When a vein is hard to find beneath a patient’s skin, doctors and nurses will sometimes tap on an arm, making the vessel visible.

A topographical map of New York from 1874 showing original water courses

On Friday afternoon, using blue chalk paint, Stacy Levy plans to palpate a few sidewalks on the Upper East Side of Manhattan to visualize the path of a stream, now out of sight, that has been running since ancient times.

Water doesn’t stop flowing because subways, shops and towers are built over streams and ponds. Much of New York before European settlement was a rich, wet archipelago. “Nature is not kicked out of the city,” said Ms. Levy, an environmental artist.

Searching for the city’s vanished waterways has become a form of specialized detective work, much of which begins with the Viele Map. Read more

Parc des Buttes-Chaumont, in northeast Paris, is an urban oasis with lush hills, a Roman-style temple, and water views from almost every area of the park

The New York Times Travel section has published a collection called “On the Water: 10 Favorite Places on European Rivers, Lakes and Coastlines” full of photos and videos of fjords, hot springs and seasides.

What is your favorite escape on or near water, whether an ocean, lake, river, creek, pool or anywhere else? Why do you like it so much? Read more

The Environmental Protection Agency just proposed to repeal critical protections for the drinking water of 117 million Americans. After tragedies like Flint, Mich., the toxic algal bloom in Ohio, and countless other tales of polluted waterways, it’s hard to overstate the importance of safe drinking water for all.

In 2015, the Clean Water Rule clarified the streams and rivers protected by the Clean Water Act, our bedrock clean water legislation. The rule also protects wetlands, which help filter out pollutants and provide wildlife habitat, as well as serve as buffers against the fiercest storms. Read more

The waterways of the West now exist as monuments to an ambitious desert civilization. Across this vast region of America, few, if any, rivers flow without hosting one or more dams, concrete channels, diversions or other human-made “improvements” that allow people and farming to flourish in this dry country. And few, if any, rivers reveal this unnatural world more than the Colorado, which no longer reaches the sea or carries along its entire 1,450-mile length much of the reddish silt that inspired its name.

Glen Canyon Dam on the Colorado River near Page, Ariz.

The prolific author and New Yorker contributor David Owen details what has happened to the river that once carved the Grand Canyon in his new book, a brisk and informative travelogue that wends from headwaters in the state of Colorado to where the water trickles to a halt in a riverbed cracked by the heat of the desert sun in Mexico. This is well-traveled territory, including Marc Reisner’s classic book from 1986, “Cadillac Desert,” which remains the definitive work on the West and its water woes. The problem then, as now, is people — and what we have chosen to do with the water. Read more

Shares of the Brazilian water utility Sabesp took a dip this week after it said it might raise new equity. Investors everywhere, however, will have to get used to such capital calls.

Citigroup estimates that water companies need to spend up to $10 trillion globally by 2029 on new and upgraded infrastructure.

It’s true that Sabesp, the world’s fourth-largest water and sanitation company, could have done a better job with communication. Its missive at the end of last week didn’t mention amounts or timing, and only when asked did executives say that nothing is likely to happen for at least a year.

Sabesp’s current ownership complicates matters, too. The State of São Paulo owns a 50.3 percent stake, and any recapitalization plan would have to keep the government in control. Investors registered their confusion by sending the stock down on Monday and on a roller-coaster ride the next two days. Read more