This publication is the first UN-led effort to make a comprehensive assessment of the state of transboundary surface and groundwater resources in the Middle East. It follows a standardised structure, with eight surface water chapters and 19 groundwater chapters that systematically address hydrology, hydrogeology, water resources development and use, international water agreements and transboundary water management efforts. The chapters cover all rivers and groundwater resources shared between Arab countries in the Middle East and include data on water resources that are shared with Iran, Israel and Turkey.