New scientific findings indicate that investing in watershed conservation is cost-effective for one in four cities worldwide

A new analysis of more than 2,000 drinking sources (rivers, forests and other ecosystems from which water comes) serving 530 cities worldwide has found that—as cities confront a water supply that is both scarce and polluted— watershed conservation can measurably improve the quality of water resources serving over 700 million people living in the world’s 100 largest cities.

The Urban Water Blueprint released today by The Nature Conservancy, in partnership with the International Water Association and the C40 Cities Climate Leadership Group, provides an in-depth analysis of the state of water for over 500 large and medium sized cities, including the 100 largest cities in the world, representing nearly 1 billion people. Collectively, these cities represent $21.8 trillion in economic activity, or 48 percent of the global urban GDP.

With more than half of humanity now living in cities, the concentration of water demand in urban areas across the globe is causing cities to confront the degradation of water quality in their water sources. The report reveals that this phenomenon is widespread, with two out of every five source watersheds experiencing significant forest loss over the past decade.

Preventing water from becoming polluted can often be more cost-effective than treatment. The analysis finds that one in four cities would see a positive return on investment from investing in watershed conservation. By using watershed conservation strategies to reduce sediment and nutrients in water sources by 10 percent, cities and water utilities could reduce water treatment costs by an average of 5 percent.

“This analysis answers for the first time, the fundamental questions of what investments can be taken to incorporate nature in the delivery of clean water and the quantitative value of these actions for water managers,” said Giulio Boccaletti, The Nature Conservancy’s global managing director for water. “Cities that invest in watershed conservation can no longer be the rare exception; rather such investments need to become a regular part of the toolbox for water managers. For this to happen, people living in cities need to understand where their water comes from so that city and water managers can support measures that will often be implemented outside of metropolitan areas.”

One in three of the largest 100 cities in the world are currently in water stress, and hundreds of millions of urbanites are drawing their water from sources with low quality due to high sediment or nutrient loading. These 100 largest cities also occupy less than one percent of the planet’s land area; however their source watersheds cover over 12 percent. That’s an area of land roughly the size of Russia – 1.7 billion hectares that collects filters and transports water to nearly a billion people before reaching man-made infrastructure.

“The IWA sees the growing strategic importance of connecting cities to their watersheds, and water utilities as pivotal players in making the various inter-dependencies work.” Tom Williams, director of programmes, at the International Water Association said. “Watershed conservation solutions will increasingly need to become mainstream options for water utilities and cities for enhancing water security”

The “Urban Water Blueprint” not only identifies the water risks facing large cities around the world, but analyses the potential for five conservation strategies that have proven performance and wide applicability across natural and working (agricultural) landscapes.  Each strategy is evaluated on how effectively it reduces sedimentation and nutrient pollution in the 2,000 watersheds that were analyzed.

The strategies and the cities with the most cost effective investment are:

Forest Protection – San Francisco, Los Angeles, Boston, Bogota, Rangoon;
Reforestation – Boston, Harbin, San Francisco, Melbourne, New York;
Agricultural Best Management Practices – Boston, San Francisco, New York, Shenzhen, Bogota;
Riparian Restoration – Medellin, Recife, Harbin, Mumbai, Sao Paulo and
Forest Fuel Reduction – Los Angeles, Melbourne, Sydney, Dar es Salaam, Monterrey.

“We found that watershed conservation can be both an economical viable and environmentally sound investment for developed and developing cities alike,” said Robert McDonald, senior scientist at The Nature Conservancy and one of the lead authors of the report. “What’s so exciting is that cities that embrace both the engineered and natural solutions to securing adequate and clean water supplies can not only meet future demand, they can literally reshape surrounding landscapes for the better.”

“Access to clean and adequate water supplies is a critical issue facing global mayors, and one made more pressing as cities grapple with the impacts of climate change. The research released today shines a spotlight on the need for urban watershed conservation strategies, and paves the way for cities around the world to share knowledge and implement viable solutions,” said Seth Schultz, director of research, measurement & planning at C40.

About The Urban Water Blueprint

The “Urban Water Blueprint – Mapping Conservation Solutions to the Global Water Challenge” was made possible through generous contributions from Ecolab through its Foundation, Starwood Hotels and Resorts Worldwide Foundation, and 100 Resilient Cities – Pioneered by The Rockefeller Foundation.

The Urban Water Blueprint has an accompanying website as a tool for city and water managers to evaluate the condition of drinking watersheds and the potential impact that conservation strategies, such as reforestation and agricultural best management practices, can have on water quality.  Displaying new information on more than 2,000 watersheds and 530 cities, the Blueprint provides science-based recommendations on where these strategies are most cost-effective. This data, along with detailed case studies of cities that have successfully adopted watershed conservation, can serve as a guide for city and water managers planning future infrastructure investments that include both engineered and natural infrastructure, as well as a learning tool for the one billion people living in the featured cities.