The journey every drop takes to get to your tap can start well over a hundred miles from your property, and depending on where you are in the country, could be sourced differently.
Unless you have a private connection, it is likely your water initially comes from either surface water sources (rivers and reservoirs) or groundwater sources (springs, wells and boreholes) before being treated and sent to your home.
When river levels are healthy, water is abstracted from rivers and sent to reservoirs or pumping stations using a network of pipes transferring water.
Reservoirs can be either man-made or naturally occurring, but their primary function is to provide a storage of water from rainfall in the wetter months, which is then used when abstraction from rivers is not viable.