Climatic elements, discharge and groundwater trends over time using Mann-Kendall Test in the Mighan Sub-basin of Arak

Document Type: Research Paper


Research Institute of Forests and Rangelands, Agricultural Research Education and Extension Organization (AREEO), Tehran, Iran


This study was an analytical research across 84 meteorological stations, performed in the Mighan sub-basin over a fifty-year study period (1961–2011).This research seeks to answer the basic question of how declining streamflow, increasing temperatures, and fluctuation in precipitation have impacted water resource allocation in the Mighan sub-basin. The research method is analytical based on Mann-Kendall method. Analysis of independent flow measures (discharge and groundwater levels) using the Mann-Kendall trend test suggests evidence for climate change trends for many of the 84 stations. The results highlighted a mix of positive (increasing) and negative (decreasing) trends (monthly, seasonal, and annual) in the Mighan sub-basin. The results showed that during the 10-year period (1961-70), the minimum temperature occurrence in the first decade at -33.5 ° C (1973) and the maximum temperature event in the same decade at 57 ° C (1974) made this decade one of the most volatile decades in a fifty year period. Despite the inter-annual climatic fluctuations, results revealed that the Mighan Sub-basin has encountered many severe fluctuations of precipitation and average annual discharge during the five decades.