Study of Relative Effectiveness of Climatic Factors on Potential Evapotranspiration Using the Factor Analysis (Case Study: Zanjan and Mahneshan Stations)

Increasing water productivity is one of the mechanisms for water consumption management and economic tools such as water price are means that can lead to a reduction in consumption and an increase in productivity. Taleghan Dam is the main supplier of water for agricultural sector of Qazvin Plain the water allocation to which has decreased in recent years due to various reasons such as climate change and population growth. Meanwhile no change in the cropping pattern and the disproportionate distribution of water to the allocated water coupled with the low price of water have caused the incorrect use of water in the Qazvin Plain irrigation network. In this research first the estimation of the water cost price was done using engineering economics relationships and its effect on the income of farmers in the Qazvin plain irrigation network was evaluated. Then the cropping and water distribution pattern in case of water supply at the cost price were optimized considering the welfare of the farmers. Genetic algorithm was used for optimization and CPD and NBPD indices were employed to check water efficiency. The price of each cubic meter of water was estimated at 8,595 rials based on the costs incurred in the Qazvin Plain irrigation network. The results showed that the supply of water at this price in the current conditions reduces the welfare of the farmers. While by optimizing the pattern of cultivation and water distribution in addition to ensuring the welfare of farmers, the amount of water demand would decrease significantly and the average CPD index would increase by 69.4% compared to the current situation. Therefore, increasing the price of water without optimizing the pattern of cultivation and water distribution in the Qazvin Plain irrigation network cannot be a suitable solution for managing water resources.