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
Grisa nera are grown almost exclusively in the Piedmont region strongly suggest that both varieties are native to Piedmont. Grisa nera is a mid to late ripening variety that is used for both wine and table grape production. The vine can be very vigorous, producing large foliage but often has low fertility and is generally low yielding. While Grisa nera has good resistance to most fungal diseases, such as downy and powdery mildew, it is susceptible to the viticultural hazard of coulure. Grisa nera is almost exclusively found in the foothills of the Alps in the Piedmont wine region of Italy. Here