The site is located on the southern side of the High Atlas a few kilometres east of the town of Ouarzazate. It consists of a large reservoir formed in 1972 by the construction of a hydroelectric dam on the Oued Drâa, near the confluence of the Oued Dadès and the Oued Ouarzazate. The reservoir is also fed by many small temporary side-streams. Where these enter the lake, the water is relatively shallow and dense vegetation of Cynodon dactylon, Cyperus spp., Juncus spp., Phragmites australis and Tamarix canariensis occurs. Elsewhere, the water depth drops off sharply, reaching 2–4 m deep only several metres from the rocky shore. Annual precipitation averages 1,500 mm.
See Box for key species. The site is chiefly notable for its populations of summer visitors, such as Marmaronetta angustirostris and Tadorna ferruginea, both of which exceed IBA thresholds. A few pairs of Marmaronetta angustirostris have bred; Tadorna ferruginea breeds regularly, but numbers of pairs are unknown. Wintering populations of waterfowl are small, although some 20 species have been recorded. The most abundant is Tadorna ferruginea, with up to 400 individuals noted.
Non-bird biodiversity: The toad Bufo brongersmai, a Moroccan endemic, occurs.
BirdLife International (2020) Important Bird Areas factsheet: Barrage al Mansour Ad-Dhabi. Downloaded from http://www.birdlife.org on 30/11/2020.