Trend analysis of the water requirements, consumption and deficit

Recent trends in European seasonal weather conditions and related crop water requirements, crop water consumption and crop water deficits were studied using the Crop Growth Monitoring System of the Joint Research Centre of the European Commission for the period 1976–2005. Soft wheat was selected as a typical winter crop. Sugar beet was selected as a typical spring/summer crop. First we analyzed the spatial and temporal variation of the average seasonal mean temperature and the average seasonal estimated global radiation, subsequently the spatial and temporal variation of the simulated seasonal water requirement, water consumption and water deficit of wheat and sugar beets were studied. We found that the weather pattern changes are not uniformly distributed across Europe. A seasonal dependence was found. The impacts of the changing weather patterns differ per crop and per region. In various European regions the wheat water requirement showed a downward trend which can be attributed to a shorter growing season as a result of higher temperatures in spring. This downward trend can also be attributed to a lower evaporative demand in winter and spring as a result of diminishing global radiation values. Only a limited number of regions showed an upward trend. For sugar beets the Mediterranean regions of France and Spain showed a downward trend in the water requirement which can be attributed to a lower evaporative demand due to reduced solar radiation in summer and autumn. Large areas with an upward trend in the water requirement are spread across the rest of Europe. These upward trends can be attributed to higher temperatures in summer and autumn. The regional trend patterns in actual crop water consumption and water deficit are less distinct than found for the crop water requirements. Changes in these variables can be attributed to the combined effect of variations in crop water requirements and rainfall.