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
Lech, Czech, and Rus name for the Polish nation. Three large oaks in the garden adjacent to the 18th-century palace in Rogalin, Greater Poland, are named after the brothers ("Lech, Czech i Rus"), and are several hundred years old. They vary between in circumference. They are part of the Rogalin Landscape Park, and together with other they have been declared nature monuments and placed under protection. Lech, Czech, and Rus Lech, Czech and Rus () refers to a founding myth of three Slavic peoples: the Poles (or Lechites), the Czechs, and the Rus' people. The three legendary brothers appear together in the "Wielkopolska Chronicle",