Water tunnel on the Doubrava

An interesting feature of the river Doubrava below the Church of the Holy Cross near Ronova nad Doubravau is an artificially constructed water channel to a high rock, through which it flows through a tunnel. After the tunnel, he is led back into the river. Unfortunately, I have not been able to find out the purpose of this channel and tunnel, I will be grateful for any information. The route described at https://www.turistika.cz/trasy/udolim-doubravy-z-tremosnice-do-zlebu passes through the place