Tracking water

Overview

Tracking water is not easy. Water footprinting is a term used these days to estimate the direct and indirect water consumption associated with a product. As suggested in the previous post, there are important issues with water. The interest is not only the consumption of water associated with something, it is the degree to which the waste water is contaminated, as well as the time element and its role in the natural world (to name a few).

Footprinting confusion

Now, it is important to differentiate the terms water footprinting and carbon footprinting from the "ecological footprint." The latter is a concept coauthored by Bill Rees and Mathis Wackernagel at the University of British Columbia ten or so years ago. The ecological footprint is about collapsing impacts to a common metric of an area of land. Basically, all we consume or produce requires an amount of land to either create what we want, or absorb the waste we don't want. There are limits to the rate at which things are made and the rate and capacity of the discharges we produce. Thus, it is common to go to those websites that give you a quiz and then tell you that if everyone on earth lived like you did, we'd need several planets. I have not studied this ecological footprint concept as I see it as being extremely uncertain since I don't believe we understand the dynamics of regeneration and absorption of land. However, I believe Mathis Wackernagel is advancing some of these issues through the Global Footprint Network.

The point is when people talk about carbon footprinting or water footprinting, you really have to check what they mean by that. Most of them are not referring to the ecological footprint which would have units of an area of land. Instead, they would have units such as kg of CO2 equivalent or liters of water.

Tracking water woes

So what do I see as the shortcomings? (I sound like a pompous academic, but please believe me when I say that this blog is just a compendium of opinions not necessarily shared by anyone else) Well, I think time is very relevant when we speak of water. This is because water is part of a cycle, so in my mind, water used for growing corn, although excessive is preferable to the perhaps smaller amount of water used to wash a concrete truck. Of course, the problem in my argument is that I am looking only at an instant in the entire life cycle of each product. Nonetheless, one could still argue that the time of resource use and discharges is important if we are to predict more accurately real impacts.

Similarly, the quality of waste water is a concern. Here is where my knowledge breaks down as I sincerely don't understand well the chemistry of water pollution. This, in turn, leads to the spatial concern of where the discharges occur, as impacts to wildlife or humans may occur.

Responsible design of buildings for reduced water use

So the primary concerns with water at a building level is to promote responsible use of water. This can be done by attacking the big water demands, such as how much water is required per flush of a toilet. Composting toilets, toilets that use greywater and ultra low flow toilets.

Another important design consideration is to offer submetering that provides immediate and continuous feedback on water use and where it occurs. This is expensive at the moment although I do suspect there must be a low cost way of doing this since all that has to be tracked is the number of uses and length for each fixture. It is really amazing that this is not mandated. If we don't know how much water we use and where, how can we change our behavior to use water more responsibly?

The last design consideration is the cheapest, but perhaps the hardest: to make people conscious of their behavior. We can wash our hands without having the water full blast, it may take a few seconds longer to complete the operation, but we will save water. This doesn't require us to spend any money on technology! Another option I have heard is to stick a brick inside your toilet water reserve provided it does not interfere with the toilet's operation.

Finally, water provides a challenge to designers. On one hand, it can be argued that green roofs are beneficial for a lot of reasons, however, their existence on a building roof, many times complicates the collection of water. The other thing is that ideally, the water collected would be stored near the roof to allow gravity (instead of pumps) to do the water distribution for things like flushing toilets. This imposes a design complication that also compromises the owner's ability to get reasonable insurance since it presents a perceived risk to insurance companies. Also, perhaps most importantly, you don't want to use all the water that falls on your roof, as part of that belongs to the water cycle and should be inflitrated down into the ground. Here the idea would be to design a system that collects what will be needed and then allows extra water to overflow into a conveyance system that allows the water to recharge the aquifer. All this, provided you live in a place that is not a desert, although either way, there are usually dry months, which mean you have to collect additional water when it rains more (thus increasing your collection reserve dimensions). Does anyone out there know of clever designs that help reduce water use?

If you'd like to learn more about water footprinting visit the Water Footprint website.

Also, I hereby promise the next post will have numbers and calculations, because after all that was a primary goal of this blog. I think by doing so we will expose the gaps that exist in our knowledge and our estimates.