The impact of climate change on water security and flood risk

Climate change is expected to change rainfall patterns globally, with some regions seeing an increase in total rainfall, and others a decrease, so the effects will vary significantly from place to place. Many areas that are currently dry, in the sub-tropics and mid-latitudes, are expected to experience less total rainfall, while wetter areas at higher latitudes are expected to see an increase in rainfall.

Changing patterns of sea surface salinity have already been observed. These changes are driven by changes to evaporation and precipitation (rainfall).  

Warmer temperatures also dry out soils by increasing the rate of water that is evaporated from the land surface. Dryer soils are expected in the Mediterranean, south-western USA and southern Africa particularly.

In addition, the amount of water vapour in the atmosphere is increasing as temperatures go up, meaning that rain is expected to fall in shorter, heavier bursts, with an increase in the frequency and intensity of heavy rain globally. There is already evidence of this where sufficient observations are available.

Researchers at Imperial are looking at the impacts that changes to the water cycle are already having globally, as well as thinking about how the risks of these impacts might increase in the future.

The Ganges river basin in India

In the Ganges Basin in northern India, irrigation practices are already reducing water availability for farmers. In the future, changing rainfall patterns and dryer soils are expected to intensify the problem, at the same time as demand for water rises due to increases in population and rapid industrialisation. Any possible impact of climate change on the Indian summer monsoon is still the subject of research. Read more

Urban flooding

In towns and cities, drainage is often obstructed by hard surfaces such as paving stones and tarmac. Urbanisation, along with changing rainfall patterns, is increasing the risk of pluvial (surface water) flooding in many cities around the world. When surface water flooding occurs in cities already vulnerable to river flooding the impacts on local people and businesses can be much worse. Researchers at Imperial College London are currently carrying out some research focusing on flood risk in Greater London, Rafina in Greece, and Coimbra in Portugal. Read more

Glacier melt and water security

As temperatures increase, glaciers across the world are shrinking. Remote upland communities in Bolivia, Peru, Chile and Argentina rely on seasonal glacier melt to boost water supplies in the summers. As glaciers decrease in size there will be less water available during the seasonal melt cycle, leaving these isolated communities even more vulnerable. Read more