Trend Analysis of Precipitation by Using Parametric and Non-Parametric Tests: A Case Study of Gheshlagh River Kurdistan Province, Iran

Changes of climate parameters can be studied in three scale fluctuations، trends and abrupt changes. The study of trend is very important in water resources management، designing of utilization systems and irrigation and drainage networks. In this regard in the present study، to analyze the trend was used Mann-Kendall nonparametric method and linear regression analysis parametric method in 95% and 99% level of confidense. In this regard، precipitation data of seven stations Khalifa Tarkhan، Hussain Abad، Taze Abad، Baharestan، Kajhi Karan and Sarab Ghamish in Gheshlagh river were used during 1987-2010. Also for estimating of trend line slope was computed Sen’s slope estimator. Results showed that the strongest annual negative trend slope belonged to Kajhi Karan and was equal to 4/17 mm/year. Also، in monthly scale، the series can prove existence of significant trend or climate change in participation، are limited and insufficient to conclude. In annual scale based on Mann-Kendall test، annual participation has a decreasing trend except in Khalifa Tarkhan and Sarab Ghamish stations. Furtheremore، due to linear regression analysis، trend of all stations is descending; but it is no significant in 1% and 5% level of confidence. This phenomenon shows that there is no climate change component in the study area.