Clean water has always been something of a dirty business. The great aqueducts of ancient Rome failed to deliver a third of their prodigious waters due to theft, leakage, waste, and whatever was taken by Caesar. Los Angeles secured its first waters from a distant mountain valley, ruining its farmers and ranchers. New York’s pure mountain waters flow here from upstate reservoirs ringed with the resentments of watershed dwellers. Now comes a report, on the first page of the New York Times (July 20, 2006), that the city’s water managers are failing to keep eroded soil from running into watershed reservoirs and that building extraordinarily expensive filtration works may be necessary to maintain water purity. Filtering the world’s finest urban water would be like draping Manet’s luncheon nude in mosquito netting. Considerate, perhaps, but far less appealing than au naturel.

It’s hard to assess the filtration threat. Suburbanization, natural soil conditions, and increasingly aggressive federal oversight are all at play here, but they are nothing new. Why it became news this summer is curious. Possibly the answer lies with the federal EPA who would like to have greater control over our water. Possibly the answer lies within the city’s own Department of Environmental Protection, the overseer of our water supply, where the official position favors watershed protection over water filtration but certain elements may have different ideas. Regardless of the identity of the forces at play, the perception of some water watchers is that the DEP has become a bit overmatched for its vast challenges. Filtration is only one of them.

The Gilboa Dam, which created the 20 billion gallon Schoharie Reservoir in 1927, is, in the DEP’s own words, “outmoded.” Emergency repairs to avoid a catastrophic failure are underway now — the start of major reconstruction has been hurried up to next year. In the 164 years of New York’s public water supply, there has not been a major dam break. The original dam on the Croton River was breached while it was under construction in 1841 and three people drowned. A breach of Gilboa would rival the devastation of the 1928 St. Francis Dam collapse which killed over five hundred people and ruined chief engineer, William Mulholland, who had designed it and the rest of the Los Angeles water supply.

Meanwhile, the DEP is contending with significant leaks in the Delaware Aqueduct, the youngest of the city’s three main aqueducts, which delivers nearly half of our water. Completed in 1945, the 85-mile conduit has been leaking for at least fifteen years 38 million gallons or more a day, or as much as 10% of its daily supply. There are no plans to begin a real fix until at least 2014. The DEP has not said that the aqueduct is likely to fail in the ten years or more before a bypass and repairs are completed but one gets the sense that certain fingers are crossed.

Of all the DEP’s ongoing projects, City Water Tunnel No. 3 is its star attraction. The largest and longest construction project in the city’s history — it cost nearly $7 billion to build it and will take from 1970-2020 to complete it — the tunnel garners breathless public notices from awed feature writers taken on the deep subterranean tour. But at least one former DEP commissioner (and tour guide) has told me that the third water tunnel is also a very romanticized project with a much more prosaic reality. The tunnel will have some value in helping to better distribute existing water supplies that have been routed through two distribution tunnels built in the early 1900s.

Way back in the 1960s, the main rationale for the new tunnel was that the old ones might fail. In fact, there is very little evidence suggesting that possibility, and the glacial pace of construction suggests that DEP is not really worried about it. And, while the third water tunnel is an engineering marvel, its cost will be appearing (unitemized) for generations on New Yorkers’ water bills, which are currently increasing by an annual rate of 9%. The debt service on the city’s water system is 50% of its budget — one of the highest ratios in the nation. The average for American utilities is less than 25%.

These are among the larger issues that confront the DEP. There are smaller ones, ones that are perhaps more obviously indicative of the current mindset at the DEP.

Five years after September 11, the DEP is still denying access to locations well-known and oft-published by photographers of New York’s water and other infrastructures they routinely have photographed in the past. These are portrayers of the special beauty of urban engineering, not security risks.

Two years ago, two sections of New York’s first water pipe were unearthed in a downtown park where they had been laid down 200 years ago by the corporate ancestor JPMorgan Chase. Learning that the DEP intended to claim them, I helped organize a working group to preserve and display these unique examples of our water history. When I wrote about them in the New York Times, the DEP threatened to pull out of the working group unless I left it. Cooler heads prevailed, but the group has since disbanded and the pine log pipes now languish in DEP-controlled storage.

Another New York city has handled its first water pipes differently. During routine water main replacement in Schenectady this summer, city workers uncovered a section of elm pipe laid by a private company in 1836. Civic interest quickly prevailed and the pipe is now on display at the Schenectady County Historical Society.”We recognize that the city itself is a unique historical resource and through intergovernmental cooperation, we can all benefit from what might be found,” city engineer, Chris Wallin, told the Albany Times Union.

Earlier this year, the DEP removed its top water quality scientist, an award-winning 25-year veteran who ran the Bureau of Water Supply. He took the hit for refusing to fire subordinates involved in a record keeping issue. The veteran is now facing unwanted retirement, leaving certain DEP insiders and observers shaking their heads.

Silted reservoirs, a dangerous dam, a leaky aqueduct, a grandiose tunnel slowly built, secrecy, petty possessiveness, imprudence — all are indicative of an agency that has become passive, reactive, guarded, and fearful — not the sort of vision and leadership that created New York’s remarkable water supply back in the 1830s and expanded and protected it for generations afterwards. Nobody expects managing the water supply of the world’s greatest city to be a lunch in the park. But concern is rising, like all the water behind an unstable dam.

Mr. Koeppel is the author of “Water for Gotham” and wrote the lead essay for the forthcoming book “Water-Works: The Architecture and Engineering of the New York City Water Supply” published by Monacelli Press.