Comprehensive assessment of hydro climatic variations and change trends is essential for understanding, mitigating, and adapting to key water resource changes in different parts of the world. We performed such an assessment on Iran, as representative of an arid semi arid and geopolitically important world region. We acquired and calculated data time series of surface temperature T , precipitation P , runoff R , evapotranspiration ET , and water storage change DS , to determine their status and changes in and among the 30 main hydrological basins in Iran over the period 1986 2016. ...