عنوان مقاله [English]
Introduction: During the last decades, climate change has been highly disjointed. Recent studies on climate change has approached the assessment of impacts of this phenomenon and adaptation strategies under biophysical or social perspectives. In the field of agriculture and water resources, most assessments have been based on biophysical modelling focusing on the agronomic dimension or the hydrological dimension. Therefore, integrate biophysical and social aspects looking at environmental and human contexts are vital for investigation of climate change and adaptation strategies effects. In line with this, varied types of integrated modelling frameworks have been developed to address the different scales (from the crop to the river basin) and the different dimensions of climate change, water and agriculture (hydrological, agronomic, socio economic). Water resources in the Halil-Rud river basin are likely to be seriously affected by climate change in the form of increased water scarcity and more frequent droughts which leads to conflicts among different water users and uses, especially between agricultural sector and Jazmourian wetland services. However, because of the multidimensional and multi-scalar nature of water management and climate change, it is needed to integrate tools for the analysis of impacts and adaptation. In line with this, current study presents an economic – hydrological model to evaluate potential effects of climate change and adaptation strategies on irrigated agriculture and to solve or mitigate water resources conflicts among different water users and uses in studied basin.
Materials and Methods: This study, combines a farm-based economic multi-objectives optimization model with the hydrologic model water evaluation and planning (WEAP) which can represent the socio-economic, agronomic and hydrologic systems in a spatially-explicit manner covering all dimensions and scales relevant to climate change. To this end, current study was organized in two sections. In the first section, the effects of a climate change under A2 scenario and balanced groundwater withdrawal (sustainable groundwater use) on hydrological and economic performance of basin level were investigated using an economic, agronomic and hydrologic model. Finally, adopting suitable adaptive strategies on hydrological and economic conditions were evaluated using that model. A2 scenario is primarily simulated through the hydrologic model, as it represents physical characteristics of the crop and water systems, through changes in climate variables. On the other hand, adaptation strategies that affect human behavior are firstly simulated by the economic multi-objectives model. The hydro-economic simulation model is started with the multi-objectives model run which include economic and hydrological objectives. Then, Using the MABIA method and WEAP irrigation water requirements would be calculated, allocating water to crops depending on water availability and established priorities, and estimating crop yields would be done. After the first economic-hydrologic model simulation, there is a second economic-hydrologic iteration. The economic model uses WEAP results on water delivered to irrigation communities (water availability constraints at farm level), crop yields (used to calculate the gross margin per crop) and irrigation water requirements under the simulated climate scenario and adaptation strategies to simulate farmers' adjustment of cropping patterns to a new optimal land allocation.
Result and Discussion: results indicates the multi-dimensional effects of climate change and adaptation strategies and show the large potential of integrated hydro-economic models for representing the multi-scale processes related to climate change and water management. The analysis of decisions taken at farm level has been proven to be necessary, as crop model results capture the potential of farm level adaptation to mitigate the damaging effects of climate change and these are relevant to climate change adaptation as highlighted by Reidsma et al. (2010). Results for the climate change under A2 scenario and balanced groundwater withdrawal scenario (combined scenario) on status of hydrological and economic in the level basin showed that crops yield, areas with available water and water demand reliability would decrease, while crops net water demand and areas water unmet demand would increase and farmers’ income would decrease between 10 to 37 percent for upstream, between 24 to 47 percent for middle and between 30 to 50 percent for downstream units in long –term horizon in comparison to base scenario. But, adopting suitable adaptive strategies and measures could mitigate the effects of climate change on hydrological conditions specially for downstream areas and economic conditions including upstream areas. Finally, combined suitable water transmission system, modern irrigation technologies, saffron crop cultivation and deficit irrigation of some crops adaptive strategies simultaneously indicated that unmet water demand significantly decreases and the total gross margin of agricultural sector increases by 68% in comparison to base scenario under climate change.