There is something quietly magical about a family walk that ends with wellies in a shallow brook and small hands cupping a net full of nothing much. Britain's streams and brooks are among our most overlooked wild places — narrow, often hidden behind hedgerows, and easy to dismiss as a bit of ditch. Yet they are the capillaries of the landscape, feeding rivers, sustaining mayflies and bullheads, and offering children their first real encounter with moving water. Keeping them clean is not a job for councils alone. It is mostly a matter of small, deliberate habits.

Take Everything Home — Including the Orange Peel

It is tempting to think that apple cores and banana skins will simply rot away, and that a dropped ribbon or plastic bottle top is too small to matter. In a stream, the maths changes. Cold, shaded water slows decomposition dramatically, so a picnic's leftovers can sit on the bed for months, suppressing the tiny invertebrates that everything else feeds on. Plastic fragments are worse: they linger for decades and are easily mistaken for food by fish and birds.

A simple rule for any walk is that whatever you carry in comes out with you, even if it is organic. Pack a small bag for rubbish at the very start, before anyone gets tired or hungry. If you spot litter in a gateway or caught in a branch, picking it up as you pass is a genuinely useful act of citizenship — but only if it is safe to reach. Never wade into deep or fast water to retrieve a bottle.

Watch What Runs Off the Land

Most pollution in our streams does not arrive in sacks. It seeps. When rain falls on driveways, patios, car parks and muddy gateway tracks, it carries whatever is sitting there into the nearest drain or ditch, and from there downhill. You can reduce that load with a few practical choices at home and on the walk.

• Wash cars on grass, not tarmac. Soapy water then filters through the soil instead of shooting straight into a surface drain that leads to a watercourse.
• Use a watering can for weedkiller and moss treatments rather than a hose or sprayer, and never apply them when rain is forecast. Even a light shower will wash the lot into the nearest ditch.
• Keep oil and fuel away from drains. A single engine-oil spill can foul hundreds of metres of stream, killing invertebrates and smothering gravel beds where fish spawn.
• Leave leaves and grass cuttings on the border, or add them to a compost heap well back from the water. A heap of green waste dumped on a bank leaks nutrients that trigger algal blooms.
• Check your septic system if you live in a rural spot. A failing tank is one of the most common causes of localised stream pollution, and often goes unnoticed for years.

Respect the Banks and the Plants That Hold Them

The banks of a stream are not just scenery. They are a rampart of roots, sedges, moss and overhanging brambles that keep the channel narrow, cool and stable. Trampled margins collapse into the water, sending silt downstream and smothering the gravels where invertebrates and young fish live. Overhanging trees and shrubs also shade the water, keeping it cold in summer — essential for species such as brown trout and the mayfly nymphs they hunt.

So keep to established paths and footbridges where they exist, and use a single well-worn crossing point where they do not. Discourage children from building dams of stones across a channel; it raises the water level upstream, drains it downstream, and cuts off movement for everything living in between. Den-building is a great game — just move it away from the water's edge and use fallen branches rather than tearing live growth.

Know What You Are Looking At

It is difficult to care about a stream you cannot read, and children learn fastest by looking. A few minutes of quiet observation can tell you a great deal about a watercourse's health.

• Clear, odourless water with visible pebbles is a good sign.
• A green, slimy coating on stones often points to too many nutrients running off the land.
• Mayfly, caddisfly and stonefly larvae are excellent indicators of clean, oxygen-rich water.
• A thick orange-brown deposit on stones may indicate iron or minewater pollution and is worth reporting.
• Fish gasping at the surface on a warm day can signal low oxygen — a problem that often follows drought or pollution.

Take photographs rather than specimens, and return every creature carefully to the water. Sweep nets are wonderful tools, but keep them gentle and never leave a net full of catch sitting dry on the bank.

Being a Useful Neighbour to Your Local Brook

Small groups of families can achieve a surprising amount. A spring litter pick along a footpath, timed before the vegetation grows up, removes far more rubbish than the same effort in July. Reporting pollution to the relevant environment agency, with a photograph, a grid reference and the date, makes a real difference — anonymous complaints rarely get followed up. If you know a farmer or landowner along the water, a friendly conversation about buffer strips beside the channel often goes further than a complaint.

Above all, be patient and be regular. Streams recover remarkably well when the pressure eases, and children who visit the same stretch of water through the seasons will notice the changes themselves — the first mayfly hatch, the autumn leaf fall, the clearing of the water after winter floods. That familiarity, passed on without fanfare, is how Britain's brooks will keep their clean, cold, chattering character for the next generation of wellie-wearers.