The Future of Water from the IPCC

The Intergovernmental Panel on Climate Change just released a report entitled Climate Change and Water. Here are some of its findings concerning climate change's direct effects on water:

Floods and droughts:

• Between 1996 and 2005, the number of great inland flood catastrophes was twice that of each of the decades between 1950 and 1980. During the same time, the monetary costs of the floods increased fivefold compared to other decades.

• Floods are the most commonly reported natural disasters, affecting 140 million people a year. Global warming, which will disturb precipitation patterns, increase water runoff, decrease natural storage capabilities (e.g. icecaps), and raise sea levels, will also increase the number of floods.

• Increased precipitation will not be evenly distributed, and many areas will actually see a decrease in rainfall. Since the 1970s, the number of very dry areas doubled. The frequency of extreme droughts will double and the average length of a drought will increase six times.

• Proportion of land experiencing extreme drought at any given moment will increase between 10 to 30-fold.

• The “100-year flood” is projected to occur every 2-5 years in the future. At the same time, the “100-year drought” is expected to occur more than once every 10 years.

Infrastructure and pollution:

• Total annual river runoff is expected to increase due to global warming because icecaps will melt earlier and rainfall in some areas will increase. While this frees up fresh water, if there is a lack of storage and capture ability (e.g. dams and reservoirs), the water will go to waste when it is needed in dry seasons.

• Even though higher levels of water flow are predicted, these periods will be relatively short. Longer periods of low flow, along with higher temperatures, will increase pollution by sediments, nutrients, pesticides, pathogens, and salts. Algal blooms are expected, and because of low flow, water systems won’t be as capable of diluting pollutants.

• And, as always, water issues can spark inter- and intra-state conflict.