System dynamics approaches to assess the impacts of climate change on surface water quality and quantity: case study of Karoun River, Iran

The aim of this research is to gain a better understanding of the effects of climate change with a comprehensive and dynamic perspective. Therefore, by using the System Dynamics (SD) approach to simulate the effects of climate change on the quality and quantity of the Karoun River and regarding the water supply and demand systems in the region and their feedback relations, a model was developed in Vensim. CGCM3 outputs under A2, B1, and A1B emission scenarios have been used to investigate the effects of climate change on both the quality/quantity of the water resources system. Also, to determine the effects of climate change on agricultural demand, the water requirement of selected crops for the next period (2015–2050) has been calculated via CROPWAT model. The results show that the maximum and minimum temperature and evaporation will increase. The results of the developed SD model show that if the current development process continues under all three climate change scenarios, the system will be able to meet the domestic, industrial, and environmental demand. However, the supply of agricultural demand will be deficient. Also, the average EC value in Ahvaz station under three emission scenarios has increased more than 21%, compared to the 15-year average. The average pH value did not change much. Then, several proposed management scenarios were evaluated to improve system performance. The results show that the scenario of optimal operation of upstream dams has the best performance. However, due to the unrealistic growing trend, despite applying this scenario, the development of the agricultural sector will fail down after a few years. Therefore, to reach a long-term solution to the problem of water shortage, the growth trend of this sector for the next period should be reviewed in light of the effects of climate change.