Replacing a mains gas boiler in a very old house – what with?

Has anyone done anything hydropower wise? We have the fairly slow flowing river Irwell outside and two run off water outlets feeding into it that run 24/7 in winter. I look at them and see untapped energy but the paperwork looks a bit intimidating for officially ‘sticking something in a river’

Edited to add – how big are the bags of pellets you mentioned?

15kg or 10kg bags are the standard. My house is upside-down so I have the boiler on the 2nd floor, and a few 15kg bags upstairs every day is no problem. 30kg of pellets a day is the absolute worst case scenario in freezing temps. I love the Klover, would get another in a heartbeat.