Title: Historical and projected future runoff over the Mekong River basin

Abstract

The Mekong River (MR) crosses the borders and connects six countries, including China, Myanmar, Laos, Thailand, Cambodia, and Vietnam. It provides critical water resources and supports natural and agricultural ecosystems, socioeconomic development, and the livelihoods of the people living in this region. Understanding changes in the runoff of this important international river under projected climate change is critical for water resource management and climate change adaptation planning. However, research on long-term runoff dynamics for the MR and the underlying drivers of runoff variability remains scarce. Here, we analyse historical runoff variations from 1971 to 2020 based on runoff gauge data collected from eight hydrological stations along the MR. With these runoff data, we then evaluate the runoff simulation performance of five global hydrological models (GHMs) forced by four global climate models (GCMs) under the Inter-Sectoral Impact Model Intercomparison Project (ISIMIP). Furthermore, based on the best simulation combination, we quantify the impact of future climate change on river runoff changes in the MR. The result shows that the annual runoff in the MR has not changed significantly in the past 5 decades, while the establishment of dams and reservoirs in the basin visibly affected the annual runoff distribution. The ensemble-averaged resultmore » of the Water Global Assessment and Prognosis version 2 (WaterGAP2; i.e. GHM) forced by four GCMs has the best runoff simulation performance. Under Representative Concentration Pathways (RCPs; i.e. RCP2.6, RCP6.0 and RCP8.5), the runoff of the MR is projected to increase significantly (p<0.05); e.g. 3.81 ± 3.47 m³s^-1a^-1 (9 ± 8 % increase in 100 years) at the upper reach under RCP2.6 and 16.36 ± 12.44 m³s^-1a^-1 (13 ±10 % increase in 100 years) at the lower reach under RCP6.0. In particular, under the RCP6.0 scenario, the increase in annual runoff is most pronounced in the middle and lower reaches, due to increased precipitation and snowmelt. Under the RCP8.5 scenario, the runoff distribution in different seasons varies obviously, increasing the risk of flooding in the wet season and drought in the dry season.« less

Authors:

Wang, Chao ^[1]; Leisz, Stephen ^[2]; Li, Li  ^[3];

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• Search DOE PAGES for ORCID "0000-0002-1641-3710"

Shi, Xiaoying  ^[4];

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• Search DOE PAGES for ORCID "0000-0001-8994-5032"

Mao, Jiafu  ^[4];

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Zheng, Yi ^[1]; Chen, Anping  ^[2]

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• Search DOE PAGES for ORCID "0000-0003-2085-3863"

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+ Show Author Affiliations

1. Southern University of Science and Technology, Shenzhen (China)
2. Colorado State University, Fort Collins, CO (United States)
3. Pennsylvania State University, University Park, PA (United States)
4. Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)

Publication Date:

Mon Jan 29 00:00:00 EST 2024

Research Org.:

Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Biological and Environmental Research (BER); National Natural Science Foundation of China (NSFC)

OSTI Identifier:

2301614

Grant/Contract Number:  

AC05-00OR22725; 92047302; 51961125203; SC0020146

Resource Type:

Accepted Manuscript

Journal Name:

Earth System Dynamics (Online)

Additional Journal Information:

Journal Name: Earth System Dynamics (Online); Journal Volume: 15; Journal Issue: 1; Journal ID: ISSN 2190-4987

Publisher:

Copernicus Publications, EGU

Country of Publication:

United States

Language:

English

Subject:

54 ENVIRONMENTAL SCIENCES