Optimal Use of Water Sources in Farming Mashhad Plain at Climate Change Situation

In this research, first water calculation and requirement of cultivation model will be proposed as tables and GIS by using different methods of evaporation and perspiration for weather stations at Mashhad plain. In the studied plain, data of the synoptic station of Mashhad were used as target station and water calculation requirement were done. Considering the found correlations between this station and other parts of the network, the map of GIS evaporation and perspiration of all the plain also will be drawn.To specify the current situation, calculations were done on 1951 to 2000. Also, water requirement for the period of 2000 to 2050 were calculated with universal models of climate change. The results show that water requirement will have the increase of 22% and cultivated lands will have the decrease of 20% with the current sources.To confront with water crisis, two approaches of change of cultivation method and change of irrigation efficiency were given to calculation model. The results show that in climate change situation, cultivation model must be changed toward the products which need less water; so that the 18.5% water requirement would be decreased and also the duration of water consumption and progress stages would be adjusted in a way to reach the cocoverage of consumption to the minimum.Three scenarios of 40, 60, and 85% irrigation efficiency were given to the model with the change possibility of irrigation method in 30, 50, and 100% of the lands until 2050. The results show that if 50% of the lands had 60% efficiency and others have 40% efficiency, the cultivated lands would not change by climate change.