Modelling and mapping the economic value of supplemental irrigation in a humid climate

•Supplemental irrigation is highly important for achieving yield and quality assurance to guarantee profitable crop production in dry years.•We modelled and mapped the financial benefits of supplemental irrigation in England and Wales.•A sensitivity analysis shows the impact of agroclimate, market and water supply conditions on irrigation benefits.•A better knowledge of the financial benefits of irrigation would support decision making in water resources planning to reduce the impacts of low flows on agriculture during drought periods. Irrigation is an essential component of crop production to meet retailer demands for premium quality when rainfall is insufficient. Under drought conditions, irrigation can be constrained by water resources availability, with consequent impacts on yield, quality and revenue. Whilst most agriculture in Europe is rainfed, greater dependence on supplemental irrigation could become more important in humid environments due to a changing climate with greater rainfall uncertainty and higher frequency of droughts. By combining industry and farm level economic data, with geospatial information on agricultural land use, agroclimate, soils and irrigation practices within a GIS, this paper estimates the total financial benefit of outdoor irrigated production in England and Wales assuming no constraints in resource availability and optimal irrigation practices. The analysis suggests that the total net benefits of irrigation in a ‘design’ dry year are around £665 million, with an average irrigation water productivity in excess of £3.3 per m3 (close to £1.1 per m3 excluding soft fruit). Map outputs highlight significant regional differences in water productivity reflecting the composition of land use and the importance of crop mix in determining economic value. A sensitivity analysis to changes in agroclimate, market conditions (crop prices) and water supply (costs) illustrates how the benefits might change under contrasting scenario. The study highlights the importance of supplemental irrigation, even in a humid climate, and the risks that future droughts and/or constraints in water resource availability might have on agricultural systems, livelihoods and the rural economy. The implications for water resources and drought management are discussed.