To mark World Water Day at Aquatic Informatics we watched the movie ‘Last Call at the Oasis’. In discussion about the issues raised by this movie one of our senior developers expressed surprise at the magnitude of the water footprint for everyday products.
For example, the water footprint for a t-shirt was given as 700 gallons!
I don’t know whether the notion of accounting for your water footprint will catch on or not. A few years ago the idea of calculating your carbon footprint got quite a bit of press and even though carbon calculators have never caught on the notion that your carbon footprint matters seemed to stick. Equating energy use with a carbon footprint is intuitive – if I turn on a light my footprint grows whereas if I walk to work my footprint shrinks.
Water is a bit more complicated – for starters you need to consider the distinctions between Green water, Blue water and Grey Water. Green water is the volume of rainwater evaporated. Blue water is the volume of surface or groundwater evaporated and Grey water is the volume of water polluted. If you total up the evaporative losses from cotton fields with the grey water effluent of cotton mills you wind up with 10,000 litres of water used for every kilogram of cotton produced.
It is difficult and possibly impossible to accurately estimate the fate of evaporated water.
In some cases, the evaporation from irrigated farmland is recycled in convective storms within the same watershed. In other cases, the evaporated water is transported downwind in a form of massive inter-basin transfer (or perhaps exported offshore). Even if recycled within the same basin future beneficial uses of the water are impacted by the increased unpredictability of water availability.
Losses of water to the atmosphere are really a re-distribution of water. The point being that we don’t know where or when that water will be available for use again. Grey water is a more persistent and troubling issue. I think the Grey water component is a greater motivator for change.
The presentation of factoids such as that a hamburger has a water footprint large enough to fill a swimming pool does not reduce my appetite for hamburgers.
However, if I knew more about the nutrients, pathogens, pesticides and pharmaceuticals released into natural streams as a direct result of my hamburger then I think that might motivate me to choose a veggie burger.
The water footprint concept is interesting but it remains to be seen if it will be useful.
It is interesting to declare that it takes 1500 litres of water to produce 1 kg of sugar, but will that information result in a change in my behavior in the absence of information about less consumptive alternatives? The water footprint campaign needs to move past the shock and awe phase and become framed in terms of helpful information to guide water smart choices.
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