The Tring Reservoirs have been a feature of the local landscape for over two hundred years. Contrary to the views of many people, they are not used to provide drinking water; the four reservoirs were built as an important and essential part of the canal network. Although long superseded by more modern means of transport, they have retained their importance right up to the present time.
The primary purpose of the reservoirs at Tring – Wilstone, Startopsend (from the local hamlet Startop’s End), Marsworth and Tringford – is to supply water to the Grand Union Canal, as it climbs over the Chiltern Hills. Every time a canal boat moves through a lock, over 200,000 litres of water have to be found to operate the locks on the flights on each side of the Tring summit.
Given that there are almost no rivers or streams around Tring, certainly none of note, the problem of where to find water was a major problem for the builders and operators of the Grand Junction Canal, as it was then called and as traffic increased during the nineteenth century.
The Chiltern Hills are composed of chalk, 70 to 100 million years old. Because chalk is porous, rainwater is absorbed and held in the chalk. This forms a massive underground reservoir of groundwater, an aquifer, which is maintained there by non-porous clay below the chalk. Some of the trapped water is drawn from the chalk through boreholes, which supply drinking water both locally and more widely.
The canal builders found that natural springs appeared wherever the base layers of chalk came close to the surface. The largest spring they found supplied a stream in Wendover, which originally flowed north-eastwards and into the River Thame near Aylesbury. In order to use the water from this stream to feed the canal, the Wendover Arm was built to divert its water to the highest point on the canal as it crossed the Chilterns at Bulbourne near Tring – the summit level. Using this supply enabled the main line of the canal to be completed in 1797-99. Although several smaller streams – all spring fed - join the Wendover Arm, the main source of its water is the spring at Wendover. Diverting the Wendover stream into the Wendover Arm cut off water supplies to the millers of Aylesbury and the Canal Company built Weston Turville reservoir – fed by other local streams - as an alternative source for their mills. In the past, water from Weston Turville was occasionally used as an emergency supply to the canal, but not anymore and it is now a BBOWT Nature Reserve.
The first of the Tring reservoirs was constructed in 1802 at Wilstone. This was used to store water for later use, as without any reserve supplies, any surplus water would simply run to waste down the locks on either side of the summit. The first Wilstone Reservoir was about one quarter of its present size - the southern corner, near the bird-watching hide - and was constructed on naturally marshy ground, with embankments to contain the water. Water could be run into it from the Wendover Arm and it is also fed by several small springs. Two small local streams enter the reservoir near the south-west corner, next to the bird-watching hide, also fed by springs rising near Drayton Beauchamp village. One can be seen from the footpath which runs round the field edges from this corner up to the Wendover Arm.
When the reservoir was completed in 1802, a steam-powered pumping station was built on the Wendover Arm, directly above the reservoir to pump water from the reservoir back up to the Wendover Arm. Whitehouses Pumping Station (as it was known) was situated close to the bridge that carries the footpath from the south-east corner of Wilstone Reservoir over the Wendover Arm. It was dismantled around 1836, but some of its remains are still visible and the Wendover Arm Trust has added a useful information board on the canal bank nearby.
As canal traffic increased, a new reservoir, Marsworth, was built in 1806, fed by a small spring from near Bulbourne and with surplus water from the summit.
After further work to increase the capacity of the original Wilstone Reservoir during the early years of the nineteenth century, it was doubled in size in 1835, by an extension eastwards towards Little Tring and in 1839 it was doubled again to its present size, by adding the northern section nearest the present car park. The still visible dividing banks, with their trees of cormorants and nesting herons, clearly show the extent of what was the original reservoir.
With the opening of the Aylesbury Arm of the canal, the final two reservoirs were built: Tringford in 1814 and Startopsend in 1815; both take surplus water from the summit, principally supplied from the Wendover stream.
In addition, both the summit and Tringford were supplied with additional water from Tring itself. The Tring Silk Mill once took water from several springs around Tring and its spent water formed part of the supplies to the canal. Two streams ran from Tring: the Tring Feeder, which runs into the Wendover Arm near Heygates Mill and the Tring Drainage, which passes beneath the Wendover Arm and runs into Tringford Reservoir. Both streams still carry water from the original springs close to Miswell Farm and near to the junction of Icknield Way and Dundale Road in Tring.
The only other significant water supplies to the summit, and hence the reservoirs if needed, are from the Tring Water Treatment Works, which discharges its fully treated water into The Wendover Arm next to the Works and from two boreholes at Cow Roast and Northchurch, whose water can pumped into the summit level using back-pumps installed at Cow Roast and Dudswell Locks.
Tringford Pumping Station was built in 1817 on the present site. Today, it is used to transfer water between Tringford, Startop’s End and Wilstone Reservoirs and, of course, to pump water from these reservoirs to the summit level on the Wendover Arm nest to the Pumping Station. Marsworth’s water cannot be pumped but can be used to supply the Canal by the stream next to the Startops Car Park, entering the Canal below Lock 39.
British Waterways measures reservoir capacities in millions of litres (megalitres, or ML). One megalitre is equal to 1,000 cubic metres of water, or 220,000 gallons, approximately four standard locks of water. Wilstone is the largest of the reservoirs, with a capacity of 1,102 ML. Startopsend is considerably smaller, at 482 ML and the two remaining reservoirs are smaller still: Marsworth is 236 ML and Tringford is 172 ML. As a very rough approximation, I often think of Wilstone as the largest, with Startopsend about half the size of Wilstone, Marsworth about half the size of Startopsend and Tringford about half the size of Marsworth.
Tringford Pumping Station, at Little Tring, pumps water from Tring Reservoirs into the Wendover Arm of the Grand Union Canal. The station sits alongside the canal, close to the southern edge of Tringford Reservoir.
Today, it has three pumping wells and their associated pumps, and a fourth, auxiliary pump house stands close by. The pumping station has changed greatly over the years, but most of the infrastructure used today is as it was originally built, a testament to the skill of the Canal’s original engineers.
Beginnings
When the first reservoirs were built at Wilstone (in 1802) and Marsworth (in 1806), they were each provided with a dedicated steam-powered pumping station, both feeding their water into the Wendover Arm: Wilstone’s was at Whitehouses and Marsworth’s close to the junction with the mail line of the canal at Bulbourne.
Tringford pumping station was built to pump water from the last of the reservoiurs to be built, at Startopsend and Tringford. In 1817, a new steam pumping engine was purchased from Boulton and Watt. It was a beam engine, like those at the other pumping stations. In these engines a heavy beam was installed above the steam engine, which was supported by a central pivot, so that as the engine operated, the beam rocked from one side to the other. The engine’s steam cylinder was connected to one end of the beam and to the other end was fixed the pump rod, reaching over 50 feet down the well to the water lift-pump. The engine was able to pump the equivalent of 80 locks of water per day. Soon after the Tringford station was built, the separate pumping station at Marsworth was closed and nothing of it now remains.
Centralisation
In the 1830s, after nearly twenty years operation, a decision was made to centralise all pumping at Tringford. A new pumping well was sunk to pump from Wilstone, but because Wilstone is over 20 feet lower than Startopsend, major modifications had to be made to the Boulton and Watt engine and pumps. The building was extended and the engine was repositioned, to pump from the new well. A second-hand steam beam engine was erected to pump from the original well. All of these modifications were completed in 1836-38, following which the Whitehouses Pumping Station was closed, leaving all pumping at Tringford.
And this is pretty well how it remained until well into the twentieth century, save for various improvements to the headings within the station and general repairs and replacements.
Electrification
Following closure of the leaky Wendover Arm in 1898, all the Wendover water was run into Wilstone, but the water ran to waste when that reservoir was full, a situation that could not continue. The solution was to take the water by a pipeline from Drayton Beauchamp to Tringford, which led to major changes at the Pumping Station.
The works were completed in 1911-12. A new high level heading was driven from Tringford Reservoir, so that water from the pipeline could be run into Tringford and thus into Startopsend reservoirs. A new pumping well was constructed to connect to this new heading so that water from the pipeline could be mixed with water from Tringford Reservoir to ensure a constant flow. An electrically powered centrifugal “suction” pump was installed over the new well (now known as No 1). At the same time, a second larger electric centrifugal pump was installed in the original well (now No 2). This pump was installed deep in the well, so that it could “suck” and lift water up from either of the Startopsend or Wilstone levels. Major work had to be carried out to the well so as to prevent the well from flooding, to keep the pump dry. There was no public electricity supply at that time and the electricity, at 220 volts D.C., was generated by two diesel-electric generating sets, of 100 and 50 H.P. The old York steam engine, bought second-hand nearly 80 years previously was scrapped.
Reconstruction
The original Boulton and Watt steam engine continued in use until it was scrapped in 1927, after almost 110 years use and the pumping station was completely rebuilt, losing its upper stories and tall chimney. Two new electric pumps were installed above the Wilstone well (now No 3). These were vertical deep well pumps, with shafts descending from the motors to their pumps deep in the well, one at the Wilstone level, one at Startopsend level, so (as with pump 2) they could pump from either source. These were powered by a 3-phase mains electricity supply, from Aylesbury.
As pumping costs rose and technology improved, a new pump house was built in 1944/5 at the end of the Wendover pipeline, just below the pumping station. This used a pair of variable-flow mains electric pumps to pump the water from the pipeline directly into the summit alongside the pumping station, avoiding first running the water into the reservoirs, all at a lower level.
The diesel electric plant was scrapped and the pumps converted to mains electricity in the early 1960s; and this how Tringford Pumping Station remains to this day, although not all of the equipment is in useable condition at present. Nonetheless, it remains a fascinating and historic building.
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(05/2010)