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
Colombana nera ripening grape variety that can be very vigorous and high yielding if not kept in check by winter pruning and green harvesting. In the early 20th century, DNA profiling found a link between Colombana nera and another Tuscan wine grape, Mammolo. The evidence suggest that Mammolo is one of the parent varieties of Colombana nera which would make the grape a sibling to Pollera nera, Caloria and Biancone di Portoferraio. In 2000, there were 172 hectares (425 acres) of Colombana nera growing in Italy. In Emilia-Romagna it is found mostly in the province of Piacena while in Tuscany it can