Where America's Drinking Water Comes From

Every city's water quality starts at its source. A protected mountain reservoir like Bull Run produces pristine, soft water that needs almost no treatment. A limestone aquifer like the Floridan produces naturally hard water loaded with dissolved minerals. A major river like the Mississippi carries whatever upstream cities and farms put into it.

These profiles explain the geology, treatment, and challenges for each major US water source - and link to every city we track that draws from it.