Predicting and mapping the future demand for irrigation water in England and Wales

A methodology has been developed for predicting the future growth in demand for irrigation in countries with supplemental irrigation such as England a nd Wales. This takes into account expected changes in agricultural policy, technical, market and other factors. The methodology has also been applied within a geographical information system (GIS) to map the growth. The GIS a pproach represents an extension of a procedure developed by Knox et al. (19 97) (Knox, J.W., Weatherhead, E.K., Bradley, R.I., 1997. Agricultural Water Management 33, 1-18). The total net volumetric actual irrigation water requirements for a 'design ' dry year (20% exceedance), are predicted to rise from 168x10(6) m(3) in 1 996 to 244x10(6) m(3) in 2021. Meanwhile, the total net volumetric theoreti cal irrigation water requirements for a 'design' dry year, are predicted to rise from 204x10(6) m(3) in 1996 to 247x10(6) m(3) in 2021. Maps are presented showing the predicted change in the spatial distribution of irrigation demand between 1996 and 2021, and the theoretical dry year i rrigation demand for all irrigated crops in 2021. The application and limit ations of the methodology are discussed. (C) 2000 Elsevier Science B.V. All rights reserved.