Water is one of our Nation’s most precious resources. We depend upon it for our livelihoods, for healthy ecosystems, and a robust economy. Yet, a host of challenges, such as biological and chemical contamination, aging water-system infrastructure, population changes, and security events, threaten the safety and sustainability of our water resources. To address these complex issues, EPA research is using an integrated, systems approach to support innovative scientific and technological solutions that ensure clean, adequate, and equitable supplies of water to protect human health and to protect and restore watersheds and aquatic ecosystems.