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Event Organiser: The Irrigation and Water Forum

The Mekong Basin – Implications of rapid transformation (part 2), online

  • Lecture
  • Watch Online
  • 12 November 2021
  • 09:00 - 12:00
The Mekong Basin – Implications of rapid transformation (part 2), online

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The Mekong River and its tributaries drain a vast area of mainland Southeast Asia. The Mekong flows more than 4,500km from the mountains of south-western China, and together with its tributaries it also drains parts of Myanmar, Laos, Thailand, Cambodia and Vietnam. This transboundary river basin feeds and waters some 66m people, but its continued ability to do so is in question as the basin has undergone an extremely rapid transformation. According to the WWF, quoted in The Economist, 16 May 2020, “All the environmental indicators are in the red.”

There are 13 dams along the Mekong mainstream: 11 in China and two in Laos. China plans eight more and Laos seven, while Cambodia has placed a moratorium on mainstream dam building. There are also dozens of dams operating and under construction on Mekong tributaries in all four lower riparian countries, with plans for many more.

This meeting will consider the implications of the rapid transformation for the basin, its region and other transboundary basins. The meeting comprises two virtual sessions. The first session, on Friday 5 November, will consider aspects of historical developments along the Mekong River and where these developments may be heading. In the second session, on Friday 12 November, looks at specific developments affecting the flow regime of the Mekong River and possibilities for developing a sustainable river system.


09:00 Start
09:00-09:05 Welcome and Introduction Dr Ian Tod (IWF Chair)
09:05-09:35 Anthropogenic impacts on tidal intrusion and flood hazard in the Mekong delta Professor Daniel Parsons, Director of the Energy and Environment Institute & Professor in Sedimentology
09:35-09:40 Q & A
09:40-10:10 Impacts of sand mining on bank erosion in the Mekong delta Dr Stephen Darby, Professor of Geography, University of Southampton
10:10-10:15 Q & A
10:15-10:45 TEFRIC-ERFA: Development of environmental flow approaches and their application to the Mekong River Basin Dr Cedric Laize, Hydro-ecological Modeller, Senior Scientist, UKCEH Professor Julian R. Thompson, Professor of Physical Geography – Hydrology and Wetlands, UCL 10:45-10:50 Q & A
10:50-11:20 From lightly impounded to engineered river: implications for the politics of governing the Mekong Professor Philip Hirsch, Emeritus Professor of Human Geography, School of Geosciences, University of Sydney, Australia
11.20-11.25 Q & A
11.25-11.50 General discussion
11.50-12.00 Closing remarks.


Prof. Daniel Parsons

Director of the Energy and Environment Institute & Professor in Sedimentology

Professor Parsons is an active researcher in areas related to fluvial, estuarine, coastal and deep marine sedimentary environments, exploring responses of these systems to climate and environmental change, for example understanding how evolving flood risk on large mega-deltas can impact populations and related regional and global food security - through to understanding the impact of plastics, particularly in coastal and marine environments. As the Director of the Energy and Environment Institute, he has gathered together a multidisciplinary team of over 170 researchers, with a portfolio of active research grants and projects of over £29M. It also hosts three flagship taught MSc programmes as well as being home to the EPSRC-NERC Aura Centre for Doctoral Training in Offshore Wind and Environment.

Talk title

Anthropogenic impacts on tidal intrusion and flood hazard in the Mekong delta


Many of the world's major river deltas face a sustainability crisis, as they come under threat of increases in salinity and the extent of tidal zones forced by combinations of sea-level rise, changes in river discharge and channel geometry. The relative contribution of these factors to future increases in tidal extent remains unconstrained, with most prior work emphasising the role of climate-driven sea-level rise.

Here we use new field data from the Mekong delta to measure variations of river discharge and changes of channel geometry, and project them into the future. We combine these with projections of future sea-level rise into a 2D hydrodynamic numerical model and quantify the influence of the different driving factors on future tidal extension into the delta.

We show that within the next two decades, tidal extension into the Mekong delta will increase by up to 56 km due to channel deepening (92%), dominantly driven by anthropogenic sediment starvation. Furthermore, even under strong mitigation scenarios, sediment starvation still drives a long-term commitment to future tidal extension.

Specifically, by 2098 eustatically rising sea-levels are predicted to contribute only modestly to the projected extension. These findings demonstrate the urgent need for policy makers to adopt evidence-based measures to reverse negative sediment budgets that drive tidal extension into sediment starved deltas.

Dr Stephen Darby

Professor of Geography, University of Southampton

Steve Darby obtained his PhD in fluvial geomorphology from the University of Nottingham in 1994. After postdoctoral positions at the University of Florence in Italy and the US Department of Agriculture National Sedimentation Laboratory in Oxford, Mississippi, Steve took up a lectureship in geography at the University of Southampton in 1997, being promoted to Professor in 2011. Steve researches the morphodynamic processes that affect large rivers and their deltas, and has undertaken a series of NERC funded studies on the Mekong system.

Talk title

Impacts of sand mining on bank erosion in the Mekong delta


The Mekong delta is strategically important both within and beyond Vietnam, as its fertile soils support a highly productive agricultural sector that sustains livelihoods and food security for around 18 million inhabitants. Similar to many other large deltas, the Mekong is increasingly coming under anthropogenic stress as a result of climate change, upstream damming, groundwater extraction that leads to accelerated subsidence, and intensive sand mining.

Indeed, changes in channel morphology induced by large-scale sand mining are already known to be significantly affecting tidal hydrodynamics and saltwater intrusion (Eslami et al., 2019; Vasilopoulos et al., 2021). However, more recently there have been concerns that intensive sand-mining is also leading to an increasing severity and frequency of major episodes of river bank erosion.

Such episodes can lead to a loss of agricultural land and river-side infrastructure, including residential dwellings, and they therefore also pose a serious risk to human life. Here I will report the findings of recent work in which my colleagues and I have explored the extent to which sand mining versus other potential drivers of change is (or is not) leading to changes in river bank erosion.

To do this we employed a numerical simulation approach in which we used a 2D finite-element seepage analysis to predict how seepage in- and outflows to and from the river banks, and consequently river bank pore-water pressures, respond to combinations of semidiurnal tidal fluctuations acting in concert with seasonal variations in monsoonal flood pulse.

The outputs of these seepage simulations are then combined with a limit equilibrium stability analysis to determine the associated variations in factor of safety (an index of propensity for bank collapse: FoS values less than 1 indicate a bank prone to collapse). We have conducted these simulations for a range of study site locations that together encompass a full range of delta morphological contexts (as represented by variable cross-section morphology), while moving from the coarser-grained and fluvially dominated reaches near the apex of the delta through to the finer-grained, tidally dominated, areas closer to the sea.

In each case simulations were undertaken for an annual cycle using water level records observed at nearby gauging stations and for years representing high, average, and low flow conditions. We used the results to develop risk diagrams that highlight the relative risk of mass failure being triggered under the varying bank morphology, sedimentological and hydrological/tidal forcings.

Our results show that severe bed erosion, caused by intense sand mining, is the dominant factor driving increased risk of bank failure, suggesting that management of sand mining is urgently needed to control dangerous bank erosion within the Mekong delta.

Dr Cedric Laize and Professor Julian R. Thompson

CL: Hydro-ecological Modeller, Senior Scientist, UKCEH JRT: Professor of Physical Geography – Hydrology and Wetlands, UCL

Dr Laize is an ecohydrologist at UKCEH. Before moving to the UK, he worked as a lecturer in hydrology and hydraulics at the Institute of Technology of Cambodia (ITC), Phnom Penh from 1999 to 2001. His research includes a particular focus on approaches for environmental flow assessment. This includes pan-European impact assessments, methodology development to inform UK-wide environmental management and studies in Africa and Asia, including the Mekong.

Professor Thompson is a hydrologist with particular research interests in wetlands, numerical modelling and climate change. He has over 30 years of research and consultancy experience that includes work in the UK, Europe, Africa and Asia. The latter includes catchment-scale modelling of the Mekong Basin and detailed assessments of wetland ecohydrological functioning within the Mekong Delta to support conservation-oriented management.

Talk title

TEFRIC-ERFA: Development of environmental flow approaches and their application to the Mekong River Basin


The hydrological characteristics of a river are key determinants of ecological processes and exert critical controls upon aquatic ecosystems. Changes in these characteristics due to factors that include climate change or water resources management may therefore impact riverine ecosystems and the people who depend upon them.

The science of environmental flows has developed with the need to assess such impacts and a range of approaches are now available. Assessment methods that are useful both to researchers and practitioners requires data and tools that are both robust and easy to use by non-specialists.

This talk will cover methodological developments and earlier results for the Mekong from collaborative research undertaken by UKCEH and UCL. This ultimately led to the UK Natural Environmental Research Council (NERC) funded project “Translation of Environmental Flow Research in Cambodia” (TEFRIC) which, in collaboration with the Institute of Technology of Cambodia and the Tonle Sap Authority, developed TEFRIC-ERFA. This user-friendly code, developed using R and shiny, is based on the Ecological Risk due to Flow Alteration (ERFA) screening method which was originally designed for application in Europe.

Tailoring the code to SE Asia, development of a user-interface and demonstration of the final software included a series of workshops in Cambodia involving participants representing governmental organisations, academia, NGOs and consultancies from lower Mekong riparian states. In the talk we will demonstrate TEFRIC ERFA, which is now freely available for download, and its application to river flow projections for the Mekong.

Professor Philip Hirsch

Emeritus Professor of Human Geography, School of Geosciences, University of Sydney, Australia

Philip Hirsch is a geographer with four decades’ experience of teaching and researching in and on mainland Southeast Asia. During his 30 years at the University of Sydney, he served as Director of the Australian Mekong Resource Centre (AMRC) from 1997-2017. Professor Hirsch has published extensively on environment, development and natural resource governance in the Mekong Region.

His work extends from detailed community level studies to the geopolitics of river basin governance, including an investigation published as National Interests and Transboundary Water Governance in the Mekong (DANIDA and AMRC, 2006). His more recent book-length publications include the co-authored The Mekong: A Socio-legal Approach to River Basin Development (Earthscan, 2016) and the edited Handbook of the Environment in Southeast Asia (Routledge, 2017). Professor Hirsch speaks and reads Thai and Lao fluently, has intermediate Vietnamese and elementary Khmer.

Talk title

From lightly impounded to engineered river: implications for the politics of governing the Mekong


The rapid shift of the Mekong from a rather lightly impounded basin to one that is increasingly heavily engineered has diverse implications for the role of transboundary institutions, strategies of civil society, regulation by governments and coordinated management of mainly corporate-owned hydropower projects. These changes require a rethinking of governance in a rapidly engineered river system.

The scope for physical flow regulation facilitated by Mekong Basin hydropower operations has proceeded much more quickly than legal and institutional regulation through advances in transboundary governance. This talk will focus mainly on civil society challenges in adapting to this rapid transformation. River basin closure implies a shift of civil society concern beyond the questioning of future dams toward the challenges of dealing with existing ones, a shift that presents a number of dilemmas to NGOs, media, university researchers and other civil society actors.

The talk commences with a quick overview of the basin transformation and history of civil society concerns. Questions of flow regulation that maintain basic ecological functions of the basin go well beyond seasonality of water flows and extend into sediment flux and fisheries in particular. Associated with this is a need to understand the redistribution of “goods” derived from the river system in both geographic terms and between public and private actors.

The talk concludes with a number of suggested questions that civil society needs to pose to state and corporate actors regarding the governance of the now physically regulated basin for the public good.

Event venue

Watch Online
United Kingdom

For more information please contact:

Elira Alushi

e: [email protected]