SCADA in control?

JOHN Dodwell appears to be promoting the hypothesis on Canal & River Trust's behalf that there is no need for lock keepers and lengthsmen because the SCADA system will control the water levels in our canals. Events clearly demonstrate this is not the case, writes Ralph Freeman.

We have had many instances of high water levels in pounds due to heavy rain of late; three in the Sandon to Aston Pound on the Trent & Mersey Canal in the last six months alone. It's not just high water levels that are a problem either.

During the summer I met a distraught hire boat crew that had struggled, due to empty pounds, (pictured) to get up the Tame Valley and Rushall Flights on the BCN. Is CaRT saying these things don't happen? Of course they do. The question is why?

More high levels at Aston

Having reported the latest high water incident at Aston Marina to CaRT on the afternoon of Friday 12th October, I received a call back from a CaRT representative Monday morning saying they 'Had had people out all weekend'.

This ties in with a report from a boater who said he arrived at Sandon Lock to find 'paddles up' and water being flushed through the lock. So why the need for manual intervention and weekend working if the SCADA system is in control?

Problem at Barton Turn Lock

It was when the bywash became blocked that the canal overflowed onto the adjacent road at Barton Turn Lock, then flooded a local resident's garage. British Waterways had received several calls from concerned boaters in Barton Turns Marina regarding very high water levels, but for whatever reason (it was the weekend?) it took the action of local residents and staff from Barton Marina to stabilise the situation on Sunday morning prior to the arrival of British Waterways staff later that day.

So why did the SCADA system, in which some appear to place so much faith, not prevent this from happening? There are several issues that may explain this:

The nearest SCADA box is at Wychnor (less than two miles away) but maybe it's primarily function is to measure flow and doesn't have a level sensor outside the lock itself? Otherwise why didn't it pick up the rising water level in the pound and raise an alarm? As far as I can see there is no SCADA unit at Barton Turns Lock to measure the water level there either.

The paddle just in front of the offside ground paddle at Wychnor has a notice on it describing it's function as water control. Note it is manually operated. In other words to change the amount of feed water entails someone visiting the site with a key for the padlock and a windless. Not exactly high tech in 2012 I would have thought?

To summarise then the SCADA system alone cannot stop water entering the Wychnor/Barton Turn pound. More importantly there is no remote controlled, powered sluice at Barton Lock either to dump excess water . So it would appear the 'Control' element (the C in SCADA) is missing!

 

Data collection

I suggest that the so called SCADA boxes are more accurately described as telemetry outstations or more simply, data collection units. The 'control' element is normally carried out by a computer system situated at a central location. The data transfer between the two is made much easier these days by the fact that high speed data can be exchanged via the mobile phone network.

So to control the level of a pound would need a level sensor to transmit the data to the processing centre, which would then display the data for an operator and if the level was too high a command could be sent, manually or automatically, to a remote power operated sluice to dump the excess water in the pound into a local water course and/or reduce the water flow into that pound depending on circumstances.

That's why in my original question to John Dodwell I referred to the number of level sensors and powered sluices on the Trent & Mersey Canal. I posed the same question to Central Shires regarding its section of the above canal but so far I have received no reply from them other than an acknowledgement of my email request.

Not covered?

If the water level is allowed to rise seven inches (or more as occurred in the last flooding in the Aston/Sandon pound) then one can conclude the SCADA system does not cover the pound in question or the system doesn't work. I believe the former to be the case.

What we have on the lower Trent & Mersey, I would suggest, is essentially flow measurement at selected points, not level control on every pound. The latter is expensive to install but should have been implemented before lengthsmen and lock keepers were removed from the canals. I contend many pounds still rely on the vigilance of boaters and their ability to summon trained staff (not as easy as it sounds), 24/7 to control water levels.

Limited scope?

Just to make it clear, I'm not in any way criticising the existing SCADA system, merely suggesting it's scope on the Trent & Mersey is limited, and so cannot control the levels of individual pounds. For instance how can a SCADA box monitor four miles of canal if the lock downstream is only two miles away?

That's why the system is so much more effective on the Shroppie with it's bunched locks and very long pounds; older canals like the Staffs & Worcs and Trent & Mersey which have relatively short pounds, with a lock every mile or two at most for much of their length, are very much more capital intensive to automate.

Marinas not protected

In the pounds quoted above, we have two modern marinas with the ability to moor approximately 500 boats in total. As far as I can see, and actual incidents confirm, the SCADA system offers no protection for boat and marina owners against high water levels.

This is despite BW/CaRT imposing a 'mooring tax' on those marinas. A small proportion of that revenue could have been invested in level sensing devices to offer 'early warning' of water level problems. There is no technical reasons why this has not been done as far as I can see. Instead the powers-that-be would rather spend the money on silly gimmicks, such as floating forests, poetry on lock gates and the like.

Doesn't this show the contempt those ex British Waterway managers, now in charge of CaRT, have not only for the boating community but marina owners too?