For more than 40 days this summer, residents of Jackson—Mississippi’s capital and home to 150,000 people—could not drink their water. Torrential rain and floodwater swamped the city’s largest water treatment plant in August; the pumps failed under the onslaught, and the city’s water supply with them. Jackson’s water systems were decades old and decrepit, no match for the onslaught of severe weather. The city became a dramatic example of what can happen when 20th century infrastructure meets the challenges of the 21st century—and, for the rest of the country, a warning.

Below the nation’s cities and towns lies a sprawling and complex system of pipes, pumps, and valves that help deliver safe drinking water to millions of homes and businesses. This vital infrastructure is now under threat: the U.S. water system is old, underfunded, and designed for a climate that no longer exists. Extreme weather patterns, including floods and freezing events, are pushing the system to the brink of collapse in some areas.