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
River systems of Thailand divides into two major branches, the " Tiền Giang" (Front River) and "Hậu Giang" (Back River). These in turn enter the South China Sea through nine estuaries. The following are the principal tributaries of Mekong River which flow through Thailand (tributaries entirely outside the Thai border not shown). The Mekong drains a considerable portion of northeast Thailand. In terms of Thai territory drained, it is second only to the Chao Phraya system. The Salawin River rises in Tibet (Tibetan: རྒྱལ་མོ་རྔུལ་ཆུ།) after which it flows through Yunnan, where it is known as the "Nujiang" River (), although either name can be