I found this book to be an excellent read / resource.
The Prepper's Water Survival Guide: Harvest, Treat, and Store Your Most Vital Resource https://www.amazon.co.uk/dp/1612434487/ref=cm_sw_r_cp_api_glt_i_YMPQZTGW6ANFPZ25H3EK
The Prepper's Water Survival Guide: Harvest, Treat, and Store Your Most Vital Resource https://www.amazon.co.uk/dp/1612434487/ref=cm_sw_r_cp_api_glt_i_NQ4BTMJC39W7XFM1QQ2W