Revealing the process of hydrological changes in Armand river basin

The phenomenon of climate change is considered one of the most important challenges of this century, and in a way, the dimensions of its effects are trans-regional and have overshadowed the earth's ecosystem. Among these effects, we can mention the process of hydrological changes in rivers. The area studied in this research is the Armand river basin in Chaharmahal and Bakhtiari province. The data used were obtained from the information of 4 hydrometric stations located in the study area in a statistical period of 35 years (1986-2020). The method used in this research is Kendall's statistical and graphic test. The results of investigating the trend and changes of runoff in Armand basin hydrometric stations (including Armand, Beheshtabad, Koh Sokhte, and Korebas) indicate the existence of a significant decrease in annual runoff, and in the seasons of winter, spring, summer, and fall. On the other hand, the comparison of the average discharge changes in different seasons showed that the summer season had the most decreasing changes in runoff compared to other seasons. The results of this research also showed that the average annual discharge of the entire basin during the statistical period was equal to 29.3 cubic meters per second. The average minimum and maximum annual discharge of the basin during the same period was recorded as 0.7 and 84.785 cubic meters per second, respectively. Armand station with an average of 137.7 cubic meters per second in the spring season has the highest flow rate, and in the same season Koh Sokhteh station has the lowest flow rate among hydrometric stations in the basin with 6.74 cubic meters per second.