Evaluation of aquifer performance affected by different climate scenarios (Case study: Qaraosso basin)

Today, considering the climate change on the planet and its impacts on water resources, management of groundwater aquifers as one of the most important sources of drinking water, agriculture and industry has a special role in water resources studies. Therefore, in order to investigate the effects of climate change on Ghareh-Sou aquifer located in Golestan province, the GMS7.1 software was used and quantitative simulation of aquifer in two steady and unsteady conditions was conducted. The results of model validation showed that the predicted and observed water levels had a good agreement and the average of root mean square error was 0.810. After ensuring the accuracy of the model, different scenarios were introduced. Based on the results of the scenarios, it was clear that the implementation of each scenario would cause a drawdown in the aquifer not only in the same month but several months later. For example, due to the large number of wells in the area, an increase in harvesting of 5 or 10 percent will have a major impact on groundwater level drawdown, and this decline is more noticeable in some places. The maximum observed drawdown due to an increase in the harvest was on July and equal to 1.66 meters in very small points of the aquifer, which is related to areas with high concentrations of harvesting wells (central and southern regions of the plain). The urban wastewater disposal has been determined that it lead to different maximum drawdown in different months over time. So, in October, this drawdown will be about 0.43 and in September to 1.99 meters and will result in a volume reduction of 0.6 to 0.7 cubic million meters per month, depending on monthly consumption. The scenario of river discharge reduction showed that the reduction in river discharge in a season will not only affect the season, but also the next season, and the decrease in river discharges in the winter will result in a much lower drawdown compared to the other seasons. So, in January, February and March, the maximum drawdown will be 1.27, 1.74 and 1.67 meters more near the Garmabdasht and Gharn-Abad rivers. An effective rainfall reduction scenario showed that a 20 percent decrease in effective rainfall during the winter season would lead to a further decline in the aquifer in the same and next seasons. This decrease in winter lead to the maximum decrease of 0.2 m in January, 0.97 m in February and 0.4 m in March, more in the southern aquifer and in the area of Shast-Kalateh, Naharkhoran and Pole-Ordougah stations which are in high altitudes.