Water conservation practices are just one component of a sustainable and resilient water system. Many more variables are involved, including protection of water quality of neighboring bodies of water, decrease of flooding in low-lying areas and minimization of erosion of local streams and hill-slopes. Here at WaterSmart we are deeply interested in increasing awareness of these issues, since the public’s relationship with and influence on their water system extends far beyond the boundaries of improved efficiency. In particular, land use practices are closely related to water supply availability, ecosystem health, and water quality. These practices present valuable opportunities for innovation moving forward. Looking to the future, communications around land use issues will be an increasingly important touch-point between water managers and their customers, and it is an area of growing interest in the broader environmental community.
Land use patterns are a leading cause of urban water pollution in the United States. Large amounts of paved and impermeable areas in cities and suburban communities lead to large pulses of stormwater runoff when it rains, which is associated with a multitude of cascading issues:
- Combined sewage and stormwater pipes combined with large precipitation events regularly cause wastewaters volumes to exceed capacity. This leads to discharge of untreated sewage and stormwater into nearby water bodies.
- For separate stormwater and sewage treatment systems, stormwater carries fertilizers, pesticides, garbage and urban contaminants through storm drains directly to surrounding rivers, drinking water reservoirs, and coastal areas. This causes degradation of recreational water bodies and drinking water supplies.
- In cities with adjacent rivers and streams, pulses of stormwater moving quickly into stream channels often overwhelm the system’s ability to deal with the excess water, which triggers local flooding events. These stormwater pulses can also cause erosion and manipulation of streams channels that degrades habitat for critical aquatic species.
In the United States, an estimated 10 trillion gallons of untreated stormwater runs off roofs, roads, parking lots and other paved surfaces per year. For example, a one-inch rainstorm in Los Angeles County can result in more than ten billion gallons of runoff flowing into the urban storm drain systems, and most of that water flows into the Pacific Ocean. That’s over 30,000 acre-feet of water, or about 5% of the region’s total annual water consumption, from just one modest rain event. While stormwater is typically treated as a waste stream, onsite retention of stormwater presents a unique opportunity to utilize local water supplies while reducing environmental damage and cutting infrastructure costs. This management technique is frequently referred to as green infrastructure.
Green infrastructure uses vegetation, soils and natural processes to manage water and create healthier urban environments. Examples of green infrastructure include green roofs, street trees, rain barrels, rain gardens and permeable pavement. Onsite retention of stormwater through green infrastructure simultaneously improves water quality, reduces water waste and protects neighboring water bodies.
Particularly in wet parts of the country, green infrastructure investments are increasingly viewed as a less expensive, more attractive alternative to traditional approaches for reduction of combined sewer overflows. In a cost-benefit analysis, the Philadelphia Water Department found that for equal investment amounts and similar combined sewage overflow volume reductions, green infrastructure would provide 20-times the monetized benefits of traditional infrastructure, such as large tunnels and pumping stations. These benefits include recreational improvements, air quality improvements, water quality improvements and ecosystem enhancement. The city of Lancaster Pennsylvania estimated that its Green Infrastructure Plan would reduce wastewater pumping and treatment costs by $661,000 per year, provide $2.8 million in energy, air quality, and climate-related benefits annually. It would drive $120 million of avoided capital costs of implementing traditional infrastructure.
In water scarce regions, green infrastructure can provide a source of much needed local water. An analysis by NRDC and the Pacific Institute found that capture of stormwater runoff for water supply across urban Southern California and San Francisco Bay Area could increase local water supplies between 420,000 and 630,000 acre-feet per year, or roughly the amount of water used by the entire City of Los Angeles annually.
There is a huge opportunity for communities to turn water “waste” into a valuable resource, while deferring capital investments and reaping extensive co-benefits. Engaging customers on issues surrounding green infrastructure will likely become increasingly important as more communities acknowledge the benefits of working with nature rather than against it.