The Perfect Storm

The Brookings Institute continued their series on Metropolitan America with the article Population surging in drought-stricken areas. Their observation is that the areas of greatest population growth are coincident with the areas of extreme drought. We reproduce their two maps below.

We have been following the drought aspect for over a year for California (read California is the Canary and the links within it) and Nevada (read Jeopardy Question: This Body of Water Determines the Fate of the Modern Day Anasazi). Many of the counties with exceptional drought condition (the darkest red area in Figure 1) are the counties registering the greatest population growth as is seen in the dark blue areas of Figure 2. Unless otherwise noted, any emphasis is ours.

Figure 1. County level drought conditions in the US.

Source: The Brookings Institute; United States Drought Monitor.

Figure 2. County growth, 2000 to July, 2014.

Source: The Brookings Institute; U.S. Census data.

Figure 2 shows aggregate population growth over a 14 year period. It doesn’t give us any idea of likely future growth. However, Figure 3 shows actual and project population figures for 10-year periods over the century from 1950 to 2050 giving us an idea of the shape of the growth curve. Growth is linear with an inflection point around 2000 where the rate of growth slows slightly (slope of the line) The rate of growth of water demand exhibits a similar behavior although with a lesser growth rate.

Figure 3. Projected growth of population and water use in California.

Source: The Press Enterprise.

The Climate Perspective on Drought

A National Geographic article, Drying of the West, summarizes the climate aspect:

… tree rings testified that in the centuries before Europeans settled the Southwest, the Colorado basin repeatedly experienced droughts more severe and protracted than any since then. During one 13-year megadrought in the 12th century, the flow in the river averaged around 12 million acre-feet, … Such a flow today would mean serious shortages, and serious water wars.

In fact research shows that The wet 20th century, [was] the wettest of the past millennium.

On the other hand, The Verge, also citing NASA scientists in an article titled The southwest will be drier over the next century than any time in the past millennium, states that climate models show the next century will be drier than anything the region has seen in the past millennium. The article also notes that:

The study didn’t control for human factors, however, which could potentially render the region even drier if water use from habitation and agriculture continues to grow.

Putting It All Together

The key points are:

  • Almost all of California is in the most exceptional drought conditions category.
  • The climate of the Southwest may be returning to a drier regime that is more normal of recent times.
  • The Southwest could be in the early stages of a megadrought (see: Another Dry Essay for discussion of megadroughts) and will certainly be drier in the next century if climate models are accurate (which they may not be; read: Global Warming Update).
  • The population of the region is growing rapidly and water demand is increasing.
  • Expect water wars between states, between cities and farmers and perhaps even countries if rivers flowing into Mexico are dry before they get there.

The economic consequences will be broadly felt as California agricultural production drops off. Water rationing may be the factor to slow population growth.

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