Modeling crop irrigation needs in Sweden under climate change

In this study we applied a large-scale hydrological model, with an irrigation routine based on the FAO guidelines for computing crop water requirements. The aim was to quantify the changes in irrigation-water demand under three different climate scenarios until the end of the century for nine different types of crops in almost 40,000 sub-basins covering Sweden (450 000 km2) located on the Scandinavian Peninsula in northern Europe. Our results showed that, on average, irrigation-water demand is projected to increase by the end of the century. However, we found that the driest years are not significantly drier but rather more frequent. There is a large discrepancy between the climate scenarios; under RCP2.6 there will be little or no significant change in irrigation-water demand while under RCP 8.5 an average year might become as dry as the driest year under the 1981-2010 reference period. A warmer climate will lead to an earlier growth start, ranging from a few days earlier under RCP2.6 to 2–4 weeks earlier on average, depending on crop, under RCP8.5. The RCP4.5 results are in between those extremes but will reach similar conditions by the end of the century as RCP8.5 shows by mid-century. The main conclusion from our study is that in a warmer climate the agricultural water demand in Sweden will increase and more water allocated for irrigation can be anticipated for climate adaptation.