Climate Change Impact on the Crop Water Requirement Using HadCM3 Model in Aidoghmoush Irrigation Network

This research work was aimed to investigate agricultural water demand and water requirement using HadCM3 model that occur due to climate change in Aidoghmoush irrigation network at time period 2026-2039. At first، monthly temperature and precipitation data of HadCM3 model were provided and downscaled in the baseline period (1987-2000) and the future period (2026-2039) under the SRES emission scenario، namely A2. Results showed that the temperature increased (Between 1. 0 to 1. 8) and precipitation varied (-28 to 33 percent) in 2026-2039 compared with baseline period (1987-2000). In order to estimate the water requirements، crop evapotranspiration and effective rainfall were calculated. The potential evapotranspiration and the crop evapotranspiration were calculated to FAO Penman-Monteith and FAO-24 method، respectively. Calculation the potential evapotranspiration in future periods (due to lack of information) through the relationship of temperature and potential evapotranspiration in the base period was conducted. Then، for risk analysis، downscaled temperature and precipitation for 2026-2039 were introduced to water requirement model and monthly net water requirement was simulated in the future and in the sequel، water demand and the risk increase of its changing considered. The study also revealed risk increase in agriculture water demand، as these increase is of 10 to 13 (for the risk of 50% and 25%). Considering the present areas of the selected crops (wheat، barley، alfalfa، soya، feed corn، forage maize، potato and walnut) and their augmented requirements، volume of 6 to 9 MCM/y for 2026-2039 period (for the probability of 50% and 25%) will be required to meet the demands. Finally، it is found that responses of the crops were different where wheat and barley more variability to this phenomenon.