This is a piece I wrote for the Food Assembly blog. For more information on the Food Assembly (it’s a great way to buy local food) see my Guardian article about it here).

When we import food, then, we effectively import the water it’s taken to produce it.

As the world’s available water supply dries up, many imported foods – including fruit and vegetables that are on our supermarket shelves all-year round – are becoming increasingly unsustainable.

When you look at an almond, the water content might not be the first thing that springs to mind. But it is one of the most water-heavy foods we eat.

Did you know it takes 5 litres of water to produce one almond? Almond milk has soared in popularity in recent years, and almonds are one of the healthiest things to eat but its production appears to have a hefty environmental impact. More than 80% of the world’s almond crop is grown in California, which has been experiencing its worst drought on record.

Why care you may think? Well, water is essential to our ecosystem.

The crop is so water-intensive, farmers drill down into untapped aquifers to pump out water. The drilling which goes hundreds of meters into the soil could lead to earthquakes and threatens vital infrastructure like bridges, roads, and irrigation canals.

“Huge amounts of water go into producing our food,” says Daniel Crossley, chief executive of the Food Ethics Council. “But how it links to food security is often underplayed and it should be higher on the agenda.”

The water in our food is an issue that’s of increasing concern, and it’s likely to become much worse. According to experts, this is due to the likelihood of increasingly frequent and widespread floods and droughts, the global expansion of the western diet and a rising world population.

It’s hard to get your head around it so let’s explain it in more detail.

The water in food is often referred to as embedded water or virtual water. With crops, it’s the water that goes into the soil to grow the food (whether that’s rainwater or ‘managed’ water – irrigated from rivers and lakes). With meat, it’s the water needed for the crops, which are grown to feed the animals, and the water involved in the process of raising and slaughtering the animals.

Like mentioned above, when we import food, we effectively import the water it’s taken to produce it. And this is a real problem, particularly when we’re importing food from parts of the world, which are being hardest hit by climate change.

For example, our supermarkets are stocked with green beans from Kenya, asparagus grown in the Ica Valley, in Peru, and potatoes from Egypt. All of which are grown in water-stressed areas.

“When we’re importing potatoes from Egypt, for example, we are literally importing water from the Nile, a precious resource,” says Melvyn Kay, a spokesperson for the UK Irrigation Association.

Other examples, of water-rich products from vulnerable parts of the world, include everyday ‘essentials’ such as tea and coffee. Tea is a very delicate crop which is highly sensitive to water. It grows predominantly in eastern sub-Saharan Africa and Asia: exactly the areas where climate change is likely to hit hardest. And over recent years, Brazil, which produces around a third of the world’s coffee, has suffered some of its worst droughts for a decade.

Some of these areas irrigate water from rivers and lakes (rather than rely more on rainwater, as it is not readily available as it is in the UK).

And it’s partly the huge demand for imported food (including to the UK, which imports around half of its food) which means that producers are taking water out of natural resources, which can lead to huge problems, including environmental damage and a lack of availability.

“Once the water is ‘consumed’ by the crops, it is no longer available to drink,” points out Kay. “Water is capable of being stored and managed, though that is harder to manage in water-deprived areas of the world. But when it’s embedded in food, it’s no longer available to use for other purposes.”

What can we do about it?

The water in food is a complex issue to which there is no quick-fix solution. What we can do, however, is be thoughtful about the water-rich foods we eat and where and how they are produced and choose better options when they’re available.

For example, it’s more water intensive to produce factory-farm meat than it is to keep animals on the land. It takes 33 bathtubs of water to produce a single kilo of pork, 24 bathtubs go into a kilo of chicken and beef soaks up 90 bathtubs.

Swapping factory-farmed meat for a grass-fed, locally-reared option and you could be eating forty times less water.

Reducing our intake of these products (or looking for alternatives like British-grown quinoa) and buying more seasonal, UK-grown fruit and vegetables can make a difference. For example, if you eat potatoes that have grown in the UK, they consume around 300-400mm of water. That compares to approx. 1,000 mm of water if they’re grown in Egypt, because of the hot, dry conditions.

“You’re not only saving water, you’re eating food that’s been grown with water in a less water deprived part of the world,” says Kay.

Another way to help is by wasting less food. This is critical because when we chuck food, we also effectively throw away the water that’s been used to produce that food. “We’re letting other countries exploit their limited natural resources,” says Kay: “And then, we’re throwing away half of it in our wasteful supermarket systems, as well as in our homes.”

However, the onus is not just on individuals to address the problem, says Crossley. “This is a complex issue that we need governments and companies need to take action on.”