How many litres of water does it take to produce a litre of wine? It seems like a pretty straight-forward question. So why does the water footprint of wine seem to range from 1 to 800 litres?

In an interview with New York Magazine Dr. Michael Burry had this to say about water:

Fresh, clean water cannot be taken for granted. What became clear to me is that food is the way to invest in water. That is, grow food in water-rich areas and transport it for sale in water-poor areas. This is the method for redistributing water that is least contentious, and ultimately it can be profitable, which will ensure that this redistribution is sustainable.

Now, I’m in no place to question the investment savvy-ness of someone who predicted the US housing crash and has been portrayed by Christian Bale in an Oscar-winning movie, but what he said next raised my eyebrows.

A bottle of wine takes over 400 bottles of water to produce.

I do know about water management in wineries, and that number came as a shock. In my experience, the ratio of water used per bottle of wine produced is typically around 8:1. I’ve seen some wineries use more, but over 400:1?? To understand what’s going on here, we need to into the messy world of impact assessment.

Boxes

Whenever we talk about measuring the amount of resources it takes to produce something, we have to set some boundaries around what we’re including to make sure we’re comparing apples to apples. Do you just include the resources used in the production process? Or do you also include the resources that are used to grow the grapes, or grow the wood for the oak barrels? There may be reasons to include or exclude any of these activities. The key when comparing numbers is to know what’s inside the box, and what’s outside. For example, BLOOM’s Water & Wine initiative is focused on water management within wineries, so we draw the box around the production facility and water used outside of production activities is excluded.

Colours

The next step is to classify the type of water being used. Water footprint analyses can classify water as  “blue”, “green”, and “grey” water depending on the role it plays and its source.

The total water footprint of wine is around 500 and 800 litres of water per litres of wine (depending on the study), but the majority of this water (>99%) comes from green and grey water, while blue water (the water used to clean tanks and barrels) accounts for a fraction of a percent. Interestingly, from my experience these broader water footprint analyses seem to underestimate the amount of water used directly in the winery.

So what is the water footprint of wine?

It depends! Are you talking about the total water footprint of wine or just one aspect like production? Total water footprint can be a good tool to evaluate the impact that winemaking has on the local watershed and it can be used to compare different winemaking regions. However, because the total water footprint is dominated by evapo-transpiration and uptake of water in the vineyard, it’s not a very good metric to compare the efficiency of different wineries. For this reason, the water-use ratio used in Water & Wine only includes water used within the winery itself.

Hopefully this little peak down the rabbit hole of impact assessment will help you out the next time the subject of water use in wine production comes up over a glass of Chardonnay.

That happens, right?