Step into the water of an English chalk stream, two or three feet deep, shaded by willows and alders, and you feel the pressure and cold of it around your knees and thighs.

The gravel underfoot is dappled with sunlight reaching down to the river floor. All around you the motion of the water is sustained and untroubled, the current never urgent. Because chalk streams are spring fed and little silt finds its way into them, visibility is aquarium clear. The trout within them seem to hang in air.

These streams take their quality from the rock over which they run: alkaline, mineral rich, with dissolved calcium carbonate but almost no sediment, flowing to the sea over many miles of clean flint-gravel bed. Bubbling up from springs that emerge from deep aquifers in the chalk, they run through valleys fringed with water mint and clusters of water forget-me-nots, often thick with life-sheltering weeds. Not subject to the surges of rivers that run over harder rocks, they flow steadily through the English chalk country, whose gentle landforms billow across the nation’s southern and eastern reaches.

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Simon Cain, a pioneer of river restoration, fishes the Bourne Rivulet in Hampshire. The small chalk stream was overly deep from dredging and cloudy with silt until Cain restored its gravel bed and revived its ecology.

The River Anton in Hampshire is healthy enough to support brown trout and grayling, but murky water is a sure sign of trouble, including polluted runoff from roads and farms.

Chalk is a pure type of limestone composed of tiny shells of marine organisms. Deposits are found worldwide, but in England the geological ripples from the rising of the Alps some 40 million years ago brought a wide swath of it to the surface. It’s porous and fractured, with up to 40 percent of its bulk made up of spaces between the rock grains. Rain that falls on chalk sinks into the ground, sometimes taking months to percolate through the hills. In that way, the rivers have a kind of steady maturity about them. Rainstorms produce no floods, and in drought the rivers continue to run. The water acquires the temperature of the rock—50 to 54 degrees Fahrenheit all year. This means that the plants and animals that live in the chalk streams can depend on continuity.

How they’re formed

Meandering through rolling hills of chalk that act as a sponge, the gentle flows emerge when groundwater rises above ancient, cleansing aquifers below. It’s all part of a process that could have began as many as 100 million years ago.

100-60 MILLION YEARS AGO DEPOSITS

Europe is covered by shallow seas teeming with phytoplankton called coccolithophores. When they die, their sunken calcium shells turn to chalk.

Coccolithophores Ocean

Chalk layer

FERNANDO G. BAPTISTA, EVE CONANT AND LUCAS PETRIN, NGM STAFF; LAWSON PARKER

SOURCES: DAVID SEAR, SCHOOL OF GEOGRAPHY AND ENVIRONMENTAL SCIENCE, UNIVERSITY OF SOUTHAMPTON; CHARLES RANGELEY-WILSON, CABA CHALK STREAM RESTORATION GROUP

If you go snorkeling in a chalk stream, you’ll find yourself “in another world, so absorbing that nothing else encroaches,” says Nicola Crockford, inveterate river snorkeler and conservationist with the Royal Society for the Protection of Birds. There are flowering water crowfoots, whose white blossoms unfold first underwater, as well as patches of bright green starworts, with trout and grayling loitering in their shadows. On the gravel bed, larval cases of caddis flies look like tiny sticks. Young trout parr, tiger striped and quivering, hold their own in some corner of the current, their bodies never still. Farther off in the green dark of the stream, larger fish melt carefully away.

Anyone connected with these rivers talks about them with undisguised love. Zam Baring, who with his brother and sisters runs the Grange at Itchen Stoke in Hampshire—one of England’s leading sparkling wine vineyards—says his vines “have their heads in the chalky Hampshire downs and their toes in the sparkling headwaters of the River Itchen.” To go wading deep in the tributary that runs below the vineyard, he says, is to “think you’ve gone to floaty heaven.” A lifelong fisherman and co-vice chair of the Wessex Rivers Trust, Baring has helped lead numberless river restorations and celebrates even the smallest streams. “You’ll find all kinds of beauties in a quarter inch of water,” he says.

Russell Biggs, who champions the needs of chalk streams in the east of the country, says the tiny River Babingley saved his life. His wasterecycling business was struggling and driving him to despair. “I would get home and … ” He pauses. “But then to come here, walk by the river … I think if I was in a flat in a city center, I just would not be around, put it that way. It gives you a reason.”

Riverkeepers cut back water crowfoots in the Hampshire Avon. Such plants provide shade and shelter for river life, but summer excess can make fishing impossible.

These are not the waterways of a remote wilderness. The fisherman, journalist, and author Charles Rangeley-Wilson calls chalk streams the rivers of “habitable” country. “It is beauty on your doorstep,” he says. “But because they are on your doorstep, they are also very threatened.”

Human damage began thousands of years ago and led to a crescendo of change and destruction in the mid-20th century. Cities and farms casually polluted them. Property owners dammed or widened them, slowing their current, ironing out their natural meanders, and removing fallen trees—which make life difficult for anglers but good for fish and other river life.

Slowing a river causes thick mats of silt to settle on the streambed and blanket the gravel, whose clean, aerated spaces the trout and salmon need to lay their eggs. Beneficial weeds—nurseries for invertebrates—grow only in bright, fast water. Without the weeds, the all-important insect life—the many different species of mayflies, stone flies, and caddis flies—collapses. Without the bug life, there is no fish life, no wild brown trout or grayling. Without the fish life, there is no otter life—and none of the magical, quick, quivering presence that gives the rivers their own life.

Natural life cycle

Chalk streams—clear, alkaline, and rich in minerals and oxygen—have all the building blocks to support a diversity of creatures.

Miles of the Itchen and the famous River Test, which runs down through the Hampshire chalk to its mouth near Southampton, have been turned into easy-fishing parks with carefully mown banks, gingerbread fishing huts, and huge nursery-raised trout. Fees to fish the most celebrated stretches can run to more than $600 a day. The fast-bubbling water and the varied ecological niches of the natural stream have been erased.

There is also, inevitably in a crowded country, the pervasive influence of pollution. Detergents, microplastics, pharmaceuticals, and heavy metals, as well as waste that’s flushed down toilets, all arrive in the streams. Fisherman Paul Jennings has seen his local sewage works discharge waste into the River Chess, north of London, for more than 90 days—68 days without a break. “It was dreadful. You didn’t want to go into it. A smell. A muddy color. Nasty, gray, and horrible, with bits in it,” he says.

Poling a punt along the Great Stour is a popular way to see historic Canterbury. The classic children’s book The Wind in the Willows celebrates such a chalk stream as a “sleek, sinuous, full-bodied animal.”

A mayfly alights on a water speedwell frond beside the River Itchen. The insect can spend two years underwater as a nymph but may live for no more than a few hours above it.

“After rain, the first thing you see coming down the river is the diesel washed off the roads,” says riverkeeper Peter Farrow, who works for a private estate that includes a stretch of the Test. Soil from careless plowing near the rivers chokes many of the clean gravels on which the fish rely. Overuse of phosphate and nitrate fertilizers in agriculture overstimulates the rivers, whose beds then clog with filamentous weeds, which “smother invertebrate eggs, get in the gills of fish, and choke out the beneficial plants, the oxygenators,” says freshwater ecologist Janina Gray, deputy CEO of the conservation group WildFish.

A political system that puts cheap tap water before river health has not helped. If anything is worse than a polluted chalk stream, it’s a river that has been denied the water that is its very life—water that has been sucked from the underlying aquifers to service human needs. In some places, the water table has dropped more than 20 feet. “If you have a river that’s dry, there is no point in worrying about water quality and habitat, because it’s just not a river,” says Rangeley-Wilson. “Flow is fundamental.”

The delicate art of catching fog in the desert

All across chalk country, river advocacy groups have emerged in the past few years. Forced to stay home during pandemic lockdowns, many people discovered their local rivers, and public pressure for change has never been more intense. Over the past 20 years or so, advocacy groups, water companies, and government departments have written a series of large-scale, multidecade plans for reservoirs, desalination plants, domestic water meters, and water transfer networks to reduce the amount of water taken from the chalk. Increasingly, rivers are having their natural form restored.

Simon Cain began almost single-handedly to invent chalk stream restoration in England after being jolted into action one grievous summer afternoon in 1984. As he fished the River Ebble in Wiltshire, “the water turned chocolate,” he says. Upstream he could see a large orange machine moving its digger arm in and out of the riverbed. The Ebble was being dredged, with government funding, to lower the water table in the surrounding meadows, perhaps to make them suitable for arable crops. In the detritus, Cain spotted hundreds of rare and endangered crayfish “all grasping at the evening air.” Forty years later, the same stretch of the Ebble remains a sad and withered thing.

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The three cardinal virtues of a healthy river are “gradient, velocity, and sinuosity,” says Cain, who founded a company specializing in river restoration. Over the past decades, his firm has reshaped numerous rivers into healthier form, removing weirs and dams, roughening their flow, adding the twists and turns that create varied habitats for plants, invertebrates, and fish.

Tree limbs are drawn by horse to the restored River Nar in Norfolk. Such woody debris diversifies water flow and habitat.

Many river restorers have followed in Cain’s path, among them Rangeley-Wilson, who has worked with Cain to reinvigorate a stretch of the River Nar in north Norfolk. For centuries it had been trapped in a straight channel leading to a mill. With no gradient, no sinuosity, and no flow, the river had died a sluggish, silty death. But over the past few years, Rangeley-Wilson has been reconnecting the Nar to its valley, restoring its meanders, dragging in some trees to disrupt the flow and diversify the habitat, and allowing natural processes free rein. The cost of restoration can run about $130,000 per mile of river, usually funded by government grants and support from landowners.

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I went fishing with Rangeley-Wilson one afternoon, and as we came to a new bit of channel less than two years old, the river ran and chuckled loosely beside us. Within 30 seconds, Rangeley-Wilson had hooked a wild trout. Then another and another. All were small, only half a pound or so, but then he spotted something more. “Ooh, there’s a nice trout. He’s going to hide under the bank there.” He landed his fly, the rod bent, and he brought the trout into the gravel shallows. The river he had made was full of life.

Slipping the barbless fly from the trout’s jaw, he held it on the surface of the stream, allowing the water to lap over the red-and-black sprinkles of its body. Then he let it ghost away, an emblem of the beauty of these streams that will all, we hope, one day be restored to life.

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The glassy surface of the Great Stour reflects the ancient history of Canterbury, its ​banks home to monasteries, mills, breweries, and other centuries-old ​structures.