Jim Smith has been walking the banks of the Ouse for 52 years, since he was 19 years old. For many of those years, he was officially the keeper of the river, hired by the local angling society to watch over the water and its banks. He is retired now, but he still walks and he still notices.

There are not many left like Smith. He is a man who knows when the winter has turned harsh in Scandinavia because he hears the wigeons outside his window at night, making that little whistling noise as they arrive in the UK in search of milder air; who knows he should stop and stand quietly when he notices two male adders on the river bank and watches them dancing, twining their bodies together in a contest for dominance. Smith knows how the river flows and how the animals who live in it and beside it behave. He is also acutely aware of what is happening around it, of threats and tensions, of the subtle impact of private profit and public bureaucracy. On several occasions while we were out walking this summer, he told me that he was worried, frightened even.

The Ouse is only a little river. It rises in the high weald of north Sussex and flows southwards for 30 miles before it pours itself into the English Channel at Newhaven. Along the way, it is fed by numerous smaller streams which, like the Ouse itself, have their source in the natural underground aquifers that hold the rainwater that seeps slowly into the chalk of the South Downs. But those aquifers are coming under so much pressure, as the demands on their water increase, that the survival of the river is in doubt.

Smith grew up on its banks, in the village of Isfield, 14 miles inland, where he still lives. His father drove a horse and cart on a local hop farm. His mother knew how to use herbs from the fields as medicines. From his earliest years, he was out here fishing with a home-made rod and line; using pet ferrets to hunt for rabbits along the railway bank, and selling his catch for pocket money. He remembers looking out of the window at school and seeing some men working on the river banks and wishing one day he could do the same.

I started to understand the importance of this river one sunny Saturday in mid-June, as we walked out in the fields near his home. Now aged 71, Jim was shuffling along, leaning on the walking stick that he had made from a holly branch (“Let it stay for a year before you work on it”), with a handle that he worked from a deer antler.

He pointed out where the Roman road crossed the ford. There was no physical sign of any road at all, but I later discovered that archeologists had dug down 12 inches a couple of miles from here, and found the surface of the road intact – still showing the rut marks of wheels nearly 2,000 years old. At this same point, where the Romans had their ford, on the far side of the river, a pattern of bumps and lumps in the undergrowth proved to be the remains of a motte-and-bailey, an old fortification that was built and rebuilt here, as first the Romans, then the Saxons and the Vikings and the Normans took over this territory by force of arms, settled by the river and set about defending it. The river’s banks proved to be riddled with clues like this, subtle remnants of the humans who had relied on it – for transport and power, for the farmers’ crops, for drinking water, for survival.

That day in Isfield, we came across a pillbox from the second world war, part of the “Stop Line” that was designed to slow down a German invasion of south-east England and ran up the western bank of the Ouse: on the walls inside, you can still read the scribbled signatures of Canadian soldiers who were based here before they were scythed down in their hundreds in the disastrous raid on Dieppe in August 1942.

The river Ouse, near Isfield in East Sussex. Photograph: Felix Clay/The Guardian

One day, as we walked down the narrow old lane towards the source of our river, Jim pointed out wildflowers that were sprayed across the verges – bright purple campion, red pimpernel, tiny blue speedwell (wide open as a marker of good weather), miniature wild ferns, bursts of honeysuckle and rhododendron bushes. We came to the bridge across the infant Ouse, with a rickety wooden fence covered in lichen and an outbreak of wild roses. A picture of wellbeing. We looked over its side in search of the babbling, bubbling stream, which for centuries has come to life here in the woods, and found ourselves peering down through the overhanging saplings at a stagnant puddle. There was no babble nor bubble. It just sat there like a sulky brat curled up in the shadow, sullen and dark and still. The only sign of life was a few tadpoles flicking around just beneath its oily surface. The stream had stopped running.

Jim was shaking his head. “I’ve seen it dry back up here before,” he said. “But never this early.”

We spent the next several hours exploring further downstream, down to Mill Pond where normally the stream flows into one end and then out of the other, but the water there was no longer high enough to reach the exit. There was nothing at all flowing out of the pond and so, as we followed the stream’s course down through the woods to the old police college, outside Slaugham village, there was not even stagnant water – just rock and shale, lying dry and naked in the riverbed. Even at Lower Rylands Bridge, more than six miles from the source, when minor streams and a reservoir had finally brought it to life, the Ouse was still only crawling along on its knees; it was flowing but, as Jim put it, “That’s not enough to float a matchbox.”

The immediate cause of the early drying out at the source of the Ouse was simply that there was not enough water in the underground aquifer on which it feeds. But that turns out to be part of something bigger. In March 2013, the local branch of the Environment Agency reported that, depending on conditions, there are now years when they can extract water from the Ouse on no more than 94 days. For the rest of the year, abstractors can use water that has been stored during the wet months in the big reservoir at Ardingly, and they can pump up water through boreholes sunk into the underground aquifers. This in turn reduces the amount of water that bubbles up into the river and its tributaries. The Environment Agency has stopped issuing new abstraction licences for the river. Meanwhile, during the summer months, nearly half of what we like to describe as a river is, in fact, recycled waste water and sewage.

The future looks even more worrying. In April this year, a report by the environmental consultants Amec Foster Wheeler for the South Downs National Park compared supply and demand in the area’s nine “water resource zones”. It concluded that, in a dry year, five of the nine zones are at risk of falling short. Two of those five take water from the Ouse. One is forecast to reach the risk of shortfall in 2019, the other to do so in 2015. Now, in other words.

And it turns out that there is nothing special about the Ouse. The whole southern and south-east region is officially classified by the Environment Agency as being under “serious water stress”. Consider this stunning statement buried in one of the agency’s reports on the south-east river basin, which runs along the south coast from Hampshire through Sussex to Kent: “There are concerns over maintaining the water resources available for people and the environment in this part of England. This river basin district has some of the highest levels of personal water use in the country while, on average, the amount of water available per person is less than for Morocco or Egypt.”

Reaching deeper into this reservoir of reports, it becomes clear that it is not only the south-east that is facing problems. In December 2011, a government white paper considered various possible scenarios for the future water supply across the whole country. It concluded: “All of the scenarios predicted a future with less water available for people, businesses and the environment. Future pressures will not be limited to the south and east of England. Under many of the scenarios, the south-west and northern England will see significant unmet demand.”

Jim Smith was perfectly clear about the source of the problem, a horrible combination of two powerful forces. The first is climate change. “The seasons have definitely changed. In the summer months, there just isn’t enough water in the system. A lot of the downland streams are dry. Areas that used to be wetlands are getting progressively drier. A lot of the ditches are dry.”

The Environment Agency is projecting a net drop in overall river flows of 15% by 2050. The Met Office predicts that by the end of the century in the UK serious droughts like the famous one of 1975/6 could be happening once a decade.

But it is the second cause that really disturbs Smith. Just as the supply of water is being reduced, so the demand for it is being increased by the apparently endless activity of property developers, driven by a rising population: “Water starvation here is a comparatively new situation, with more and more development in the last 30 years. I don’t want to shout at developers, but they build more and more houses and they don’t think about water, without which they can’t survive. People look at a reservoir and think ‘plenty of water’ – there might be to some degree – but that water can only last for so long, can only be pumped to so many people.

“There is more and more pressure on this little river. I feel that it is being sacrificed because they have to build more houses.”

The government’s Natural Capital Committee last year reported that household consumption of water had risen from just over 5bn litres a day in 1990 to more like 8.5bn litres in 2010-2011. The government white paper of December 2011 predicted that the combination of a higher population with more single households would push up demand for water by around 5% by 2020 and by as much as 35% by 2050. That’s the same year that the Environment Agency predicts that overall river flows may have fallen by 15%. It is like two hurtling trucks on a collision course.

Jim Smith likes to say that the jewels in the crown of his river are the sea trout, partly because of the extraordinary distances they will swim to come home to breed. But more than that, they are important because they are an indicator species: “If things go wrong, they will go wrong first with the sea trout.” Jim minds them like a parent. He watches the hens as they use their tails to build nests in the riverbed and then to flip gravel over the eggs to keep them safe. At times, he has organised tonnes of new gravel to be laid in the river to help them. He and other local volunteers have built passes by the side of weirs and locks so that they can make their way upstream to the mating grounds. He listens for them at night. “You get used to the sound of water running over pebbles and you can hear little slapping sounds, which is the cock trout fighting each other for the right to fertilise.”

It is a measure of the ill-health of this river that, during this summer, Jim and those volunteers have been finding some of the precious sea trout, which have survived so much, now turning belly-up and dying in the Ouse. Simply, they are suffocating for want of oxygen in the water. “To see fish dying in the river is a bit disconcerting when you have been looking after it all,” said Smith. “Not just the sea trout. All the fish are valuable because they are part of the ecosystem of the river. And if that ecosystem goes, you have had it.”

To see fish dying in the river is a bit disconcerting. The fish are part of the ecosystem. If that goes, you have had it

Human activity is not only draining the river and its aquifers of water, it is spitting gobs of poison into the flow that remains. Sometimes, this is the result of accident. Back in August 2001, fishermen started contacting Smith to report sea trout twisting and flipping on the river’s surface, obviously in distress. The dead trout floated downstream. And dead roach and bream and perch and chub. Within a couple of days, there were dead fish over an 11-mile stretch of the river. Smith and a partner were out day and night, wearing white “goon suits”, picking up fish whose flesh would then fall apart in their hands. The Environment Agency sent out a team who discovered that a strawberry farm had accidentally swilled pesticide down a drain and into the river. Within two days, 80% of the fish in the affected area were dead – five tonnes of them.

More often, the poison is simply the product of modern life on a river bank. Farmers and gardeners protect their crops and plants from slugs and snails with metaldehyde. The rain then washes it into the river: the Ouse is polluted with it from Jim’s village of Isfield to the coast. The same happens with pesticides from sheep dips and gardens and parks. It all trickles down. But for rivers now, the most common enemy is phosphates, which create thick blankets of green algae. By day the algae smothers plants. By night it sucks oxygen out of the water. At any time, it will sink down to the river bed, ruining the habitat of the creatures that live there. Phosphates get into the river from fertiliser on farmers’ fields and from excrement – cattle manure on the fields, dog shit on the streets and the human stuff too. Particularly the human stuff.

Up and down the banks of the Ouse, there are little red-brick buildings with pipework and wire mesh fences: treatment works that clean up waste water and human sewage. There are 38 of them in all. “If you had red dots on a map to mark every one of them, the map would look like it had measles,” Smith said. Treated effluent from these works is routinely discharged into the river – 856,000 cubic metres of it every month. And routinely it contains phosphates.

One of the volunteers who has worked to protect the Ouse is Dr Clive Fetter, a chemist who fished the river as a boy. He checks the quality of water that other volunteers collect at key points on the river and its tributaries. He regularly finds phosphate levels that are officially classified as “bad” or “poor” in water that is immediately downstream from treatment works. Fetter’s conclusion is simple: the water companies should be required to take all the phosphates out of the effluent before they release it in the river. “The need for this to happen soon is clear,” he told me.

His findings also point to something nastier. In the chalkland streams that feed the Ouse, he sometimes finds sudden very high spikes in the level of phosphates. Fetter strongly suspects that somebody is dumping raw human sewage into the river. Some of the hotspots are upstream from the treatment works and are almost certainly from private houses that use septic tanks. Years ago, they would have been emptied by the rural district council. Now, this has all been privatised and, Fetter fears, some owners may not want to pay for their tanks to be emptied, so they are dumping their contents for free. However, sometimes the raw sewage is coming direct from the treatment works.

The law allows the water companies to dump raw sewage in any river if their systems are overloaded, as long as the Environment Agency agrees. At other times, the companies do it because of some error or malfunction. Over the years, Jim has seen numerous horrors: treatment works fail, animals die, the company pays a fine and moves on. This summer, Southern Water was convicted in court of breaching its environmental permit after dumping 40m litres of raw human sewage into the sea at Worthing in September 2012, because three pumps had failed at a treatment works and were threatening to push the sewage back into the town. “Three pumps?” said Jim. “That sounds to me like a maintenance problem. They’re not checking them often enough, the way they used to before they were privatised.”

Barcombe in East Sussex, after the Ouse burst its banks in 1999. Photograph: Evening Standard/Rex/Shutterstock

When a team from the University of Brighton spent two years from 2009 to 2011 testing the water along the length of the Ouse, it found traces of faeces in all 26 test sites – 22 of them including human muck. At 19 of the 26 sites, the associated bacteria were above the level deemed sufficiently safe for swimming by the EU Bathing Water Directive. Southern Water has pointed out that the river is not officially designated as a swimming area, but during the summer months, it is a common sight to see people playing and swimming in its water.

Nationally, the nine water companies that treat sewage were involved in 2,358 pollution incidents last year. Sixty one of them were rated “serious”. Southern Water, which handles sewage for all of the Ouse, has been prosecuted or cautioned for these incidents 166 times in the past 25 years.

At root, there is a cultural problem – of taking water for granted and treating rivers as bottomless waste-disposal units. A few years ago, Jim Smith joined a group of volunteers in Lewes who decided to clear rubbish out of the Ouse in the middle of the town. They removed 28 shopping trolleys, 12 bikes, six scooters, 14 traffic cones, six car tyres, one skateboard, four roadworks signs, several scaffolding poles, a metal beer keg and two full-size steel football goals. That was all in one six-metre stretch.

Fishing rubbish out of the river is comparatively easy. Beyond that, the solution is hard to grasp. Governments have spent several decades fiddling around the edges of climate change without confronting its profound implications for their voters’ lifestyle. The government knows the danger. Its white paper of December 2011 said: “In the coming years, the combined effects of climate change and a growing population are likely to put increasing pressure on our rivers, lakes and aquifers. If we do not act, the security of our water supplies could be compromised ... We must halt and reverse the damage we have done to water ecosystems.” It is not clear that the solutions it is offering go deep enough to solve the problem.

Big solutions such as desalinating sea water or pumping water from one end of the country to the other have been ruled out on grounds of cost. Instead, government agencies are relying primarily on the water companies installing meters to encourage households to cut their consumption. The government’s own National Capital Committee, in its 2014 report, has pointed out the problem with that: “While personal consumption is expected to fall between now and 2030, the expected growth in population will offset this, and total demand is, therefore, expected to rise significantly.”

In addition, the government is pressing the water companies to do more to stop leakage from their pipes. The difficulty there is that the companies have already taken the cheap and easy steps and may find it difficult to hit the required target. But even on the optimistic assumption that government can hit its targets for both cutting consumption and reducing leaks, the numbers do not seem to add up.

In a paper for the thinktank Policy Exchange in 2011, Dr Simon Less, the former director of the water regulator, Ofwat, cited the Environment Agency as reckoning that households in England and Wales collectively are already using between 1.1bn and 3.3bn litres a day more than our water bodies can deliver without being damaged. Defra says it hopes that installing meters will cut consumption by 215m litres a day, and that reducing leaks will save a further 158m litres, ie a total daily saving of 373m litres. Even on the lowest estimate, that seems to fall short by 727m litres. One million litres provides enough water for some 7,000 households. It does not matter how often you check the maths, the implication is that we would have enough water if 5m households would stop using it. And if you take the higher estimate – a shortfall of 3.3bn litres – we would need 20.5m households to stop.

The risk here is not that millions of people in Britain are suddenly going to die of thirst. It is that after all those years in which humans settled by rivers and thrived, we are now locked in conflict with our natural surroundings. Either the humans or the rivers have to suffer. At the moment, it is the rivers, although in the longer term a sick river will produce less water, so the humans will end up in trouble as well. In his Policy Exchange paper, Less reported that a third of our river catchments are already classed as “over abstracted”, that is, their health is being damaged by the amount of water being taken out of them.

Our water bodies are protected primarily by two forces. There is the Environment Agency, which in the last seven years has reviewed some 1,500 of the licences that have been granted to water companies, farmers and others to abstract water. It has altered the terms of 228 of them to deal with “unsustainable abstraction”, but it says that it has a problem: many of these licences were issued years ago and without limits to protect tired water bodies, and so it has no legal power to require them to change. The agency has also been weakened by having its budget cut every year since 2009, including losing 26% of staff who used to deal with applications for new houses and factories.

Fire officers rescue a woman after the River Ouse flooded Lewes, East Sussex, in October 2000. Photograph: Alastair Grant/AP

Then there is the unpopular European Union with its water framework directive (WFD), which has been embedded in UK law since December 2003. It requires all UK water bodies to be checked for ecological and chemical problems and for all of them to be rated as “good” by 2015. We are nowhere near that goal. Indeed, faced with the enormity of the problem, the authorities had to drop the target. Instead of aiming for 100%, the Environment Agency set out nationally to achieve a “good” target in 2015 of only 31% of water bodies. The WFD has a loophole that allows governments that are faced with disproportionate costs to set the target back by 12 years, to a final deadline of 2027. But even that is beyond the UK’s reach. The agency reports that it “believes that achieving ‘good’ status in all water bodies by 2027 will not be possible using current technologies. Even achieving 75% ‘good’ status will require marked changes in land use and water infrastructure ... By current standards, such changes are extremely unlikely to be economically or socially acceptable.”

The agency has generated a lot of creative local schemes, and it argues that rivers are healthier than they have been for 20 years and that many of the water bodies – 27% of them – are failing on only a single test from a long list. But the underlying problem is that the legacy of indifference towards our water means that the estimated cost of hitting the WFD targets by 2027 is £16.4bn. On the Ouse alone, it estimates that it would cost £43m.

Autumn came early. By the last week of August, the air was thick with falling rain, and Jim Smith reported that the top of the Ouse had come to life again. And, as the river rose, a more familiar problem rose with it: the risk of flood, now provoked by the same factors that underlie scarcity – climate change and building.

The effect of climate change is not simply to reduce rain during the summer months, but also to increase the number of torrential storms. When the rain falls that hard and fast, it cannot sink into the ground and go down to the aquifers. It runs off the fields and races through the streets and almost all of it ends up in the rivers. Smith watched from the fields near his village in October 2000 after a month’s worth of winter rain fell in only four days. He realised that it had broken through the walls upstream to invade the town of Uckfield when tins of biscuits from the supermarket and thousands of video cassettes from Blockbuster started careering downstream. He saw the water surging out into the old flood plains and then hurtling back towards the river, breaking through the embankment of the old railway line which stood in its way, tossing aside lumps of concrete, and then hurling itself southwards, down to Lewes, where it broke through the flood walls and erupted into the town. That day, the rampant Ouse broke into 1,033 buildings, spraying them with sewage and waste water, and wrecking 682 vehicles as it passed. Total estimated cost: £130m.

He realised that the river had invaded the town when tins of biscuits and video cassettes started careering downstream

Yet, in spite of this and numerous other similar recent disasters across the UK, as the pressure for more housing has increased, local authorities have granted permission for more building to take place on flood plains, a move that may be asking for trouble but that is now backed, where there is no suitable alternative, by the National Planning Policy Framework. This, in turn, has created a policy clash.

In his classic book, Taming the Flood, which has just been reissued, the ecologist Jeremy Purseglove has traced the impact of official policy in actively – albeit accidentally – encouraging the risk of flooding. After big floods in 1947 and 1953, the government organised a campaign to have rivers straightened and dredged in the hope that this would allow them to carry away excess water. That policy then coincided with farmers being given grants to drain ancient flood plains to create more space for crops. Purseglove argues that the combined effect was that more rainwater poured into rivers, which were more able to carry great surges of water. “Effectively, we were accumulating the threat and passing it to some point downstream.” It was like designing floods.

Purseglove and others are pushing the case for natural flood management, to restore the old wetlands and flood plains and to allow the rivers to overflow into them. They have had some success, and Purseglove is optimistic. But after the floods in rural Somerset last year, there was a backlash from local farmers and others claiming that the floods would never have happened if the rivers had been dredged. Purseglove rejects the argument: “They could have dredged to the absolute maximum in Somerset and it would not have stopped those floods. There was just too much water.” Nevertheless, the then secretary of state for local government and communities, Eric Pickles, heard warning words from the Environment Agency about the dangers of dredging and denounced them as “politically correct eco-fanatics”. Some 1,400 possible sites for dredging are believed to have been identified in an initial government study, though the Environment Agency says it aims to check each one before anything goes ahead.

Meanwhile, the property developers are busy. In Lewes, the biggest town through which the Ouse flows, there are plans to build 667 new houses in locations where the risk of flooding is officially recognised as “high”. And, according to a specialist report by environmental consultants, Southern Water has refused to release its data to identify the parts of the town that are vulnerable not just to flooding but to being swamped with sewage during a flood, on the grounds that it would affect property values.

When he was officially the river bailiff, Jim Smith had to deal with poachers stealing fish. He had a constable’s powers to make arrests. He even carried handcuffs, and once was injured by a poacher who attacked him. It is different now. There has been a river bailiff here since Victorian times but when Jim retired a few years ago, he was not replaced. He stills walks the river and watches, but he no longer has any power to protect the water and the life that depends on it. Maybe no one really does.

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