Shared surface water resources are only found in the Mashrek and Mesopotamia regions of Western Asia where humid conditions prevail in the northern, north-eastern and Mediterranean parts and where water resources are renewable. In the north, mountain ranges capture significant precipitation that feeds the Euphrates and Tigris Rivers; in the north-east, the Mediterranean mountain ranges feed the headwaters of the Jordan River, the Orontes River and the Nahr el Kabir.
The shared perennial rivers that flow through the Western Asia region have generally been recorded and therefore do not need to be identified in the same way as shared groundwater resources. The challenge for the Inventory was to apply a unified approach in delineating shared surface basins, as their boundaries differ from one publication and/or map to another. Furthermore, the Inventory offers complete coverage of shared water resources in Western Asia, featuring key shared basins such as the Euphrates, Tigris and Jordan Basins, but also less prominent basins such as the Nahr el Kabir and the Qweik Basins.
The 'Overview & Methodology: Surface Water' chapter presents the methodology and approaches used to identify, delineate, characterize and describe the shared water resources in the Inventory. After defining the terminology used in the surface water chapters, all shared surface water resources in the region are listed together with the list of chapters for Part I of the Inventory. The section also explains why certain shared tributaries were covered in a single chapter and why an entire river network was dealt with in separate chapters. The second part of the chapter outlines the Inventory's approach to basin delineation, describes the structure of the surface water basin chapters and explains how the content of basin chapters was prepared and collated in a structured and unified way.