Seasonal Changes to Look for in a British River

Reading the River Through the Year

A British river is never the same twice. The same stretch of water that dawdles past the churchyard in July can be a roaring, brown torrent by Bonfire Night, and the wildlife that lives there shifts with every change. If you walk the same bank once a month, you will notice that the river has its own calendar, written in hatches, flows, and fallen leaves. Learning to read that calendar is one of the great quiet pleasures of riverside living, and it makes every walk a bit more rewarding.

Here is what to look for as the year turns, season by season.

Spring: Hatches, Herons and New Growth

Spring arrives on the river earlier than you might expect. By late March, the first mayfly nymphs are stirring in the silt, and by mid-April the famous hatches begin. The large dark olives tend to appear first, followed by the grannom caddis and, later, the mayfly proper in late May and early June on southern chalk streams. If you fish, this is the season that justifies the whole sport. If you do not, it is still worth watching: swallows and martins will be skimming low over the water, taking spent spinners off the surface at dusk.

Look out for the following as spring takes hold:

• Banded demoiselles appearing along the banks from May, flashing their metallic blue-green bodies in the sun.
• Grey wagtails patrolling weir sills and gravel bars, bobbing their tails as they hunt insects.
• Otter spraints — dark, fishy-smelling droppings left on flat stones, often a sign of a territory being marked.
• Water vole burrows in steep earth banks, with neat nibbled grass stems nearby, a good sign on rivers where they have been in decline.

Nesting herons and goosanders are easy to spot, and swans begin building or repairing their huge nests on islands and cut banks. Keep a respectful distance; a disturbed nest can mean lost eggs.

Summer: Low Flows and Clear Water

By July, many rivers drop to their lowest levels of the year. Chalk streams run gin-clear, and you can often see every stone on the bed. This is brilliant for watching fish — chub basking under alder roots, barbel grubbing on gravel shallows, and dace shoaling in the riffles. It is also a time of stress for wildlife, because warm water holds less oxygen and low flows concentrate everything into smaller pools.

Two things are worth doing in summer. First, look after the margins: bankside vegetation in full flower is where damselflies, dragonflies and countless invertebrates live. Second, take care when wading or paddling. Trampling gravel redds is a winter problem, but disturbing submerged weed beds in summer destroys cover for juvenile fish and the small creatures they eat.

Hot days also bring out the mammals. Daubenton's bats hunt low over the water at dusk, often within a metre of the surface. If you sit still on a bridge just after sunset, you may hear their echolocation clicks on a simple bat detector.

Autumn: Leaf Fall and the Drift Downstream

Autumn is the season of change on the riverbank, and it happens fast. As the trees shed, leaf litter falls into the water and becomes the base of the food web. Shredders such as caddis larvae and freshwater shrimp break it down, and the whole river runs on that autumn subsidy through the winter.

What to watch for:

• Salmon and sea trout running upstream on spates in October and November, particularly on rivers in Wales, Scotland and the north of England.
• Fungi on fallen timber along the bank, from sulphur tuft to the vivid scarlet elf cup in milder spells.
• Fieldfares and redwings arriving from Scandinavia to feed on hawthorn and rowan berries along the riverside.
• Kingfishers more visible as leaves drop and the banks open up, flashing low and fast between perches.

Avoid the temptation to clear every fallen branch. Large woody debris in the channel is valuable habitat, creating scour pools and shelter for fish and invertebrates.

Winter: Spates and High Water

Winter is when the river shows its strength. Atlantic fronts dump rain on the catchments, and within hours a quiet stream can become a brown, roaring spate carrying silt, branches and anything else left loose on the bank. A spate resets the river — scouring gravel, moving dead wood and flushing fine sediment out of the spaces between stones where fish eggs need to breathe.

Safety comes first in winter. Stay well back from the edge, avoid flooded footpaths, and never try to cross a swollen ford. If you walk a riverside path regularly, note the high-water marks and use them as your guide when levels rise.

Wildlife-wise, winter is surprisingly active. Cormorants and goosanders fish the deeper pools, otters are most territorial, and pike move into the margins to spawn in late winter. On milder days, you may spot a flash of blue as a kingfisher works a sheltered backwater.

For the angler, grayling and chub provide sport through the colder months, though rivers on a rising spate are best left alone. Frosty mornings, a flask in the bag, and a quiet stretch of bank are reward enough.

Living With the Rhythms of the River

The best way to enjoy a British river is to slow down and revisit it often. Keep a notebook, or a note on your phone, of what you see and when. After a year, you will have your own local record: the day the mayfly first appeared, the week the first salmon ran, the morning the river broke its banks. That record is more valuable than any guidebook, because it belongs to your stretch of water.

It also makes you a better custodian. Riverside living comes with responsibilities — not clearing every fallen tree, not pouring garden chemicals onto the bank, and keeping dogs and children out of the shallows during spawning season. Do that, and the river will keep giving you reasons to walk down to the bridge, whatever the month.