Nera (Danube) basin and it is not navigable. After the filling of the artificial Lake Đerdap, as a result of the Iron Gate I Hydroelectric Power Station which was finished in 1972, the mouth of the river into the Danube was flooded. In order to allow the optimal electricity production, the water level of the Nera at the mouth should not go below , while it must not exceed it if the flooding of the banks is to be avoided. Since the mid-1990s, there are significant problems in fixing the river's level, as the process is costly and complicated. In 2018, representatives
Valdostana Pezzata Nera des Races Bovines de l'Arc Alpin, the others being: the Pinzgauer and Tiroler Grauvieh from Austria; the Abondance, Tarentaise and Vosgienne from France; the Hinterwälder and Vordelwälder from Germany; the Rendena from Italy; and the Hérens from Switzerland. The Valdostana Pezzata Nera is black-pied. The legs and belly are often white; the head is usually black, often with a white star. Unlike the Valdostana Castana, which has both red and black hair in its coat, the Pezzata Nera has only black hair in the black areas. The hooves, muzzle and mucosa are slate-black, and the horns short and black-tipped. The