By Jeff Opperman, The Nature Conservancy
Most people love blue skies and clearly prefer being drenched with sunshine rather than rain. The sunny regions of the country are booming as people move to where they know the calendar will be filled with blue-sky days.
But think a bit more about what a blue sky means. In other words, think about the absence of clouds.
If you know where your water comes from, you know towns and cities draw their water from rivers, lakes or groundwater. These sources are replenished by rain and snow, and we all know that rain and snow come from… clouds.
So clouds are like water-delivery trucks rolling into town. What does this say about places with clear, blue—and cloud-free—skies?
To better understand the relationship between clouds and water supply, I did a very quick analysis of some readily available numbers.
- First, I looked at SustainLane’s ranking of the sustainability of major U.S. cities’ water supply systems. These rankings provide an indication of how reliable or, on the other hand, how stressed or vulnerable a city’s source of water is.
- Second, for each city I looked at the average number of cloudy days per year, from the National Weather Service.
The result shows that the most water-sustainable cities are the most cloudy, and the least water-sustainable cities are those with the most sun. (See the graph on the next page; the most water-sustainable cities have low numbers and are on the left side of the graph.) This correlation will not shock anyone who remembers the hydrological cycle from high school.