One night at dinner, a while back, when Bob was over, the three of us had a discussion about the tidal differences on the Thames. (Having checked the very handy tide timetable, I can verify that the difference between low and high tide is somewhere around 5-6 metres.)
This discussion led to a query about the water level in the docks at Canary Wharf. Mirinda wondered why there was no tidal difference. My answer, spoken with utter confidence even though I was merely guessing, was “sluice gates.”
Mirinda met this assertion with disdain, decrying my ability to guess with the correct opinion that I was “…only guessing.” I couldn’t deny it.
This led to a lively discussion about sluice gates. And it’s never really gone away. So, today, I decided to settle the argument once and for all.
First up, I should admit that I was (partly) wrong. The water in and around Canary Wharf is controlled by lock gates and a few pumping stations for overflow. I say ‘partly’ because I class pumping stations and sluice gates in the same category.
I found out by walking to the end of the docks to where the Thames crosses them at a right angle. And there, I found the Blue Bridge.
The Blue Bridge (because it’s blue and a bridge) is the sixth bridge to span this entrance to the river. The first one was built in 1805 and, when the docks were particularly busy, horses and carts, pedestrians, sheep and goats and all manner of other creatures were forced to wait for anything up to half an hour as the big ships jostled to get in.
You see, it is a draw bridge. These days it only inconveniences pedestrians and motorists and not very often even though it is now the only working entrance from the Thames to the West India and Millwall docks.
The water level is controlled by the lock gates. There are three sets of these. I was there halfway between high and low tide and the water on the Thames side of the second set of lock gates was low. You can, sort of, see the arrangement here:
The third set of lock gates were open. They are beneath the Blue Bridge. I can’t figure out what these ones are used for unless it’s for emergencies. But that would be a guess and I’ll only get into trouble for it…so I’m not saying anything further about them.
Ships wishing to enter the Docks must approach at around high tide when the water is equalised either side of the lock gates. The gates are opened and the boat comes in. Easy as that. Very clever and very simple.
On the way back, I spotted this gorgeous (even though the sky wasn’t blue) reflective view.
I should also mention that today was a big celebration as Mirinda’s first acquisition finally went through! It’s been a long, hard slog and, at times, she’s been tempted to throw in the towel but she’s persevered and now it’s over. We’ll be having a celebration dinner on Saturday. And then the next one will start…