Abstract
River flows are one of the main and influential parameters in the water resources of a region, which has a close relationship with other climatic factors. The study of changes in river flow over a long period of time can determine the effects of possible changes in the climatic conditions of a region. According to this issue, in this research, after examining the statistics of all the stations covered in Mazandaran province in terms of statistical duration, the uniformity of the statistics of different years and the absence of years without statistics, as well as the appropriate distribution at the level of the province from Ramsar city in In the west of the province, the border of Behshahr city, in the east of the province, there are 7 river stations were selected, including the Rig Cheshme station in the Tajan Sari river, Shirgah and Kiakola in the Talar Quamshahr river, Baldeh, Panjab and Kareh Sang in the Haraz Amol river, and the Pole Zoghal in the Chalus river for studying studies of the trends of river flows. The discharge trends of the above-mentioned selected stations in the four seasons of spring, summer, autumn and winter and in the annual scales in the total of 7 stations in the west, center and east of the province with the length of the statistical periods considered for each station by non-parametric Mann-Kendall test was also used to determine the magnitude of this trend. Without considering the exceptions, the results of this research indicate that the river trend of the station in the eastern and central parts of the province is decreasing in most seasons of the year or in some cases, it lacks a specific trend. In the western part of the province, from the study of the selected river flows, in a general conclusion it is clear that the seasonal and annual series under investigation, lack a specific trend, which shows during the study period ,the temporary stability of the water resource condition of area, but in the coming years, if there is no accurate planning for the optimal use of water, this relative stability can lead to the negative trend of the river and increase the vulnerability of river ecosystem will intensify due to Climatic changes in recent years as well as the pressure of the population around of river and increase for the need of water resources.

Introduction
Water plays an important and key role in the stages of economic, social and cultural development of the country, the increase of agricultural production and food security, the expansion of urban and rural population centers and improvement of the quality of life require making necessary and coordinated investments in various dimensions of development and exploitation. It is one of the sources of water. Surface water, especially the base stream, is one of the essential water resources to meet the needs of agriculture, drinking and industry. In recent years, excessive pressure has been placed on surface water sources and indiscriminate withdrawals have taken place. Studying the trend of low and basic flow in most of the country's rivers shows that this trend is decreasing and sometimes it is significant.On the other hand, river flows as one of the important parameters in hydrology and water resources are closely related to climatic factors. Considering this issue, the study of changes in river flow over time can reveal the impact of changes or lack of changes in the climatic conditions of a region.The hydrological cycle of the watershed is influenced by climatic processes, topographic features, soil and vegetation, and human activities. Climate changes and global warming make the importance of studying and investigating these factors more obvious. One of the most important factors affecting regional climate changes is changes in hydrological processes and river flow in watersheds. The increase in intensity of floods and droughts in recent years has been noticed by managers and experts as one of the harmful results of climate change.

Methodology
In this research, after examining the statistics of the total discharge of the stations covered by the province in terms of statistical duration, the uniformity of the statistics of different years and the absence of years without statistics, the appropriate distribution at the level of the province from the border of Ramsar city in the west of the province to the border of Behshahr city in the east of the province. 7 river stations including Rig Cheshme station on Tajan Sari River, Shirgah and Kiakola in Talar QuaemShahr River, Baladeh, Panjab and Karesang in Haraz Amol River and pole zoghal in Chalus River were selected to study the trends of river flows. To achieve the objectives of this research, the coverage of Mazandaran province is divided into three areas: west from Ramsar to Amol, center from Amol to Quaemshahr and east from Quaemshahr to Behshahr, and the trend of river flow changes in these three areas is evaluated at the selected stations and was investigated.According to the steps carried out in this research, the discharge trend of the river currents of the aforementioned selected stations in the four seasons of spring, summer, autumn and winter and in annual scales in the total of 7 stations in the west, center and east of the province with the length of the statistical periods was analyzed with the non-parametric Man-Kendall test. Also, the Sen test was used to determine the magnitude of this trend.

Conclusion
Based on the results of this research, it is clear that there is an upward trend in the Rig Cheshme station of Tajan river located in Sari city only in the summer season and in the rest of the year as well as this year. The annual scale of this station has a downward trend. The use of water for agriculture in the region, climate changes, the symptoms of which have become more obvious in recent years, the increase in population and the pressure on the ecosystem of this river can be the reasons for the fluctuations of this river. The river in the surveyed stations of the Talar river, which includes the Talar sub-station at a higher altitude and the Kiakola in Talar station at a lower altitude than this river, the investigation of the river flow trend indicates that the seasons either lack a specific trend or a downward trend and This conclusion also indicates that the process of changes in the water supply of this river, in a general summary, is moving towards a sharp decrease in water resources and an increase in droughts, which can lead to drought if there is no detailed planning for this sector.To be Due to the increase in the population of this river and more water consumption in agriculture, in this field, the optimal use of water resources, the non-waste of water in the form of evaporation and transpiration, according to the correct pattern of cultivation, the use of modern watershed management methods can be a pioneer.