To refine the indicators of total water use and to optimize the water supply pattern for watershed-district coupling area, we built a water allocation optimization model with multiple water sources and multiple targets under the common constraints of the water usage red lines of watersheds and districts. We applied the model to Liuyang-Laodao River Basin to analyze the optimal scheme and the maximum volume of water supply from different water sources to different districts. Results reveal an excessive or insufficient water supply in Liuyang-Laodao River Basin in current years. The optimal water supply model compresses the water usage exceeding the red line in both normal and wet years and increases the water supply in both drought and extremely drought years. The water shortage rate of the Liuyang-Laodao River Basin in planning extremely drought years is 11.63% lower than that in current extremely drought years, which indicates that the optimal water supply model can optimize the patterns of water supply and determine the refined indicators of total water use in coupled watersheds and districts for years of different inflow frequencies. The results offer effective technical support for the monitoring of control process and the early warning of excessive total water usage.