Development of Reservoir Operation Simulation System In Medium Scale Reservoirs is an application to help monitor the water situation in the reservoir of the Royal Irrigation Department. By linking the data from the Big Data database, the Royal Irrigation Department, analyzing and processing from the developed model. to predict the amount of water cost in the reservoir It improves the efficiency of water management and supports the planning of water allocation and crop cultivation. and help to access information on the water situation of farmers and the general public