Estimation of Net Irrigation Water Demand under Possible Climate Change Scenarios: Case of Menemen Left Bank

In the Mediterranean climate zone, where the effects of climate change are expected to be felt very much, changes in rainfall and temperature values are inevitable for the plants grown in the region to affect the irrigation water requirement (IWR). For this reason, it is aimed to evaluate the effect of possible climate change on the net irrigation water demand in Menemen Sol Sahil Irrigation Association. For this purpose, statistical downscaling models based on artificial neural networks have been established for predicting precipitation and temperature values of Menemen station, which is the nearest station to irrigation association. In the models, the NCEP / NCAR reanalysis variables were used as the estimators, and which of these variables will be used in the downscaling models was decided by using linear regression analysis and performance criteria. Rainfall and temperature estimates of the station were obtained by operating the downscaling model models established, with ECHAM5 climate model 20C3M 1961-1990 reference period and 2021-2100 with A2, A1B and B1 scenario results. Bias correction was applied to reduce the amount of bias in the results. Using adjusted temperature and precipitation values, evapotranspiration were calculated by using Blaney-Criddle method and effective rainfall values obtained. Using this value, net irrigation water needs were obtained. According to the A2, A1B and B1 scenarios, the mean temperatures of the period 2021-2100 could increase by 2.8, 3.0 and 2.4 oC and the precipitation could decrease by 17.6%, 30.7% and 17.2% respectively. It is expected that average net irrigation water demand will increase by 9.8%, 12.1% and 8.4%