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 of Colombana nera was likely in the posthumous work of the Italian viticulturist Giovan Vettorio Soderini that described a grape known as "San Colombane" growing in Tuscany and Emilia-Romagna in 1600. That early synonym and the grape's current name is believed to be taken from the Abbey of San Colombano in Bobbio where Colombana nera has a long history of being grown. The exact origin of Colombana nera is unknown but DNA evidence showing a parent-offspring relationship between the grape and the old Tuscan wine grape Mammolo suggest that Tuscany may be the variety's homeland. Colombana nera is a late