

The draft sheds additional light on the circumstances surrounding the explosive decision by top officials in the Justice Department to halt the prosecution of Mr. Adams. The decision set off a political crisis in New York City, where the mayor immediately faced questions about his indebtedness to the Trump administration, which sought the dismissal in part so that Mr. Adams could aid its deportation agenda in New York City.

A Justice Department spokesman said in a statement that Mr. Blanche had no role in decisions at the agency before he was confirmed.

“Todd Blanche was not involved in the Department’s decision-making prior to his confirmation,” the statement said.

During the confirmation hearing, Mr. Blanche was questioned about the Justice Department’s decision making in seeking the dismissal of the Adams case.

When Senator Peter Welch, a Vermont Democrat, asked Mr. Blanche about whether the decisions in the case had been directed by officials in Washington, Mr. Blanche suggested that he had no direct knowledge.

“I have the same information you have,” he said. “It appears it was, yes, I don’t know.”

Reached for comment on Tuesday, Senator Welch said, “If this is true, it clearly indicates Blanche ‘misled’ — in plain English, lied — to the committee.”

It was not immediately clear when Ms. Sassoon drafted the letter. When it was originally filed, under seal, Mr. Bove wrote that Ms. Sassoon sent it to herself on Feb. 12. But the unsealed documents show that Ms. Sassoon sent herself an email that appeared to include the drafted letter as an attachment on Feb. 11 — the day before Mr. Blanche’s hearing.

This is a developing story and will be updated.

Emma G. Fitzsimmons contributed reporting. Susan C. Beachy contributed research.

Road salt is leaching into the reservoirs that hold New York City’s tap water and could make some of it unhealthy to drink by the turn of the century, according to a new study commissioned by city environmental officials.

The study, released last week by the city’s Department of Environmental Protection, found that while salt was edging upward throughout New York’s vast watershed, it was especially pronounced in the New Croton Reservoir, just north of the city.

In that supply, which provides about 10 percent of the city’s drinking water, levels of chloride — a chemical found in salt and an indicator of salinity — tripled over the last 30 years.

If the trend continues, drinking water from the New Croton Reservoir may not meet current safety standards by 2108, according to the report.

While road salt is a main driver of salinity levels in drinking water throughout the United States, other contributing factors include wastewater treatment plant discharges and agriculture, according to the report. Elevated salt levels in fresh water can contribute to health issues like high blood pressure and can also damage the ecosystem, the study said.

Reducing salinity levels throughout New York City’s water system should start with more prudent use of road salt, said Rohit T. Aggarwala, the head of the environmental protection department, which manages the water supply and commissioned the report.

“We just need people who operate roads to start realizing that this is a chemical that we are adding to our environment, and we have to take that seriously,” Mr. Aggarwala said.

Road salt is cheap and plentiful, but it is also dangerous for the environment and corrosive for infrastructure.

In general, local municipalities, and often the state’s Department of Transportation, make the decision to use salt on roadways — a crucial safety measure that melts ice.

“We understand that there is a delicate balance between protecting the environment and maintaining safe highways for motorists,” said Joseph Morrissey, a spokesman for the Department of Transportation. The department minimizes salt usage, Mr. Morrissey said, with methods that include adhering to prescribed application rates, calibrating equipment throughout the winter, training drivers on best practices and using brine, a liquid version of salt that is less concentrated but more expensive.

Officials are focused on curbing the use of salt, while continuing to explore other affordable alternatives, like beet juice — which lessens salt’s corrosive qualities when mixed with brine — and sand, which does not melt ice but provides traction.

Recently, Pete Harckham, a Democratic state senator who represents parts of Westchester County and the Hudson Valley, introduced legislation to create a city and state task force that would explore the issue. “We’ve got to use this as a teachable moment and rethink how we do things,” Mr. Harckham said.

New York City’s pristine tap water is a source of pride among residents and local leaders. Most of it, about 90 percent, comes from rural areas in the Catskill Mountains, a range that extends more than 125 miles north of New York City. It represents the largest unfiltered water supply in the United States.

The remaining 10 percent from the New Croton Reservoir, a collection of 11 smaller reservoirs and three lakes, is filtered, but not for chloride. New Croton is in Westchester County, a relatively dense suburban area, which offers less of an opportunity for the natural environment to absorb runoff from salt on the road. In the less populated Catskills, more vacant land surrounds the water supply, and there have been only marginal increases of chloride levels, Mr. Aggarwala explained.

Last fall, the city temporarily relied on the Croton reservoir for more of its drinking water when half the Catskills supply went offline for repairs to a major aqueduct. An unexpected drought halted the repairs.

Should salinity levels continue to rise in the Croton reservoir, the city could lose a valuable resource, Mr. Aggarwala said.

“One of New York’s greatest strengths is the fact that we have so many different sources of water, 19 reservoirs,” he said. “If we lose the Croton system, that just makes New York City’s water supply much less resilient, and that makes it much less reliable.”

For several suburban towns that draw water directly from smaller reservoirs that feed into the New Croton, the salinity levels are more of an immediate concern. Somers, Yorktown and the City of Peekskill, all in Westchester, draw water from one of those smaller reservoirs, the Amawalk, where chloride levels could exceed safety standards in about 30 years, the study said.

“While I was alarmed by the report, I was not surprised in any way, because we’ve been dealing with this for some years now,” said Mr. Harckham, who represents many of these towns.

Several private wells in the area have had to be taken offline because of salinity levels, he said.

Methods that can help with over-salting roads, Mr. Harckham said, include thermal devices that can take a road’s temperature, to avoid unnecessary applications.

The solution, Mr. Harckham said, “is an equation of knowledge, technology, best practices and money.”