The influence of an eleven-dam cascade in the
Lower Mekong Basin on fisheries of the Mekong
Delta
Gijs Drenth (11045892), Berend Schoone (11039981), Leonie Bouma (10898050) & Evelien van Maarseveen (10770585)
Interdisciplinary Project
Student teacher: A. ter Schure Expert supervisor: A. Verzijl 22-12-2017
This research is focussed on researching the impact of a cascade of eleven dams in the Lower Mekong Basin on the fisheries in the Mekong Delta.
Abstract
Fisheries in the Mekong Delta (MD) are an import food source for the approximately 60 million inhabitants of this region. However, the Lower Mekong Basin (LMB) has a great hydropower potential of generating 3000 MegaWatt (MW) and is therefore also used for extensive hydropower development. This resulted in the planning of the construction of an eleven-dam cascade in the LMB. Therefore, this research was aimed at answering the question: how will
the the eleven dam cascade in the Lower Mekong Basin influence the Mekong Delta fisheries from now until 2050? To assess this complex problem we have made use of the disciplinary insights from hydrology, sedimentology, biology and spatial planning. However each discipline
identified radically different underlying reasons for the impact of the eleven dams on fisheries in the MD: hydrological features played a major role, but so did sediment transportation and subsequent nutrient availability, habitat quality and connectivity and policy implementations. It is therefore highly important to not look at this problem from just a hydrology, sedimentology, biology or social perspective and not to try find the answer within just one field. But to integrate these disciplines based on their common ground. The research demonstrates that the eleven dam cascade will highly influence the hydrology of the Mekong River by balancing the wet and dry season discharge. This induces less nutrient availability, habitat fragmentation, habitat loss, and habitat degradation in the first place in addition to hindering of migratory behaviour of migratory fish species. It is estimated that, in 2050, all consequences of the eleven dam cascade will lead to a decrease of the fishery productivity of approximately 40 percent, compared to the year 2000. As dams could reduce the yields downstream of migrating catfish by approximately 70 percent. This will correspond to an annual economic loss of 200 to 480 million USD. Using a framework for sustainable development generated insight and an understanding of how the the hydropower development projects are navigated. Losses of fish productivity will have a great impact on local people who are dependent for their lives and livelihoods on fisheries. Furthermore, the arrival of the dams brings new opportunities for the development of the LMB as a whole. How this new situation will look like, is dependant on decision making.
Introduction
The Mekong delta (MD), located in Vietnam, serves as a main source of food and income for approximately sixty million people due to its large fisheries (Kang et al., 2009; Käkönen, 2008; Stone, 2016). The fisheries in the Lower Mekong Basin (LMB) and MD provide a large ecosystem service in terms of food availability and security for approximately sixty million inhabitants of the region: around eighty percent of their total annual protein intake depends on these fisheries and the fisheries have an estimated economic value of almost two billion USD (Kang et al., 2009; Stone, 2016; Baran & Myschowoda, 2009; Dugan et al., 2010). The Mekong basin is also an area that is known for its poverty and low development rates: of all inhabitants, 19 percent is classified as poor, 21 percent lacks access to drinking water and 30 percent does not have the possibility of using closed sanitation systems (Grumbine & Xu, 2011; Population Reference Bureau, 2010; U.S. Central Intelligence Agency, 2010). Most of those people - classified as poor - rely on the MD fisheries as their main food source (U.S. Central Intelligence Agency, 2010). In addition, they are also economically dependent on these fisheries for their livelihoods.
Since the river is ranked 10th on the list of the world’s largest rivers based on water discharge, it has a high hydropower potential, which has resulted in extensive hydropower development (Bakker, 1999; Grumbine & Xu, 2011). As a consequence, China is currently developing a series of eight dams in the Upper Mekong Basin (UMB), while plans for eleven dams in the main stem in the Lower Mekong Basin (LMB) are also advancing1 (see figure x; Grumbine & Xu, 2011; Orr et al., 2012). These eleven dams are scheduled to be constructed within the next ten years; seven will be located in Laos, two in Cambodia, and two will be shared between Thailand and Laos (Dugan et al., 2010). Together, this eleven dam cascade has the potential to generate 15000 megawatt (MW) of hydroelectricity with a potential of approximately 30000 MW for the entire LMB (Grumbine & Xu, 2011; Sivongxay, Greiner &
1
Figure @: map of the Mekong River Basin with the locations of mainstem dams constructed, under construction, and
proposed. The area downstream of the proposed Pak Beng dam is considered the LMB; the area indicated within the red rectangle is considered the Mekong Delta (thus, the Mekong Delta is a part of the Lower Mekong Basin) (Ferguson et al., 2011).
Garnett, 2017). This 15000 MW will accommodate for eight percent of the growing energy demand in the region (Bakker, 1999; Grumbine & Xu, 2011).
When built, it is expected that these eleven dams will inevitably influence those millions of people dependent on the ecosystem services of the MD. The physical presence of a cascade of eleven dams will definitely alter the characteristics of the MD in different fashions (Grumbine & Xu, 2011; Orr et al., 2012). Since the first dam (Xayaburi) is already under construction, it is necessary to give an overview of the ways in which the dams can do this (Sivongxay, Greiner & Garnett, 2017). This has already been done for individual cases of one or two dams, but an assessment of the influences of a project as large as eleven dams in total has never been done before. This paper also includes
multiple disciplines in studying the influences since the main processes influencing fisheries in the MD are completely intertwined. The disciplines included are earth sciences for the hydrology and sedimentology, biology and spatial planning. These were necessary perspectives since dam-induced changes in earth scientific processes regarding hydrology, nutrient fluxes and sediment transport influence life in the MD, which strongly affects fish population dynamics. Since the MD fisheries are a lifeline for approximately sixty million inhabitants, insights from spatial planning and social geography were essential to understand development incentives and the arising resource conflict for water usage. Since millions of people are dependent on the fisheries in the MD, it is also of societal relevance to understand the consequences of hydropower development on the fisheries in the MD.
Therefore, this study was aimed at answering the question: what is the influence of the eleven dams is on
the fisheries in the MD from now until 2050? As will be
explained further in the problem definition, the impact of a cascade of eleven dams on fisheries in the MD is a complex problem. A characteristic of complex problem is the unpredictability in the long term due to the nonlinearity of the problem (Rabin & Miller, 2000). Especially for this casus setting a time frame was necessary since climate change will most likely play a (unknown) part in the future (Marmulla, 2001).
In order to answer the research question an understanding of the status quo is need. What are the contributors to the current fishery productivity in the MD? An assement of the status quo and the is provided in section 1.1. Subsequently, in section 1.2 the eleven dams will be introduced, after which the conflicts that result from dam building will be discussed using the sustainable development triangle created by Campbell (1996). Using the information provided in section 1, there will be formulated a problem definition in section 2. In this section there will also be reflected on the complexity of the research problem. In section 3 the research methods and interdisciplinary integration methods will be discussed, combined with an explanation of the need of an interdisciplinary approach for the research problem described under section 2. Thereafter, the impact of the eleven dam cascade on the MD fisheries by 2050 will be assessed in section 4. In this assessment multiple sub questions are answered such as: how will the cascade of dams influence the overall nutrient flux? And to what extent
might the hydrology change in the MD and how will this impact the migratory fish species? The
underlying background mechanisms that are influenced by the dams will be discussed under section 4.1, after which the actual impact on the fisheries will be addressed under section 4.2. The resulting socioeconomic effects will be discussed under section 4.3, sustained by the sustainable development theory addressed under 1.2. Finally, in section 5 there will be given a short discussion and conclusion, followed by some policy recommendations and suggestions for future research.
In order to answer the research question, there are several subquestions that need to be answered as well. First of all, it is necessary to understand how the cascade of dams will influence the overall nutrient flux in the MD. Secondly, the most important fish for commercial fishing are migratory fish such as the Pangasius: at least 35 percent of all fish harvest consists of migratory fish (Stone, 2016). The behaviour and survival of migratory fish heavily depends on certain hydrological features. Therefore, the second sub question is: to what extent might the hydrology in the Mekong Delta change and what is the impact on the migratory fish species?
The questions stated above were answered through an extensive literature study in which outcomes in comparable situations in the past were applied and extrapolated to our eleven dam case. This was done from the perspectives of earth science, biology and spatial planning, which were integrated into an interdisciplinary whole. Using interdisciplinary research for answering the stated research questions was vital since the main processes going on in the system of research are completely intertwined: dam-induced changes in earth scientific processes regarding hydrology, nutrient fluxes and sediment transport influence life in the MD, which strongly affects fish population dynamics. Since the MD fisheries are a lifeline for approximately sixty million inhabitants, insights from spatial planning and social geography were essential to estimate the consequences of these biological and earth scientific processes for the fisheries in the MD.
In order to answer the research question, first there will be made an assessment of the status quo of the fisheries of the MD in section 1.1. In this section there will also be given some general characteristics of the research are.
1 Status quo of the MD fisheries and its associated conflicts
In this section, a theoretical framework will be provided regarding the case of the eleven dam cascade in the MD. This framework will in the first place assess the current status of the MD fisheries from earth scientific, biological and spatial planning (socioeconomic) points of view, including some the associated processes (section 1.1). Thereafter, in section 1.2 there will be provided insight into the resource conflict between preservation of ecology and industrial development (i.e. construction of hydropower dams) that will result when the dams are being built.
1.1 Status quo of the Mekong Delta fisheries
The Mekong river flows through China, Myanmar and Lao PDR, which means the prevailing climate in the river basin gradually changes to a tropical and seasonal climate (Dudgeon, 2000). This is the main climate class in the LMB; the Mekong hydrology is dominated by a wet season flow peak that prompts a 20-fold increase in discharge for August and September (ibid.; Lu & Siew, 2006; Kummu & Varis, 2007; Kuenzer et al., 2013a). During these months, discharge reaches 40 000 m3/s, which is being reduced to roughly 2100 m3/s
in dry season; these amounts also include suspended solids (Le et al., 2007; Piman et al., 2012). The timing of the floods in wet season is partly dependent on when the flow direction in the Tonle Sap rivers reverses, since this lake functions like a buffer for the LMB (Hung et al., 2012; Kummu et al., 2014). The Tonle Sap also affects the intensity of floods: if more water flows into the Tonle Sap and more water is released at high water levels, the flood pulse intensifies and flood intensity increases (Kummu & Sarkkula, 2008). Because of these seasonal dynamics, the Mekong has the most concentrated riverine biodiversity per hectare on earth with 850 different fish species (Hortle, 2009). Additionally, duration of these floods depends mostly on the water level in the Mekong River and its discharge: the higher discharge and water level during wet season ultimately results in longer and more intense floods (Delgado, Apel & Merz, 2010; Kuenzer et al., 2013b). This induces a predictable floodplain inundation during these months (Kuenzer et al., 2013b). However, nowadays, the MD has a canal system of approximately 45 000 segments with a length of 87 500 km in total, which is accompanied by extensive dyke and sluices development (Hung et al., 2012; Hung et al., 2014). Consequently, floods are increasingly regulated and floodplains are cut off from the natural flooding processes (Hung et al., 2012).
The general characteristics of the MD and LMB mentioned above together are responsible for the current fish stocks and fisheries in the MD. However, the Mekong River Commission (MRC; 2016) assessed the ecological health of the whole LMB, and they already classified the MD as ‘moderate’ to ‘poor’ (see figure @ and @).23 This means that the current fish stocks are
already not in a good state. Together, these LMB fish stocks provide around 4
2 Figure @: the temporal change of ecological health in the LMB during 2004-2008. Ecological health is
defined based on three characteristics: species richness (number of species or species groups), abundance (number of individuals), and Average Tolerance Score per Taxon (ATST). The ATST is an indicator of the tolerance to pollution of plant and animal groups (taxa) found at each site and re ects how disturbed the site is (MRC, 2016). The four classes of ecological health are A (excellent), B (good), C (moderate), and D (poor). All MD assessments were made in Vietnam (VTP, VTT, VCL, and VVL) and they were all classified as ‘moderate’ in 2008 (MRC, 2016; MRC, 2008).
3 Figure @: visualisation of the LMB ecological health assessment of 2008. These data correspond to the
million tonnes of fish annually, of which 2.1 million tonnes are from capture fisheries, and 1.5 million tonnes from aquaculture (MRC, 2016; MRC, 2010b). Of those 1.5 million tonnes from aquaculture, around 1 million tonnes are being exported. These commercial fisheries employ millions of people and have a value of almost 2 billion USD (ibid.; Van Zalinge et al., 2004). Compared to 2004, a slight decline is visible in the fishery productivity, and there is a tendency towards catching more smaller, fast reproducing species instead of larger specimen of a species (MRC, 2016; Van Zalinge et al., 2004). Since a high species diversity with high abundances indicates good river circumstances, this could mean that the environmental quality is already declining because catching only small, fast reproducing fish could mean that the species that need more time to grow have already almost disappeared from the ecosystem (MRC, 2016).
Of all fish harvest, at least 35 percent is a migratory fish species; the lion’s share of those migratory fish consists of catfish (Pangasiidae, Siluridae, Bagridae) and Cyprinidae (Stone, 2016; ICEM, 2010). Catfish – especially Pangasiidae – are very important for aquaculture and are highly economically profitable for the MD region (Pukinskis & Geheb, 2012; Ferguson et al., 2011). Most catfish are long distance migratory fish, which together account for at least 35 percent of the fish harvest in the LMB (Pukinskis & Geheb, 2012; Stone, 2016; ICEM, 2010). Moreover, almost ninety percent (165 species) of all fish individuals in the MB are migratory (Baran & Myschowoda, 2009; Ferguson et al., 2011). Fish migration involves longitudinal movement on the one side, going hundreds of kilometers along the Mekong basin and its tributaries, and lateral migration on the other side, with movement towards floodplains and back (MRC, 2016; Poulsen et al., 2002). Migratory fish need to migrate for foraging and breeding, because the habitats they need for feeding and reproducing differ temporally and spatially (ibid.). For instance, when fish migrate upstream in order to reproduce, at the start of wet season their offspring will use the rising flows to drift towards the floodplains: this is where they are most productive (Baran, 2006).
Accordingly, fish use certain parameters in order to decide whether they are going to migrate in the LMB (Baran & Myschowoda, 2009). However, these environmental conditions are only known for 30 out of the 165 known
migratory species (see figure @; Baran, 2006). As can be seen in figure @,4 most (80 percent) fish species react to changing water levels in their migration behaviour; this can either be when they are rising (wet season) or when they are declining (dry season) (Baran, 2006; MRC, 2016; Kang et al., 2010). Other migration triggering parameters are changes in water colour (light availability) caused by sediments flowing from the land into the Mekong, and changes in rainfall, discharge, and insect abundances (insects are a vital food source) (ibid.). By any means, all migratory fish use the signs of the ending of the dry season to
decide the initiation of their journey upstream (Marmulla, 2001; Kang et al., 2010; Baran, 2006; Baran & Myschowoda, 2009).
Fish migration is directly linked to the nutrient supply in the Mekong River. After all, upstream fish migration also forms a major part of the nutrient supply: the organic matter migratory fish leave behind when they die after spawning is a direct food source for their fry and for plankton, which in the end is a food source as well (Marmulla, 2001; Stone, 2016; Walling & Fang, 2003). These nutrients are an addition to the large supply provided by the river sediment fluxes, which are a vital nutrient source for all fish in the Mekong River (Marmulla, 2001; Kondolf et al., 2014). The current sediment flux of the Mekong River into the
4 Figure @: the environmental conditions which trigger fish migration in the LMB for all migrant species.
However, these are known for only 30 of the 165 known migrant species. Despite this, there can easily be seen that most species will react to water level changes (MRC, 2016).
MD and South Chinese Sea has been estimated to be approximately 160 million tonnes per year (Kondolf et al., 2012). This sediment consists of two types: suspended load (smaller size particles held aloft by turbulence) and bedload (coarser sized sediment that moves along the river bed) (ibid.) For the fisheries, the most important function of sediment is nutrient transport, which happens in nutrient clumps called flocs (Droppo, 2011).
Another important nutrient source originates in the floodplains of the MD: floods directly deliver nutrients to the water body by flushing in decaying terrestrial organic matter (Baran & Myschowoda, 2009). These types of nutrient supply contain biological and non-biological components that are valuable for river primary productivity (Droppo, 2011). Moreover, floodplains in the LMB are vital for maintaining fish stock sizes and inland fishery productivity in the MD, because they form massive feeding and breeding grounds for most fish species during wet season (Pukinskis & Geheb, 2012; MRC, 2016). These floodplains normally occupy roughly 84 thousand km2 (Baran & Myschowoda, 2009; Le et al., 2007). Part of the floodplain
environment are deep pools (Poulsen et al., 2002). These should not be seen as segregated fish habitats, but more as integrated components of the Mekong ecosystem (ibid.). Like floodplains are the main refuge environments during wet season, deep pools bear the same function during dry season: they literally are the deeper parts of floodplains and ever-inundated water bodies, and mainly provide spawning, foraging and hiding habitats when the Mekong water levels recede and seasonal floodplain habitats disappear (ibid.; Baird, 2009). Fish inhabit the deep pools until the water levels rise again: hence, deep pools mainly contribute to the support and stability of the fishery productivity (Poulsen et al., 2002; Baird, 2009). Consequently, the more deep pools available in dry season, the more replenishment of fish stocks (Baran & Myschowoda, 2009).
1.2 The relationship between economic development and ecological preservation
The current ecological status described in section 1.1 is going to be altered: as already has been made clear in the introduction, there is a cascade of eleven dams planned to be built in the LMB, mainly aimed at providing hydropower to the region. Of the eleven dams, Sambor Dam (located in Cambodia) will have the largest mean energy output per year of around 15 thousand GWh (MRC, 2011). However, the rated head of Sambor dam will not be larger than the other ten planned dams, i.e. around 33 metres (ibid.). These other dams will all produce between 2 and 10 thousand GWh per year (ibid.). The live storages (the amount of water retained by the dam under the minimum operating water level; MRC, 2011) of the eleven dams will differ depending on changes in river flow and energy demand (ibid.). Sambor dam will have the largest live storage of 2000 million m3; this is relatively low when compared to the largest
existing dam, Nam Ngum, which has a live storage of 4700 million m3 (ibid.). The other planned
dams will store between 70 and 734 million m3 water under minimum operating water level (ibid.). However, the reservoir areas of the dams will be much larger than those of the already existing dams: six of the planned dams in Cambodia are estimated to have reservoir areas of more than 300 km2, while the largest existing reservoir area (that of Nam Ngum dam) is only
294 km2 (MRC, 2011). Generally, the larger the reservoir area, the more people will be affected
and forced to move, and the more agricultural and forest losses will be induced (ibid.). Finally, three out of the eleven dams will be supplied with a fish ladder (Baumann & Stefanella, 2012; Grumbine & Xu, 2011).
Hence, the size of the planned dams will absolutely lead to problems within fisheries since these are both so dependent on the hydrological features of the river (see section 1.1). Besides the fact that the fisheries provide large economic benefits, fishing also forms an important cultural heritage in the countries of the LMB (MRC, 2011). Consequently, the fisheries do not only have a financial value, but also an intrinsic value that also has to be preserved. However, in order to achieve this economic prosperity whilst preserving the ecological conditions required for sustaining the fisheries in the region, developing in the LMB is important (MRC, 2010a). From a planning perspective, these goals of sustainable development are generally conflicting (MRC, 2011). Therefore, it is useful to look into the
development of the LMB from a planning perspective in order to elaborate how the development of hydropower relates to ecological preservation that is required to sustain fisheries.
The complexity of governing water bodies is often accompanied by the influence of political and institutional influence and affected by power relations, which is also the case for the development of the LMB (Sneddon & Fox, 2006). Therefore, it is assumable that decision-making processes of the MRC are affected by such power relations as well. However, these power relations are not relevant to the scope if this research. Since the MRC is the institution that carries the final responsibility for the development of the LMB, they are considered to be the overarching responsible planning agency of the region in this research (ibid.).
To provide insight in the relation between different goals that are required for sustainable development, this research adopts a framework by Campbell (1996). According to Campbell (1996), the conditions of green, profitable, and fair sustainable development are defined by a balance between three goals: social justice, economic growth and environmental protection. In an ideal world, planners would strive to achieve these goals simultaneously. However, in practice, planners are limited by professional and fiscal constraints in focussing on assembling these goals (Campbell, 1996). Planners commonly represent a narrow goal of their clients, which often are authorities and bureaucracies, making it difficult to combine the three goals for sustainable
development (ibid.). Therefore, planners eventually represent one of these goals while neglecting the other two (ibid.).
Campbell (1996) uses a triangular model to demonstrate how the three different goals in planning for sustainable development contradict and conflict in practice. Although he reflects his model on cities, the model gives interesting insight in planning larger areas, such as the LMB, as well. Although this model is not representative for the practice of planning as a whole, it is useful for its conceptual simplicity (Campbell, 1996). It shows three points that represent different interests and therefore lead to three different conflicts, by which conflicts of achieving two goals at the same time is meant (see figure @5; Campbell, 1996). The first conflict arises from the goal of economic growth and equity, leading to the property conflict. It arises from competing claims on property and raises questions when decision makers decide to develop an area. How is the equal distribution of the benefits among the people who are reliant on the area and those who are responsible for the development to be ensured? The second conflict is the resource conflict, since economic growth is often associated with environmental impact; i.e. it is a conflict between economic growth and environmental protection (Panayotou, 1993). The third and final conflict is the development conflict, between social justice and environmental protection. According to Campbell (1996), efforts to protect the environment often lead to lower economic growth in many countries, exacerbating the inequalities between rich and poor nations, which shows the importance of economic growth.
Considering the MRC to be the planning institution for the LMB, insight into the relationship between the contrasting three goals of sustainable development helps to place the MRC in this framework and to determine the priorities of the MRC. Subsequently, this insight generates an understanding of how the MRC navigates the hydropower development projects and its motives to do so, and what this implies for fisheries that are predominantly contingent upon ecological preservation of the habitat that is required for fisheries to be productive.
5 Figure @: the triangle of conflicting goals for planning and the three associated conflicts. Planners
implicitly define themselves by where they stand on the triangle. The elusive ideal of sustainable development leads one to the center (Campbell, 1996).
2 Problem definition
The interconnected concepts that form the basis for the status quo of the fisheries in the MD are presented in the theoretical framework. In this framework the developmental incentive for hydropower dams is explored as well along with the resulting resource conflict. It turned out that it is a choice of local leaders whether industrial development is deemed more profitable and desired than preserving the ecosystem; sacrifices simply must be made in order to advance the industrial development of a region. Therefore, the hydropower dams will result in a resource conflict with the ecosystem of the LMB (and the MD included). As already has been made clear, this paper is focussed on the fisheries, which are a food and livelihood providing ecosystem service. A shared feature between these fisheries and the hydropower dams is that they both rely upon water, i.e. certain hydrological features. For the fisheries the hydrological features play a large role since 90 percent of the fish in the LMB is migratory: hydrological changes are their migration indicator (Ferguson et al., 2011). However, at the same time these hydrological features are the driver behind possible hydropower exploitation, as already pointed out. This results in a conflict.
It is very important to understand the consequences of changing the status quo. While this change might be good in certain situations if it advances economic opportunities, the byproducts of the desired outcome must not be neglected. There is a definite consensus in the scientific community that dams will alter the hydrological features of a river (Le et al., 2007; Xi, Jian-Jun & Grundy-Warr, 2008; Lu et al., 2014). To illustrate this, Poff et al. (2007) reviewed 165 papers that assessed rivers with various flow alterations, and 88 of those showed flow alterations due to the construction of a dam cascade. This also shows that the impact of dam cascades on hydrology is well researched within the discipline of hydrology. However, the impact of a dam cascade on fisheries - especially fisheries that rely mainly on migratory fish which involves multiple disciplines - is not fully researched and clear yet. Especially the case addressed in this paper, a cascade of eleven dams, is still full of uncertainties and unforeseen consequences within the disciplines of spatial planning, biology and earth sciences. While the overarching problem is that hydropower development will require sacrifices in terms of the LMB ecosystem’s health and productivity, this research tries to bridge the knowledge gap of the impact from the cascade of dams on fisheries in the MD.
The problem addressed here is a complex problem, in the first place because the future will remain partially unknown due to other factors such as climate change. Therefore, in order to frame the problem and to prevent climate change from influencing the results, there was added a timeframe of now until 2050 to the stated research question (what are the influences of the cascade of eleven dams on the fisheries in the Mekong Delta from now until 2050?). What further makes this problem a complex problem is that it is unknown what the trade-off between industrial development and ecology consists of and what it will lead to. The different perspectives from which the problem is being evaluated in this paper might identify radically different underlying reasons for the impact of this trade-off and the subsequent impact of dams on fisheries in the MD: hydrological features may play a major role, but so will sediment transportation and subsequent nutrient availability, habitat quality and connectivity and policy implementations. It is therefore highly important to not look at this problem from just a hydrology, sedimentology, biology or social perspective and not to try find the answer within just one field. Complex problems are a result of and result in multiple and interrelated disturbances that cannot be seen separately.
In the theoretical framework the status quo is already evaluated from integrated perspectives, which is necessary since the status quo does not only rely on e.g. hydrology or nutrient availability alone. Therefore, it is also essential to assess the influence of a cascade of eleven dams on the fisheries in the MD from an integrated perspective. If the problem is assessed from just one perspective, you will never be able to expose the complete problem and underlying links but only a part of it. The following section will demonstrate how this research has integrated the multiple disciplines.
3 Methods for research and interdisciplinary integration
To understand the influences a cascade of eleven dams will have on fisheries in the MD, it is important to know what contributes to a productive fishery and how dams will influence these contributors. In addition, the underlying reasons for wanting to change the status quo are important as well to understand the drivers for change. Therefore, when conducting this research, we first studied these contributors and drivers separately through a literature review for each discipline. In these reviews the impacts that dams may have on each field were included as well. The data were collected by combining search terms such as hydrology, sediments, policy, migratory fish, or dams with Mekong Delta or Lower Mekong Basin. Researches specifically concerning another situation without general conclusions have been mostly excluded. Since each complex problem is unique, finding data was essentially focused on the MR, LMB and MD. The MRC proved to be a useful guideline in searching for information and data, since this commission does a lot of research in the region of which all reports are available on their website. The MRC is an intergovernmental organisation that regulates the use of the ecosystem services the Mekong River provides to all countries it flows through (i.e. Cambodia, Lao PDR, Thailand and Vietnam; MRC, 2017). It also aims to guarantee that those water resources are exploited in a sustainable way (MRC, 2017). Their research varies from simple statistical analyses to large-scale assessments regarding issues about policy, hydrology, economy and biology in the Mekong Basin.
The literature (either scientific, governmental or from NGOs) formed the basis for clarifying causal relations within the disciplinary systems. Through summarizing this information we were able to create a foundation from which we could integrate and expose underlying links between different disciplinary systems and represent the system as a whole. When integrating the disciplines, we looked for the common ground within the casus. This turned out to be the productivity of the fisheries in the MD and the resource conflict which arises from hydropower development, since each discipline plays an important role in this. However, each discipline has its own way of contributing to fishery productivity that led to conflicts identifying the keystones for the fishery productivity in the MD. Acknowledging that fishery productivity relies on aspects from multiple disciplinary fields and that a resource confluct will arise from hydropower development; allowed for reorganising and modifying the disciplinary concepts to answer the common underlying question: how do these concepts contribute to the fishery productivity in the MD? And how will a resource conflict arise with implementation of hydropower development?
With this underlying question in mind it was much easier to expose the causal relations within and between each discipline. It also allowed the more beta oriented perspectives to understand the context in which policies and decisions are made. Through researching the
effects of a cascade of eleven dams on these causal relations that contribute to fishery productivity we have tried answering the research question. While also taking the trade-off between industrial development and ecology into account.
4 Results
Now that the contributing factors to fishery productivity are fully understood; the impact of the eleven dams on this status quo can be assessed. This will be done in two phases: in section 4.1 the underlying mechanisms that determine the influence of the dams on the fisheries will be discussed using a framework that shows all relationships (figure @). After elaborating these crucial processes, in section 4.2 the ecological impacts of the eleven dams will be assessed, and the socioeconomic consequences of these will be explained in section 4.3.
4.1 Background processes influenced by the dam cascade
In figure @ all underlying processes determining the influence of dams on fisheries are displayed. In the earth sciences and hydrology field there is a general consensus that the physical blockage of the eleven dams will alter the hydrological features of the Mekong River described in section 1.1 (Bunn & Arthington, 2002; Poff et al., 2007; Poff & Zimmerman, 2010; Mims & Olden, 2013). To begin with, the physical blockages of the eleven planned dams will let the wet season virtually disappear from the hydrological cycle by storing water during monsoons (Baran & Myschowoda, 2009). In the first place, this will result in a delay of flooding initiation in wet season (ibid.). This results in an average decrease in wet season discharge (40 000 m3/s) up to 24 percent during wet season, mainly because the dam reservoirs have to
be refilled after dry season (Lauri et al., 2012). Consequently, this delays the onset of floods during the dry season, while these floods will be higher: the dry season discharge (2100 m3/s)
may increase with 41 to 108 percent because water will be released from the dam reservoirs for irrigation and navigation purposes (ibid.; Baran & Myschowoda, 2009; Räsänen et al., 2017).
Moreover, the planned eleven dams in the LMB are also estimated to induce a wet season shortening of approximately one week (altered flood timing; Baran & Myschowoda, 2009). In addition, the floods will not only be delayed, but they will also be shortened due to the changed flow regimes (Baran & Myschowoda, 2009). Therefore, the inflow reduces during the wet season as water levels are lower in the Mekong river, which will also result in a reduction of the outflow from the Tonle Sap (ibid.). Since the outflow of the Tonle Sap and flood intensity are positively correlated (see section 1.1), this will mean that the flood intensity will decrease (ibid.; Kummu & Sarkkula, 2008; Sakamoto et al., 2007). Moreover, the delayed, shortened floods will also be lower during wet season, which will result in smaller fish habitats (i.e. less habitat quality) and decreased available foraging surface area (Baran, Starr & Kura, 2007; Baran & Myschowoda, 2009; Stone, 2016; Darby et al., 2016; Manh et al., 2015). Since most species spawn in wet season, this form of habitat loss is a serious threat to the fishery production (Baran & Myschowoda, 2009). Moreover, as a consequence of the lower watermark, the (smaller) habitats in the MD also lose their connectivity and become fragmented (Baran, Starr & Kura, 2007).
Apart from the loss of habitat area, the fish habitats will also decrease in quality regarding the nutrient availability (Grumbine & Xu, 2011). The bedload and suspended load carried by the river water (see section 1.1) will be trapped by the dams: when the eleven dams are built, it is estimated that in total half to three quarters of the total river sediment weight will be trapped (Grumbine & Xu, 2011; Kondolf et al., 2014). This will result in filling of the reservoirs, which is expected to lead to a decrease of the total reservoir volume of approximately one percent per year (Kondolf et al., 2014). This can also be expressed as the ‘live storage’, which is the main determinant of dam sediment trapping (MRC, 2011). Larger dams will have a larger live storage because the flow velocities downstream will be slower.
Not only does this result in a decreasing usefulness of the reservoir, it also negatively impacts the dam itself because it decreases turbine efficiency and the stability of the dam wall (MRC, 2011). Moreover, sediment trapping is also a strong driver for sediment and nutrient starvation downstream (ibid.). This nutrient starvation is further being increased due to the
changing hydrological regime: normally, floods deliver nutrients by moving nutrients and sediment downstream and by flushing in decaying terrestrial organic matter, but in periods of less and lower floods – as will be the case when the eleven dam cascade is finished – the fish production will decrease immediately as a cause of the declined nutrient flux; this is referred to as the flood pulse concept (Baran & Myschowoda, 2009).
In addition, the sediment trapping and nutrient starvation also disturb the stream of the biological and nonbiological components captured in sediment flocs (Droppo, 2011). This hinders the nutrients from flowing towards the MD, which leads to a decrease of the river primary productivity and sediment-starved waters (i.e. hungry waters) that induce erosion of the riverbed and riverbank (ibid.; Pukinskis & Geheb, 2012). Erosion of the riverbed and riverbank will result in exposure of bedrock material because smaller sediments and aquatic plants, animals, and vegetation debris are being removed by the water (Droppo, 2011; Pukinskis & Geheb, 2012; Grumbine & Xu, 2011). It is estimated that this erosion of the basin will also let a minimum of 250 thousand hectares of vital floodplain habitat in the LMB disappear (ICEM, 2010; Marmulla, 2001).
4.2 Ecological impacts on fisheries
Now the underlying processes that are influenced by the eleven dams have been made clear, the actual impacts of the dams on the fisheries can be assessed. In this way it will become clear how the status quo described under section 1 will be altered. To begin with, the altered hydrological features described under 4.1 induce a wet season shortening of approximately one week (Baran & Myschowoda, 2009). On the scale of the five-month wet season, this does not seem extremely harmful, but the effects are significant: a shortened flood season will also imply a shorter nutrient flux towards the MD, which normally should provide juvenile fish the nutrients they need to grow (Arthington et al., 2004; Stone, 2016). Moreover, since early floods in the season are of vital importance for fish larvae and juveniles, this will negatively affect their survival rate (ibid.; Stone, 2016). This will yet again result in lower fishery productivity in the MD caused by the fact that the fish are smaller and thus have lower surviving and mating chances (Arthington et al., Stone, 2016).
Moreover, the hydrological changes will also subject the deep pools (see 1.1) to siltation; this is also a form of habitat quality decrease (Poulsen et al., 2002). This, in combination with the habitat degradation addressed in 4.1, means that fish have less places to hide and forage and will thus lower the habitat quality and fishery productivity (Pukinskis & Geheb, 2012). Because the habitats become smaller due to lower floods, they will also end up being fragmented; since habitat fragmentation decreases habitat diversity, this will pose serious threats to the fishery productivity (Pukinskis & Geheb, 2012; Costanza et al., 2011).
After all, the habitat diversity – maintained by the seasonal hydrological pattern that the dams will alter – is the main contributor to the high biodiversity rate that the Mekong boasts; consequently, habitat diversity loss will eventually lead to biodiversity (species) loss (Valbo-Jørgensen, Coates & Hortle, 2009; Ziv et al., 2012; Chea et al., 2017). Consequently, species loss will pose serious threats to the fishery productivity (Hortle, 2009).
Apart from the influences the dams will have on habitat quality, their large physical presence will also directly affect fish in the entire Mekong Basin. First of all, the dams also block organisms from moving in the river system by forming barriers (Pukinskis & Geheb, 2012). Since anything that directly hinders fish migration in the downstream river parts will have significant negative consequences for the fishery production, the eleven physical barriers in the LMB are a very serious concern for the fisheries in the MD: it is estimated that, if the eleven dams are fully built, in 2030 more than eighty percent of the LMB will be obstructed and thus unreachable to migratory fish (Stone, 2011; Stone, 2016; Baran, 2010). This poses major threats to the migratory fish species populations: the physical blockage of the dams will interrupt their migration route between feeding and breeding zones, preventing them from migrating upstream to spawn and completing their lifecycle (Pukinskis & Geheb, 2012; Stone, 2016). This effect can become really serious: it could result in no remaining breeding grounds in the river, leading to species extinction (MRC, 2011). Because the migratory fish will be delayed and end up very concentrated near the dams, the areas just below the dams will become a favorable habitat for predatory fish species (Larinier, 2014). A case study conducted in France showed that the hindering of free upstream migration has much more severe effects than for example pollution, overexploitation or habitat destruction (ibid.).
Moreover, migratory fish species will be harmed most by dams located more downstream near floodplains – which includes the eleven dams cascade – because downstream located dams interfere with a larger fraction of the longitudinal fish migration network (Ferguson et al., 2011). A case study conducted in the Amazon Basin by Bergkamp et al. (2000) concluded that dams hinder long-distance migrations of catfish in such a way that the yields downstream were reduced by approximately seventy percent. This is mainly caused by the fact that the altered hydrological features (see section 4.1) caused by the dam cascade will blur the migration parameters addressed in section 1.1. Blurring the migration parameters will inhibit the upstream spawning, resulting in lower fishery productivity (Baran & Myschowoda, 2009). An important consequence of this is that the downstream nutrient supply will be lowered even further. After all, upstream fish migration also forms a major part of the nutrient supply: the organic matter migratory fish leave behind when they die after spawning is a direct food source for their fry and for plankton, which in the end is a food source as well (Marmulla, 2001). This process will be inhibited when the construction of the eleven dam cascade is finished, which will lead to less nutrient provision for the juveniles that should return to the MD (ibid.). In the end, this will lead to a lower fishery productivity in the region. Barlow et al. (2008) estimate that the annual loss of migratory fish biomass will be between 0.7 to 1.6 million tonnes; this is a quarter to almost a half of the annual catch of 4 million tonnes of fish mentioned in section 1.1.
As has become clear in this section so far, most of the problematic impacts induced by the dams eventually have its effects on different components of the nutrient flux, habitat quality, or migration behaviour and opportunities of migratory fish species. All of the above-mentioned impacts will eventually result in a large decrease in fish stock and thus fishery productivity. Bart Geenen (WWF, personal comment on 29 Nov 2017) stated that, around 2050, this decrease will be approximately 40 percent after the eleven dams are completed, compared to the year 2000. This will correspond to an annual economic loss of 200 to 480 million USD (Baird, 2011; ICEM, 2010).
4.3 Socioeconomic consequences
Reports of the MRC pay a lot of attention to benefit sharing. According to the MRC, benefit sharing is being driven by a societal responsibility to ensure that local communities end up with
something better than pre-project economic conditions. For benefit sharing to work, certain core mechanisms must be in place: policies and the regulatory framework (government), corporate social responsibility policies (project proponent), and community acceptance of the project.
Ha (2011) examined the role of the MRC, by reviewing the first fifteen years of the MRC, which was founded in 1995. He emphasizes the role of the MRC as the institute that is responsible for development, investment and regulation, but he concluded that the MRC has been unable to effectively manage water usage and development along the Mekong region. Sustainable development for the poorest Mekong residents still has a long way to go, and large-scale infrastructure and agricultural projects have resulted in an overall economic growth, but also in greater income inequalities (Ha, 2011). Ha (2011) also describes a shift in attracting investment for development projects from collaboration with international financial institutions towards projects with private investors. This is particularly true for the market of hydropower development, demonstrating a shift from a basin management and knowledge organization towards an investment attracting organization (Ha, 2011).
This shows that the development of the Mekong River Basin is dominated by the achievement of economic growth, which helps to place the commission in the triangular model by Campbell (1996). It shows that the MRC is concentrated on achieving the goal of overall economic growth. From this goal, the resource conflict arises. In the case of the MRB, the resource of the conflict is water. The water is used by dams as a resource to generate energy, impacting the environment by affecting the ecological conditions to sustain fish biodiversity. Since there is a large concentration on economic growth, it is likely that there is minor attention for the impact on fisheries in the developing process of the LMB.
Moreover, as has been made clear in section 4.2, a case study conducted in the Amazon Basin by Bergkamp et al. (2000) concluded that dams will reduce the yields downstream of migrations of catfish by approximately seventy percent. This will have relatively large socioeconomic consequences since migratory fish such as catfish - especially Pangasiidae - are very important for aquaculture and are highly economically profitable for the MD region (Pukinskis & Geheb, 2012). Although it is not possible to measure the exact impact of the eleven dams, losses of fish productivity will have a great impact on local people who are dependent for their lives and livelihoods on fisheries, if no alternatives will be provided (Pukinskis & Geheb, 2012; Ferguson et al., 2011).
However, the arrival of the dams also brings new opportunities for the development of the LMB region as a whole, such as the development of new industries (MRC, 2011). Furthermore, it is likely that the development of hydropower is associated with development opportunities and economic benefits for the region. The outcome of this economic development process is highly dependent on policies and decisions making. Therefore, it is likely that the development of the dams has a great impact on local people who are dependent on fisheries for their livelihoods and for the development of the region as a whole. What the new situation will look like, is depending on decision making and therefore unclear.
5 Discussion, conclusion and recommendations
5.1 Discussion
Now all (predominantly negative) consequences of the eleven dams on the MD fisheries have been addressed, it is time to also have a look at the positive side of the eleven dam cascade. While the fisheries will definitely be impacted in a negative way, the highly controlled floods could also be beneficial to fish farms and other forms of aquaculture (MRC, 2011). In this way, the nutrient streams can be more regulated so that the efficiency will be maximised, the farms can be adjusted to the water levels (that will be known by then), and the fisheries can rely on a constant water flow so that they will always have enough water to maintain their farms (MRC, 2011). This could also create jobs for the fishermen that now rely on wild fish captures. However, whether aquaculture could fully replace the ‘wild’ fisheries has not been assessed yet; this is something we would recommend for future research.
Another point of discussion that has to be mentioned concerns the canal system in the MD. As has been addressed in section 1.1, the MD has a canal system of approximately 45 000 segments with a length of 87 500 km in total, which is accompanied by extensive dyke and sluices development (Hung et al., 2012; Hung et al., 2014). In this way, floods are increasingly regulated and floodplains are cut off from the natural flooding processes (Hung et al., 2012). However, what Hung et al. (2012 and 2014) do not mention, is that this canal system might also regulate the excess of water that the dams will cause during dry season, so that the floods will not come unexpected and in very high amounts of water compared to the ‘normal’ dry season. This might also be beneficial to the fish farms mentioned above.
Like was already mentioned in section 1.2, three out of the eleven dams had incorporated a fish ladder in their blueprint (Stone, 2016; Grumbine & Xu, 2011). Because current-day fish ladders are not functioning very well, it is suggested that there will be conducted more research regarding innovating those (Da Silva et al., 2017). However, this will not mitigate the dam influences for the eleven dam cascade since the fish ladders have to be incorporated in the blueprint and all blueprints for the eleven dams have already been made (Stone, 2016).
The last discussion case concerns the role of the Mekong River Commission. As turned out from section 4.3, Ha (2011) examined this role, and he concluded that the MRC has been unable to effectively manage water usage and development along the Mekong region. This above-mentioned indicates that the MRC might not be the best organization to conduct policy in the region; therefore, we suggest future research aimed at the functioning of the MRC and how this could be improved.
5.2 Conclusion
This research was aimed at answering the question how the the eleven dam cascade in the LMB will influence the MD fisheries from now until 2050. These fisheries provide a large ecosystem service in terms of food availability and security for approximately sixty million inhabitants of the region. The fisheries rely on the hydrological features of the Mekong River, characterized by a wet and dry season. Because of these seasonal dynamics, the Mekong has the most concentrated riverine biodiversity per hectare on earth with 850 different fish species, of which migratory fish species (which are very profitable) make up almost 90 percent of the individuals.
However, because the Mekong River Basin is so large, it is also used for extensive hydropower developments that resulted in the planning of the construction of an eleven-dam cascade in the LMB. Sadly, the current ecological health of the LMB is already classified as ‘moderate to poor’, and the eleven dams were expected to aggravate this. The problem addressed here is a complex problem, in the first place because the future will remain partially unknown due to other factors such as climate change and the nonlinearity of the problem, and
in the second place because it is unknown what the trade-off between industrial development and ecology consists of and what it will lead to. Therefore, the problem was approached from three different perspectives: earth sciences, biology and spatial planning. These identified radically different underlying reasons for the impact of the eleven dams on fisheries in the MD: hydrological features played a major role, but so did sediment transportation and subsequent nutrient availability, habitat quality and connectivity and policy implementations. It was therefore highly important to not look at this problem from just a hydrology, sedimentology, biology or social perspective and not to try find the answer within just one field.
From our research it turned out that the eleven dam cascade will highly influence the hydrology of the Mekong River by balancing the wet and dry season discharge. This induces less nutrient availability, habitat fragmentation, habitat loss, and habitat degradation in the first place in addition to hindering of migratory behaviour of migratory fish species. The physical barriers of the dams makes it nearly impossible for migratory fish to migrate upstream to their spawning grounds. This also creates accumulation of fish just below dams, which might attract predators that subsequently eat a lot of the migratory fish populations. Moreover, since the hydrological features of the river provide important migration parameters, the dams will blur these parameters and confuse fish in deciding whether they should start their migration journey. It is estimated that, in 2050, all consequences of the eleven dam cascade will lead to a decrease of the fishery productivity of approximately 40 percent, compared to the year 2000. This will correspond to an annual economic loss of 200 to 480 million USD.
By using a framework for sustainable development, there has been generated insight and an understanding of how the MRC navigates the hydropower development projects and its motives to do so, along with the implications for fisheries that are predominantly contingent upon ecological preservation of the habitat that is required for fisheries to be productive. Although it is not possible to measure the exact impact of the eleven dams, losses of fish productivity will have a great impact on local people who are dependent for their lives and livelihoods on fisheries. However, the arrival of the dams brings new opportunities for the development of the LMB as a whole, such as the development of new industries. Therefore, it is likely that the development of the dams has a great impact on local people who are dependant on fisheries for their livelihoods and for the development of the region as a whole. What the new situation will look like, is dependant on decision making and is therefore unclear.
5.3 Policy recommendations
Since the development of the eleven dam cascade is considered to have environmental and socioeconomic consequences, it is important that these consequences are acknowledged in the process of policy conductance. One way to do so, is by looking into innovations and techniques that reduce the consequences of the dam development project, such as fish ladders that offer sufficient room for migratory fish (see also 5.1). Recent studies show that fish ladders vary in effectiveness and are characterized by passage failure (Roscoe & Hinch, 2010; Schmetterling et al., 2002). By examining this, the effects of future dams on fishery productivity could possibly be reduced.
Furthermore, it is important to have a clear development plan for the LMB region as a whole. The generation of energy goes along with new opportunities for the development of other industries. However, the development of the area is determined by external factors such as changes in population composition and the degree of urbanisation. Therefore, it is advisable to conduct a scenario analysis in order to determine which direction is appropriate for the region. This will provide insight in how the region can adapt to the new circumstances in order to guarantee employment opportunities for the local people.
Lastly, the current use of the fisheries in the MD goes under inconsistent governmental law, which may be disadvantageous to conservation management in the different countries of the MD (MRC, 2010a). In order to overcome these problems, the governmental policy has to be adjusted and straightened. To make this even more effective, it is advised that the national fishery governance policy underscores local aspects facets of fisheries too, since the current
government mainly focuses on national importances, while forgetting the local people that are involved in the fisheries (ibid.). In this way, the preservation of the MD fisheries will be easier and this could benefit the mitigation of the impacts assessed in this research.
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