GLOBAL: Climate change's threat to water needs more study

Thursday, October 23, 2008

Models to predict the impact of climate change on potable water and the management of wastewater are needed to deal with the expected increase in water-related illnesses as result of global warming, says a new policy brief by the United Nations University (UNU).

"We need greater investment in the development of models to aid decision-making, reduce uncertainty and augment costly monitoring programmes," said Corinne Wallace, a leading water health researcher at UNU's International Network on Water, Environment and Health, and one of the authors of a new policy brief.

"Combining these efforts with a vulnerability map for water-associated diseases can form the basis for evidence-based policy development," she said. "Validated models need to be developed that will predict the impact of climate change on water and wastewater infrastructure, water availability, water quality and waterborne/water-associated diseases."

The results could be used for policy development, intervention, adaptation and mitigation purposes, as well as determining the effects on achieving Millennium Development Goals (MDGs) and global migration patterns.

Climate change is expected to bring more frequent and intense rain to many places, leading to floods and shallow subsurface water flow, which can mobilise pathogens and other contaminants, the brief noted. 

Higher temperatures could also change the rates of reproduction, survival and infectivity of various pathogens. "Even if not directly linked to health, these threats can have a devastating effect on the ecosystem, indirectly threatening water supplies."

The Intergovernmental Panel on Climate Change (IPCC) has said that global warming will affect not only the function of water infrastructure, but operation and management practices as well, according to the UNU brief.
"Generally, water treatment plants and distribution systems are built to withstand weather events of a given return period or probability (e.g. the 100-year flood). Under changing climate conditions, these return periods are likely to alter, increasing the likelihood of and frequency at which drinking- and wastewater-infrastructure systems will be overwhelmed."

Water and sanitation services need to be scaled up to address the impact of climate change, the authors of the brief said. Flooding can also affect chemical storage and sewage facilities, compromising water supply quality. 

Sea-level rise will affect groundwater aquifers in coastal areas and flood low-lying areas, reducing freshwater availability. It is estimated that by 2030 the risk of diarrhoea will be up to 10 percent higher in some countries due to climate change.

Greater migration as a result of water stress or increased food insecurity means that diseases will be transported to other regions, where they may or may not be able to survive, potentially exposing host communities to new diseases. "Policies at various levels and their implementation, however, do not reflect this principle," the authors noted.

"Improved access to clean water can reduce diarrhoea and waterborne diseases by at least 25 percent; improved sanitation is accompanied by more than a 30 percent reduction in child mortality. This urgent global challenge is pragmatically achievable, politically feasible and ethically important."