Water is at the heart of America’s national parks, yet many of these rivers, lakes, coasts, and wetlands are under growing stress from pollution, climate impacts, and decisions made outside park boundaries. In this episode from the Reservoir Center in Washington, D.C., Ed Stierli of the National Parks Conservation Association explains how his organization serves as the independent voice for 433 national park sites, backed by nearly 2 million members. He breaks down why more than half of waterways in national parks remain impaired, connecting the dots between upstream land use, aging infrastructure, and weakened protections that shape water quality. Stierli highlights how bedrock laws like the Clean Water Act and modern restoration programs have helped bring back iconic species and improve water conditions, while warning that political rollbacks could erode decades of progress. He also points to large-scale, watershed-based collaborations—uniting federal agencies, states, local governments, and nonprofits—to restore wetlands, rebuild natural buffers, and invest in resilient infrastructure. Throughout, Stierli stresses the power of public engagement and broad coalitions to secure funding, defend protections, and keep national parks functioning as living classrooms where people can experience and learn from healthy waters.waterloop is a nonprofit news outlet exploring solutions for water sustainability.