Conserving Water Lowers Greenhouse Gas Footprint - Significantly


Lawn irrigation spray head. Image credit:Louss Sprinklers

This headline seems confusing but is easily explained. Water did not magically show up at your shower on the 31'st floor. It was pushed up to your bareness by a series of massive electric pumps. Water your lawn in the suburbs: same thing. Water distribution is the most energy-intensive in the high-and-dry. Nevada and California, for example, have especially 'energy intensive' water due to the extensive labyrinth of supply canals and pipes relied upon. Astoundingly, an estimated one quarter (25%) of America's electricity consumption is associated with moving and treating water. Las Vegas Sun put this in a western US context in their report: Water usage, treatment brings increased power consumption

Southern Nevada used about 853.8 million kilowatt-hours of electricity in 2008 to move 439,187 acre-feet of water into valley homes and businesses, according the Southern Nevada Water Authority. Another 119.2 million kilowatt-hours of electricity was used that year to treat 22,501 acre-feet of water and send it back to the lake, according to figures from the Clean Water Coalition, a consortium of local wastewater agencies.

A kilowatt-hour is enough energy to power a 100-watt lightbulb for 10 hours. One acre-foot is about the same amount of water the average Las Vegas Valley home uses in two years.

Here's is the money quote. The GHG footprint of moving all that water varies by an amazing full order of magnitude, depending on locale.
Southern Nevada used 2,107 kilowatt-hours for every acre-foot, or 325,851 gallons, of water delivered, treated and sent back to the lake last year. Nationally, most agencies use between 652 and 6,517 kilowatt-hours per acre-foot, according to Lisa Maddaus, a senior engineer with environmental engineering firm Brown and Caldwell.

What is the 'worst possible' situation among US States?
By my estimation, the hypothetical worst-case is a highly water-consuming household, supplied by an especially energy intensive water system (approaching the 6500+ kilowatt-hours/acre-foot end), in a state that is highly coal dependent.

Just to throw an example out there: Utah is 93% coal dependent and has the largest average household size (3.01) - meaning water consuming appliances will be used intensively in the average home.

Beyond that, a Utah source states the per-capita water consumption average in Utah is 250 gallons, way over the 75 gallon national average, with 60% of all water consumed going for yard irrigation. So, yes, my worst case hypothetical seems credible - in a handful of states.

Rules to reduce by.
Every gallon of water not-used represents a significant reduction in greenhouse gas emissions. So:


  • Use flow reducers on your shower and kitchen sink.

  • Make your next washing machine or dish washer a low water-consuming model.

  • Skip watering the lawn.


Do these things and you are indirectly lowering your GHG footprint to a significant extent.

Corollaries.


  • Where you choose to live affects your water-related greenhouse gas footprint as much as how you live (lifestyle). Example: a gallon of Lake Michigan water consumed in a distant Chicago suburb is more energy intensive than that same gallon consumed in the City proper, assuming point of consumption elevations are similar.

  • Historic Federal government water policies determined the energy intensity of water. Nevada. New Mexico. Arizona. California. And so on. Need I say more?

  • Design of water systems affects energy intensity. See the Nevada Sun article for detailed examples.


More related posts on water use.
Is Brown the New Green? Not Watering Lawns Works
6 Grasses for Low-maintenance Drought-resistant Lawns
The Greener Gardening Idea: Drip Irrigation or Xeriscaping?

Tags: Nevada | Water Conservation

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