Adapting to rapidly changing conditions on a crowded planet. Looking forward to 2050, the challenges of adding 2 billion more people to an already resource-constrained planet will require major changes in the resources efficiency, energy efficiency and cost of urban water systems of the future. A step change including the integration of city planning and urban water system design will be required to optimize the efficiency and resilience of urban water systems in addition to the development of physical and institutional linkages between agricultural, energy and urban water uses.
I. The World in 2050
Let’s begin with the bottom line: the manner in which water is produced, used and returned to the environment will need to be substantially different in the next 40 years, compared to the previous century, if the well being of the planet and its human population is to be assured.
Focusing specifically on the urban dimension of this challenge, as we begin the “second half” of urbanization of the planet (2009 marked the time when 50% of population was urbanized), many would conclude that we are at a tipping point in terms of upcoming urban water needs versus resource availability. Accordingly, the sources and management of water for cities will of necessity change a lot—dramatically in some cases. Scarcity of locally available water supplies, competition for water with agriculture and energy, climate change impacts, rising energy prices and the need to mitigate for greenhouse gas emissions, environmental restoration and basic economics in combination will require cities to use water far more efficiently compared with today’s systems—perhaps by a factor of two.
I believe that we are capable of doubling the efficiency of urban water use, at least in developed countries, through a combination of high levels of conservation, water reuse enabled through membrane technology, and energy and nutrient recovery. Success will be found through a combination of measures within the urban area, together with strategic trades of water with agriculture and energy. For example, the city might gain additional water by investing in irrigation efficiency in adjacent farmlands, while returning reclaimed water and nutrients to agriculture to further expand crop production.
In developing countries where 80–90% of future urban growth is estimated to occur through 2050, we have the twin challenge of building highly efficient water systems capable of absorbing growth in population and rising per capita use, and doing it at a much lower per capita cost than that of conventional systems that are found in the U.S. and Europe today. While this may be possible in emerging middle-income economies like China, Turkey and Brazil, we are obviously going to need a portfolio of approaches to match the range of physical and economic circumstances in lower-income countries.
Beyond the economic challenges are cultural ones. Water engineers are a conservative lot. There are few rewards for the bold innovation required in the future and many penalties for things going badly. In this environment, significant changes in thinking and the development of truly innovative solutions will require conscious strategies that permit and reward controlled experimentation. Finally, because the developed countries are fairly or unfairly held up as role models when it comes to water systems, the change we need to see in how water is used and systems are built will need to include examples from developed countries.
In these matters, time is not on our side. If one considers that the key elements of urban water systems—networks, treatment plants, pumping stations—are by design or circumstance in place for at least 50 years (sometimes 100 years), it is evident that we urgently need to think about what the water systems of the future looks like, and begin implementing the basic design principles beginning now.
If we are to produce a step change in water system design, how do we start the process of thinking outside the box that has shaped conventional design in developed countries and has more or less been universally adapted as the desired solution for water supply and sanitation?
And in lower-income countries, where peri-urban slums currently dominate the urban water challenges, can we challenge ourselves to think far outside the box? Can we think about affordable, incremental steps that over the long run lead to a growth in drinking water and sanitation service levels commensurate with the community’s ability to pay?
These questions underlie the need to think creatively in the near future. Working through the International Water Association, and its Cities of the Future Program, leading water professionals alongside city planners have been working hard on the question of how cities can achieve water security in the context of rising demands and increasingly scarce water resources on the path to 2050.
While working “bottom up” on the question such as how density affects consumption, how reuse could be facilitated through different treatment and network modalities, and how to build more resilient systems and networks capable of adaptation to changing conditions, they have been assembling case studies of new and innovative approaches to urban water management.
Cases such as Xing Dao, China, reveal the potential as well as some of the difficulties in rethinking the urban water nexus. In Xing Dao, research engineers from Germany and China have teamed up to develop a full-scale demonstration of the highly efficient water system of the future. Situated at the edge of the city in an area designated for the next round of development, they are working in a greenfield circumstance where they could start from scratch. In designing an integrated system for water treatment, wastewater treatment, water reuse and energy production, they chose a service area that was “as small as possible but as big as necessary.”
This led the team to what they call a “semi-centralized” system design, optimally serving 20,000–70,000 people and in their case, about 50,000. The service area or “cluster” is centered around the integrated treatment plant, thereby minimizing network costs and energy while facilitating the repeated household-level reuse of gray water. They anticipate a 50 percent reduction in water use, significantly lower network costs and the production of energy from the plant that is twice the plant's own energy requirements.
Clearly, examples like this of which there are several in China, constitute water systems of the future. They exemplify innovation and the potential for increased efficiency that will be required to meet the challenges leading to 2050. But these kind of innovations are only possible if they are co-designed alongside the buildings, road and parks which make up traditional city planning.
Israel provides another useful case in considering how to achieve water security—in their case for both cities and agricultural areas. Historically dependent on contested water from the Jordan River, Israel decided to use seawater desalination and reuse in combination as the principle source of new water. In fewer than 10 years, five desalination plants were built along the coast—plants that supply water to the major urban centers.
Once employed for urban uses and subsequently collected, the urban wastewater is highly treated and transported south for agricultural use. Israel currently reuses 70 percent of its urban wastewater and will soon reach a reuse level of 95 percent. Through efficient irrigation and reuse, Israel has one of the lowest per capita uses of water in the world and is one of the leaders in innovative water technologies.
Melbourne, Australia provides a third case where climate-change induced drought dramatically affected the Murray Darling River system, the agricultural sector including high-value orchard crops and vineyards, and the urban settlements in and around Melbourne. A comprehensive program of action has included high levels of urban and agricultural water conservation, water transfers between all water uses, the addition of major desalination and reuse capabilities in Melbourne, revisions to urban design and pilot testing of in situ water facilities in newly built suburbs. In the end, multi-level comprehensive planning and integration were required to address Melbourne’s problems.
Xing Dao, Israel and Melbourne are but three of a growing list of cities and countries that are fundamentally rethinking water in the city/region/country in terms of efficiency, urban design and urban security. This list includes Las Vegas in the U.S., Perth and Gold Coast in Australia, Tenerife and Madrid in Spain, and Xian and Tianjin in China.
Through these case studies and analytical work involving a number of task groups, it is evident that the design of highly efficient water systems within the city—and their linkages to other users of water outside the city—can only be achieved through integrating water system design with city and regional planning.
Also evident is the fact that the traditional objectives for water system design in the city—capacity, health and safety—need to be augmented with some new and important objectives. They include:
The adoption and implementation of these objectives will need to be widespread by 2050.
Finally, work to date through the IWA Cities of the Future program has revealed the enormity of the challenge of applying these concepts to the yet-to-be built water systems in the lower half of the income scale of developing countries. The basic question is whether it is possible to design highly efficient yet low-cost systems that can be implemented incrementally, in line with increases in the community’s ability to pay over time.
Looking at the challenges ahead, one could conclude that we are facing a very dark future. I believe instead that we face a basic choice: we can continue down the lane marked “business as usual” and watch a year-by-year decline in heath and well being of all but the wealthy, marked by increasing water pollution and growing shortages of all thing related to water.
Alternatively, we can face up to our challenges and create a fundamentally brighter future by dramatically increasing the efficiency with which we use water in all sectors. Paradigm shifts in urban water management of the nature described above will enhance the water and economic security of cities and could, through innovation, reduce both the capital and operating of urban water systems thereby lowering the barriers to entry in developing countries.
The choice is ours.
Keywords: Water scarcity Urbanization Development, Urban water systems, Joint use, Innovation, Energy, Agriculture
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1 Comment on this article.
Thanks for this interesting article, I especially enjoyed the exploration of links between agriculture and urban water use. In terms of water quantity, the vast majority of water resources (~70%) goes towards agriculture. More urbanization may not change that unequal distribution between food-water and drinking water because urbanites’ food-water footprint will increase proportionally to population growth. However, the fact that we use vastly more water to grow our food than we do to drink strengthens Mr. Reiter’s most astute argument - increasing agricultural efficiency will go a long ways towards ensuring a more reliable drinking water supply. A small increase in agricultural efficiency may lead to a large increase in drinking water reservoir capacity.
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