Analysis of streamflow trend in Mazandaran rivers using non-parametric Mann-Kendal test

Nowadays, the impacts of climate change evaluation on watershed hydrological resources is the most important task before any water resources planning. Stream flow trend was analyzed using non parametric Man-Kendall test conducted for 30, 40, 50 and 60 year periods in three, monthly, seasonal and annual time-scales and also peak discharge in Mazandaran Province watersheds. Results showed that the increase in Greenhouse gases and consequently climate change influenced severely on river stream flow which led to reduced river stream flows, especially in the eastern parts of the region the trend analysis results showed that most of hydrometric stations had significant downward trend especially in summer season and only they experienced positive trend in winter. It seems that increase in winter season is due to temperature rise and consequently melting of snow which led to increase of base-flow and upward trend during the studied period. Results of peak flow trend analysis showed that upward trend for recent four decades is due to changes in precipitation pattern. The research achievement may considerably help in forecasting the upcoming drought, irrigation planning and water resources management.