[en] Considering future projects, this paper examines the effects of hydropower dam projects on downstream communities. This study was conducted in the multi-purpose hydropower and irrigated areas of the Nam Mang 3 hydropower. Using a survey study with various stakeholders, household survey, several interviews were held with key informants in addition to field work observation. It was determined that this project has caused a number of negative impacts on farmers, especially those in downstream areas, directly concerned water releases from dam and affecting the benefits from irrigation. The main findings show that farmers are able to grow a second season of rice crops, but the electricity generated in the rainy season from the dam leads to the rice fields flooding along the downstream areas.