Document Type : Research Paper
Authors
1
Department of Water Engineering and Management, Faculty of Agriculture, Tarbiat Modares University Specialization: Irrigation Networks
2
Department of Water Engineering and Management, Faculty of Agriculture, University of Tarbiat Modares, Tehran, Iran
3
Department of Water Engineering and Management, Faculty of Agriculture, Tarbiat Mofares University, Tehran, Iran
10.22059/jwim.2025.393855.1222
Abstract
In this study, the impact of climate change on crop water requirements and water demand in the Moghan irrigation network for the future period was examined using the climate models MIRCO6, ACCESS-ESM1-5, ACCESS-CM2, MPI-ESM1-2-LR, and MRI-ESM2-0. For this purpose, daily temperature and precipitation values from the models under the scenarios SSP1-2.6 (optimistic), SSP2-4.5 (intermediate), and SSP5-8.5 (pessimistic) for the baseline period (1985-2014), and the future period (2025-2044) were prepared and downscaled. The results indicate an increase of 0.68 to 2.05 degrees in maximum temperature, an increase of 1.21 to 3.12 degrees in minimum temperature, and changes of -21.06% to +14.27% in annual precipitation in the future period compared to the baseline period.
Subsequently, the water requirements of crops such as wheat (46%, 26848 hectares), alfalfa (15%, 8539 hectares), cotton (6%, 3468 hectares), peanuts (5%, 2915 hectares), other cereals (15%, 8771 hectares), vegetables (12%, 7116 hectares), and legumes (1%, 645 hectares) were calculated. Initially, using the method recommended by FAO 56 for calculating reference crop evapotranspiration in the absence of data, reference evapotranspiration was calculated based on the mentioned models and scenarios. Finally, considering the effective daily precipitation, the crop water requirements were estimated.
Assuming no change in the cropping pattern, and cultivated area of the irrigation network, the net irrigation water requirement of the network was calculated. The results show that under the mentioned scenarios for the period 2025-2044, the average water requirement, and water demand volume of the network, will increase by 3.05%-6.72% and 13.85%-20.69% per year, respectively. The irrigation adequacy index in the Moghan network for the 2025–2044 period will be decreased by 15%, and is far below one, indicating that the volume of water delivered to farms will be insufficient to meet estimated net irrigation demand. This shortage is driven by increased water demand due to higher temperatures and evapotranspiration, and reduced effective rainfall. Consequently, water stress, reduced crop yields, and increased vulnerability of farmers are expected. This situation highlights the need to revise water allocation, modify cropping patterns, and improve irrigation network efficiency for sustainable agricultural water management.
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