McDonald, Robert I.; Weber, Katherine F.; Padowski, Julie; Boucher, Tim; Shemie, Daniel. 2016. Estimating watershed degradation over the last century and its impact on water-treatment costs for the world’s large cities. Proceedings of the National Academy of Sciences of the United States of America. Vol: 113(32). (Abstract)
Urban water-treatment costs depend on the water quality at the city’s source, which in turn depends on the land use in the source watersheds. Here, we show that globally urban source watershed degradation is widespread, with 9 in 10 cities losing significant amounts of natural land cover in their source watersheds to agriculture and development. This watershed degradation has impacted the cost of water treatment for about one in three large cities globally, increasing those costs by about half. This increase in cost matters because increases in water-treatment costs are paid for by those living in cities, so watershed degradation has had a real quantitative cost to hundreds of millions of urbanites.