Kettle River Q&A: Eating water – daily water use much higher than it seems

By the time you finished breakfast this morning, you may have already used 1,000 litres of water. But for the average B.C. resident, showering, flushing, washing dishes, making coffee adds up to 160 or so litres. So what’s going on?

Our daily water use, or footprint, is only partly made up of what flows out of our taps and toilets. The other part is virtual – water that was used to grow or produce the foods, goods, and energy we use every day.

If you add up the total water use required to manufacture, grow or produce a food product or consumer good, you have its water footprint.

The best we can do is to coarsely estimate this footprint.

For your breakfast, the egg (200 litres), toast (40 litres), milk (255 litres), cereal (100 litres) and coffee (140 litres) used far more water than your five minute shower (100 litres) or toilet flush (15 to 20 litres).

Add a sausage for 1,700 litres! Drive to work and you need to include up to 100 litres per litre of fuel plus the 60,000 litres used to make your car.

A few key terms help us understand water use. Consumptive use is where the water is evaporated, transpired by plants or incorporated into products. It is no longer useable as a water source until it condenses, falls as precipitation and is stored, usually somewhere else.

With non-consumptive water use, water just passes through our bodies, homes or fields before flowing back into the ground or into the wastewater treatment facility, and ultimately the river.

The important thing about non-consumptive use is that the water is altered in some way. On its way from the surface to the aquifers, it picks up all sorts of substances – nitrates, salts and pesticides.

As it passes through our bodies, water picks up lots of nutrients as well as whatever medications, hormones and personal care products we’ve applied. It’s altered and conventional treatment can only take out some of the additives.

So the source of our virtual water determines its impact. If our products come from areas with high water scarcity and ecosystems that are stressed by pollution, the overall impact may be much higher than products from wetter areas with lower pollution loads.

And when it comes to virtual water, everywhere is someone’s backyard and drinking water source. It can make a big difference to someone’s water when we lower our water footprint.

Find out more about water footprints at www.waterfootprint.org.

– Contact Graham Watt ([email protected]) about this or any other watershed questions.

[Originally published in the Grand Forks Gazette on May 7, 2013]