Présentations Colloques

Irrigated agriculture is an important economic factor in the rural parts of the metropolitan area of Hamburg (Germany, approx. 22,400 kmC). It is commonly expected that climate change will reduce the groundwater quantities available for field irrigation. Against this background the ratio of irrigation need and groundwater recharge (IGR-ratio) is suggested as an indicator to assess climate change impacts on the vulnerability of groundwater resources towards overexploitation by agricultural irrigation. The IGR-ratio has been assessed based on the distributed water balance model mGROWA (Herrmann et al, 2015), i.e. under consideration of the simulated groundwater recharge levels and the field crop specific irrigation need of the commonly cultivated field crops. The resulting IGR-ratio maps may serve as decision support in governmental institutions when allocating water rights for agricultural production.**The spatial IGR-ratio distribution determined for the observed reference period 1971-2000 has shown that the delineated vulnerable areas coincide with the regions for which high irrigation quantities have been documented at present. The possible impact of future climate on IGR-ratios was determined by using a model chain of mGROWA and the regional climate models REMO and WETTREG2010. Depending on the magnitude of future precipitation and reference evapotranspiration increase during winter, groundwater recharge may possibly increase. In contrast, decreasing precipitation and increasing reference evapotranspiration during summer will cause rising irrigation need of field crops. As a consequence, the mGROWA-WETTREG2010 ensemble indicates a severe increase of IGR-ratios until 2100, whereas the mGROWA-REMO realisations suggest only a moderate increase.****Reference-****Herrmann F, Keller L, Kunkel R, Vereecken H, Wendland F. Determination of spatially differentiated water balance components including groundwater recharge on the Federal State level – A case study using the mGROWA model in North Rhine-Westphalia (Germany). Journal of Hydrology- Regional Studies 2015+ 4- 294-312. **