Reservoirs and Dams

Caution: The most comprehensive global dam database, the World Register of Dams, is compiled by the International Commission on Large Dams (ICOLD) and currently lists more than 58,000 records of large dams. This inventory is not georeferenced and therefore cannot be displayed on Resource Watch, but the number of dams it has recorded indicates the large data gaps that exist in this dataset.

The various sources used to create this dataset showed different characteristics regarding their resolution, accuracy, comprehensiveness, and the type of attributes—mostly due to the different objectives and needs when assembling them.

While no criterion for minimum height of dams was applied in the generation of this dataset, many of the source datasets used a threshold of 15 m in their original collections, introducing a bias in the initial selection toward higher dams.

Reservoir outlines are typically subject to strong seasonal fluctuations. As most polygons in the first version of this dataset are originally depicted from remote sensing imagery (i.e., a snapshot in time) they may reflect a low-fill or dry-season state with significantly smaller than maximum area.

Not all data sources provided a clear distinction on whether their attribute data refers strictly to a physical dam or to the impounded reservoir behind it, or both.