My last post on water footprint has generated quite a bit of feedback. The concept definitely resonates with a lot of people. I was thinking about water smart choices on the menu of a restaurant at the SeaTac airport yesterday and came to one of my favorites:
The waiter was no doubt puzzled by how long I was taking to make my selection. I was trying to figure out how to even calculate the water demand for a serving of salmon. What I came to was that it is the product of contact surface area times contact water velocity integrated over time divided by the number of servings per fish. The contact surface area has to be calculated for all phases of the life cycle from egg to spawned-out carcass. The velocity has to be calculated as if measured by pitot tube for the water flowing over the eggs in the Redd and even past an mature adult swimming up a waterfall. I estimated this would be a very large number.
I ordered Atlantic Cod.
The cold, clear water needed to produce a serving of Salmon is very different from the water needed to produce a hamburger. This difference can be expressed in terms of the inequality that must be managed for sustainable water development:
Where WA is Water Availability, WDC is Water Demand for Consumptive use (a.k.a. water footprint) and WDIFN is Water Demand for In-stream Flow Needs.
This inequality may be logically coherent but is practically useless. Sustainable water management cannot really be simplified to such a trivial inequality. It is a continuous and instantaneous problem. A Salmon does not care if, on average, there is enough flow to meet its needs. If it does not have enough water for 5 minutes it is dead.
The notion of a carbon footprint does not have this challenge and is therefore easier to understand. If I leave the lights on when I leave the room my carbon footprint is relatively insensitive to the time of year. However, a product that consumes a large volume of water but only during the monsoon season may not be as harmful to water conservation efforts as a product that has a smaller overall water demand but where the demand is only during dry periods at the expense of critical aquatic habitat.
There is also the effect of time-shifting of water availability. Leaving the lights on creates a demand for water to be released from a storage reservoir to drive a turbine to generate electricity for my convenience. This water has not been consumed; it has merely been delayed in its journey to the ocean. This delay may, however, be more than an inconvenience to inhabitants of downstream aquatic habitats who would prefer the water to be available in a different season. This inconvenience may even be deadly for some species that are stranded by rapid fluctuations in water level as we, collectively, switch our lights on and off.
The water footprint is calculated at time and space scales that are largely irrelevant to in-stream flow needs.
I am not saying that public education about the water footprint for everyday goods and services is a bad idea. It is just that there is a risk of unintended consequences. The water footprint numbers are so shocking that people may react with guilt fatigue in the absence of actionable redemption.
So what would redemption look like?
One idea would be to extend the concept from demand side management to include supply side management. Beef and dairy are examples of sectors with very high water footprints but how can we reward ranchers and farmers who adopt beneficial management practices for water use? They certainly understand their productivity as a function of water-use but using water wisely and efficiently carries some cost, risk and an awful lot of work.
Let’s look at some examples of beneficial water management at the farm scale. Starting with drainage tiles, a farmer that installs drainage tiles can get on the field sooner to work the field and gets rewarded with a longer growing season reducing risk. The water cost of drainage tiling is improved soil drainage even when water needs to be conserved which means that more irrigation water is needed and the drain tiles also provide a direct path for nutrients, pathogens and pesticides to the receiving waters. Composting manure, improves the manure as a soil additive and source of nutrients but is more work and hence more expensive than applying wet manure to the field. Wet manure is far more likely to over-spray and contaminate nearby water courses. Construction and maintenance of systems to recycle and re-use barn wash water are relatively expensive but ensure almost no contaminated water gets into the groundwater or surface water. There are many beneficial practices that farmers can use to reduce, re-use and re-cycle their water and in so doing they ensure that all of the unwanted by-products of nutrients, pathogens and pesticides are managed within farm boundaries and above the aquifer.
There is currently no way of rewarding farmers who adopt beneficial water management strategies. Perhaps, in combination with education about the water footprint of farm products there could a mechanism to certify qualified farmers as being water smart. It is clear that people will pay more for goods that are certified as being organic. Is it possible they would pay more for food that is water smart? Might that be a way to actually ensure that people change their behavior in a way that will lead to sustainable use?
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