The Global Trend of the Net Irrigation Water Requirement of Maize from 1960 to 2050

Irrigated production around the world has significantly increased over the last decade. However, climate change is a new threat that could seriously aggravate the irrigation water supplies and request. In this study, the data is derived from the IPCC Fifth Assessment Report (AR5). For the climate change scenarios, five Global Climate Models (GCMs) have been used. By using the CROPWAT approach of Smith, the net irrigation water requirement (IRnet) was calculated. For the estimation of the potential evapotranspiration (Epot), the method in Raziei and Pereira was used. According to representative concentration pathway (RCP) 4.5, these increases vary between 0.74% (North America) and 20.92% (North America) while the RCP 8.5 predict increases of 4.06% (sub-Saharan Africa) to more than 68% (North America). The results also show that the region of Latin America is the region with the large amount of IRnet with coprime value between 1.39 km 3 /yr (GFDL 4.5) and 1.48 km 3 /yr (CSIRO 4.5) while sub-Saharan Africa has the smallest IRnet amount between 0.13 km 3 /yr (GFDL 8.5) and 0.14 km 3 /yr (ECHAM 8.5). However, the most affected countries by this impact are those in sub-Saharan Africa. This study will probably help decision-makers to make corrections in making their decision.