Balancing Act: The main feeder for the Union Canal

by Vicky Whyte

As you're enjoying a walk, cycle or boat trip along the Union Canal, you may not be aware that its serene surface level is maintained only by a feat of engineering which keeps it topped up to the tune of an average 2 million gallons of water per day...

The civil engineers who built the Union Canal (which opened in 1822 after five years of construction) knew that it would have to be continually replenished.

So in 1818 began one of the most marvellous feats of engineering – the construction of the main feeder for the Union Canal on its original 32 mile stretch. A brilliant Scottish civil engineer from Dumfries, James Bruce Jardine - who was also a mathematician, geologist and the first person to determine mean sea level - was appointed to construct and enlarge the then very small Cobbinshaw Loch which lies between Carnwath and West Calder. The loch was the ideal spot, situated in a vast watershed approx 879ft above sea level. The loch would eventually cover a 310 acre site and become the reservoir for the Canal Feeder via the Bog Burn and Murieston Water.

The feeder has been largely underestimated and is taken for granted as the much smaller sister of the mighty Union Canal. To get an idea of how important it is I spoke to Ronnie Russack, former owner of the Bridge Inn at Ratho and recipient of an MBE in recognition of his role in the rebirth of the Union Canal as a leisure waterway. He told me that one morning when he came in to work at the Bridge Inn, his canal boats were high and dry; it was obvious that the level of the canal had seriously dropped overnight, and this was not liable to happen unless something really unusual had occurred. They discovered that the bank had fallen into the feeder, blocking it on the stretch above Almondell Country Park before it runs into the Lin’s Mill Aqueduct and preventing it from flowing into the canal. When the bank was repaired and the feeder cleared, the canal was duly replenished and they were back in business again.

My grandfather used to tell me that when he was a young man he and other young lads from East Calder swam in the feeder, but by around 1950 it was quite badly silted up. In its heyday, the sluices were looked after and it was kept free of weeds and silt as it was essential to the functioning of the canal with its cargoes of coal into Edinburgh from Scotland's coalfields. Now the canal has been opened up for leisure, the feeder is once again being maintained by Scottish Canals under the auspices of the Scottish Government.

The famous Scottish engineer Hugh Baird was appointed to oversee the construction of the feeder itself. A large weir was built at Mid Calder, and a smaller weir (known to locals as the Scaler) down river at East Calder where the feeder starts its run-off from the River Almond. The feeder flows along the bottom of the hill under a small stone bridge with a sluice gate then under the railway viaduct, which was built much later in 1885. (The railway viaduct is 23 metres high and has nine segmented arches. It was under threat of being demolished a good few years ago but fortunately after much protest it was saved and is a wonderful walkway through the park with marvellous views of Almondell). From here the feeder has a short stretch until it reaches the Iron Bridge Aqueduct. This beautiful green cast iron bridge was based on the design of one of Shropshire’s most famous landmarks, the bridge that spans the Ironbridge Gorge. The aqueduct carries the feeder over the Almond at a height of 6 metres above the river in a cast iron trough 1.8m wide and 1m deep. Before the solid walkway was constructed, the original walkway was constructed of large sections of cast iron mesh bolted together, and when walking across you could see the feeder running underneath. After leaving the aqueduct the feeder runs for a short distance until it reaches a spot near the Nasmyth Bridge on the East Calder side of the river where it disappears into the hillside in a series of tunnels until it reaches its destination – the Union Canal at Lin’s Mill Aqueduct.

This quite magnificent aqueduct was also built by Hugh Baird in collusion with another great Scottish civil engineer, Thomas Telford. It is said that Thomas Telford came to inspect it. Its five magnificent arches carry the canal over the river in a 128 metre long cast iron trough. It is the fifth largest aqueduct in Scotland, stands 23 metres above the River Almond and when the water in the canal gets too high the main sluice gate is opened and the water pours back into the river in a most beautiful cascade. In the heyday of the canal, parties would sail from Edinburgh to the aqueduct where the main sluice would be opened for their entertainment. Ronnie Russack told me that he also was also given permission in the past to open the large sluice for his customers when they reached the aqueduct on his restaurant canal boats.

The canal and its feeder were built by navvies - mainly Highlanders who had to abandon their crofts during the clearances, and the Irish who were fleeing the hardship of their own country. It was hard, back breaking work. The length of the feeder from the weir at the Scaler to Lin’s Mill Aqueduct is three miles. The river dips by approximately 50 metres over this distance, so the design of the feeder maintains the water at sufficient height to allow it to feed into the canal.

© Lothian Publications Ltd