Water quality trading is gaining traction in a number of watersheds around the world. It is a market-based approach that works alongside water quality regulation to improve water quality, providing flexibility in how regulations are met and potentially lowering regulatory compliance and abatement costs. The research identified 57 water quality trading programs worldwide. Of these, 26 are active, 21 are under consideration or development, and 10 are inactive or are completed pilots with no plans for future trades. The majority of programs were located in the United States, with only six programs existing outside the United States