Water use in agricultural production including the embedded water in imported agricultural commodities and goods such as food and clothes made from agricultural produce; contributes 73% of the UK’s water footprint. Water use in agricultural production, therefore, presents a key target for improvement strategies to be implemented.
Rising population and standards of living are increasing water use and putting increasing pressure on the world's freshwater resource. The withdrawal of fresh water in unsustainable quantities, including use for agriculture, is having devastating effects on freshwater ecosystems.
Water that is used to grow and manufacture everyday products, such as food, drinks and clothes, can be referred to as ‘virtual’ or ‘embedded’ water and this is additional to the water that we use directly.
A water footprint is the total volume of virtual water required to produce a good or service along the whole production and supply chain and considers where and when the water was used. Measuring the water footprint of a product or business allows investigation of water use in relation to water availability, and environmental impacts of water use. This can be followed by risk mitigation strategies.
In a recent piece of research undertaken by ADAS, the water footprint of winter wheat and potatoes was assessed at three locations across England.
Water use was assessed in terms of water volumes consumed (evaporated) or polluted and the water footprint broken down into three components: the blue, green and grey water footprints:
• The blue water footprint is defined as the volume of freshwater evaporated from global water resources, e.g. rivers, lakes, and groundwater, used to produce a product.
• The green water footprint is defined as the volume of water stored in the soil from rainfall that is evaporated to produce a product.
• The grey water footprint is the volume of water that is required to dilute pollutants to an extent that the quality of the discharged water is above the agreed water quality standards.
The results showed that whilst the water footprint of each crop did not vary much between locations, when you overlay the water scarcity at each site, the environmental impact of this water use is considerably different.
In particular one site in the Midlands is in a region where water resources are under stress, with water abstractions causing damage to the environment at times of low flows.
Another key finding from the analysis was the significant contribution that grey water made to the overall crop water footprint, which was as much as 80% for potatoes.
There are a variety of options that could be taken to reduce the water footprint of crops. The green water footprint (per tonne of production) can be reduced by increasing yield through improved agricultural practice. The blue water footprint can be reduced by careful timing of water abstraction into storage and optimising storage reservoirs to decrease evaporation losses. The implementation of land management strategies such as adopting soil, nutrient, manure and crop protection plans will reduce diffuse pollution and hence the grey water footprint.
ADAS’s expert science-based understanding of crop production and diffuse pollution puts it in an unrivalled position to provide advice to food and drink clients to identify water use hotspots in supply chains and business operations for both short term and strategic planning purposes.
ADAS is a partner of the Water Footprint Network which is working to further develop and apply the water footprint methodology and tools for sustainable management of water resources.
For more information on ADAS water footprinting services please contact Chris Fawcett on 01902 693479 or email Chris.Fawcett@adas.co.uk .