Sponge City: Is it another term on the growing list next to:
- future proofing,
- smart and so on?
What is a Sponge City?: A re-imagining of the urban environment, where almost every raindrop is captured, controlled and reused. The Sponge City indicates a particular type of city that does not act like an impermeable system, not allowing any water to filter through the ground, however more like a sponge, to actually absorb the rainwater. This water is then naturally filtered by the soil and allowed to reach into the urban aquifers. This allows for the extraction of water from the ground through urban or peri-urban wells. This water can be easily treated and used for the city water supply. This also contributes towards making the Green Spaces as Adaptive Measures to Flooding in the Face of Climate Change.
Sponge cities has actually gained a huge amount of support recently, especially in China. The Chinese government has already chosen 16 pilot cities and allocated to each of them between 400 and 600 million yuan for the implementation of innovative water management strategies that would gradually transform these cities into “Sponge Cities”.
Key issues the Sponge City wants to solve?
There are mainly five drivers of urban water crisis (population, rising middle class, climate change, tainted water, leaks) according to a recent book by Seth M. Siegel titled, Let There Be Water: Israel’s Solution for a Water-Starved World. The sponge cities work towards solving these crises by doing the following:
- Less water available in urban and peri-urban areas. Since less rain water is allowed to filter through the urban soil, less water is available to be extracted from aquifers in urban and peri-urban areas.
- Polluted water discharged into rivers or the sea. Much of rainwater mixed with wastewater is discharged untreated into rivers. The more impermeable the city is, the more water will be mixed with wastewater and will not be able to be treated but discharged directly into rivers. This increases the level of pollution of local water bodies.
- Degradation of urban ecosystems and green areas due to sprawling. This leads to a considerable loss of urban biodiversity, a drop in available green areas for natural ground filtration of storm water, a decrease in CO2 capture by plants, fewer spaces for natural cooling through urban green microclimates and generally less liveable, healthy, comfortable and attractive public spaces.
- Increase in the intensity and frequency of urban flooding As the absorbing capacity of the urban surface is decreased, storm flooding risk is increased. Flooding leads to increased groundwater pollution and has considerable impact in terms of damage to properties and health related issues. The most recent examples are the flooding incidences in the US and Chennai, the southern Indian capital city of the state of Tamilnadu in 2015.
Sponge City needs in practice:
A sponge cities needs to be abundant with spaces that allow water to seep through them.
- Contiguous open green spaces, interconnected waterways, aquifers, channels and ponds across neighborhoods that can naturally detain and filter water as well as foster urban ecosystems, boost biodiversity and create cultural and recreational opportunities.
- Green roofs that can retain rainwater and naturally filters it before it is recycled or released into the ground.
- Porous design interventions across the city, including construction of bioswales and bioretention systems to detain run-off and allow for groundwater infiltration; porous roads and pavements that can safely accommodate car and pedestrian traffic while allowing water to be absorbed, permeate and recharge groundwater; drainage systems that allow trickling of water into the ground or that direct storm water run-off into green spaces for natural absorption
- Water savings and recycling, including extending water recycling, particularly of grey water at the building block level, incentivize consumers to save water through increased tariffs for increase in consumption, raising awareness campaigns, and improved smart monitoring systems to identify leakages and inefficient use of water.
Benefits of a Sponge City:
The obvious short and long term benefits include:
- More clean water for the city. Replenished groundwater and thus greater accessibility to water resources for the cities.
- Cleaner groundwater due to the increased volume of naturally filtered storm water.
- Reduction in flood risk as the city offers more permeable spaces for the natural retention and percolation of water.
- Lower burdens on drainage systems, water treatment plant, artificial channels and natural streams.
- Greener, healthier, more enjoyable urban spaces. Greener urban spaces improve quality of life, create more pleasant landscape aesthetics and recreational areas that are enjoyable and attract people.
- Enriched biodiversity around green open spaces, wetlands, urban gardens and green rooftops
- Solves the Twin Crises of Energy and Water Scarcity for most major and upcoming cities across the world.
Countries like India and the US should take a cue from China and learn from their experience for implementing the Sponge Cities.
Disclaimer: This article has been adopted from the original article that appeared in the Power to the People blog of World Future Council. All views and hyperlinks provided have been taken from my past posts and information available online. Please acknowledge the appropriate sources while citing.
It is widely agreed that initiating dialogue and cooperation on water and related issues at all levels, along with the identified stakeholders, is one approach (out of many) that needs to be emphasized, scaled and strengthened even further. That said it means that underrepresented groups such as women, the grassroots communities and civil society organizations cannot be left out from the dialogue and decision making process. At the same time it cannot be ignored that both technical and political solutions are needed to reap the benefits and alleviate the danger from proposed solutions, especially the ones around trans-boundary infrastructure projects.
International Cooperation in water management:
In 2003, the United Nations General Assembly declared 2005 to 2015 to be the decade of “water for life”. In summing up the last 10 years, it is noted that “water cooperation” had been promoted widely. Water cooperation is described to have the potential to enable peace and sustainable development. We cannot ignore the following too for making the cooperation more effective:
- Untapped Waterways
- Making Treaties More Comprehensive and Responsive
- Information Helps, But Political Will and Process are Crucial
- Overcoming the status quo
- What kind of cooperation and for whom
- Trans-boundary cooperation
Way forward until 2025:
Water cooperation and issues and challenges surrounding it being global, it is true that no one country or approach can solve the rapidly increasing problems around water. Water related issues and challenges have a wide range such as the availability of water in the natural and man made channels, clean and safe drinking water for all, water for irrigation, wastewater management in the wake of rapid urbanization and so on to name a few.
Looking at 2025, we will need to consider the opportunities such as market based approaches, economical, geo-political, non-tangible and non-materials as well as service based value attached to the water and water resources. Esoteric approaches may not work in these situations and settings.
According to a new research, more than 40% of the world’s great cities supplied by surface water could become freshwater vulnerable to shortages and drought by 2040. More than 3 out of 10 were already vulnerable in 2010, the study states.
For the first time in history, more than half the world’s population is now concentrated in cities, and this proportion is predicted to increase to two-thirds by 2050. Cities expand near abundant water supplies. As population explodes, so does the demand. The environmental flows (E-Flows) remain much the same.
Some major cities are already under drought stress. Chennai and Hyderabad in South India had to be supplied with tankers in 2004 and 2005 and so was Delhi in North India. These cities in India depend on River Krishna and River Yamuna’s freshwater resources. Delhi also gets part of it’s supply from neighboring states of Rajasthan and Haryana. São Paulo in Brazil in LatAm is now at a crisis point and cities in CA are struggling with unprecedented droughts.
Demand and supply:
Environmental scientist Julie Padowski and Steven Gorelick, director of the Global Freshwater Initiative at Stanford University in California, analyzed supplies to 70 cities in 39 countries, all of them with more than 750,000 inhabitants, and reliant on surface water.
Vulnerability is the failure of an urban supply basin to meet demands from human, environmental and agricultural users, and they set the supply target as 4,600 litres per person per day. This factors in “virtual water”, defined as the total volume of water needed to produce and process a commodity or service.
They proposed three different kinds of measure of supply.
- If a city failed to meet one or two of these metrics, it was considered threatened.
- If it failed to meet all three, it was rated as vulnerable.
The six cities that will begin to face water shortages are Dublin in Ireland, Charlotte in the US, Ouagadougou in Burkina Faso, and Guangzhou, Wuhan and Nanjing in China. Curiously, none of the cities in India have been listed to be freshwater vulnerable in the assessment. Most of the cities that are already vulnerable rely on reservoirs, and the study implies that urban planners will need to think about
- More reservoirs,
- Deeper wells or
- Desalination plants, or
- Will have to contemplate the diversion of rivers from somewhere else.
The article states that the scientists cannot rely on rainfall data because, the network of dedicated satellites “fails to meet operational data needs for flood management”.
4 of the 10 satellites have exceeded their design life. There are already weak spots in the network, especially in developing countries, which means that floods could take people by surprise. When 4 fail to deliver, the potential for catastrophe will be even worse. The scientists call for better international co-ordination of satellite replacement.
Vulnerable versus threatened status:
For both categories reservoir and river supplied cities were considered vulnerable, if all demand thresholds were violated. If a city had one or two but not all three metrics exceeding a threshold, then it was considered threatened, as these supplies may no longer be able to support urban demand without causing damage to agriculture, the environment, or both. The scientists referred to a city as susceptible if it has either threatened or vulnerable status; the number of susceptible cities is the sum of those that are threatened or vulnerable. Finally, cities were considered non-threatened if no demand thresholds were violated.
Importantly, the scientists did not factor in climate change, which might make conditions worse. Instead, they simply considered current demand and supply, and then projected demand in 2040.
Of the 70 cities, they found that 25 (36%) could already be considered to have become vulnerable by 2010. By 2040, this number will grow to 31 (44%).
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