Adv. Geosci., 27, 79–85, 2010 www.adv-geosci.net/27/79/2010/ doi:10.5194/adgeo-27-79-2010 © Author(s) 2010. CC Attribution 3.0 License. Advances in Geosciences Modelling historical and current irrigation water demand on the continental scale: Europe T. aus der Beek, M. Fl¨ orke, D. M. Lapola, R. Schaldach, F. Voß, and E. Teichert Center for Environmental Systems Research, University of Kassel, Kassel, Germany Received: 19 January 2010 – Revised: 28 May 2010 – Accepted: 30 May 2010 – Published: 7 September 2010 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 mod- elling experiment assesses historic and current irrigation wa- ter demands for different crops in five arc minute spatial resolution for pan-Europe. Two different modelling frame- works 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 irri- gation water demands, which are rather high in the southern Mediterranean countries. This can be explained by unlim- ited water supply in the model structure and illegal or not gauged water abstractions in the reported data sets. The sec- ond modelling framework is WaterGAP3, which has an inte- grated conceptual crop specific irrigation module. Irrigation water requirements as modelled with WaterGAP3 feature a more realistic representation of pan-European water with- drawals. 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 in- tegrated in both model frameworks. 1 Introduction Large scale irrigation modelling has made significant progress during the last years (Siebert and D ¨ oll, 2008), which has been fuelled by the availability of new data sets (e.g. Port- mann et al., 2008; Thenkabail et al., 2008). The overall aim of this modelling experiment was to assess historic irrigation water demand for different crops in five arc minute resolution for pan-Europe. Two different modelling Correspondence to: T. aus der Beek (ausderbeek@usf.uni-kassel.de) frameworks have been applied to analyze their suitability for simulating time series of crop specific irrigation require- ments. The first framework refers to soft-coupling a dynami- cal vegetation model with a land use model, whereas the sec- ond framework relies on conceptual modelling of crop evap- otranspiration. Both frameworks produce gridded data sets of net and gross irrigation requirements with high spatial and temporal resolution. This offers new opportunities for hy- drological modellers, as integrating information about water abstractions is crucial for the realistic representation of most European river basins. 2 Data and methods 2.1 Data Climate forcing data used in this study has been compiled and regionalised by the Climate Research Unit (CRU) of the University of East Anglia, Norwich, UK (versions TS 1.2 and TS 2.1, Mitchell and Jones, 2005). CRU data covers the time period from 1901 to 2002 in 10 ′ and 0.5 ◦ resolution and monthly time steps, providing nine climatic parameters, e.g. precipitation, air temperature, cloud cover. The land use data is based on the Corine 2000 data base (EEA, 2007) for the EU-25 countries. Land use data for the remaining pan-European countries (for spatial extent see Fig. 2) is taken from Heistermann (2006), who provides a crop specific version of the GLCC land use map (USGS, 2006). Both, Corine and GLCC have been harmonized to eighteen classes and aggregated to 5 ′ (∼6×9 km) spatial res- olution. Most large scale irrigation modelling approaches, such as Thomas (2008) for China, employ the global 5 ′ map “Area Equipped for Irrigation” (AEI, Siebert et al., 2007) to spa- tially allocate irrigated area in their models. However, in many regions not all of the entire AEI is actually irrigated. Published by Copernicus Publications on behalf of the European Geosciences Union.