This entry is also posted on the Sustainable Cities International blog, which gives updates of work from SCI’s Affiliated Researchers and interns working with member cities throughout the world.
A quiet evolution is taking place in how we use and move water within cities throughout the world. In Los Cabos, Mexico, where I am working with the local office of the Instituto Municipal de Planeación (IMPLAN) this summer as part of the Affiliated Researcher Program of Sustainable Cities International, we are planning for this evolution.
Traditionally, cities have built infrastructure that supplied residents with water from distant sources and quickly removed rainfall and sewage. Cities acquire water from more pristine sources in rural areas or deep underground. Sewer pipes remove water used in homes, businesses, and industries, while storm drains collect and move water to prevent floods. Treatment plants, which were installed throughout the twentieth century, prevent diseases and environmental pollution.
Today, many cities are developing and deploying a new set of strategies that emphasize conservation and reuse of water, while also trying to reduce contamination in local watersheds.
The evolution is driven by stricter environmental regulations, higher costs for acquiring and treating water, and changing social attitudes. The tools to promote this evolution are numerous, including landscape measures such as bioswales and green roofs, low-flow shower heads and efficient toilets, permeable pavements, and new water treatment technologies.
For established, industrialized cities, water infrastructure is expensive and often decades old, meaning they must find new approaches to meet economic and regulatory requirements at a reasonable cost. Meanwhile, the growing cities of emerging economies face the challenge of funding and building new infrastructure to ensure reliable, quality water for swelling populations.
Sustainable designs for urban water infrastructure consider how drinking water supplies, sewage, urban landscaping, and energy use are intimately connected. The new approaches cities are using, often referred to as integrated urban water management, use these linkages to develop more efficient and environmentally-friendly plans.
Cities are also intimately shaped by their surrounding environments and rainfall patterns. Los Cabos, at the southern tip of the Baja California Peninsula, has what is called an extremely “flashy” hydrology. For many months of the year, little or no rain falls. From September to November, however, very large storms can generate nearly all of the year’s precipitation. When heavy rain does fall in the dry landscape, it quickly overwhelms the natural capacity of the soil to absorb, or infiltrate, the water. Instead, water runs off the landscape and into channels to flow to the ocean. In some parts of the region, the geology allows for significant recharge through rock fractures, while in other parts, infiltration is much slower.
The Southern Baja California landscape is crossed by these dry riverbeds, called arroyos. Most visitors to Los Cabos see dry, sandy, unattractive channels running underneath highways and between resort hotels along the beach. Residents, however, understand the local precipitation patterns and the vital function that arroyos serve to prevent flooding. The larger the storm and the faster the rain falls, the more the channels will temporarily fill. The largest storms in the region, hurricanes and tropical storms, often cause localized or widespread flooding.
As vital components of the region, the arroyos of Los Cabos offer an opportunity to consider how sustainable design and water management can more closely integrate urban residents with local landscapes. Many local arroyos are already important areas for agriculture, recreation, and even residences. As urbanized areas in the region, including the corridor from San Jose del Cabo and Cabo San Lucas, continue to expand and surround the arroyos, urban planning discussions can weave public dialogue, technical analysis, and community development to promote the arroyos as a resource for many integrated needs. Arroyos can provide a collection of services that support smart growth in the region, including removal of flood flows, stormwater detention, wastewater treatment, groundwater for drinking, habitat, recreation, and transit corridors.
Such plans require merging water resources engineering with urban design to create arroyos that balance many needs. Working with the Los Cabos office of IMPLAN, I am conducting analysis and collaborative design work to understand how local municipalities can allocate lands in arroyos for different environmental, resource, and human uses.
We have developed tools to model rainfall and stormwater runoff for the watersheds, including how large storms affect the quantity of timing and runoff in urban arroyos. Such modeling supports collaborative processes that connect municipal leaders, residents, designers, and technical experts and promotes healthy, safe, and sustainable urban growth.
My work with IMPLAN is creating a framework for technical analysis and urban planning that can be applied to arroyos throughout the region, beginning with a pilot project near San Jose del Cabo. Urban planners and municipal leaders in Los Cabos have an opportunity to make the community a leader for water management and sustainable urban landscapes in rapidly urbanizing, dry climate communities.
As urban populations increase and clean water becomes scarcer, the tools for integrated water planning will be vital for the continued growth of healthy, productive cities.
Novotny, Vladimir, Jack Ahern, and Paul Brown. 2010. Water Centric Sustainable Communities: Planning, Retrofitting, and Building the Next Urban Environment. Hoboken, N.J: Wiley
Melosi, Martin. 2000. The Sanitary City: Urban Infrastructure in America from Colonial Times to the Present. Baltimore: Johns Hopkins University Press