Trend variations of water balance components affected by climate changes (Case study: Atrak river basin, Iran)

Global warming will lead to changes in spatiotemporal distributions of regional water resources and the global hydrological cycles. Thus, an important task in climate change detection is represented by the analysis of changes in meteorological variables. The current paper aimed to detect the trends of hydro-meteorological variables such as precipitation and river discharge by focusing on the impacts of climate change. In order to achieve the stated purpose, linear regression and non-parametric test of Mann–Kendal were used on water balance components such as runoff, actual evapotranspiration and precipitation using Palmer equation in eight north eastern basins of Khorasan province. Thirty years of data results of Mann–Kendall test indicated that, the trends in average precipitation were inhomogeneous across the watersheds. The analysis of time series of discharge in most of the watersheds showed an obvious falling trend at 95 and 99 percentage levels of confidence monthly, seasonally and annually. Also, an ascending trend in evapotranspiration rate and temperature was found throughout the years. Generally, the global climate change has no significant effect on the hydrological inputs in the studied area. However, evapotranspiration component, as a part of output factors, has been increased due to the observed warming trend. Thus, a drastic strategic management is highly recommended to reduce the amount of loss.