Articles | Volume 20, issue 7
Hydrol. Earth Syst. Sci., 20, 3027–3041, 2016
Hydrol. Earth Syst. Sci., 20, 3027–3041, 2016

Research article 29 Jul 2016

Research article | 29 Jul 2016

Mekong River flow and hydrological extremes under climate change

Long Phi Hoang1, Hannu Lauri2, Matti Kummu3, Jorma Koponen2, Michelle T. H. van Vliet1, Iwan Supit1, Rik Leemans4, Pavel Kabat1,5, and Fulco Ludwig1 Long Phi Hoang et al.
  • 1Water Systems and Global Change Group, Wageningen University, P.O. Box 47, 6700 AA Wageningen, the Netherlands
  • 2EIA Finland Ltd., Sinimäentie 10B, 02630 Espoo, Finland
  • 3Water & Development Research Group, Aalto University, P.O. Box 15200, Aalto, Finland
  • 4Environmental Systems Analysis group, Wageningen University, P.O. Box 47, 6700 AA Wageningen, the Netherlands
  • 5International Institute for Applied System Analysis, Schlossplatz 1, 2361 Laxenburg, Austria

Abstract. Climate change poses critical threats to water-related safety and sustainability in the Mekong River basin. Hydrological impact signals from earlier Coupled Model Intercomparison Project phase 3 (CMIP3)-based assessments, however, are highly uncertain and largely ignore hydrological extremes. This paper provides one of the first hydrological impact assessments using the CMIP5 climate projections. Furthermore, we model and analyse changes in river flow regimes and hydrological extremes (i.e. high-flow and low-flow conditions). In general, the Mekong's hydrological cycle intensifies under future climate change. The scenario's ensemble mean shows increases in both seasonal and annual river discharges (annual change between +5 and +16 %, depending on location). Despite the overall increasing trend, the individual scenarios show differences in the magnitude of discharge changes and, to a lesser extent, contrasting directional changes. The scenario's ensemble, however, shows reduced uncertainties in climate projection and hydrological impacts compared to earlier CMIP3-based assessments. We further found that extremely high-flow events increase in both magnitude and frequency. Extremely low flows, on the other hand, are projected to occur less often under climate change. Higher low flows can help reducing dry season water shortage and controlling salinization in the downstream Mekong Delta. However, higher and more frequent peak discharges will exacerbate flood risks in the basin. Climate-change-induced hydrological changes will have important implications for safety, economic development, and ecosystem dynamics and thus require special attention in climate change adaptation and water management.

Short summary
We modelled hydrological changes under climate change in the Mekong River, focusing on extreme events. The scenario ensemble shows an intensification of the hydrological cycle under climate change. Annual river flow increases between 5 and 16 % depending on locations. Extreme high flows increase substantially in both magnitude and frequency, posing threats to flood safety in the basin. Extreme low-flow events are projected to reduce as a result of increased river flow during the dry season.