AccScience Publishing / AJWEP / Online First / DOI: 10.36922/AJWEP025300237
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ORIGINAL RESEARCH ARTICLE

Emergence of wet-season hydrological droughts and the development of a “brittle” river system in the Vietnamese Mekong Delta

Thanh Cong Nguyen1,2 ,  Truong An Dang1,2*
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1 Department of Oceanology, Meteorology and Hydrology, Faculty of Physics and Engineering Physics, University of Science, Ho Chi Minh City, Vietnam
2 Viet Nam National University-Ho Chi Minh, Ho Chi Minh City, Vietnam
AJWEP, 025300237 https://doi.org/10.36922/AJWEP025300237
Received: 25 July 2025 | Revised: 20 August 2025 | Accepted: 27 August 2025 | Published online: 15 October 2025
© 2025 by the Author(s). This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution 4.0 International License ( https://creativecommons.org/licenses/by/4.0/ )
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Abstract

River regulation works (RRWs) are a globally implemented strategy to enhance water security, primarily by increasing dry-season flows. However, this intervention can trigger unintended and often paradoxical consequences, fundamentally altering the nature of hydrological risk. This study investigates the profound impact of RRW development on drought characteristics in the Vietnamese Mekong Delta, a region of immense agricultural importance and ecological sensitivity. Building upon the established understanding of the Mekong’s altered flow regimen, we analyze how this engineered shift has transformed drought dynamics. Using the standardized precipitation index-3 and standardized streamflow index (SSI-3) from 2000 to 2024, we uncover a critical paradigm shift. While the frequency of traditional dry-season hydrological droughts has significantly decreased as intended, the system’s vulnerability to severe, prolonged wet-season droughts has increased dramatically. Correlation analysis reveals a significant “decoupling” between regional rainfall and streamflow in the current mega-dam era (2010–2024). The most alarming finding is the emergence of wet-season hydrological droughts, with the 2019–2020 event being the most extreme in the 25-year record, during which SSI values dropped to below −2.0 despite only a moderate meteorological drought. We introduce and define the concept of a “brittle” river system: By dampening the natural flood pulse, intensive regulation has removed the river’s inherent buffering capacity against monsoon rainfall deficits, making the delta extremely vulnerable to climatic shocks. These findings challenge the conventional understanding of drought in the Vietnamese Mekong Delta and have urgent implications for water management, emphasizing the need for strategies that enhance wet-season resilience while addressing growing risks.

Keywords
Drought paradigm
Hydrological drought
River regulation
Standardized streamflow index
Brittle river system
Funding
This study is supported by the Vietnam National University Ho Chi Minh City (VNU–HCM) through the project entitled “Identifying and quantifying drivers causing water level fluctuations in the Vietnamese Mekong Delta” (grant number: B2024-18-01).
Conflict of interest
The authors declare that they have no competing interests.
References
  1. Grill G, Lehner B, Thieme M, et al. An index-based framework for assessing patterns and trends in river fragmentation and connectivity worldwide. Sci Data. 2019;6(1):1-12. doi: 10.1038/s41597-019-0040-y

 

  1. Zarfl C, Lumsdon AE, Berlekamp J, Tydecks L, Tockner K. A global boom in hydropower dam construction. Aquat Sci. 2015;77(1):161-170. doi: 10.1007/s00027-014-0377-0

 

  1. Kondolf GM, Rubin ZK, Minear JT. Dams on the Mekong: Cumulative sediment starvation. Water Resour Res. 2014;50(6):5158-5169. doi: 10.1002/2013WR014651

 

  1. Poff NL, Olden JD. Can we stop assuming that fiscal flows trump ecological ones in freshwater conservation? Front Ecol Environ. 2017;15(9):490-496. doi: 10.1002/fee.1633

 

  1. Oweis T, Hachum A. Water harvesting and supplemental irrigation for improved water productivity of dry farming systems in West Asia and North Africa. Agric Water Manag. 2006;80(1-3):57-73. doi: 10.1016/j.agwat.2005.07.004

 

  1. Vörösmarty CJ, McIntyre PB, Gessner MO, et al. Global threats to human water security and river biodiversity. Nature. 2010;467(7315):555-561. doi: 10.1038/nature09440

 

  1. Grumbine RE, Xu J. Mekong hydropower development. Science. 2011;332(6026):178-179. doi: 10.1126/science.1200990

 

  1. Eslami S, Hakimpour F, El-Shafie A, Parnian A, Ghaderi K. The role of reservoir operation in aggravating or mitigating water scarcity downstream of multi-purpose reservoirs. J Hydrol. 2021;603:126986. doi: 10.1016/j.jhydrol.2021.126986

 

  1. Hecht JS, Lacombe G, Arias ME, Dang TD, Piman T. Hydropower dams of the Mekong River basin: A review of their hydrological impacts. J Hydrol. 2019;568:285-300. doi: 10.1016/j.jhydrol.2018.10.063

 

  1. Manh NV, Dung NV, Hung NN, Merz B, Apel H. Large-scale drivers of floods in the Vietnamese Mekong Delta. Hydrol Earth Syst Sci. 2015;19(11):4707-4720. doi: 10.5194/hess-19-4707-2015

 

  1. Binh DV, Kantoush S, Sumi T, Mai NTP. Long-term alterations of flow regimes of the Mekong River and adaptation strategies for the Vietnamese Mekong Delta. J Hydrol Reg Stud. 2020;32:100742. doi: 10.1016/j.ejrh.2020.100742

 

  1. Wild TB, Loucks DP. Managing flow, sediment, and hydropower regimes in the Sre Pok, Se San, and Se Kong Rivers of the Mekong basin. Water Resour Res. 2014;50(6):5141-5157. doi: 10.1002/2013WR014917

 

  1. Sabo JL, Ruhi A, Holtgrieve GW, et al. Designing river flows to improve food security futures in the Lower Mekong Basin. Science. 2017;358(6368):eaao1053. doi: 10.1126/science.aao1053

 

  1. Li D, Long D, Zhao J, Lu H, Hong Y. Observed changes in flow regimes in the Mekong River basin. J Hydrol. 2017;551:217-232. doi: 10.1016/j.jhydrol.2017.05.061

 

  1. Ziv G, Baran E, Nam S, Rodríguez-Iturbe I, Levin SA. Trading-off fish biodiversity, food security, and hydropower in the Mekong River Basin. Proc Natl Acad Sci U S A. 2012;109(15):5609-5614. doi: 10.1073/pnas.1201423109

 

  1. Räsänen TA, Someth P, Lauri H, Koponen J, Sarkkula J, Kummu M. Observed river discharge changes due to hydropower operations in the Upper Mekong Basin. J Hydrol. 2017;545:28-41. doi: 10.1016/j.jhydrol.2016.12.023

 

  1. Mekong River Commission. Hydrological Conditions in the Lower Mekong River Basin in January-July 2020. Laos: Mekong River Commission Secretariat; 2020.

 

  1. Yun X, Tang Q, Li J, et al. Impacts of climate change and reservoir operation on streamflow and flood characteristics in the Lancang-Mekong River Basin. J Hydrol. 2020;590:125472. doi: 10.1016/j.jhydrol.2020.125472

 

  1. Wang D, Hejazi M, Cai X, Valocchi AJ. Climate change impact on meteorological, agricultural, and hydrological drought in central Illinois. Water Resour Res. 2011;47(9):W09527. doi: 10.1029/2010WR009845

 

  1. Dang TD, Cochrane TA, Arias ME, Van PTT. The Mekong River’s flow alterations and their effects on the Vietnamese Mekong Delta. Water. 2018;10(7):843. doi: 10.3390/w10070843

 

  1. Räsänen TA, Kummu M. Spatiotemporal influences of ENSO on precipitation and flood pulse in the Mekong River Basin. J Hydrol. 2013;476:154-168. doi: 10.1016/j.jhydrol.2012.10.029

 

  1. Hoang LP, Lauri H, Kummu M, et al. The Mekong’s future flows under multiple drivers: How climate change, hydropower development and irrigation expansion drive streamflow changes. Sci Total Environ. 2019;649:601-609. doi: 10.1016/j.scitotenv.2018.08.337

 

  1. Thanh NC, An DT. Assessing water level variability in the Mekong Delta under the impacts of anthropogenic and climatic factors. J Environ Earth Sci. 2024;7(1):123-131.

 

  1. Anthony EJ, Brunier G, Besset M, Goichot M, Dussouillez P, Nguyen VL. Linking rapid erosion of the Mekong River delta to human activities. Sci Rep. 2015;5(1):14745. doi: 10.1038/srep14745

 

  1. Schmitt RJP, Rubin Z, Kondolf GM. Losing ground-scenarios for subsidence and sea-level rise in the Mekong Delta. Sci Total Environ. 2017;596:70-79. doi: 10.1016/j.scitotenv.2017.04.043

 

  1. Jordan C, Tuan LH, Binh TTT, Ruessink G. A remote sensing-based assessment of long-term mangrove change in the Mekong Delta, Vietnam. Estuar Coast Shelf Sci. 2022;265:107722. doi: 10.1016/j.ecss.2021.107722

 

  1. van Vliet MTH, Franssen WHP, Yearsley JR, et al. Global river discharge and water temperature under climate change. Glob Environ Change. 2013;23(2):450-464. doi: 10.1016/j.gloenvcha.2012.11.002

 

  1. Lee SK, Dang TA. Extreme rainfall trends over the Mekong Delta under the impacts of climate change. Int J Clim Chang Strateg Manag. 2020;12(5):639-652. doi: 10.1108/IJCCSM-11-2019-0063

 

  1. Sridhar V, Thilakarathne M. Characterization of future drought conditions in the Lower Mekong River Basin. Weather Clim Extremes. 2019;25:100213. doi: 10.1016/j.wace.2019.100213

 

  1. McKee TB, Doesken NJ, Kleist J. The relationship of drought frequency and duration to time scales. In: Presented at: 8th Conference on Applied Climatology, Anaheim, CA; 1993.

 

  1. Telesca L, Lovallo M, Lopez I, Kanevski M. Investigation of scaling properties in monthly streamflow and Standardized Streamflow Index time series in the Apulia region (Southern Italy). Physica A. 2012;391(4):1662-1678. doi: 10.1016/j.physa.2011.09.028

 

  1. Gudmundsson L, Seneviratne SI. Anthropogenic climate change affects meteorological drought risk in Europe. Environ Res Lett. 2016;11(4):044005. Correction in: Environ Res Lett. 2017;12(5):059501. doi: 10.1088/1748-9326/11/4/044005

 

  1. Pokhrel YN, Felfelani F, Satoh Y, et al. Global terrestrial water storage and its drivers: A review. WIREs Water. 2021;8(5):e1528. doi: 10.1002/wat2.1528

 

  1. Vicente-Serrano SM, Beguería S, López-Moreno JI. A multiscalar drought index sensitive to global warming: The standardized precipitation evapotranspiration index. J Climate. 2010;23(7):1696-1718. doi: 10.1175/2009JCLI2909.1

 

  1. Guttman NB. Accepting the standardized precipitation index: A calculation algorithm. J Am Water Resour Assoc. 1999;35(2):311-322. doi: 10.1111/j.1752-1688.1999.tb03592.x

 

  1. Stanley JD, Warne AG. The engineered Nile River delta: A losing battle against nature. Chrono. 2006;12(1):1-13.

 

  1. Ho HL, Umetsu C, Quang NH, Du Bui D, Van L, Dung T. Assessing the impact of sea-level rise and upstream development on saltwater intrusion in the Mekong Delta, Vietnam. Hydrol Process. 2022;36(1):e14457. doi: 10.1002/hyp.14457

 

  1. Holling CS. Resilience and stability of ecological systems. Annu Rev Ecol Syst. 1973;4(1):1-23. doi: 10.1146/annurev.es.04.110173.000245

 

  1. Sadoff CW, Grey D. Beyond the river: The benefits of cooperation on international rivers. Water Policy. 2002;4(5):389-403. doi: 10.1016/S1366-7017(02)00031-4

 

  1. Tran DD, van Halsema G, Hellegers PJGJ, Ludwig F, Wyatt A. A stakeholder-based assessment of the impacts of and adaptation to water-level changes in the Vietnamese Mekong Delta. Water Int. 2019;44(5):517-536. doi: 10.1080/02508060.2019.1627993
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Asian Journal of Water, Environment and Pollution, Electronic ISSN: 1875-8568 Print ISSN: 0972-9860, Published by AccScience Publishing
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