Urban Water Security in Asia

The Asia-Pacific region is one of the most rapidly urbanising regions in the world. Currently, seven of the world‘s mega-cities (cities with populations of 10 million or more) are located in Asia-Pacific. However, by 2025 there will be 21 mega-cities in the region. With three out of four Asia-Pacific countries already experiencing water scarcity, urban centres in the region will face threats to urban water security as a result of climate change and the various impacts of urbanisation, where urban water security is the ability of a population to access good quality water of suf¬ficient quantity necessary for sustaining livelihoods, human well-being and socio-economic development.

Climate change threatening urban water security

Climate change is likely to decrease urban water security in the Asia-Pacific region, with increases in the frequency and magnitude of floods and droughts. In particular, flooding will decrease the availability of good quality water through contamination of surface and groundwater supplies, while droughts decrease the quantity of water available and increase demand for water for cooling and drinking. Climate change is projected to impact on urban water security in the following ways:

• Precipitation and storm events: Storm events (flooding) wash pollutants from urban areas into surface water bodies, as well as contaminate groundwater supplies.
• Heat-island effects: Air temperatures in urban areas compared to surrounding rural areas are 3.5 to 4 degrees Celsius higher. The result is an increase in demand for water for cooling and drinking.
• Heat waves and droughts: During heat waves and droughts, demand for water increases (drinking water and water for cooling). In addition, higher temperatures mean algal levels increase, which degrades the quality of water resources and leads to increased treatment costs and energy use in the treatment process.
• Sea-level rise and coastal flooding: Globally, cities are mainly concentrated in coastal zones, leaving a large portion of the world’s urban population exposed to the risk of sea-level rise and intensifying storm-surges, which contaminate groundwater supplies and damage water infrastructure.

Impacts of urbanisation on water security

The Asia-Pacific region is one of the most rapidly urbanising regions in the world, with urban populations growing at 2.3% per annum compared to the global average of 2%. Currently, there are 10 mega-cities in the region (cities with 10 million or more residents). This will increase to 21 by 2025 leading to significantly increased demand for water resources. In addition, water quality is threatened by land-use changes that degrade ecosystems, as well as increased pollution. Patterns of urbanisation are projected to impact water security in a number of ways:

• Increase in population: Rapid population growth has increased demand for water for both domestic and non-domestic use, frequently leading to over-exploitation of water resources. This results in excessive withdrawals and water scarcity.
• Land-use change: Urbanisation (urban sprawl or encroachment into river basin catchment areas) lowers the availability of good quality water of sufficient quantity through direct (point source) pollution (industrial, domestic wastewater) and indirect (non-point source) pollution (pathogens, organic and inorganic).
• Degradation of ecosystems: Over-exploitation of ground and surface water degrades ecosystems and their services (e.g. reduced ability to purify water etc.).
• Competition: Over-exploitation can lead to inter-sectoral, inter-regional and even international competition over scarce water resources.

Demand management to ensure urban water security

For all of these reasons, the Asia-Pacific region will be characterised by growing water scarcity over the coming decades, and policymakers will need to make full use of demand management techniques to mitigate these challenges, where demand management involves better use of existing water supplies before plans are made to further increase supply. In particular, demand management promotes water conservation, during times of both normal conditions and uncertainty, through changes in practices, cultures and people’s attitudes towards water resources. In addition to the environmental benefits of preserving ecosystems and their habitats, demand management is cost-effective compared to supply-side management because it allows the better allocation of scarce financial resources, which would otherwise be required to build expensive dams and water transfer schemes from one river basin to another.