Certain crops may have a high water requirement but be grown in areas where there is abundant rainfall that meets that requirement. For example, grass production in the UK requires large volumes of water which it gets entirely from natural rainfall. However, in some locations, there is insufficient rainfall to meet the needs of the crop and supplementary irrigation is required. This irrigation requires water to be extracted from other sources such as rivers or aquifers and this can have a negative impact on the environment.
The level of irrigation required is in part dictated by the location the crop is grown, and in part by the water demands of the crop. For example, most crops grown in arid regions of the world such as California will require irrigation, whilst in the UK, it is only crops that have a particularly high water demand (e.g. potatoes, vegetable crops and some soft fruit) that require irrigation.
All livestock require water to drink, but this is a small part of the water embedded in their production; the largest part is the water used to produce their feed. Therefore, if an animal is fed on ingredients that have a high reliance on irrigation, the embedded water in their production will have a greater negative impact on the environment than those fed on a diet that is mostly rain-fed.
Making the right food choices
If you want to eat foods that require less water, buy foods from countries that have low levels of water stress or are grown in season, when water stress is lower and are therefore less reliant on irrigation. Work by the World Resources Institute has mapped water stress by country, mapping total water withdrawals against total renewable water available (Figure 1). When buying cattle products, focus on those that are grass-fed or have low use of imported feed crops.