This study aimed to make a choice in the allocation water on shortage condition. An economic management, allocate reliability for all water uses, a compromise on water use activities of balance for supply and demand were considered in study process in order to reduce water shortage during insufficient condition. These choices were made for administrative authority using in decision support and decision making on the water allocation from the Lam Pao reservoir, Thailand. These three criterions of the economy, equity and reliability were created to analyze for determining the best choice from eight made choices. The analysis hierarchy process was used for analysis process. The priority criterion for water allocation was ranked as economy of 41.26%, equity of 33.79% and reliability of 24.95% respectively. The highest priority consist of the reduction of irrigation area 3% (1,277.60 hectares) reduction of aquatic farm area 3%, (35.68 hectares) and reduction the amount of water to maintain ecological balance of 3% (0.39x10⁶ m³/month).