Healthy cities need reliable clean water to thrive. Conservation strategies could benefit more than 700 million people in the world’s 100 largest cities.
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The urban sprawl of Quito, the capital city of Ecuador, and surrounding farms. Quito is located in a high altitude valley at 9,350 feet above sea level, 15 miles south of the equator in the Guayllabamba river basin. The city sits on the slopes of the active Pichincha volcano in the Andes mountains or north central Ecuador.
CREDIT: © Bridget Besaw
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Rain falling in Kimbe Bay, West New Britain, Papua New Guinea. This area is one of the Marine Protected Areas (MPAs) which The Nature Conservancy helped design to protect the biodiversity of the bay.
CREDIT: Mark Godfrey © 2008 The Nature Conservancy
Overview
Nature plays an important role in keeping urban water sources reliable and clean, one that has gone largely untapped. Natural solutions such as reforestation, better farming practices and stream bank restoration can reduce erosion and run-off that pollutes water. These solutions can improve water quality for more than 700 million people and reduce treatment costs felt by cities and utilities.
The Urban Water Blueprint analyzes the state of water in more than 2,000 watersheds and 530 cities worldwide to provide science-based recommendations for natural solutions that can be integrated alongside traditional infrastructure to improve water quality. City and utility leaders who embrace both natural and engineered water infrastructure will not only meet future water demand; they will reshape our planet’s landscape for the better.
We have continued to improve our scientific analysis over time, correcting reported errors and improving our methodology. None of these updates change the overall results of our study, but can significantly change the estimates for a few cities. These updated results are not reflected in the report or website, but we urge anyone considering using the results from the Urban Water Blueprint for analysis or decision-making to contact us at water@tnc.org to obtain the most current estimates.
Read the full report
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TNC staff members and representatives from the US Army Corps of Engineers (USACE) visit Davis Pond, the word's largest freshwater diversion project located 23 miles up the Mississippi River from New Orleans. Davis Pond Freshwater Diversion Project was built by a partnership of the USACE and the Louisiana Department of Natural Resources in an effort to reintroduce fresh water, nutrients and sediment to the salt-threatene Barataria estuary, which stretches south to the Gulf of Mexico. The project does more than reduce salinity, it actually helps built new marsh. The trip to Davis Pond was part of a week-long trip to see two regions along the Mississippi River. The purpose of this visit was to develop a partnership between TNC, USACE and Cormagdalena to advance the conservation and sustainable development of the Magdalena River in Colombia. The Mississippi River has faced similar development and conservation issues, and the meeting allowed attendees to see on-the-ground experiences, draw comparisons of management practices and share technical and scientific expertise.
CREDIT: © Erika Nortemann/TNC
Risks
People around the world depend on clean drinking water — yet hundreds of millions of city residents draw water from poor quality sources. Water quality is often degraded by nutrients from excess fertilizer or sediment from working landscapes such as cropland or pastures. Protecting water at its source can be cheaper and more efficient than treating it after it has been polluted.
Phosphorus sources in surface waters are grouped based on the phosphorus yield in kilograms per square kilometer: low (< 0.019), medium (0.019-0.2275) and high (> 0.2275). Sediment sources are grouped based on the sediment yield in metric tons per square kilometer: low (< 25), medium (25-225) and high (> 225). No data available means that the source is not a surface source.
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After 2011 record temperature, Medina Lake is filled to just 25 percent of its capacity. Located northwest of San Antonia, the reservoir sits along the recharge zone and helps filter water underground to the Edwards Aquifer. Photograph from the 2012 issue number 2 of Nature Conservancy Magazine. Photograph taken to illustrate a story on the Edwards Aquifer, "Can Texas Ranchers Save San Antonio's Drinking Water?". The Edwards Aquifer is one of the most prolific artesian aquifers in the world. Located on the eastern edge of Edwards Plateau in the U.S. state of Texas, it discharges about 900,000 acre feet of water a year and directly serves about two million people.
CREDIT: © Blake Gordon
Risks
We live in an urbanizing world. Without an ample, consistent supply of clean water, no city can thrive. Today, cities are looking farther and farther beyond their city limits for clean water. On average, cities secure 43 percent of their water supply via interbasin transfers—moving water from one river basin to another.
Natural solutions can complement built infrastructure by reducing sediment and nutrients that pollute local drinking water supplies and make them unusable.
Annual stress is defined as the ratio of water withdrawn from a watershed to water available. A value above 0.4 is defined as stressed, by convention. The Water Blueprint only evaluates surface sources.
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Farm equipment at work in the fields of the Franklin family farm, located on the banks of the Mackinaw River near Lexington, Illinois. The Franklin family works in Partnership with The Nature Conservancy to test and demonstrate conservation related agricultural practices that protect and preserve the river watershed.
CREDIT: © Tim Lindenbaum/TNC
Solutions
Changes in agricultural land management offer the biggest opportunities to improve water quality for many large cities. This measure examines agricultural best management practices aimed at reducing erosion and nutrient runoff on croplands and estimates the area of agricultural land that would have to be managed better to measurably reduce nutrient or sediment loading by 10 percent.
Lower number of hectares are better, since for less work you still get a 10 percent reduction: high potential (< 1,000), medium potential (1,000-10,000) and low potential (>10,000). Unlikely scope means that it is unlikely to get to a 10 percent reduction with this particular strategy.
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Illinois River and its floodplain. As a part of the inland waterway transportation system, the Illinois River is a key component of the Conservancy's Upper Mississippi River program.
CREDIT: © Doug Blodgett/TNC
Solutions
Strips of natural land along streams and rivers, called riparian buffers, play an important role in filtering runoff from farm fields and preventing nutrients and sediment from entering waterways. When riparian buffers are improved, some cities see lower water treatment costs. The opportunities in the map are defined by the area of stream bank that would need to be restored in upstream watersheds to reduce nutrient or sediment loading by 10 percent.
Lower number of hectares are better, since for less work you still get a 10 percent reduction: high potential (< 1,000), medium potential (1,000-10,000) and low potential (>10,000). Unlikely scope means that it is unlikely to get to a 10 percent reduction with this strategy.
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The Mink River estuary in Door County, Wisconsin. As of July 24, 2013, the Conservancy has protected 1,919 acres at Mink River Estuary. This figure includes lands owned and managed by the Conservancy, conservation easements, government co-ops and assists. The Mink River Estuary is a Great Lakes estuary with regionally important natural values. As a Great Lakes coastal wetland and forest landscape, it provides habitat for a number of important plants and animals including Great Lakes fish, many species of migratory and breeding birds, and many mammals representative of a northern Wisconsin mixed conifer hardwood forest. Seen in some of the Mink River photos are The Nature Conservancy's Land Stewart Kari Hagenow (wearing blue jacket) with Conservancy intern Amand Pike (black jacket).
CREDIT: Mark Godfrey © The Nature Conservancy
Solutions
Forests can act as natural sponges and filters, preventing sediment and nutrients from polluting water supplies. Protecting forests from development or other human uses — through purchase, conservation easements, or government designation of protected areas — can lead to higher quality water in a city’s watersheds. This measure shows the amount of forestland that would need to be protected in upstream watersheds to reduce by 10 percent the risk of future nutrient or sediment loading.
Lower numbers are better, since for less work you still get a 10 percent reduction: high potential (< 1000 hectares), medium potential (1,000-10,000 hectares) and low potential (>10,000 hectares). Unlikely scope means that it is unlikely to get to a 10 percent reduction with this strategy.
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Red spruce tree saplings are planted on what was once a strip mining operation to create habitat for West Virginia Northern flying squirrels.
CREDIT: © Patrick Cavan Brown for The Nature Conservancy
Solutions
Returning once-forested pastures to natural tree cover, through tree planting or natural regeneration, can improve a city’s water security. Trees stabilize soil, reduce erosion, and prevent fertilizer and manure runoff that can lead to river and stream pollution. This measure shows the amount of pasture that would need to be reforested to reduce nutrient or sediment loading by 10 percent.
Lower numbers are better, since for less work you still get a 10 percent reduction: high potential (< 1,000 hectares), medium potential (1,000-10,000 hectares) and low potential (>10,000 hectares). Unlikely scope means that it is unlikely to get to a 10 percent reduction with this strategy.
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At Piney Grove Preserve, firefighter Rick Barnett reports in after igniting a line of fire. Prescribed burns, like this one, are conducted to restore habitat for the red-cockaded woodpecker (Picoides borealis), a federally-endangered species. Piney Grove Preserve is home to the only remaining population in Virginia.
CREDIT: Robert Clontz/© 2010 The Nature Conservancy
Solutions
In some areas, overgrown forests are prone to catastrophic wildfires transforming forested hillsides into barren land. If fires are followed by large rainstorms, sediment and ash can muddy once clean waterways. Mechanical thinning or controlled burns can reduce the risk of catastrophic fires. This measure shows the area of forestland that would need to be treated to reduce future sediment risk by 10 percent.
Lower numbers are better, since for less work you still get a 10 percent reduction: high potential (< 1,000 hectares), medium potential (1,000-10,000 hectares) and low potential (>10,000 hectares). Unlikely scope means that it is unlikely to get to a 10 percent reduction with this strategy.
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