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We Must Stop Ignoring the Role of Population in Our Water Problems

Addressing water problems comes down to three choices: increase the water supply, decrease the water demand per person, or change the number of people.
 
 
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Population discussions raise lots of hackles. And they bring the crazies out of the woodwork like termites when the Orkin Man appears. But I hope to post a series of pieces on population and water because we must stop ignoring the role of population in our environmental and water problems.

The amount of water on Earth is fixed. We're not losing it to space and we're not getting more (with negligible exceptions). The amount of water in a river basin or watershed is fixed. It goes up and down with natural variability, and it may change over time due to climate changes, but water is a renewable resources and our use of it does not affect the amount we get next year.

But population is not fixed. It is growing, and growing rapidly in some places. As a result, the amount of water available per person ("per capita") is declining. Here is a simple example: assume that the average flow of water in a river basin is 10 million acre-feet per year and the population using that water is 20 million people. Then on average, the water available for use is around 450 gallons per person per day, if you could use it all (which would, of course, destroy the river ecosystem, but that's another topic). If the population of the basin doubles to 40 million, the water availability per person drops in half, to around 225 gallons per person per day. If the population doubles again, water availability drops to just over 100 gallons per person per day.

The math is easy, but the consequences can be severe: abundance can become shortage. In simple terms, addressing water problems in the face of population growth come down to three choices: (1) increase the water supply, (2) decrease the water demand per person, or (3) change the number of people. Water policy in the past century focused only on increasing supply. Most of the work of the Pacific Institute has focused on the second because we believe the options for new supply in most places are increasingly limited, expensive, and environmentally damaging, and we see enormous potential for reducing demand. Almost no discussion, anywhere, focuses on the third choice. But the failure to address population in the long run will be disastrous. And the "long-run" is no longer so far away.

Water (Population) Numbers: While total water availability remains fixed, the population of the United States has grown from around 150 million in 1950 to over 305 million today. The population of California in 1950 was 10.5 million; today it is around 37 million. The population of the state of Georgia in 1950 was under 4 million; today it is approaching 10 million. The population of Jordan in 1960 was around a million; today it is 6 million. The population of Israel in 1960 was just over 2 million; today it exceeds 7 million. The population of Iraq in 1960 was around 7.3 million; today it exceeds 31 million.

Is it any wonder that California's, or Georgia's, or the Middle East's water problems have worsened?

In a recent paper, Richard Seager of Columbia and his colleagues analyzed the recent drought in the southeastern United States. This drought led to water use restrictions, depleted flows in the major river basins of the region, and growing political tensions over water sharing between Georgia, Alabama, and Florida. The authors of this paper concluded that the recent drought in the Southeast was not climatologically different from past droughts, but was felt more severely largely due to the growth in population in the region. In July, a Federal judge ruled that Atlanta had to fundamentally change the way it obtains its water, and noted that

 
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