this paper deals with the similarities between the Yellow River Basin and Murray - Darling River Basin. It is found that two of them are facing similar problems, such as water shortage, poor quality for water supply and decreasing runoff etc. Two basins suffer the sharp temporal and spatial variation in water resources, which results in flood threat and water stress alternatively. Consequently these two rivers have attracted global attention due to their significant impacts on their local economical development and ecological system. To alleviate the water stress conditions, this paper investigates the feasibility of coastal reservoirs at the river mouths to develop its runoff lost to the sea. The preliminary study shows that after the coastal reservoirs are built, the water supply in these two basins can be significantly increased and the water quality can be improved and the river runoff could be also increased. This is because (1) coastal reservoirs can retain the flood water in the sea without pollution from the seawater; (2) the contaminant concentration of floodwater is less than the river water in dry seasons; (3) the river flow can be increased if the water users drink from the coastal reservoirs.