Zambezi Region with the United Kingdom. Leo von Caprivi arranged for the Caprivi strip to be annexed to German South West Africa in order to give Germany access to the Zambezi River as part of the Heligoland-Zanzibar Treaty. The German motivation behind the swap was to acquire a strip of land linking German South West Africa with the Zambezi River, providing easy access to Tanganyika (Tanzania) and an outlet to the Indian Ocean. Unfortunately for the Germans, the British colonisation of Rhodesia (Zimbabwe and Zambia) stopped them well upstream of Victoria Falls, which proved a considerable barrier to navigation on the Zambezi.
Castlereagh River travel the distance, and up to 47 hours. Usually in peak floods, the greater the water volume, the faster the travel times of the peak. However, the flattening of the terrain upstream of Coonamble results in decreased flow velocity (but means a greater area for the flow is needed to avoid flooding). It is not correct that the Castlereagh River is an underground river (subterranean river) or an 'upside down' river. However, water that once was in the river bed on the surface does flow through the extensive sands under the riverbed. This water is therefore part of the underground