Weirs and canals are applied in water resource management system in the upper northern area of Thailand. GAE PHAI is a weir controller who is elected from local villagers. GAE PHAI estimates the water level and adjusts the weir sluice gate levels for providing the water to agriculture areas. The levels of sluice gates are adjusted from the estimated water level and traditional rules by GAE PHAI. However, with the climate changes, the hydrological characteristics are lucidly changed. GAE PHAIs’experiences may not be enough to adjust the sluice gate levels correctly. Thus, this research proposed to develop a decision support system for weir sluice gate level adjustment. The study area is Mae Chan, Chiang Rai. This research started with surveying of weir and canals system to analyze the volume of river water of the present method of water resource management. Then, with the community cooperation, the decision support system of water resource management is developed. The proposed decision support system consists of 1) water level monitoring stations, 2) a flow through weirs model, and 3) a website to show the suggested sluice gate level results. After the deployment of the decision support system in the study area, the results show that the proposed system is practically used, the water level data is reported accurately, and the sluice gate levels suggested from the system can reduce the water volume error for farming irrigation.