alt Hacker NewsWe have been here before with the waterwheels that powered the mills at the start of the Industrial Revolution, allegedly.
Allegedly this was a problem in the Cotswolds, UK, when the woollen industry was where the big money was. I only know this from school history classes, not from Google, hence my use of the word 'allegedly'. Allegedly, mills placed upstream slowed the flow to existing mills downstream, leading to disputes.
In time, mills were built with big chimneys, meaning coal. But why would you go for expensive coal that had to be transported when you had 'free' power from the river? It has been hypothesised that drought may have played a part in this, not the over use of waterwheels.
It's quite obvious if you look at how a watermill is built. Upstream, there's a wier which diverts water along a culvert into a pond at the level of the weir. The watermill is then driven by water falling from the pond to the level of the river at that point. Depending on the gradient of the river, this can be some distance from the weir. If the weir diverts on average a substantial portion of the flow, anyone wanting to use the river between the weir and the mill will find there's much less water for the purpose. Many British rivers in areas where there were (literal) cottage industries like little mesters are not that big (only a few metres across and under a metre deep) so you can see where conflicts could arise. And also they do dry up to almost trickles in dry weather.