19. Use of Irrigation Water for Agriculture
DH Lister and JP Palutikof

Amounts of water abstracted from rivers and boreholes for irrigation in England and Wales (expressed in million litres per day) shown in relation to May-July rainfall in England and Wales

Specific indicator
The amount of water taken from rivers and boreholes by farmers for irrigation depends in part on their decisions regarding costs and benefits, but it is also clearly related to dryness of the soil and hence climate. Abstraction is licenced and the volume abstracted has to be reported to the Environment Agency. The specific indicator is the annual amount of water used for crop irrigation in England and Wales.
[Source: Environment Agency, Waterside Drive, Aztec West, Almondsbury, Bristol BS12 4UD]

Relevance
A significant and increasing proportion of the UK's root and vegetable harvest is produced using irrigation (see Indicator 20). In 1995, potatoes, vegetables and sugar beet accounted for 40%, 18% and 17% of the total area irrigated and the value of the main irrigated crops in England and Wales totaled £2,637 million.

Sensitivity to climatic and other factors
The amount of water abstracted from rivers and boreholes for irrigation is obviously greater in dry summers, but also shows a persistent increase over time. Installed capacity to apply irrigation water is increasing, partly in response to supermarket demand for a consistently high quality product, but also no doubt in response to the more frequent occurrence of dry growing seasons in recent years.
There is a clear inverse relationship between rainfall in England and Wales in May-July and the amount of water abstracted for irrigation over the growing season.

Change over time
Since 1981, water abstractions have averaged at least 100 million litres per day, even in wet years. In 1989, which was a notably dry year, there was a step-jump in abstraction amounts. Since then, levels have dropped below 250 million litres per day in only one year, 1993. Superimposed on these trends, there is a clear inverse relationship between rainfall and amounts abstracted. Relatively high abstraction levels are found in the earlier years, including the dry year of 1976. However, whereas in 1976, 150 million litres per day represented a substantial increase in water abstractions against average levels, in recent dry growing seasons, such as 1990 and 1996, abstractions have averaged more than 350 million litres per day. The winter and spring preceding the 1996 growing season was exceptionally dry in most areas of England and Wales, unlike the winter 1994-95, when rainfall was above average. This difference probably accounts for the greater amount of irrigation water used in 1996. Since 1996, summer rainfall amounts have been higher, and this is reflected in a reduction in irrigation water use, although abstractions still remain above 250 Ml/day.

The amount of water used to irrigate crops is expected to increase in future, regardless of any trend in climate, due to pressure from retailers to produce crops of high and predictable quality. However, lower rainfall and increased evaporation (in response to higher temperatures) could lead to increased water abstraction, unless voluntary and mandatory measures are taken to conserve water supplies in the face of growing water shortages - perhaps forcing a shift away from spray irrigation towards more efficient trickle irrigation.