Asia and the Pacific has the highest annual water withdrawal of all the world’s regions, owing to its geographic size, large population and irrigation practices. Expanding urban populations and changing demand patterns, combined with the impacts of climate change, are challenges to water security that need to be addressed through more efficient use of water and shared approaches to water resource management.

Water security is an increasingly important development issue in Asia and the Pacific, where growing populations and rapid urbanization have expanded demand and competition for, as well as driven reallocation of, water resources. The demand pattern for water is changing with an increasing proportion of water being used in the industrial and domestic sectors, concurrently with proportional reduction in water use in the agricultural sector. The relative and absolute increase in the urban population means that more food will need to be produced by fewer people in the agricultural sector in future and likely with more intensive farming practices, which highlights the need to improve efficiency in water use.

Water quality is also impacted by urbanization. Rapid urbanization has resulted in the pollution of water bodies in many urbanized areas of Asia and the Pacific, where wastewater has been discharged untreated into natural water systems or leached into ambient soils. Pollution of water bodies will continue to rank among the critical issues impacting water security as more than half of the population of the region is expected to live in towns and cities by 2030.¹

Climate change impacts the hydrological patterns and freshwater systems, thereby posing a risk to overall water security. Climate change results in changes in spatial distribution and shifting of precipitation patterns, such as the start of the rainy season and snowmelt. Across the world, changes in weather patterns have increased the occurrences and intensities of extreme events of rain, floods, droughts and cyclones, such as those afflicting Australia, China, Myanmar and Pakistan in recent years. Besides increasing the occurrences and intensities of extreme weather events, climate change causes sea level rise, which in turn increases salt levels in river deltas and lakes, further diminishing the availability of fresh water.

Unfortunately, data related to water availability and use are scarce. As water scarcity is becoming a critical problem in Asia and the Pacific, the need for more reliable statistics with greater and more frequent coverage is vital to countries in improving their water governance.

Water availability

Total long-term annual average renewable water resources represent the maximum theoretical amount of water expected to be available under natural conditions, excluding human influence and the effects of climate change. Renewable water resources are not expected to change over the long term, being a combination of the ambient surface-water, groundwater and soilmoisture factors.

Across Asia and the Pacific, water availability varies greatly. South-East Asia has more than 150,000 cubic metres of available water per square kilometre, whereas the Pacific subregion (including Australia and New Zealand) has less than 30,000. Both the availability of water and the population size are important in forecasting access to water supplies. The Pacific has high per capita water availability with around 50,000 cubic metres of water available per person annually. Other Asia-Pacific subregions with high population densities have limited water availability per capita; for example, East and North-East Asia and South and South-West Asia have less than 2,500 cubic metres per capita per year.

Figure II.5 – Availability of natural water resources per unit area by world, region and subregion, 2008

Figure II.6 – Availability of water resources per capita by world, region and subregion, 2008

Water utilization

Asia and the Pacific has the highest annual water withdrawal of the world’s regions. That scale is attributed to the geographic size and population of the region and to extensive and intensive irrigation practices. In the region, South and South-West Asia and North and Central Asia (excluding the Russian Federation) have the highest relative water withdrawals.

In all subregions of Asia and the Pacific, between 60% and 90% of water withdrawal is used for agriculture. At the regional level, the proportional use for domestic and industrial purposes rose from 13% to 22% between 1992 and 2002. Within the subregions, water-use patterns differ dramatically, reflecting differential levels of economic activity. For example, within South- East Asia, water use for agriculture in Myanmar and Cambodia is above 90% of the total use, whereas in Malaysia agriculture accounts for just over 60% of water use.

Worldwide, for more developed economies, the proportional share of total water resources used in agriculture has declined concurrently with the proportional increase in total water use for nonagricultural sectors, owing to increase in multiple economic activities.

The relationship between water availability and water use in each river basin must be balanced to preserve water security. In shared basins, imbalance between water availability and demand for its use can threaten multilateral cooperation and harmony among riparian States. Shared water management is therefore essential in preventing conflict as well as ensuring water security, especially in the basins of the Aral Sea, Ganges-Brahmaputra-Meghna, Tarim and Mekong, each of which is shared by five to eight countries.

Figure II.7 – Proportional use of water withdrawals by sector, regionally and subregionally, 2002

Figure II.8 – Proportional use of water withdrawals by sector, South-East Asia and North and Central Asia, 2002

Water “hotspots”

The multiple water-related challenges of access, depletion, pollution and disaster in the Asian and Pacific region represent different components of water security. A country facing a combination of those challenges is highly vulnerable to water scarcity, which may impede progress in implementing its development agenda. Water scarcity affects food security through reduced availability of water for irrigation. It affects human health through the loss of capacity to dispose of human waste that in turn results in contaminated water supplies and increased prevalence of waterborne pathogens. Persons living in poverty, especially women, can suffer severe consequences from inequitable access to health care and food. Ultimately, environmental sustainability is threatened as countries deplete their water sources.

Good water governance is a vital element of water security. The actual access to water that any citizen may have can vary greatly within a country and depend largely on the time of year.

To facilitate region-wide priority-setting as well as decision-making at the national level, ESCAP has identified hotspots of multiple water-related challenges, as illustrated in the accompanying figure. Hotspots are countries, areas or ecosystems with overlapping challenges of poor access to water and sanitation, deteriorating water quality, inadequate water availability and increased exposure to climate change and water-related disasters.

As the figure shows, many Asian and Pacific countries face challenges related to water. At the same time, climate change, population growth and increasing urbanization will likely exacerbate those challenges. Therefore, continuous monitoring, priority-setting and decision-making at the national and multinational levels are a vital support for implementing national development agendas.

Water “hotspots” in Asia and the Pacific²

² Details of the measures used to identify water hotspots and criteria for threat ranking are contained in United Nations ESCAP, Asian Development Bank and United Nations Environment Programme. Preview Green Growth, Resources and Resilience Environmental sustainability in Asia and the Pacific, 2010. Available from http://www.unep.org/greeneconomy/Portals/30/docs/ESCAP%20Green%20Growth.pdf.