Water stress in the United States This image comes from a paper…

Water stress in the United States

This image comes from a paper just published in the journal Environmental Research Letters, showing research from a group led by scientists at CU Boulder. The color-coding shows areas in the United States that the paper finds to be “Water-stressed”.

This paper and this map give a very interesting look at how water is used in the United States. Obviously, the expected result is that there are many areas in the west that are water-stressed, but there are many seemingly-surprising areas around the country that show up as water-stressed as well.

To come up with this map, the authors had to define the term “stress”, and they were conservative in that choice. Areas appearing in yellow on this map are areas where society’s demands for water equal the total available flow from precipitation and rivers, areas in red show spots where demand for water significantly exceeds those supplies. The authors could have made many more areas appear yellow; in general, when societal demands for water become greater than 40% of river flows, the water withdrawals begin to have a significant impact on life in those rivers, while yellow in this plot shows areas close to 100%, so clearly the definitions used here are conservative ones.

The areas in the west are drawing down significantly more water than is available in their streams and that shows up very well on this plot. It definitely does display how vulnerable areas in California, Nevada, Arizona, New Mexico, Utah, and Colorado are to drought; they’re using several times the available water supply at present. Since there isn’t water available from rain to meet the current demand, those are areas where water is either supplied through aqueducts or pumped out of the limited resource that is groundwater.

What might surprise in this plot is that there are areas of water-stress in the eastern U.S., in areas that receive plenty of rain, including one where this author is sitting. Many of these localized areas of stress are actually driven by power generation. Based on numbers they compile and other studies, they estimate that the U.S.’s water demands can be broken down into agriculture (37%), thermoelectric power generation (41%), and municipal requirements (19%).

Many of the sites in the eastern U.S. that are water-stressed are driven to that state by the requirements of power generation. These plants take in very large amounts of water; enough to stress watersheds in those areas significantly. There have been multiple reports in these areas over recent years of power plants shutting down temporarily as a consequence of low water supplies; the fact that power generation is able to be a major driver for water stress illustrates how at-risk these areas might be for economic losses in the event that precipitation patterns continue to change as a consequence of climate change.

Finally, this type of map should drive home that even in wet areas; there are major gains available from conservation of electricity or generation of electricity from methods other than fossil fuels. It doesn’t just cut down on CO2 and air pollution; it also protects local water supplies.

-JBB

Image credit and original paper:
http://iopscience.iop.org/1748-9326/8/3/035046/article

Press report:
http://newswatch.nationalgeographic.com/2013/10/09/more-water-stress-than-meets-the-eye/

Got a very hypothetical question here. Suppose we can levitate a sphere of 50 gallons of water in mid air – maybe someone was waterbending – in the middle of daylight. Would it appear blue? If not, would it appear bluer with larger volumes?

I believe you’re correct – it would not appear blue itself, although a blue sky in the background would make it have something of a blue background to it. Eventually a big enough volume to scatter light on its own and you might get that effect to start.