Impacts of the upstream dams in the Mekong river basin on the peak flood change in the Mekong delta of Vietnam

Abstract

    The Mekong Delta of Vietnam is annually affected by floods from the Mekong River Basin with the annual flood prone area varies from 1-2 million ha and the flood peak at Tan Chau- the upstream station in Vietnam - varies from 2.4-5.1m. Big floods (flood peak >4.5m at Tan Chau) often cause much damage for agricultural production, infrastructure, people and properties. Normal floods or beautiful floods (>4m) may bring a lot of benefits to the Delta such as Alluvial sediment to fertile the soils, fisheries resources, water quality improvement and soil reclemation. Small floods (<3.5m) may not cause direct negative impacts, but may bring disadvantages to agricultural production in the areas affected by acid sulphate soils because of less improvement of water and soil environment due to floods. The upstream hydropower development plans may change the flooding condition in the Mekong Delta in future. In this paper, the historical data of flow coming into the Mekong Delta from 1924 to 2014 have been analyzed, the correlation between the flood features (total flood volume and discharge) and the annual flood peak at Tan Chau station has been established and the change in flood peaks at Tan Chau due to the influence of the upstream hydropower development plans has been evaluated and presented. The result provides as the scientific basis for long-term planning orientation for flood protection and damage mitigation as well as for effective land use during the flood season in the Mekong Delta in future.