Abstract: Australia's Murray-Darling Basin is extremely important for its economic, resource, environmental and ecological values. The two most important rivers-River Murray and River Darling crosses through the basin. In recent years, due to the “millennial drought”, a series of ecological and environmental problems such as rising salinity, large fish death events and soil acidification phenomenon have caused a shortage of freshwater resources in the downstream Adelaide region. This paper draws lessons from the failure of the design of the downstream Alexander Lake’s reservoir, and attempts to improve the regional natural environment and water supply ability through the application of multi-purpose coastal reservoir technology. So that the Adelaide region has sufficient high-quality drinking water supply to alleviate the phenomenon of river dryness in the region. Trying to improve regional natural environment and water supply environment by applying multi-purpose coastal reservoir technology. In addition, through the research of coastal reservoir technology, it provides suggestions for the improvement of natural environment and water supply ability in China's coastal areas, and realizes the effective management of China's freshwater resources.