CHALK STREAMS
Pure waters
Beautiful and globally rare, healthy chalk streams teem with life, from brown trout to water voles and dancing mayflies. Charles Rangeley-Wilson celebrates one of England’s greatest natural marvels – and explains how we can best protect them
If you live south and east of a line drawn between the western edge of Dorset and the north-east corner of Yorkshire, the chances are you live close to a chalk stream, even if you may not know it.
I grew up within a few miles of one – the Hogsmill Stream in Kingstonupon-Thames – and spent my summers exploring and fishing several more in Norfolk, without ever knowing that these were chalk streams. I fell in love with their clear flows and the many fish that swam in them, nonetheless. Not until I left university and started teaching in Dorset did I get to more fully understand the significance of this very English type of river.
Wessex holds many of the really well-known chalk streams – the Frome,Avon, Test and Itchen – and their many tributaries. But, in fact, there are chalk streams throughout half of England, in Sussex, Kent, Oxfordshire, Berkshire,Buckinghamshire and Hertfordshire, and on through Cambridgeshire,Norfolk, Lincolnshire and Yorkshire.There are three within Greater London, and over 280 in total. A number that partly defines why they are so special, because it amounts to the majority of chalk streams in the world. We share the stewardship of that global total with Normandy and Denmark.
ANCIENT PEACE
The other part of what makes them special can be understood once you are standing beside one. I can take or leave football, so last summer I left it and, knowing that most of the world was watching a certain cup final, I went down to my local chalk stream and sat beside it in the monastic quiet that had enveloped the landscape. I listened to reed buntings, kingfishers, even a distant bittern (no,I wasn’t imagining that) and the kissing sounds of trout rising to the surface to pick off mayflies.
“Water from chalk streams is an unvarying 10°C, it is alkaline, mineral-rich and the flow is constant”
In the meadow beside me stood the craggy walls of a priory sacked by Henry VIII. Just upstream was a Domesday watermill and a castle built by Seigneur de Varrene, one of William the Conqueror’s loyal henchmen. Sit still for long enough beside a chalk stream and you will see, hear and feel all of this, within the context of a landscape that is, to coin Ted Hughes’ poem about another fishy denizen of chalk streams, “as deep as England”.
A brown trout swims through the clear waters of the River Test in Hampshire, as the webbed feet of ducks paddle above 
Brook water crowfoot blooms on the Teffont chalk stream in Wiltshire
But to understand why these streams are unique, we need to go deeper than that, back many millions of years to a time when the world was much hotter, and our corner of Europe was under the waves of a shallow and clear sea.In those sunlit waters swarmed clouds of a tiny plankton whose minute shells, over countless millennia, rained down to the floor of the sea and formed a deep bed of the purest calcium carbonate: chalk. Now, the world is colder, the seas have retreated, and the Indian continent has crashed into Europe, buckling that sea bed into undulating hills. Glaciers have scraped over the rippled land-mass, wearing it away until only a fraction of the lip of that bowl of chalk remains at the surface: this is the downland that defines England, that makes the white cliffs of Dover, the Needles on the Isle of Wight, the Cerne Giant and the White Horse.And that English Great Barrier Reef – our chalk streams.
PURE FLOW
Chalk is, of course, porous.Most of the rain that falls on the chalk hills – in winter especially – sinks into the ground, and percolates through fissures in the rock down to the ‘sunless sea’ of the chalk aquifer. In the valley bottoms, that water rises as springs and these coalesce one by one to form chalk streams. The underground journey of the water and the buffering effect of the aquifer give rise to the properties that define a chalk stream: the water from chalk springs is an unvarying 10°C (comparatively warm in winter and cool in summer), it is alkaline, mineralrich and – under natural conditions – the flow is constant.
Once common on chalk streams, water voles are the UK’s fastest declining mammal due to habitat loss and predation; 
a brown trout swims with grayling in the River Anton, a Hampshire chalk stream; 
the scarce brown sedge, a rare caddisfly, lays its eggs on dead leaves on the beds of chalk streams
This allows a stunning diversity of natural life to flourish and indeed chalk streams are the most biodiverse of English rivers. They nurture waterweeds such as starwort (bright emerald-green, with star-shaped leaves in tresses like an Assyrian beard) and stream-water crowfoot (a darker green, in longer, more Druidic tresses, decked out in early summer with constellations of daisy-like flowers). They are inhabited by myriad species of fish, including trout, grayling, dace, pike, perch and, most notably perhaps, the Atlantic salmon, because the chalk stream strain of this fish is genetically distinct, as well as river-loving mammals and birds, such as the water vole and otter, together with Bewick’s and mute swans, wagtails, reed warblers, dippers, grebe, moorhens and even the rare water rail.
Above all, the calcareous waters of a chalk stream provide the calcium with which invertebrates make their exoskeletons – recycling calcium from those prehistoric oceans – and thus chalk streams are rich in insects, in terms of abundance and diversity: so much so that a complete list would require the word-count of this entire magazine, let alone one feature. Of special mention, then, are the globally rare insects that have evolved to live in the ephemeral reaches of chalk stream headwaters: little creatures such as the winterbourne stonefly or the scarce brown sedge. And, of course, that diva of the chalk streams: the mayfly Ephemera danica, which lives for a day (at least in winged form) and might well land on your Guinness if you are drinking by the Thames near Reading sometime in early summer.
CHALK STREAM CARE
Arguably, it was the malleable, homely and reliably watered chalk hills of England that allowed our early society to flourish and is the reason why these rivers are under such pressure now. They flow through the most densely populated, heavily industrialised and intensely farmed part of England.All these people, all this activity, put a huge strain on our chalk streams. We suck the water from them to flush our loos. We pollute them with our dishwashers and effluent. We have corralled them to drive watermills and, when they were inconvenient, we shoved them out of the way, or even buried them. All in all, we have made very poor stewards of this most incredible natural treasure.
It is perfectly possible to live side by side with vibrant, wild and well-cared for rivers. Chalk streams, because they are globally unique, should be our challenge. With a little care and cost, we can let the rivers enjoy their flow before we use it, not after. And when we return that water to the natural world, we can make sure it’s fit for anything to swim in, let alone people. Where we have shoved the rivers carelessly aside, we can make a bit of room and rebuild them as nature intended, with meandering bends, pools and riffles, and wet spaces in which wildlife can thrive and bless us with its company.
Charles Rangeley-Wilson is a writer, conservationist and river restorationist.His books include Silver Shoals, Silt Road, Somewhere Else and The Acccidental Angler. charlesrangeleywilson.com
CHALK STREAM FIELD GUIDE
1 Atlantic salmon A close cousin of the more adaptable trout, the chalk stream salmon is unique and on the very edge of survival – reason enough to look after our chalk streams.
2 Kingfisher A high-pitched screech and a flash of blue, the kingfisher arrows along the chalk stream highway looking for minnows. It nests in wind-blown root-plates and high banks (see page 36).
3 Ranunculus, or stream-water crowfoot The chalk-stream defining plant, with long tresses and infinite constellations of white flowers swaying in the current.
4 Bullhead It’s easy to ignore the little fish, but bullhead (also known as miller’s thumb) form a vast part of the fishy bio-mass. For every trout, there will be 10 of these.
5 Otter Once driven close to extinction by hunting and chemical pollution, the otter is the comeback kid of English chalk streams, and now their apex predator once again.
6 Water vole Otherwise known as ‘Ratty’ from The Wind in the Willows. Bug-eyed, cute and too tame for their own good, they are also rare, and threatened by another invasive species, the mink.
7 Mayfly The Mayfly spends most its two-year lifespan burrowing in the riverbed before metamorphosing into the winged fly to mate, fluttering over the water in early summer. As a grub or a fly, it is a staple food for all fish.
8 Brown trout The beautiful brown trout thrives in the clean, well-oxygenated waters of healthy chalk streams and is a notable quarry for fly fishermen.
9 White-clawed crayfish Our native crayfish, now increasingly threatened by the invasive signal crayfish, is in need of special conservation.
Don’t miss
Chris Packham walks Hampshire’s River Itchen while exploring nature’s power to boost wellbeing in The Walk That Made Me, available on BBC iPlayer.
CHALK STREAM WALKS
For any of these walks you will need an OS map
1 THE ITCHEN WAY, HAMPSHIRE
The 31-mile Itchen Way runs the length of our most idyllic chalk stream, the River Itchen, from its source near Hinton Ampner House to its mouth at Woolston. There are many lovely sections, including the half-mile from the Bush Inn at Ovington along the river’s edge to Itchen Stoke, and from the headwaters of the Alre at Old Alresford Pond (of which there are good views from the garden of The Globe pub) just over one mile west to Drove Lane. Or walk from Winchester’s St Cross Hospital, north along St Swithun’s Way through the city and on to the Hampshire Wildlife Trust site at Winnall Moors (hiwwt.org.uk/nature-reserves/winnallmoors-nature-reserve).
2 THE RIVER KENNET, WILTSHIRE
From the Church of St Mary in Chilton Foliat, footpaths cross, intersect or run close to the River Kennet south then west, past Littlecote House and the villages of Ramsbury and Axford, all the way to Marlborough, a stretch of around 10 miles.
3 THE RIVER CHESS, BUCKINGHAMSHIRE
You can follow this jewel of a chalk stream for 10 miles, from the playing fields in Rickmansworth upstream past Loudwater, Sarratt Mill, Chenies and Latimer, all the way to the source above Chesham.
4 THE RIVER CERNE, DORSET
There is a three-mile, history-soaked walk from Cerne Abbas, under the shadow of the late-Saxon, chalk-carved Cerne Giant and by the sacred springs of Cerne Abbey, south past the villages of Nether Cerne and Godmanstone. For refreshments, there are good tea rooms and pubs in Cerne Abbas and Feed the Soul farm shop in Godmanstone (feedthesoul.co.uk).
5 THE WANDLE TRAIL, SOUTH-WEST LONDON
The London chalk stream that Nelson once fished. A footpath takes you 12.5 miles along the river from the National Trust’s Morden Hall Park (nationaltrust.org. uk/morden-hall-park) north past Beddington and all the way to the springs at Carshalton. Keep an eye out for an urban trout, once extinct from this stream but now restored thanks to the Wandle Trust. wandlevalleypark.co.uk/map
For more spectacular river walks, go to countryfile.com