The Effect of Climate Change on Rice Irrigation Requirement under RCP Scenarios (Case Study: Anzali)

Agriculture is directly affected by climate conditions and changes; therefore, it is essential to understand the effects of climate change on agricultural water resources in order to adapt negative effects on sustainable crop production. In this study using three scenarios; RCP2.6, RCP4.5 and RCP8.5 of the HadGEM2-ES climate model, the future climate data (precipitation, minimum and maximum temperatures) for two periods (2020-2039 and 2040-2059) were forecasted under climate change and based on a 20-years basic period (1985-2005) climate data using LARS-WG software. The base-period evapotranspiration was estimated using Hargreaves-Samani method and they were converted to Fao-Penman-Monteith method by Coefficient (G) in order to improve accyracy. According to this, irrigation requirement of rice (most important and major crop in Gilan province) and evapotranspiration were compared between the past and future. Results declared that the average annual maximum and minimum temperatures for the periods of (2020-2039) and (2040-2059) in comparison to the base period, will increase 2.2 and 2.1, 3.2 and 2.8 ˚C respectively. Also, the average monthly rainfall under all three scenarios will increase 11.8 and 13.6 millimeters for the proposed future periods, respectively. In addition, the net irrigation changes of rice for the both proposed periods will increase 0-31% and 0-45%, respectively. The trend of evapotranspiration changes is ascending and the range of changes during the two periods will be 0.4%-13.6% and 6.1%-27.6%, respectively. This method demonstrated the outlook of climate change impacts on irrigation to the farmers. The results of this study suggest that it is necessary to understand climate change impacts on agriculture, for improved agricultural management planning. The results of this study highlight the need to pay more attention to the effects of climate change on reliable agricultural management and planning.