River basins in arid and semi-arid regions worldwide serve as lifelines for ecosystems, agriculture, and human populations. However, the impacts of climate change expose them to severe stress and pose significant challenges to their management. This review and synthesis present the current state of perennial river basins in Namibia, namely the Orange, Kunene, Okavango, and Zambezi. Historical observations reveal alarming declines in river discharge, with reductions of up to 70% in the Zambezi, 60% in the Orange, 50% in the Kunene, and 40% in the Okavango River during prolonged droughts. Recent hydrological data show that they are currently experiencing declines in their respective discharges. Transboundary agreements, such as the Kunene River Agreement and participation in the Orange-Senqu River Commission (ORASECOM), are some of the initiatives incorporated in management to improve regional cooperation. The review emphasises the need for stronger climate adaptation policies and initiatives to ensure long-term water security. By synthesising hydrological data, the paper provides insights for management to safeguard the country's river basins in an era of escalating climate uncertainty, offering a novel dual perspective approach rarely applied in semi-arid Southern African context.