Boating without water

Where did all the water go?
At the top and ready to go down
Sleeping in to recover from pies and pints, we were woken up by a knock on the hatch. "Are you ready to go?" asked a cheery, windlass wielding man from British Waterways. Well we weren't but we had to be.
This side of the canal has critically low water levels and the BW team were to guide us down through the next twenty-odd locks, passing a similar team doing the same thing coming up. It's all a question of saving water - making sure that what comes out of one lock goes to fill the next one down rather than being wasted round the sides in the over-flow 'by-washes'.
And it all went swingingly well until about lock 31 when I found myself trying to boat over a coating of mud decorated with a rock garden along the edges. Star had to be flushed-through to the next lock. Not quite toilet style but similar in fashion -- fill up the lock above, empty its contents and flush Star through with the extra water.
Repeat several times as necesary over the succeeding locks. It's a recurring problem on the HNC: apparently when BW gave up on the canal after the war they leased away the reservoir water supply that fed it. Now we've got the canal back but not the water to fill it!
Still, we finally made it to Slaithwaite and our overnight halt, 21 locks later. And all on a couple of teacups of water. The next 21 to Huddersfield will hopefully be easier.