[en] The Lao Government emphasizes on economic development to exit from the list of the Least Developed Countries by 2020. Endowed with abundant water resources, the potential of the country for hydropower is huge and the revenue may finance the poverty reduction policy. However, this approach is widely debated for its environmental and socio‐economic impact. The current research focuses on the impact downstream of a dam, using as a case study in the Vientiane plain. Construction of hydropower dams around the Vientiane plain contributed to modifying the livelihood of the 14 500 people from 12 villages living in the Nam Nyam valley. Hydropower operations notably changed the flood flow in rainy season and have affected paddy fields; it increased the flood flow in the 1980s following the construction of the first dam (Nam Ngum1) and reduced in the 2000s when a new dam (Nam Mang3) was built. Although the Government attempted to prevent the negative impacts of Nam Mang 3 dam by funding an irrigated scheme in the Nam Nyam valley, few hundred people that gained access to the new infrastructure were not those people impacted directly by the change of flood flow. This study shows how the Nam Mang 3 dam contributed to the changes of land use in the Vientiane plain, as well as to the socio‐economic differentiation between villagers.
