Modelling historical and current irrigation water demand on the continental scale: Europe

Abstract

Abstract. Water abstractions for irrigation purposes are higher than for any other pan-European water use sector and have a large influence on river runoff regimes. This modelling experiment assesses historic and current irrigation water demands for different crops in five arc minute spatial resolution for pan-Europe. Two different modelling frameworks have been applied in this study. First, soft-coupling the dynamic vegetation model LPJmL with the land use model LandSHIFT leads to overestimations of national irrigation water demands, which are rather high in the southern Mediterranean countries. This can be explained by unlimited water supply in the model structure and illegal or not gauged water abstractions in the reported data sets. The second modelling framework is WaterGAP3, which has an integrated conceptual crop specific irrigation module. Irrigation water requirements as modelled with WaterGAP3 feature a more realistic representation of pan-European water withdrawals. However, in colder humid regions, irrigation water demands are often underestimated. Additionally, a national database on crop-specific irrigated area and water withdrawal for all 42 countries within pan-Europe has been set up and integrated in both model frameworks.

Modelling Current and Future Pan-European Irrigation Water Demands and Their Impact on Water Resources

“…The water demand is highest in the Mediterranean countries, especially in Turkey, Spain, and Italy, which account with 92040 km² for about 55% of the total real irrigated area in Europe (Aus der Beek et al, 2010). Also, the riparian zones of the Nile River as well as its Delta are heavily irrigated, both in area and quantity, which can be explained by the concurring semi-arid to arid climate conditions and population pressures.…”

“…Future changes in irrigation efficiency, have been derived by stakeholder meetings within the European research project SCENES. An overview of the performance of the WaterGAP3 irrigation module can be found in Aus der Beek et al, (2010), where its output has been compared to simulated gross irrigation requirements from a vegetation model and to reported values for all pan-European countries on a national basis.…”

“…The high agreement of both data sets is reflected in the high model performance of 0.86 for both criteria, R² and NSE. An analysis of the performance of the irrigation module in WaterGAP3 has been carried out in Aus der Beek et al (2010 Here, the differentiation between climate change and socio-economic effects on irrigation water use has shown that model drivers such as land use change, due to changes in food demand, feature the largest impact on irrigation and thus hydrological quantities. Especially, as adaptive measures, such as shifts in crop sowing dates due to the elongated vegetation period, are already integrated in this study set-up and have shown to save 15% water for irrigation purposes.…”

“…Furthermore, the need of irrigating field crops highly correlates with climatic conditions, which leads to intense irrigation applications in warm and water scarce regions. In pan-Europe this especially holds true for the semi-arid regions in Mediterranean countries, such as in Spain, Israel, and Turkey (Aus der Beek et al, 2010). Therefore, it is important to analyze the impact of these water withdrawals on existing water resources in order to evaluate the consequences for sustainable water management.…”

European Scenario Studies on Future In-Stream Nutrient Concentrations

“…The global model WaterGAP3 comprises three different submodels to simulate current and future conditions of freshwater resources: a hydrology model (Alcamo et al, 2003;Verzano, 2009;Schneider et al, 2011), a water use model (Aus der Beek et al, 2010;Flörke et al, 2013), and the water quality model WorldQual (Malve et al, 2012;Voß et al, 2012;Williams et al, 2012). Figure 1 gives an overview of the model framework and shows the interactions between the three submodels.…”