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The hydrology section is divided into two main components, surface water and groundwater. Estimation of water surplus and natural groundwater recharge in Iraq meteorological data was the aim of this research. In thirty two meteorological stations, the corrected potential evapotranspiration (PEc) was compared with monthly and annual rainfall in order to estimate actual evapotranspiration (AE) using water balance equation. Water surplus was divided into runoff and natural groundwater recharge where runoff coefficient method was used to estimate runoff. The obtained mathematical relationship between rainfall with both water surplus and actual evapotranspiration can be used to estimate these two parameters directly from rainfall. The results indicate that water surplus increased towards north-east direction of Iraq, while the minimum values of runoff and groundwater recharge located in western desert of Iraq. The climate conditions of desert was the major influence on reducing rainfall and rising temperature resulting decreasing water surplus, runoff and groundwater recharge.