Environmental Study of Climate Change on Rainfall Trend Using Mann-Kendall Nonparametric and Sen Tests at Selected Stations in Mazandaran Province

In order to achieve the objectives of this study, among 80 River Watershed of North Shore (covered Mazandaran Province), 17 stations were selected in three western, central and eastern sections. Based on period of records, the 44 water years from 1966-19767 to 2010-2011 were selected as a common period. To evaluate the existence of trends, the most common nonparametric time series called Mann-Kendall test was used. And if there is a trend to assess for ascending or descending time series, Sen test was used. According to the results of the three stations in the western part of the province, there is not a clear trend in the annual series. But for winter and autumn seasonal series, some stations showed positive trends and the rest of stations with no trend, which is an indication of the impact of climate change, particularly in cold seasons. Based on six stations in central part of province, stations in region of plain Mazandaran; Mahmoodabad, Haraz and Miandasht and Babol show ascending winter trend. Namaerstaq- Namarestagh mountainous stations show summer ascending trend and also Babolrood-Qarantalar stations show ascending autumn and winter trend. The only station in the eastern parts, the Arab Khayl- Talar of annual rainfall and summer trend is upward and the rest of the stations show no clear trend.