Irrigation and hydrometeorological extremes


In the present study, the Max-Planck-Institute for Meteorology’s Earth System Model is used to investigate irrigation’s general effect on severe and extreme hydrometeorological regimes. Our idealized simulations show a large potential to modulate the magnitude and occurrence frequency of severe and extreme precipitation rates, indicating the possibility to mitigate some of the detrimental effects of future climate change, but also a substantial risk due to the declining water availability in drying regions. Irrigation almost exclusively reduces the magnitude and occurrence frequency of severely and extremely dry conditions and has the potential to counter the drying trends that result from the 21st century increase in greenhouse gas concentrations—according to the RCP4.5 scenario. At the same time, irrigation does not only have a mitigating effect, as it increases the occurrence frequency and intensity of severely wet conditions in many regions. The study aims at irrigation’s theoretical (maximum) impact and investigates a highly idealized trajectory in which global irrigation is being maximized within hydrologically sustainable limits. However, even for this scenario, we find large regions in which present-day water extractions are not sustainable as they often rely on exhaustible sources. Especially, a depletion of non-renewable ground water in South Asia would lead to a strong reduction in irrigation and, consequently, a substantial increase in the occurrence frequency of severely and extremely dry months throughout the region.
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