The Thames and Severn Canal entered the River Thames just west of the town of Lechlade from where boats could use the river to make their way to London.
The main water supply for the canal was taken from the River Churn, with the pump at the Thames source providing extra supply in the summer. The Churn joins the Thames at Cricklade. (If you’ve signed up, there will be a map in your inbox, that shows how all this fits together.)
So at Cricklade there was less water coming down the Thames, as the spring was drying up, and less water coming down the Churn as it was being pumped into the top section of the canal, not all of which would find its way back to the Thames.
At Lechlade some water would come in from the canal, but not as much as had been put into the canal originally.
Lower river levels made it hard for boats to get through and during periods of low rainfall it was even more difficult.
When the river was low more water was taken from the ground, which meant that more springs dried up and the river got even lower. In the end there is only a certain amount of water available.
The Thames and Severn Canal closed in 1933. The railway was now used to carry goods to and from London, whereas the canal needed repair and the water shortage was a major problem.
The Thames is still used by boats as far as Lechlade but most of them are carrying holidaymakers.
There are 45 locks enabling boats to safely pass the changes in level of the river.
Many of these have a lock keeper, part of whose job is to monitor the flow of the river. Too much water can lead to flooding. Too little causes problems for boats. At each lock the water that is not needed for the lock passes over a weir. The lock keeper can control how much water is allowed over the weir to maintain the correct water level upstream of his lock.
Quite a spectacular amount of water by the time you get further downstream.
Join me next week for a look at how the power of the water is being used.