The great heritage of our waterways is under threat. Jack O'Sullivan reports
For 35 years David Blagrove has plied the country's waterways, selling coal here, picking up building material there, delivering timber somewhere else, scratching a living on canals that were once essential to Britain's economic growth. But this year, it's not been the decline in trade that has worried him. He's been thinking the unthinkable: that the canals might run out of water.

A succession of dry winters, following on from hot summers, have left some of the most popular inland waterways in Britain - the Grand Union and the Oxford Canal - facing a shallow few months. The prospect is not of empty canals, their foot-puddled clay bottoms and banks cracking in the midday sun - that outcome would be disastrous. The canals would spring a thousand leaks come the next thunder storm. The great fear is a repeat of 1976 when drought led to the closure of locks for July, August and September, so that Blagrove was confined to shore for the summer. For him, it was the equivalent of the Tarmac melting for three months on the M1.

"It caused terrible problems for my business," Blagrove said preparing to cast off from his moorings on the Grand Union Canal at Stoke Bruerne, just south of Northampton, on a two-week trip. The journey will use the two water-short canals, which connect the Midlands to the Thames, for their historic purpose - the transport of coal to London.

Full summer closure of the two canals would also prove disastrous for Stoke Bruerne village, home to one of Britain's finest canal museums, which is on three floors of an old mill. Stoke Bruerne, with its traditional cottages, whose unusual fronts are speckled with a combination of local light limestone and dark ironstone, is a place where many narrow boat users like to tie up for the night for a few pints in The Boat, overlooking the canal.

"It's important that the canal continues to be a place where people can work," says Blagrove. "People come here and they see us moving around and they can see what the canals were originally built for. If the canals are just run for pleasure they become like a theme-park."

The water shortage means that Blagrove cast off specially early yesterday. From this week, British Waterways, in an attempt to save water, began closing locks on the two canals overnight, from 6pm to 8am. So on Good Friday, Mr Blagrove and his convoy of three, ancient brightly-painted narrowboats, dating from the last century, had to pass through the one- and-three-quarter-mile Blisworth tunnel (the longest navigable in Britain), pick up his cargo of coal upstream and then negotiate a flight of seven locks at Buckby before nightfall.

"Sometimes, we will boat all around the clock," Blagrove says. "But if the locks are locked, we will arrange our journey so that we are above or below them before closure." He delivers coal to the islands along the Thames - Pharoah's Island, Ham Hough Island, Tagg's Island near Molesey and Eel Pie island near Richmond. Over the fortnight, after reaching Braunston over Easter (the Swindon of the canal system with dockyards and wharves), he will head south, joining the Thames at Oxford.

Some users of the canals are angry about the lock closures. The National Association of Boat Owners, representing 2,500 users, has warned that restrictions could prove disastrous for tourism. But Blagrove supports the lock-closure programme. "It's a good thing. In 1976, there was no water control and then they panicked in June and closed the locks. Forty years ago, when the Grand Union was a major transport route, all the flights were locked at night."

Norman Large agrees. He and his wife Angela, from Revesby in Lincolnshire, this week were negotiating the spectacular Rothersthorpe flight of 13 locks, north of Stoke Bruerne, in a boat that Large, 49, built four years ago in his garage.

"I don't want to be boating 12 hours a day," Large says . "Anything between four and eight hours is OK with me. I want to be in the pub. The trouble is that some of the hire companies who set tourists off on a circular route set impossible targets. And some people, in all innocence, make mistakes. I came through this stretch last year and just about every paddle [the doors which control the flow of water] had been left open."

British Waterways says that it is doing everything it can to ensure that there is plenty of water in the canals this summer both for pleasure use and for the few, such as Blagrove, who continue to work the waterways. Neil Edwards, executive director of the Inland Waterways Association, which campaigns on behalf of users, has backed this week's limited restrictions, which will be reviewed next month. "The measures taken so far are an inconvenience but not an enormous problem. Users can do a lot to save water, like making sure that paddles are shut when they leave a lock and keeping an eye out for any leakage under a culvert."

Edwards's advice is that boat lovers should be able to get through the summer without further restrictions if they take their time at locks and wait for another boat coming the other way, so that only half the water is used by each. "It's like sharing a bath with a friend."