Where does canal water come from?

[srah1953]

This is going to seem like a stupid question – but how do canal locks work? I know how the gates work but where does the canal water come from?
If you take as an example the Crinan canal, it's at sea level at either end and rises in the centre. Any time the lower gates are opened, the water will flow out to reach it's own level, ie, sea level. What is it replaced by?

 

[Poignard]

This is going to seem like a stupid question – but how do canal locks work? I know how the gates work but where does the canal water come from?
If you take as an example the Crinan canal, it's at sea level at either end and rises in the centre. Any time the lower gates are opened, the water will flow out to reach it's own level, ie, sea level. What is it replaced by?

If the canal builder is lucky, rain will replace what is lost. If there is insufficient rain, water may have to be pumped uphill to replenish the upper pounds.

 

[Momac]

Some canals do rely on water being pumped in.
Others are fed by rivers.

 

[halcyon]

This is going to seem like a stupid question – but how do canal locks work? I know how the gates work but where does the canal water come from?
If you take as an example the Crinan canal, it's at sea level at either end and rises in the centre. Any time the lower gates are opened, the water will flow out to reach it's own level, ie, sea level. What is it replaced by?

From the Loch's above the canal, or elsewhere from reservoirs built for the purpose.

Brian

 

[srah1953]

Thank you. I thought that must have been the case but I couldn't find any reference to prove it.
Cheers

 

[VicMallows]

If you find yourself over in England, visit one of the great old pumping stations such as CROFTON on the Kennet and Avon canal. Incredible heavy steam engineering .... even more so when you realise that today a small quiet electric pump does the same job most of the time (except on the special days when the original is 'in steam').

 

[awol]

Have a look at the Crinan Canal on GoogleEarth. There is Loch a' Bharain beside the canal and the Dunardry Burn brings water from Daill Loch and Loch an Add. Despite these and the rainfall, there are times, usually while England is suffering floods, that the waters run short and canal movements are restricted.

 

[oldharry]

The old canal builders had to go to considerable lengths to ensure a sufficient water supply to the top 'pound'. Solutions like the Crofton steam pump were just one of a number of quite ingenious solutions dreamed up by the builders. It is also why in extended droughts, canal movements can be limited or even stopped to conserve water.

On long lock flights, like the Caen flight at Devizes - again on the Kennet and Avon - elaborate arrangements had to be engineered to ensure a sufficient supply to all the 16 locks.

 

[Reptile Smile]

Pumping was rare, though. It was usually either a bloody great bit summit pound or a bloody great big reservoir.

 

[ffiill]

Feeder resevoirs at the highest level-a good example is the old Lancaster to Kendal Canal where the feeder reservoir Killington Lake can be seen in the Lune Gorge from the M6 motorway.
On the Caley Canal Loch Oich feeds the Canal in both directions down to Lochs Lochy and Ness respectively.The Canal to Fort Augustus follows the bed of the River Oich which was diverted and the Locks at Fort Augustus are built on the bedrock carved out by the River which runs out in to Loch Ness via a man made chanel.
Similarly the canal locks at the south end of Loch Lochy follow the bed of the River Lochy at Gairlochy which itself drains via a man made cut into the River Spean at Muchomir.

 

[Poignard]

If you find yourself over in England, visit one of the great old pumping stations such as CROFTON on the Kennet and Avon canal. Incredible heavy steam engineering .... even more so when you realise that today a small quiet electric pump does the same job most of the time (except on the special days when the original is 'in steam').

Yes - well worth visiting

http://www.croftonbeamengines.org/

 

[awol]

... and Loch Garry feeds Loch Oich

On the Caley Canal Loch Oich feeds the Canal in both directions down to Lochs Lochy and Ness respectively.The Canal to Fort Augustus follows the bed of the River Oich which was diverted and the Locks at Fort Augustus are built on the bedrock carved out by the River which runs out in to Loch Ness via a man made chanel.
Similarly the canal locks at the south end of Loch Lochy follow the bed of the River Lochy at Gairlochy which itself drains via a man made cut into the River Spean at Muchomir.

 

[NormanS]

... and Loch Garry feeds Loch Oich

And Loch Arkaig feeds Loch Lochy. The Caley canal has more water than it can use.

 

[Bodach na mara]

And Loch Arkaig feeds Loch Lochy. The Caley canal has more water than it can use.

Unlike Crinan, which often runs short in a dry period. This results in restrictions on use of sealocks and inposition of a convoy system. There are several lochs in the hills to the south that supply water to the top reach. Because the Crinan sealock is heavily used by fishing boats and boats from the pontoons at Bellanoch, the BWB installed pumps near Crinan that pump water from the river Add to a point above lock 14. As a result, the water in this reach at the crinan end is brackish.

 

[fisherman]

Canal companies were very jealous of their water and there is a guillotine lock at King's Norton in Birmingham designed to be closed if there was any danger that water was migrating from one system to the next.

http://en.wikipedia.org/wiki/King's_Norton_Stop_Lock

 

[rotrax]

If the canal builder is lucky, rain will replace what is lost. If there is insufficient rain, water may have to be pumped uphill to replenish the upper pounds.

I fear, as others have said, that rain will never be enough to make good water used in locking.

IIRC a Grand Union broad lock-72 feet x 15 feet with say 6 foot drop uses about 186,000 gallons every time it is operated.

The water is not lost untill it reaches the lowest point-it keeps lifting or lowering boats untill then.

Once the water has been used from the highest point-the summit level-it must be made up. Feeder streams, resevoirs and rivers usually help with this.

A big obstruction and expense to the early canal builders came from Millers who jealously guarded their water supplies.

The Grand Union Summit Level is maintained by the Wendover Arm which has water pumped from underground aquifers into the canal.

It is a nice walk with plenty of wildlife if you are in that area with a couple of hours to kill.

 

[AntarcticPilot]

I fear, as others have said, that rain will never be enough to make good water used in locking.

IIRC a Grand Union broad lock-72 feet x 15 feet with say 6 foot drop uses about 186,000 gallons every time it is operated.

The water is not lost untill it reaches the lowest point-it keeps lifting or lowering boats untill then.

Once the water has been used from the highest point-the summit level-it must be made up. Feeder streams, resevoirs and rivers usually help with this.

A big obstruction and expense to the early canal builders came from Millers who jealously guarded their water supplies.

The Grand Union Summit Level is maintained by the Wendover Arm which has water pumped from underground aquifers into the canal.

It is a nice walk with plenty of wildlife if you are in that area with a couple of hours to kill.

The water in the said streams, lochs, reservoirs etc. comes from rainfall in the catchment area of the water sources. Ultimately, canals depend on rainfall, except in the rare cases where pumping has been found necessary.

The problem with the Crinan Canal is that the potential catchment area for rainfall is small; it is on a narrow peninsula, with hills either side of it, so the maximum possible catchment area is insufficient in times of low rainfall and high traffic.

 

[Bru]

Water supply was always a problem for the canal builders

A surprising number of reservoirs, some of them many miles from the canal they supply, were built by the canal companies

Back pumping, the "modern" solution much favoured by the late and not much lamented British Waterways, was not in fact that unusual either

 

[reeac]

If you find yourself over in England, visit one of the great old pumping stations such as CROFTON on the Kennet and Avon canal. Incredible heavy steam engineering .... even more so when you realise that today a small quiet electric pump does the same job most of the time (except on the special days when the original is 'in steam').

The Crofton station pumped water from a natural lake close by into a 3 mile long "leat" from which the water flowed into the K&A canal at its highest point. The station was fuelled with coal which was brought by barges which used the canal. I always wondered how much nett transport the canal provided after you'd subtracted the coal barge traffic. Nevertheless some fine steam machinery there.