In an ideal world, canals wouldn’t need pumps to supply their water – and many don’t. Provided with adequate reservoirs, often tucked away high in the hills some miles away, they can draw on enough supplies by gravity alone to see them through a typical summer, before the winter rains replenish their stocks.
Other canals are less well-equipped with supplies which over the years, as the canals got busier, needed to be supplemented with back-pumping schemes, returning water used by lock operation back up to the summit level for re-use. In recent years, the revival of the canals for leisure led to several of these systems being reinstated or new ones installed, for example enabling water to be pumped all the way east up the Kennet & Avon from Bath to the summit at Wootton Rivers, or right through from the Black Country to the southern Grand Union.
But there’s another possible reason for canal water supplies to need pumping – and not just in dry summers when it runs short. Occasionally, the local geography meant that it wasn’t possible to find water supplies (or to find suitable sites for reservoirs to store the water) sufficiently high up to feed the canal’s highest levels. There might be no alternative but to site the reservoirs at a level where water would need to be routinely pumped out of them and up into the canal.
We caught up with the Canal & River Trust’s Charles Baker, who is familiar with such situations. In his role as Senior Project Manager for the London & South East Region with a focus on mechanical, electrical and pumping equipment, he and his team have got two of them on their patch. They’re both the subject of current major works which, as he explains is aimed at keeping them performing their vital function by matching up modern technology (in the form of new electric pumps) to the historic infrastructure dating back to the days when the job was done by coal-fired beam engines.
One of these is on the Kennet & Avon and results from a dilemma faced by the canal’s 18th-century planners. Ideally, they would have liked a long, relatively low -level summit running all the way from Crofton through to Devizes, a distance of 20 miles at an altitude where supplying it with water by gravity from local springs and streams wouldn’t have been an issue. But that would have needed a tunnel 4312 yards long (which would have been second only to Standedge on the Huddersfield Canal as the country’s longest), adding to the cost, difficulty and time taken for the work. So instead, they opted for extra locks leading up to a shorter higher summit level with a much shorter tunnel – but that meant climbing to a height where no water supplies were available.
The solution was to raise water from a lower level (and later from a reservoir Wilton Water - constructed at that level) up to the summit by the celebrated Crofton Pumping station, whose restored beam engines still carry out their original function on certain summer weekends. For the rest of the time, the job is done today by electric pumps, but still using Wilton Water and still feeding into the same leat (water supply channel) leading to the summit level that was built to serve the steam pumps. CRT is currently part way through a programme of replacement of the electric pumping system in use since the canal was restored 30-plus years ago. Readers may remember that their reliability went under the spotlight a few years ago when the steam pumps had to be fired unexpectedly thanks to the failure of their modern replacements.
The project is divided into three stages: the first part, replacing the pipeline across the pumping station site, has already been completed. The second, the replacement of the electric pumping station, is due to take place this summer, with the final phase replacement of the pipe running under the canal bed from Wilton Water – due to start in the autumn.
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