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Green Infrastructure: Cost Effective Strategy to Preserve Water Quality

By: Kate Gazzo

Even though drinking water is disinfected and filtered, anthropogenic pollution to surface waters may be lowering the quality of your drinking water. As you turn on your tap, pharmaceuticals, industrial and agricultural chemicals, heavy metals, and in some cases pathogens may be flowing out. Human health effects from lowered water quality range from acute illness stemming from microbial outbreaks to more common, chronic exposure to a wide range of aforementioned contaminants. Even though water filtration and disinfection can remove a lot of these contaminants, some are still present in domestic supplies. During a five year study (2004-2009) analyzing tap water from across the U.S., over 300 different contaminants were identified; 200 of these contaminants were not under federal or state regulation and a quarter of these 200 unregulated contaminants were above human health guidelines.

A combination of increasing chemicals and chemical loads in waterways stemming from Nonpoint Source Pollution (NPS) combined with urban sprawl and development are elevating the risk for contaminants to enter drinking water sources. Sprawl and development contribute to habitat loss and fragmentation, including a loss of natural watershed areas such as forests and floodplains which are essential for the protection of water supplies.

An increasing diversity, as well as magnitude, of these pollutants necessitates the preservation and protection of watershed areas, especially those upstream of drinking water sources. Drinking water sources are headwater areas to an end route, such as a lake or river. Protecting upper watershed lands and key buffer areas provide an effective barrier against common drinking water contaminants including, agricultural, industrial, and urban water pollution sources. Currently water utilities spend $4 billion each year on chemicals alone to treat drinking water; in contrast, only $200 million (one twentieth of this amount) is spent on the protection of source waters and watershed protection efforts. Increasing drinking water treatment costs are leading to costly water bills for consumers.

Although humans have engineered drinking water filtration plants to filter and purify drinking water, these services are provided by ecosystems for free and are often just as effective at meeting water quality standards. Multiple cities, including some of the largest cities in the U.S. including New York, Boston, and Seattle consistently meet drinking water quality standards with limited use of human engineered filtration systems. These cities rely primarily on green infrastructure (forests, grasslands, and riparian areas) to safeguard their water supplies. As a result these cities have saved millions and in some cases, such as New York City billions of dollars in potential human engineered or gray infrastructure.

Proposed cost-savings shown in blue (millions of dollars) for Portland, ME who is investing in green infrastructure including, restoration and preservation. Potential gray infrastructure costs shown in gray. (Figure courtesy of Gartner et al., 2013)

Proposed cost-savings shown in blue (millions of dollars) for Portland from investing in green infrastructure including, restoration and preservation. Potential gray infrastructure costs shown in gray. Figure courtesy of Gartner et al., 2013.

In New York City, a drinking water filtration system, the Croton Water Filtration Plant, was necessitated in the 1990’s by the U.S. EPA and NY State Department of Health mostly as a result of the developing upstream watershed. When completed, the Croton Water Filtration Plant will supply 10 % of the city with water from the Croton watershed, however, 90% of NYC, or eight million people still receive unfiltered drinking water from the protected Catskill-Delaware (Cat-Del) watershed. Due to the continued protection of the Cat-Del watershed, New York City is well known for the best tasting and purest drinking water in the world. The city also avoided $6 billion in the construction of a second water filtration plant by committing $1.5 billion to watershed protection over a 10 year period, further enhancing the upstream Cat-Del watershed.

The protection of the Cat-Del watershed exemplifies how protection and restoration of key land areas is a wise investment to reduce human health risks and water treatment costs. Soil and vegetation within protected watersheds degrade and filter pollutants transported form upstream areas and thereby lower the risk of downstream water contamination. Cities that invest in green infrastructure save money on treatment costs because ecosystem services decrease the level of treatment needed. For every 10 percent increase in forest cover, treatment costs decrease by 20%. Considering an average treatment plant may treat 20 million gallons/day, a 20% decrease in treatment costs may save thousands of dollars.

The percentage of forested area within a watershed is directly related to treatment costs. (Table courtesy of Ernst et al., 2004)

The percentage of forested area within a watershed is directly related to treatment costs. Table courtesy of Ernst et al., 2004.

References

Ernst, C., Gullick, R., & Nixon, K. (2004). Protecting the Source Conserving Forests to Protect Water. American Water Works Association. Opflow, 30(5).

Gartner, T., Mulligan, J. Schmidt, R., Gunn, J. (2013). Natural Infrastructure: Investing in Forested Landscapes for Source Water Protection in the U.S. World Resources Institute. Washington, DC. doi:ISBN 978-1-56973-813-9

National Research Council. (2000). Watershed Management for Potable Water Supply: Assessing the New York City Strategy (p. 545). Washington DC. Retrieved from

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