The Breakdown of Water Use

As a society, we use water for drinking, washing, agriculture, industry, landscape watering, and carrying wastes. Overall, agriculture uses about two thirds of all the consumptive use water, but this varies quite a lot across the USA and is less in New England. Thermal cooling and power supply are also major uses of water, exceeding agriculture, but are generally non-consumptive (nearly all the water is put back into the system from which it came). Public supply water, used in residential, commercial and some industrial operations, accounts for about 11% of the total consumed; most of that is used for irrigating ornamental landscapes. Inside the house, water is used for drinking and cooking, but much more is used in bathtubs, washing machines, and toilets.

There is certainly variability over geographic areas, but most of the northern USA has a consumptive use of between 70,000 and 110,000 gallons per person per year. Arid southern areas can use as much as 200,000 gallons per person per day, but most of the difference is landscape watering. If a person used 5 gallons per day for drinking, cooking and washing, all uses where having very high water quality is important, that would equate to 1825 gallons per year, less than 2% of total consumptive use.

This raises some interesting questions. Should we be applying the same high level of treatment to meet stringent standards for the vast majority of water used in ways where that treatment is essentially wasted? The answer appears to be yes, but only because it all arrives at our homes in the same distribution system. Should we be pushing so hard for water conservation in the home when it represents such a small portion of water used? A yes answer is more philosophically satisfying than practical. If irrigation is the dominant use, why is so little effort expended on conservation of that use and so much attention paid to minor uses like bottled water? The answer may be that we have less apparent control, but there is technology to improve irrigation efficiency and we could do without some crops at some times of year to avoid all that water use in arid areas.

A truly comprehensive water policy at federal and state levels should demonstrate a clear understanding of how much water is used for what purpose and apply proper technology and restrictions to conserve a valued resource while recognizing economic limits. We should be pursuing multiple distribution systems that can carry water of the appropriate quality for corresponding uses. Landscape watering needs to be cut by a lot, or even eliminated. Irrigation water conservation should be a top priority. We have a long way to go to reach a sound water management position.

Irrigated cropland.