System dynamics for assessing anthropogenic and climate change impacts on agro-hydrological sustainability, leveraging the newly developed evapotranspiration model. Case study: Qaranqu watershed

Study region: Qaranqu watershed, Iran Study focus: Complex interactions among climate change, anthropogenic activities and water resource management examined via system dynamics and Penman-Monteith-Leuning (PML) Evapotranspiration (ET) model. New hydrological insights for the region: Through crop pattern modification scenario, variations in vegetation type resulted in 6 and 3.8 million cubic meters per year in available water by PML and PM models, respectively, which is approximately 10 and 2.5 percent higher than the current available water trend due to increase in rainfed wheat areas and in turn, reduction in leaf area index. However, cessation of land development due to high ET in pastures might cause a decrease in available water about 1 million cubic meters in the early years and 18 million cubic meters in the later years, corresponding to 1–27 % of available water compared to the existing trend from 2020 to 2045. Also, cessation of agricultural land development has resulted in decrease in GDP for this sector in contrast to other economic sectors. Given that agricultural sector’s investment share regard to total investment has risen to 23 %, its GDP share may be decreased by 12 % until 2045. The shift of this investment to other economic sectors, by 10 and 13 percent in industry and services sectors, respectively, indicates changes in GDP ratio of these sectors to total GDP by 7 and 5 percent until 2045.