By Micha Gisser
Economist
From 1995 to 2005 water usage per person in Albuquerque, as reported by the Albuquerque-Bernalillo County Water Utility Authority, fell from 250 to 174 gallons per day.
Although some of our Water Authority officials would like us to believe that rebates for low-flow toilets induced this welcomed conservation, in fact it reflects consumers' healthy response to rising water prices. I estimated that from 1994 to 2006 the price of water, adjusted for inflation, increased by from 35 to 45 percent. Surprise, surprise— consumers use less water when its price rises.
The new decree from our Water Utility Authority proclaims that new homes shall have gutters, rain barrels (or cisterns) and toilets flushing no more than 1.2 gallons.
The low-flow toilet regulation is— to say it politely— misguided. Hundreds of thousands water users, just by their sheer number, have more and better ideas than the six members of the authority board.
Having recovered from the mayor's idea of planting roof gardens, we have to consider the absurdity of mandated gutters and rain barrels to collect roof runoff. If only the bureaucrats could make up their mind: Irrigate on rooftops or on the ground?
Let's examine the facts. Assuming daily water usage of 174 gallons per person, the annual consumption of a household of three would amount to 190,530 gallons, or 255 city units (of 748 gallons). The average annual precipitation in Albuquerque is approximately 9.5 inches. Assuming a 2,000-square-feet roof covers the household, its annual runoff is 11,842 gallons, or 16 city units. That is roughly equal to 6 percent of the total water usage.
If you look at your monthly water bill you will find out that the variable charge per unit is not in excess of $2 or $3. Consequently, at the most, the annual saving for the household be $50. Assuming that the gutters-and-barrel structure has a lifetime of 20 years, at a 5 percent annual interest the break-even investment is approximately $625.
Hence, any investment above $625 is a net loss for the household. And doesn't make much difference to the river and groundwater acquifer, either, because roof runoff that doesn't get capture by rain barrels percolates to the aquifer or runs to the Rio Grande.
Adding special gutters and rain barrels to new homes should be decided between homebuilders and their clients in the free market. The authority can be helpful by putting hydrologic and economic information on their web site.
Let the price of water— reflecting all production costs, including the cost of the new conversion dam and the rental cost of water rights— guide users on how much water to consume.
People do not need water nannies, they can decide for themselves how to conserve toilet water and if and when to replace their lawns by desert shrubs and invest in rain barrels.
Micha Gisser is professor emeritus of economics, University of New Mexico.
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