The article pasted below is by Jessica Orwig, a science writing intern at the American Geophysicist Union; it reports on a study led by Wouter Buytaert, of Imperial College London, which took a look at the population and water availability dynamics in the tropical Andes. The abstract of that study is as follows:
Globally, water resources for cities are under increasing stress. Two main stressors are climate change and population growth, but evaluating their relative impact is difficult, especially because of the complex topology of water supply. This is especially true in the tropical Andes, which is a region with strong climatic gradients and topographical limits to water resources. This paper presents an evaluation of both stressors on water resources in a geospatial framework to identify gradients in water availability that may lead to conflicts over water use. We focus on 4 major cities in, or receiving water from the tropical Andes… In all cases, the median projection of climate change suggests a relatively limited impact on water availability but uncertainties are large. Despite these uncertainties, we find that the expected demographic changes are very likely to outpace the impact of climate change on water availability and should therefore be the priority for local policy making.
Water scarcity in the tropical Andes: Population growth outweighs climate change
As the Earth’s surface warms, climate models predict that the amount of fresh water for human consumption will likely decrease in parts of the globe. While that prospect looms for many cities around the world, a new study finds a more imminent threat to water supplies of cities in the tropical Andes, such as Lima, Peru and Quito, Ecuador.
“Despite all the uncertainty of the future impact of climate change, the impact of population growth is much bigger,” said Wouter Buytaert of Imperial College London, an environmental engineer and lead author of the study. This could mean harsher times ahead for millions including the 7.6 and 2.2 million inhabitants of the fast growing cities of Lima and Quito.
Some parts of the tropical Andes, a region along the northwestern coast of South America, already lack sufficient water to meet demand. To help policy makers combat this water scarcity, Buytaert and his colleague, Bert De Bièvre of the Consortium for the Sustainable Development of the Andean Ecoregion in Quito, Ecuador, compared the two main drivers of water depletion in that region – climate change and population growth.
The scientists used 19 climate models to project how climate change may affect urban water resources of the tropical Andes over the next 60 years. While the most pessimistic findings from models projected an average water depletion of up to 10 percent of current values, some optimistic outlooks estimated a 10 percent increase in water availability.
When the researchers separately modeled the impact of population growth, they found a drop of 38 to 62 percent in the amount of water available for each person. In their projections, the demand for more water as populations increase surpasses the amount of water lost through evaporation from warmer temperatures due to climate change.
To read the full article, please click here: http://blogs.agu.org/geospace/2012/07/17/water-scarcity-andes-population-growth/