From Meteorology to Mitigation: Understanding Global Warming

Shifting Water Resources


Water is essential to life and it is essential to human civilization. Either too much or too little is a problem. And as we have seen in Lesson 7, climate change may, ironically, give us both.

Left: example of flooding; Right: example of drought
Figure 9.12: Examples of Flooding (left) and Drought (right).
Credit: Both photos are in the public domain

As atmospheric circulation patterns and storm tracks shift, and changing rainfall patterns combine with the effects of changing evaporation and changing runoff patterns, one thing is for certain—water resources will be impacted. The greatest threat is the uncertainty of increasingly irregular and shifting patterns of precipitation.

In some regions, like the desert southwest of the U.S., climate change threatens to reduce fresh water availability due to both decreased winter rainfall and snowfall that ultimately feeds major reservoirs through spring runoff. Current projections are that Lake Powell, which provides southern Nevada with much of its fresh water supply, may run dry within a matter of decades, extrapolating recent drying trends. These decreases in water supply are on a collision course with demographic trends, as population centers, such as Las Vegas and Phoenix continue to expand in size. Similar scenarios are likely to play out in Southern Europe and the Mediterranean, the Middle East, southern Africa, and parts of Australia.

Other regions, meanwhile, are projected to get too much water. Bangladesh, already threatened by rising sea level, is likely to see increased flooding from the intense rainfalls expected with a warmer, more moisture-laden atmosphere.

Worldwide effects of shifting water resources
Figure 9.13: Shifting Water Resources [Enlarge].
Click Here for Text Alternative for Figure 9.13

The negative impacts of changing precipitation patterns outweigh the benefits. For example, the increases in annual rainfall and runoff in some regions are offset by the negative impacts of increased precipitation variability, including diminished water supply, decreased water quality, and greater flood risks. Ther is hope, however, that in some cases, adaptations (e.g. the expansion of reservoirs) may offset some of the negative impacts of shifting patterns of water availability.

Credit: Mann & Kump, Dire Predictions: Understanding Climate Change, 2nd Edition
© 2015 Pearson Education, Inc.