Impact of climate change on sediment yield in the Mekong River basin: a case study of the Nam Ou basin, Lao PDR
- 1Water Engineering and Management, School of Engineering and Technology, Asian Institute of Technology, P.O. Box 4 Klong Luang, Pathum Thani 12120, Thailand
- 2Department of Water Science and Engineering, UNESCO-IHE Institute for Water Education, P.O. Box 3015, 261DA Delft, The Netherlands
- 3Department of Hydrology and Hydraulic Engineering, Vrije Universiteit Brussels, Pleinlaan 2, 1050 Brussels, Belgium
- 4Department of Water Resources, Delft University of Technology, P.O. Box 5048, 2600 GA Delft, The Netherlands
- 5Mekong River Commission Secretariat, Office of the Secretariat in Phnom Penh (OSP), P.O. Box 623, 576 National Road # 2, Sangkat Chak Angre Krom, Khan Menachey, Phnom Penh, Cambodia
Abstract. This paper evaluates the impact of climate change on sediment yield in the Nam Ou basin located in northern Laos. Future climate (temperature and precipitation) from four general circulation models (GCMs) that are found to perform well in the Mekong region and a regional circulation model (PRECIS) are downscaled using a delta change approach. The Soil and Water Assessment Tool (SWAT) is used to assess future changes in sediment flux attributable to climate change. Results indicate up to 3.0 °C shift in seasonal temperature and 27% (decrease) to 41% (increase) in seasonal precipitation. The largest increase in temperature is observed in the dry season while the largest change in precipitation is observed in the wet season. In general, temperature shows increasing trends but changes in precipitation are not unidirectional and vary depending on the greenhouse gas emission scenarios (GHGES), climate models, prediction period and season. The simulation results show that the changes in annual stream discharges are likely to range from a 17% decrease to 66% increase in the future, which will lead to predicted changes in annual sediment yield ranging from a 27% decrease to about 160% increase. Changes in intra-annual (monthly) discharge as well as sediment yield are even greater (−62 to 105% in discharge and −88 to 243% in sediment yield). A higher discharge and sediment flux are expected during the wet seasons, although the highest relative changes are observed during the dry months. The results indicate high uncertainties in the direction and magnitude of changes of discharge as well as sediment yields due to climate change. As the projected climate change impact on sediment varies remarkably between the different climate models, the uncertainty should be taken into account in both sediment management and climate change adaptation.