{
  "abstract": "Sand mining, dam construction, and climate change have profoundly altered the hydrological dynamics of the Mekong River-Tonle Sap Lake floodplain system, one of the world's most ecologically productive river-lake complexes. This study provides an integrated, multi-scale assessment of flow regime alteration across the Mekong mainstream and its coupling with the Tonle Sap Lake across three periods: pre-dam (1976–1991), transition (1992–2009), and post-dam (2010–2024). Using daily and sub-daily data from eight mainstream stations, we quantify shifts in long-term flow memory, short-term variability, and flow amplitude. We use a hydrodynamic response-time model to link upstream regime change to the Mekong–Tonle Sap flow exchange. During the post-dam period, flow memory increased in the upper mainstream but decreased slightly downstream, indicating growing upstream–downstream divergence in flow-regime characteristics and increasing hydrological fragmentation. Upstream stations, particularly Chiang Saen, exhibit a 33.3 % increase in minimum flows and a 40 % decrease in maximum flows during the post-dam period compared to the pre-dam period, alongside higher flow memory (+0.11), reflecting flow smoothing by reservoir operations. At the most downstream station at Kratie, a key control point for Tonle Sap inflow, maximum flows decreased by 9.4 %, while minimum flows increased by 117 % relative to the pre-dam baseline; the seasonal timing of peak discharge was also delayed by approximately two to three weeks. Critically, the combined effects of the altered mainstream flow regime and sand-mining-driven riverbed lowering have shifted the conditions under which Tonle Sap flow reversal initiates. Using the lag-adjusted Kratie discharge at onset as a proxy for the Mekong-Tonle Sap confluence stage/head condition, we find that the median onset discharge increased from ∼ 3200 m ³ s ⁻¹ (pre-dam) to ∼ 4300 m ³ s ⁻¹ under the post-dam fixed-bed scenario (2010–2024 hydrology with reference morphology), and to ∼ 7200 m ³ s ⁻¹ once sand-mining-driven channel incision is added. This indicates that post-2010 hydrological alteration reduced the probability of exceeding the discharge threshold for initiating reverse flow, while sand-mining-driven riverbed lowering substantially amplified this shift by modifying local stage–discharge relationships. Together, these interacting drivers shorten the reverse-flow season by approximately 28 d relative to the pre-dam baseline. Sustaining the Mekong–Tonle Sap flood pulse will therefore require basin-wide monitoring and transboundary governance that address flow timing and variability, not volume alone.",
  "abstract_shown": true,
  "affiliations": [
    "Tsinghua University (Beijing, China)"
  ],
  "article_type": null,
  "arxiv": null,
  "author_total": 3,
  "authors": [
    {
      "name": "Khosro Morovati",
      "orcid": "0000-0002-8867-4194"
    },
    {
      "name": "Hongling Zhao"
    },
    {
      "affs": [
        0
      ],
      "name": "Fuqiang Tian",
      "orcid": "0000-0001-9414-7019"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/9b2b2d3wb7zpb.bib",
  "cited_by": 0,
  "doi": "10.5194/hess-30-6821-2026",
  "fulltext_url": null,
  "id": "9b2b2d3wb7zpb",
  "issns": [
    "1607-7938"
  ],
  "landing_url": "https://doi.org/10.5194/hess-30-6821-2026",
  "language": null,
  "licence": "CC-BY-4.0",
  "licence_label": "CC BY 4.0",
  "licence_source": "article",
  "licence_url": "https://creativecommons.org/licenses/by/4.0/",
  "metadata_licence": null,
  "native_subjects": [
    [
      "feed-journal",
      "earth/hydrology-soils"
    ]
  ],
  "openalex": null,
  "pdf_url": null,
  "pmcid": null,
  "pmid": null,
  "published": "2026-11-05",
  "publisher": "Copernicus GmbH",
  "ris": "https://research.draconitic.com/paper/9b2b2d3wb7zpb.ris",
  "sources": [
    {
      "first_seen": "2026-11-06T00:20:51Z",
      "native_id": "10.5194/hess-30-6821-2026",
      "source": "feed-copernicus",
      "url": "https://doi.org/10.5194/hess-30-6821-2026"
    },
    {
      "first_seen": "2026-11-06T00:21:30Z",
      "native_id": "10.5194/hess-30-6821-2026",
      "source": "crossref",
      "url": "https://hess.copernicus.org/articles/30/6821/2026/"
    }
  ],
  "subjects": [
    {
      "field": "earth",
      "origin": "feed-journal:earth/hydrology-soils",
      "subfield": "hydrology-soils"
    }
  ],
  "title": "Dam-regulated flow fragmentation and sand-mining-driven threshold shifts shorten the Mekong–Tonle Sap reverse-flow season",
  "title_text": "Dam-regulated flow fragmentation and sand-mining-driven threshold shifts shorten the Mekong–Tonle Sap reverse-flow season",
  "type": "peer-reviewed",
  "updated_at": "2026-11-07T00:21:28Z",
  "url": "https://research.draconitic.com/paper/9b2b2d3wb7zpb",
  "venue": "Hydrology and Earth System Sciences",
  "versions": [
    {
      "doi": "10.5194/egusphere-2025-3472",
      "pid": null,
      "relation": "preprint",
      "title": null,
      "venue": null
    }
  ]
}