Impacts of agricultural expansion on floodplain water and sediment budgets in the Mekong River

In this paper, we address the impact of agricultural expansion on hydrological patterns water and sediment budget in one largest floodplains along Cambodian Mekong since 1980s, using field (water level, discharge, sediment, rainfall, groundwater level) remote sensing (land use, surface suspended sediment) data, numerical simulations. Specifically, while both concentration level River around Kampong Cham Neak Luong decreased, floodplain seasonal storage increased. addition, rate input from river to was almost constant throughout studied period. The investigation floodplain’s annual budget, however, reveals a significant drop during analyzed period, mainly due decreased trapping (66% 1980s 46% 2010s). Currently, good amount bypass return back river. observed could have been triggered by that has increased erodibility (due removals primary vegetation) lowered land elevation extraction). Despite well-known impacts hydropower dams Delta conditions, particularly reduction reaching delta dam reservoirs, our observations point new more localized driving factors deficit floodplain: expansion. Finally, used 2D hydrodynamic simulation (Telemac-2D) visualize processes routing sedimentation accounting for cover change 1980s. hydrology reported paper is an unexplored environmental consequence lower Mekong. Geomorphologically, study presents peculiar case showing how can diminish role as sink through decreasing rate.