Water Use Trends

This post from Tyler Cowen from Saturday illustrates some interesting features of our water use over the past 30 years. Evidently, our aggregate water use has not changed in 20 years:

The flat trend in consumption came even as the USA’s population grew and electricity production, the largest user of water, increased.

Of course, one of the cool things about hydro power is that you can reuse the same water over and over again, by pumping it back up to the top at night when it’s cheap to generate power to do so. That’s called pump storage. But I digress …

What amazes me is that this decrease has come notwithstanding the fact that water is one of the most illogically and inefficiently priced and used resources on the planet.

Tyler notes that 70 percent of water use is in agriculture, and at least in the US, a lot of water gets used in agriculture that may not be needed because of the lack of transferability between potential uses and the “use it or lose it” bureaucratic mentality that has overtaken the interpretation of historic water rights. In my ideal world, the historic water rights that farmers have would be a fully transferable and alienable property right. So if San Diego, for example, is willing to pay more for water than the value that the water represents to my crops, then I’m gonna sell. Such transactions can’t really happen now, so we get locked into inefficient and non-value-maximizing uses of water.

Put it another way: our water use has not gone up in 20 years. If we paid prices for water that reflected the true cost of its use, and if farmers could transfer their property rights over water to non-agricultural users, think how much less water we could be using than we did 20 years ago.

I also think Tyler’s point about nanotech desalinization is pretty cool. So in my lifetime I could have a Nalgene bottle with a filter that would turn salt water into fresh? Sweet! La vita e bella.

3 thoughts on “Water Use Trends

  1. “70 percent of water use is in agriculture”

    That’s a world figure. In the US it’s half that, 34%, while 48% is used by thermoelectric power plants. But, the fine print notes that nearly a third of thermoelectric use is saline water.

    Most of those are “once-through” systems and much of the progress in water withdrawal reduction comes from the increasing use of closed-loop systems that capture the steam and use it again. But “withdrawal” and “consumptive use” are different things since once through systems circulate used steam through heat exchangers and return it to a surface-water body. Based on figures from closed loop systems half of withdrawals are consumed (evaporation, blowdown, drift, and leakage) and the rest is returned.

    Transferable and alienable property rights would rationalize water use but not just in simple ways such as reduced use in ag. For example, 20% of water used for public supply, 11% of total use, is lost through leakage. It isn’t metered or charged. The cost of fixing leaks exceeeds the value of the water.

  2. A bit of a digression but your comment about a bottle that could turn salt water into fresh reminded me of an interesting article a while back in Tech Central Station. It was a water container you could toss into any water source, no matter how dirty. The water would pass through a membrane that wouldn’t allow contamints to pass, so you ended up with drinkable water. Not quite as big of a challenge as desalinization, but still pretty slick.

    Article is here http://www.techcentralstation.com/073103E.html

  3. The train has left the station as far as farm irrigation in large parts of the country. Water for irrigation in the arid states of the Great Plains comes largely from aquifers, many of which have been depleted after decades of withdrawals. Water use for that purpose would therefore have declined regardless of how the water is valued now.

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