Lời giới thiệu của Viet Ecology Press
KS Phạm Phan Long khám phá sông Hậu đã bị xóa mờ, thậm chí xóa bỏ trên các bản đồ của Mekong River Commission (MRC), đã viết và gởi thư báo cáo và yêu cầu MRC vẽ cả hai nhánh sông Mekong rõ ràng như nhau, cùng có mặt trên tất cả các bản đồ của họ; đến nay vẫn chưa được trả lời; do đó tác giả viết thêm tài liệu này gửi cho đại diện các nước trong MRC Joint Committee khuyến cáo họ đặt Mekong River Secretariat trước trách nhiệm giải thích và giải quyết sự việc này.
Lời giới thiệu của KS Nguyễn Khắc Toản
Đây là một cảnh báo nghiêm túc và rất đáng suy ngẫm về tính chính xác khoa học và trung lập địa lý trong các sản phẩm bản đồ - dữ liệu của Mekong River Commission. Việc Sông Hậu (Bassac) - một nhánh phân lưu mang gần 50% lưu lượng, đóng vai trò then chốt về phù sa, đa dạng sinh học và chống xâm nhập mặn - bị làm mờ hoặc “biến mất” trên nhiều bản đồ gần đây không còn là lỗi kỹ thuật thuần túy, mà đã chạm đến chuẩn mực khoa học và trách nhiệm thể chế.
Việc đối chiếu chặt chẽ giữa bản đồ, trạm quan trắc và dữ liệu thủy văn đã cho thấy sự thiếu nhất quán trong biểu đạt không gian. Trong bối cảnh ĐBSCL chịu sức ép lớn từ biến đổi khí hậu và quy hoạch thượng nguồn, việc “im lặng hóa” một dòng sông là điều không thể xem nhẹ. Đây là lời nhắc rõ ràng rằng: minh bạch dữ liệu không gian chính là nền tảng của quản trị bền vững.
Nếu không lên tiếng kịp thời, việc “xóa mờ trên bản đồ” rất dễ dẫn đến xóa mờ trong chính sách và đầu tư. Đây là lời nhắc mạnh mẽ rằng: bản đồ không trung lập; nó định hình nhận thức, và nhận thức sẽ định hình số phận dòng sông.
Lời cảm ơn
Tác giả trân trọng ghi nhận những hiểu biết và đóng góp quý báu của Bác sĩ Ngô Thế Vinh và Tiến sĩ Lê Anh Tuấn, đã nâng cao chất lượng và chiều sâu của tài liệu này.
***
The Mekong River—or Sông Tiền in Vietnam—and its sister, the Bassac River, called Sông Hậu there, form two crucial waterways through the Mekong Delta. They branch apart near Phnom Penh, Cambodia, cross into Vietnam, and empty into the sea. With matching roles in hydrology and nearly equal in annual discharge, they have traditionally shown up side by side on every Delta map—even MRC ones. Lately though, to the surprise of keen Mekong observers, Bassac River-Sông Hậu’s been fading out in the background and even diminished on several Commission maps.
The Mekong River Commission (MRC), is the intergovernmental body coordinating sustainable management among Cambodia, Laos, Thailand, and Vietnam.The MRC is indispensable for sustainable management of the Lower Mekong Basin.
Figure 1: The current MRC website shows the Mekong River-Sông Tiền and its five minor distributaries highlighted in dark blue on the foreground, while the Bassac River-Sông Hậu, a major Mekong distributary in light gray color on the background causing Kok Khel and Tan Chau river monitoring stations appear stranded on land.
Figure 2: The Bassac River (Sông Hậu) simply diminished, causing four more river monitoring stations: Phụng Hiệp, Đại Ngải và Vị Thanh appear to monitor land.
The Mekong River-Sông Tiền in Vietnam and its sister, the Bassac River-Sông Hậu are two equal major distribitaries of the Mekong mainstream
Both the Bassac River (Sông Hậu) and Mekong River (Sông Tiền) play comparable vital roles in the Mekong Delta's hydrology. The Bassac River-Sông Hậu has more fish diversity, sediment transport and more important for slowing salt water intrusion.
The Bassac (Sông Hậu) carries ~48% of the Mekong's annual water discharge (with the Mekong/Sông Tiền taking ~52%) and has more fish diversity, productivity, and wild catch due to the slower flow. Dr. Ngô Thế Vinh, the author of Mekong – the Occluding River pointed out that Sông Hậu has more fish species. Although specific studies on the main Mekong channel (Sông Tiền/Tien River) in the Vietnamese Delta are limited, but related branches like the Co Chien River (a major distributary of the Sông Tiền) recorded 133 fish species. For comparison, the Sông Hậu (Bassac/Hau River) had 176 species in a dedicated survey.
Sediment delivery shows greater differences: during the flood season (when ~80–90% of annual sediment moves), a large share (around 61–81% in the Hậu during floods) diverts to the Bassac via channels like Vàm Nao, making it disproportionately important for sediment supply to the western delta in high-flow periods.
Dr. Lê Anh Tuấn of Cần Thơ University, Vietnam pointed out from the Mekong Delta Master Plan that the role of sông Hậu is vital to The Delta, in the dry season—when saltwater intrusion peaks in the Mekong Delta—the Hau River, despite conveying merely forty-six percent of total Mekong outflow through its bifurcation into two mouths, maintains superior hydrodynamic velocity and momentum. Conversely, the Tien River, channelling more than fifty percent yet subdivided into five outlets, exhibits diminished force. Hence, the Hau River assumes paramount significance in mitigating salinity advance; its concentrated discharge warrants precedence in hydrological surveillance vis-à-vis the Tien.
The Hậu River and its floodplain (Long Xuyên Quadrangle) form an open system with superior connectivity to the Gulf of Thailand via extensive natural rivers and engineered canals. This enables:
- More effective flood regulation during the wet season,
- Greater storage and supply of freshwater in the dry season,
- Stronger defense against saltwater intrusion through better flushing and freshwater pushback.
In contrast, the Tiền River and its Đồng Tháp Mười depression are more enclosed due to natural topographic barriers and widespread closed dike systems. This leads to poorer sea connectivity, less efficient freshwater storage and distribution, and weaker protection against salinity intrusion.
Considering all of the above information and the long list of key wet lands and UNESCO Recognized Biosphere Reserves that depend on Hậu River (Attachment 2) Mekong River Commission, accordingly, ought to accord equal prominence to Hau in all hydrology and geography reports.
The MRC produced 600 reports in MRC Flood and Drought Portal, from July 6, 2009, to mid-August 2024, consistently mapped both channels and sub-channels to the sea prominently on the foreground. Starting with some reports from August 26, 2024, onward (affecting dozens of recent entries), Bassac details have been moved to the background or removed altogether in some maps.
The inconsistency and omission raise legitimate concerns about geographic accuracy and scientific clarity in representing the delta's dual-branch system. The equal importance of the two branches underscores the need for consistent and balanced presentation in hydrological and environmental studies of the Mekong Delta. The MRC should consider the importance of both river channels, acknowledge their significance, and show Bassac River-Sông Hậu and Mekong River-Sông Tiền together in all MRC Mekong River maps.
Pham Phan Long is former Chairman of the Viet Ecology Foundation, a professional engineer and researcher in Mekong River environmentprotection and energy solutions.
Acknowledgment: The author gratefully acknowledges the valuable insights and contributions from Dr. Ngô Thế Vinh and Dr. Lê Anh Tuấn, which enhanced the quality and depth of this document.
List of Attachments
ATTACHMENT 1: Screen Prints of Mekong Delta Maps and Where Bassac/Hậu River missing.
ATTACHMENT 2: List of wetlands and UNESCO recognized reserve dependent on Hậu River.
ATTACHMENT 1
Screen Prints of Mekong Delta Maps and Where Bassac/Hậu River missing.
While MRC reports reliably reference Bassac stations in text and tables (e.g., Phnom Penh (Bassac), Koh Khel, Chau Doc), visual depictions for the river system vary even within the same document. A clear example is the Weekly Dry Season Situation Report for November 11–17, 2025 (See Attachment)
- Figure 4 (Weekly Accumulated Rainfall Distribution) and Figure 12 (Accumulated Rainfall Forecast) show the Mekong mainstream as a prominent bold blue line through the delta. The Bassac branch is present but subtly rendered—its divergence from Phnom Penh appears less emphasized (thinner lines, lower visual weight) compared to the main channel, potentially downplaying its role amid rainfall-focused shading.
- In contrast, Figure 5 (Key Stations Along LMB for River Flood Forecasting) depicts the Bassac more fully and proportionally: a clear split near Phnom Penh, distinct lines comparable in visibility to the Sông Tiền, and monitoring stations connected along continuous channels. No stations appear isolated, and the Bassac is treated equally.
Such internal discrepancies—subtle de-emphasis in rainfall maps versus balanced detail in station maps—highlight a lack of standardization.
Mekong River Commission
Weekly Dry Season Situation Report in the Lower Mekong River Basin 11 – 17 November 2025.
Figure 12: Accumulated rainfall forecast from CHIRP-GFS (18 - 24 November 2025
Page 38
Mekong River Commission
Weekly Dry Season Situation Report in the Lower Mekong River Basin 11 – 17 November 2025.
Figure 5: The key stations along LMB for river forecasting
Page 31
Mekong River Commission
Weekly Dry Season Situation Report in the Lower Mekong River Basin 06 – 12 August 2024.
This MRC report on 12 August 2024 is the last that shows Bassac River-Sông Hậu.
Mekong River Commission
Weekly Dry Season Situation Report in the Lower Mekong River Basin 20 – 26 August 2024.
The MRC report of 26 August 2024 the first that does not show the Bassac River-Sông Hậu.
https://www.mekongdeltaplan.com/storage/files/files/mekong-delta-plan.pdf?1
Figure 7-6 Highest flows are from two distributaries of Sông Hậu
ATTACHMENT 2
List of key wetlands and
UNESCO recognized reserve dependent on Hậu River
Ramsar Sites (Wetlands of International Importance)
These are internationally recognized wetlands, often supported by the Hậu River’s flows:
- U Minh Thuong National Park (Kien Giang Province)
A Ramsar site (designated 2016) featuring one of Vietnam’s last major peat swamp forests, Melaleuca forests, seasonally inundated grasslands, and canals. It depends on the Hậu River for freshwater input and flood dynamics. - Area: ~21,800 ha
- Key features: Rich biodiversity (over 243 plant species, 187 bird species, rare mammals like hairy-nosed otters). Recognized as a high-priority wetland in the Mekong Delta.
- Lang Sen Wetland Reserve (Long An Province)
A Ramsar site (designated 2015) in the Dong Thap Muoi (Plain of Reeds) area, with seasonally inundated grasslands, riverine Melaleuca forests, and open swamps. It benefits from Hậu River overflows and connectivity. - Area: ~5,030 ha
- Key features: Supports diverse flora (156 plant species) and fauna (149 vertebrates), including rare species.
- Tram Chim National Park (Dong Thap Province)
A Ramsar site (designated 2012, the 2,000th globally) in the Plain of Reeds, with flooded grasslands, Melaleuca forests, and lotus communities. It receives seasonal flooding from Mekong/Hậu River systems. - Area: ~7,313 ha
- Key features: Famous for Sarus cranes and over 230 bird species.
UNESCO Biosphere Reserves
These UNESCO-designated areas encompass wetlands influenced by the Hậu River:
- Kien Giang Biosphere Reserve (Kien Giang Province)
Designated in 2006, this large reserve includes coastal mangroves, Melaleuca wetlands, and peat swamps. Parts are linked to the Hậu River’s downstream flows and tidal influences. - Key features: Diverse ecosystems (mangroves, seagrass, intertidal flats) and high biodiversity.
- Ca Mau Cape Biosphere Reserve, established in 2009, covers 371,506 hectares in Ca Mau Province, Vietnam, with a 17,329-hectare core zone including Mui Ca Mau and U Minh Ha National Parks. It protects diverse ecosystems—mangroves, peat Melaleuca forests, and marine habitats—hosting 239 plant species, 36 mammals (many endangered), and 208 birds, plus valuable migratory populations.
Other Notable Wetlands Dependent on the Hậu River
- Tra Su Melaleuca Forest (An Giang Province)
A protected Melaleuca wetland and bird sanctuary along the Hậu River, with flooded forests and canals that rely on river flooding for seasonal inundation. - Lung Ngoc Hoang Nature Reserve (Hau Giang Province)
A grassland and wetland reserve along the Hậu River, supporting diverse fish, birds, and plant life through river-fed hydrology.
These sites highlight the Hậu River’s critical role in sustaining freshwater wetlands, preventing salinity intrusion, and supporting biodiversity in the Mekong Delta. Many face threats from dikes, climate change, and upstream dams, making their conservation vital.
Letter of Transmittal
Subject: Request for Consistent and Accurate Depiction of the Bassac River (Sông Hậu) by the Mekong River Commission
January 2026
From: Pham Phan Long, P.E.
To: Members of the Mekong River Commission Joint Committee
Dear Sirs and Madam,
I am transmitting the attached document to draw your attention to a recent, unexplained change and resulting inconsistency in how the Mekong River Commission presents the Bassac River (Sông Hậu) across its various platforms.
In the attached paper, I outline the hydrological, ecological, and environmental significance of the Bassac River and compare it to the Mekong River (Sông Tiền). I respectfully request that you direct the MRC to restore consistent graphical depiction of both rivers—reflecting their equal importance—as was the standard in all MRC reports prior to August 2024.
Thank you for your attention to this matter.
Sincerely,
Pham Phan Long, P.E.
Former Chairman, Viet Ecology Foundation
