This study investigated the impact of climate change on the Tuul River flow in a semiarid region in Mongolia using statistical methods and the Soil and Water Assessment Tool (SWAT). The authors found that the precipitation showed cyclic variability (three dry and two wet periods) at inter- and multi-decadal scales throughout the study period (1945-2012). Both river flow and actual evapotranspiration (ET) showed a positive relationship with precipitation. In addition, the river flow further decreased due to increased water loss in percentage via actual ET even though the amount of actual ET decreased during dry periods. A significant increase in air temperature by 1.3 to 1.8 °C was recorded during latest dry period (1996-2012). Increase in temperature resulted in an added stressor, where water loss in percentage via actual ET increased more and resulted in an additional decrease in the river flow. This study concluded that precipitation has a stronger influence on the Tuul River flow than temperature.