We adopted a spectral clustering algorithm to divide the document co-citation network of 1,776 papers in the field of Lancang-Mekong water, and 14 clusters were identified. For each cluster, the top-cited references construct the knowledge base, and the most-coverage cities are taken as the research frontier. Three indicators, namely betweenness centrality, citation burstness strength, and Sigma, were used to identify the research outputs with pioneering and transformative value. The changes in the research topics and hotspots are closely related to the planning, construction, and operation progress of hydropower engineering, that affected by the gaming results of all parties. The 2009–2010 is an important time boundary, with the original research hotspots including the impact of upstream reservoirs on the hydrological regime and sediment (Clu#3) and arsenic contamination of groundwater in the Lower Mekong (Clu#4) that obtained periodical achievements and reached consensus to some extent around 2008, and the new research boom turns to the Tonle Sap Lake and flood pulse (Clu#2) in short-term characterized literatures with the highest burstness strength mainly concentrated around 2012.

  • The intellectual bases and research frontiers of 14 identified topics were analyzed based on Document Co-citation Network analysis.

  • Vietnamese Mekong Delta is the topic with the largest size and arsenic contamination is the cluster with the longest time span.

  • Evolution of research hotspots is related to the widespread controversy over the planned dams in the Lower Mekong mainstream and the progress of the multi-party games.

As one of the most prominent waterways in the world, the Lancang-Mekong River is the longest river in Southeast Asia and the most crucial transboundary river, flowing through six countries, namely China, Myanmar, Laos, Thailand, Cambodia, and Vietnam. The development and utilization of the Lancang-Mekong water resources and hydropower resources and their possible impacts have always been the focus of close attention of scholars in and outside the region, as well as the central topic of frequent debates in the international communities and civil organizations (Hecht et al., 2019). Among various actors involved in water governance in the Lancang-Mekong Region, including the United Nations, countries' governments in the Lancang-Mekong Basin, news media, NGOs, financial institutions, and enterprises, of which scientific research institutions or researchers can take a relatively neutral position based on technical analysis results and facts (Dore et al., 2012). As an objective record of human understanding of the Lancang-Mekong River and the main form of research results, scientific literature can help us sort out the research context, hotspots, important discoveries, and development frontiers of the Lancang-Mekong River water issue.

Scientometrics is a powerful tool for the quantitative evaluation of scientific literature. Recently, a series of software for knowledge graphs and bibliometrics were figured out, such as CiteSpace (Chen, 2006) and VOSviewer (van Eck & Waltman, 2010). Based on this, scholars can conduct scientific measurement, graph construction, and visual display of knowledge units such as titles, authors, institutions, countries/regions, abstract, keywords, references, published journals, and other index information, and co-word analysis, cooperation network analysis, review of research history, and capture of research hotspots in the areas of interest. Scientometrics has been used in many research fields for co-word analysis, cooperative network analysis, review of research history, and capture of research hotspots, early mainly concentrated in the fields of management and humanities and social sciences. In recent years, it has been rapidly applied in the fields of natural science and engineering technology, but there is still relatively little research in the field of water resources and environment.

Based on scientometrics-related theories, methods, and tools, we retrieved and analyzed relevant literature in the water field of Lancang-Mekong River and explored the main research topics, research hotspots at different stages, and the context of important achievements in the water field of Lancang-Mekong River.

Literature retrieval is one of the key links in the whole knowledge graph research, which is directly related to the quality of the analysis results. We used TOPIC: (‘Mekong’) AND TOPIC: (‘WATER’), without limitation of time span to retrieve the Mekong water-related literature in Web of Science (WoS) core collection database, and a total of 2,061 papers were obtained. The literature data were last updated on April 28, 2021. Since this study takes journal articles as its main research object, conference papers, and book chapters, as well as other editorial materials, book reviews, letters, and other literatures that do not belong to the scope of this study were excluded. After preliminary screening of the search results, a total of 1,776 literatures were selected as the research data of this paper.

In this paper, HistCite (Garfield et al., 2006) was used to conduct statistical analysis research on citation and construct citation history network based on citation relationships of local documents. In HistCite, citation scores include Local Citation Score (LCS) and Global Citation Score (GCS), which represent the number of times a paper has been cited by the other articles in the local dataset and in the WoS Database, respectively. Document Co-citation Analysis (DCA) was adopted for constructing citation network relationship, and spectral clustering algorithm derived from spectral Graph theory was used to divide the overall citation network into several non-overlapping clusters in CiteSpace II V5.8.R1.

The current research front is identified based on such burst terms extracted from titles, abstracts, descriptors, and identifiers of bibliographic records. These terms are subsequently used as labels of clusters in heterogeneous networks of terms and articles (Chen, 2006). Based on the structural holes concept proposed by Burt in his book Structural Holes: The Social Structure of Competition (Burt, 1992), the betweenness centrality was used to measure the structural holes, articles with high betweenness centrality in document co-citation network could guide us to discover potential work and novel ideas as quickly as possible. Kleinberg's frequency burstness detection algorithm originally used to detect single word bursts (Kleinberg, 2003) was used in the burstness detection of citation. The basic logic is that if the number of citations of a paper suddenly shows a rapid increase, it is most likely due to the fact that it is on the key point of an academic field, and it usually indicates that it is a potential or interesting research direction. Based on the two indicators, betweenness centrality and citation burstness, Chen et al. (2010) proposed Sigma (∑) as an indicator of scientific novelty and transformative discoveries, and previous studies have shown that Nobel Prize and other award-winning research tend to have higher Sigma values. It is calculated as follows.
formula

Research outputs trend and discipline identification

The research outputs in the Lancang-Mekong water field are increasing yearly, in line with the exponential growth law of scientific literature, and still in the stage of ‘primary science’, indicating the outputs in this field will probably continue to increase in the future. The first Mekong water-related paper was published in 1974, and there were only 7 papers published during 1974 and 1993. Figure 1 shows the annual number of publications on Lancang-Mekong water issues at home and abroad from 1994 to 2020. Except for a short decline in 2009 and 2010, the number of publications showed a significant upward trend. In terms of LCS and GCS, there are two obvious peaks in 2008 and 2013/2014, respectively.
Fig. 1

The study history of water-related issues in the Mekong.

Fig. 1

The study history of water-related issues in the Mekong.

Close modal

From the perspective of the number of published papers and citations in this field, the research process can be divided into five stages: the seed stage (before 1994), the budding stage (1995–2002), the fluctuation stage (2003–2010), the stabilization stage (2010–2016), and the rapid growth stage (2017–present). Before 1994, the research outputs were sporadic. During the budding period (1995–2002), the number of publications increased slowly with the annual publications of 4 in 1995 increasing to 12 in 2002, and it could be attributed to the 1995 Mekong agreement signed by the four member countries. From 2003 to 2010, the research outputs increased rapidly and then decreased sharply, which could be related to the widespread controversy over the planned dams in the Lower Mekong mainstream and the progress of the multi-party games.

Since 2011, the number of papers published on the Lancang-Mekong water issue has reversed the downward trend and continued to increase. Scholars used new theoretical frameworks, such as the ‘Water-Energy-Food (WEF) Nexus’, to evaluate and analyze the possible impacts of natural and anthropogenic factors on the Mekong Region from a more comprehensive and comprehensive perspective. From 2017 to now, the number of published articles has accelerated, with more than 100 published annually and even reaching 244 in 2020. The number of publications is closely related to the international financial assistance provided, and there are various launches of cooperation and dialogue mechanisms which can be seen in the significant increase in studies on Lancang-Mekong water issues since the Lancang-Mekong Mechanism was proposed.

The 1776 selected papers are distributed in 569 journals, of which 26 core journals are identified based on Bradford's law, accounting for 4.57% of the total number of journals and 33.78% of the total number of papers. The journals with the largest number of articles in this field are Water, Science of the Total Environment, Remote Sensing, Journal of Hydrology, and Hydrological Processes, with the number of papers published of 67, 57, 53, 42, and 33, respectively. Regarding the disciplines' distribution of published articles, it can be roughly divided into five categories based on the journals and their mutual citation relationships (Figure 2), including the fields of hydrology and water resources, environmental science and ecology, fisheries and marine and freshwater biology, earth science and physical geography and remote sensing. Among these, hydrology and water resources is the main research field, remote sensing has become one of the important research directions as important research means and method in the field of hydrology and water resources.
Fig. 2

Citation network diagram of scientific journals.

Fig. 2

Citation network diagram of scientific journals.

Close modal

Research topics identification based on clustering analysis

Based on the g-index (k = 25), 1,266 references and 4,850 co-citation links were divided into 14 clusters in total, and the sizes of different clusters vary greatly (Figure 3). Of which, the largest Clu#0 contained 130 members, accounting for 17.4% of the total 748 citations. The top 5 largest clusters accounted for 66.4%, and the three smallest clusters only had less than 10 members. As the widely used measurement indicators of clustering quality, Modularity Q is 0.8144 and Silhouete coefficient S value is 0.9182, indicating the excellent clustering structure and convincing clustering results (Chen et al., 2010). The silhouette values of 14 identified clusters all exceeded 0.8, indicating their high cohesion and good differentiation from other clusters. Table 1 shows automatically chosen cluster labels of the 14 DCA clusters along with their size, silhouette value, and top-ranked terms. The top terms by Log-Likelihood Ratio (LLR) algorithm with minor manual revision were selected as cluster labels, the top terms of single words and noun phrases for 14 clusters by LLR are listed in Table 1. The terms are generated from the noun phrases and indexing words of citers of member articles within each cluster, and the noun phrases are mainly from the titles and abstracts of citing articles.
Table 1

14 Top terms of the largest 9 identified clusters based on spectral clustering.

IDSizeS valueTop terms – single wordsTop terms – noun phrases
130 0.885 Vietnamese Mekong Delta; Mekong Delta; case study; Mekong River Delta; global change land subsidence; wet season; Mekong floodplains; hydropower dams; water infrastructure 
116 0.836 Lancang-Mekong River Basin; Mekong River Basin; Mekong River; Southeast Asia; upper Mekong River Lancang River; water area; flood season; runoff alterations; possible linkage 
90 0.903 Mekong River Basin; Mekong Basin; Mekong River; flood pulse; hydrological alteration flood pulse; largest wetland; fundamental knowledge; integrated water resources management; inter-annual fluxes 
85 0.867 Mekong River; Mekong Basin; dam construction; social learning; water management dam construction; Lancang River; reservoir impoundment; land use; influencing distance 
76 0.997 arsenic contamination; modeling arsenic hazard; geostatistical approach; using ancillary data; Mekong Delta risk assessment; Mekong River Basin; paddy rice; daily dose; Kampong Cham Province 
62 0.927 Water-Energy-Food Nexus; Mekong River Basin; Mekong Region; large Asian river; transboundary context food security; Water-Energy-Food Nexus; nexus approach; integrated planning; cross-sectoral collaboration 
51 0.963 striped catfish; integrated rice-fish farming; food security; tumultuous path; global success integrated rice-fish farming; rice monoculture; integrated farming system; food security; integrated farming 
50 0.933 cropping pattern; Sentinel-1 SAR data; Google Earth Engine platform; growth stage; Vietnamese Mekong Delta Sentinel-1a data; water infrastructure; Vietnamese Mekong Delta; cropping systems; cropping pattern 
30 0.970 deltaic social-ecological system; Mekong Delta; vulnerability indicator; hydropower development; upstream–downstream relation water security; river Mayur; water sources; Bengal delta; Khulna City Corporation 
IDSizeS valueTop terms – single wordsTop terms – noun phrases
130 0.885 Vietnamese Mekong Delta; Mekong Delta; case study; Mekong River Delta; global change land subsidence; wet season; Mekong floodplains; hydropower dams; water infrastructure 
116 0.836 Lancang-Mekong River Basin; Mekong River Basin; Mekong River; Southeast Asia; upper Mekong River Lancang River; water area; flood season; runoff alterations; possible linkage 
90 0.903 Mekong River Basin; Mekong Basin; Mekong River; flood pulse; hydrological alteration flood pulse; largest wetland; fundamental knowledge; integrated water resources management; inter-annual fluxes 
85 0.867 Mekong River; Mekong Basin; dam construction; social learning; water management dam construction; Lancang River; reservoir impoundment; land use; influencing distance 
76 0.997 arsenic contamination; modeling arsenic hazard; geostatistical approach; using ancillary data; Mekong Delta risk assessment; Mekong River Basin; paddy rice; daily dose; Kampong Cham Province 
62 0.927 Water-Energy-Food Nexus; Mekong River Basin; Mekong Region; large Asian river; transboundary context food security; Water-Energy-Food Nexus; nexus approach; integrated planning; cross-sectoral collaboration 
51 0.963 striped catfish; integrated rice-fish farming; food security; tumultuous path; global success integrated rice-fish farming; rice monoculture; integrated farming system; food security; integrated farming 
50 0.933 cropping pattern; Sentinel-1 SAR data; Google Earth Engine platform; growth stage; Vietnamese Mekong Delta Sentinel-1a data; water infrastructure; Vietnamese Mekong Delta; cropping systems; cropping pattern 
30 0.970 deltaic social-ecological system; Mekong Delta; vulnerability indicator; hydropower development; upstream–downstream relation water security; river Mayur; water sources; Bengal delta; Khulna City Corporation 
Fig. 3

Document Co-citation Analysis Clusters (1974–2021; CiteSpace parameters: nodes N = 1,266, edges E = 4,832, time slice length = 1, modularity = 0.8146, mean silhouette = 0.9138, clusters = 14).

Fig. 3

Document Co-citation Analysis Clusters (1974–2021; CiteSpace parameters: nodes N = 1,266, edges E = 4,832, time slice length = 1, modularity = 0.8146, mean silhouette = 0.9138, clusters = 14).

Close modal

The top 9 largest clusters with more than 20 members are Clu#0 (Vietnamese Mekong Delta/Land Subsidence), Clu#1 (Lancang-Mekong River Basin/Lancang River), Clu#2 (Mekong River Basin/Flood Pulse), Clu#3 (Mekong River/Dam Construction), Clu#4 (Arsenic Contamination/Risk Assessment), Clu#5 (Water-Energy-Food Nexus/Food Security), Clu#6 (Striped Catfish/Integrated Rice-Fish Farming), Clu#7 (Cropping Pattern/Sentinel-1a), and Clu#9 (Deltaic Social-ecological System/Water Security). The other five clusters with relatively small sizes include Clu#12 (Monsoonal Asia/water resources), Clu#19 (Flood-Prone Area/Winter-Spring Rice), Clu#27 (Seabed Morphology/Drag coefficients), Clu#28 (Aquaculture Environment Interaction/Nutritional Inputs), and Clu#40 (Redox Control/Organic Carbon).

History of citation

The top 50 papers with the highest LCS values had a clear boundary during 2009–2010 (Figure 4). From 1996 to 2008, the number of documents with high-LCS values increased year by year, the research topics were relatively broad, each research topic was self-contained, and there were few mutual citations among the documents, which could be regarded as the foundational stage. During 2007 and 2008, important research results appeared intensively and were characterized by mutual citation, and there were no highly cited articles in subsequent years, indicating that periodical achievements and consensus were achieved in some research directions during this period. During 2009–2010, no heavyweight achievements were produced in the original research direction, but new research topics emerged, which is manifested in that the articles with high-LCS values published during this period were frequently cited in the subsequent years, but rarely citing the literatures of previous years, which can refer to article labeled No. 349. After 2011, there has been a new research boom in the Mekong water field. Articles with high LCSs appeared in a concentrated manner, with the highly cited articles published in 2012, 2013, and 2014 ranked in the top 50 LCS articles of 4, 5, and 5, respectively, second only to 2008, which is a high-yield period of important literatures. Since 2016, the number of papers published has continuously reached new highs, but due to the short publication time and insufficient citation, there are relatively few papers with high LCSs.
Fig. 4

The citation history diagram of top 50 papers with the highest LCS values.

Fig. 4

The citation history diagram of top 50 papers with the highest LCS values.

Close modal

Top-cited references as intellectual base

For each cluster, predominant members of a cluster as the intellectual base and themes identified in the citers of this cluster as research front were analyzed. The top-cited cluster members and their structural, temporal, and saliency metrics including citation counts (φ), citation burstness (τ), degree centrality (Deg), betweenness centrality (σ), and sigma (Σ) are summarized in Table 2. The top citers to each of the nine largest clusters are listed in Table 2.

Table 2

Most-cited references in the nine largest document co-citation clusters ranked by citation counts.

ClusterφτDegσΣCited reference
#0 52 8.73 26 0.02 1.14 Smajgl et al. (2015) Responding to rising sea levels in the Mekong Delta 
47 10.94 32 0.02 1.22 Hoang et al. (2016) Mekong River flow and hydrological extremes under climate change 
45 10.28 38 0.01 1.16 Anthony et al. (2015) Linking rapid erosion of the Mekong River Delta to human activities 
38 6.57 41 0.04 1.27 Manh et al. (2015) Future sediment dynamics in the Mekong Delta floodplains 
#1 54 12.20 29 0.01 1.08 Rasanen et al. (2017) Observed river discharge changes due to hydropower operations in the Upper Mekong Basin 
49 12.48 21 0.01 1.09 Winemiller et al. (2016) Balancing hydropower and biodiversity in the Amazon, Congo, and Mekong 
45  10  Hecht et al. (2019) Hydropower dams of the Mekong River Basin: a review of their hydrological impacts 
42 10.28 26 0.01 1.12 Fan et al. (2015) Environmental consequences of damming the mainstream Lancang-Mekong River: a review 
#2 46 18.53 36 0.02 1.51 Ziv et al. (2012) Trading-off fish biodiversity, food security, and hydropower in the Mekong River Basin 
41 16.50 31 0.02 1.34 Lauri et al. (2012) Future changes in Mekong River hydrology: impact of climate change and reservoir operation on discharge 
37 8.94 50 0.04 1.45 Arias et al. (2014a) Impacts of hydropower and climate change on drivers of ecological productivity of Southeast Asia's most important wetland 
31 13.71 25 0.03 1.51 Grumbine & Xu (2011) Mekong hydropower development 
#3 27 12.61  1.05 MRC (2010) State of Basin Report (SoBR) 
16 8.44 17 0.01 1.06 Kummu & Varis (2007) Sediment-related impacts due to upstream reservoir trapping, the Lower Mekong River 
14 7.76 21 0.07 1.74 Lu & Siew (2006) Water discharge and sediment flux changes over the past decades in the Lower Mekong River: possible impacts of the Chinese dams 
12 6.81 17 0.01 1.1 Fu et al. (2008) Sedimentation in the Manwan reservoir in the Upper Mekong and its downstream impacts 
#4 28 4.03 11  Berg et al. (2001) Arsenic contamination of groundwater and drinking water in Vietnam: a human health threat 
17 3.94 14 0.01 1.04 Smedley & Kinniburgh (2002) A review of the source, behaviour, and distribution of arsenic in natural waters 
16   JICA (2001) The study on groundwater development in central Cambodia 
14   Kinniburgh & Kosmus (2002) Arsenic contamination in groundwater: some analytical considerations 
#5 27 9.83 41 0.04 1.43 Grumbine et al. (2012) Mekong hydropower: drivers of change and governance challenges 
15 7.64 21 0.01 1.05 Orr et al. (2012) Dams on the Mekong River: lost fish protein and the implications for land and water resources 
10  11 0.01 Mirumachi (2015) Transboundary water politics in the developing world 
 20 0.01 Keskinen et al. (2015) Water-Energy-Food Nexus in a transboundary river basin: the case of Tonle Sap Lake, Mekong River Basin 
#6 12 7.07 0.01 1.06 Phan et al. (2009) Current status of farming practices of striped catfish, Pangasianodon hypophthalmus in the Mekong Delta, Vietnam 
 16 0.03 Kummu & Sarkkula (2008) Impact of the Mekong River flow alteration on the Tonle Sap flood pulse 
  MRC (2005) Overview of the hydrology of the Mekong Basin 
 10 0.01 Nhan et al. (2007) Integrated freshwater aquaculture, crop, and livestock production in the Mekong Delta, Vietnam: determinants and the role of the pond 
#7 25 8.78 24 0.05 1.55 Kuenzer et al. (2013b) Flood mapping and flood dynamics of the Mekong Delta: ENVISAT-ASAR-WSM based time series analyses 
21 5.79 12  1.01 Gorelick et al. (2017) Google Earth Engine: planetary-scale geospatial analysis for everyone 
12  21 0.02 Kontgis et al. (2015) Mapping rice paddy extent and intensification in the Vietnamese Mekong River Delta with dense time stacks of Landsat data 
10  15  Mosleh et al. (2015) Application of remote sensors in mapping rice area and forecasting its production: a review 
#9 19 7.78 Toan et al. (2013) Pesticide management and their residues in sediments and surface and drinking water in the Mekong Delta, Vietnam 
 19 0.01 Kuenzer & Renaud (2012) Climate and environmental change in river deltas globally: expected impacts, resilience, and adaptation 
 10 0.01 Berg & Tam (2012) Use of pesticides and attitude to pest management strategies among rice and rice-fish farmers in the Mekong Delta, Vietnam 
 13 0.01 Auerbach et al. (2015) Flood risk of natural and embanked landscapes on the Ganges-Brahmaputra tidal delta plain 
ClusterφτDegσΣCited reference
#0 52 8.73 26 0.02 1.14 Smajgl et al. (2015) Responding to rising sea levels in the Mekong Delta 
47 10.94 32 0.02 1.22 Hoang et al. (2016) Mekong River flow and hydrological extremes under climate change 
45 10.28 38 0.01 1.16 Anthony et al. (2015) Linking rapid erosion of the Mekong River Delta to human activities 
38 6.57 41 0.04 1.27 Manh et al. (2015) Future sediment dynamics in the Mekong Delta floodplains 
#1 54 12.20 29 0.01 1.08 Rasanen et al. (2017) Observed river discharge changes due to hydropower operations in the Upper Mekong Basin 
49 12.48 21 0.01 1.09 Winemiller et al. (2016) Balancing hydropower and biodiversity in the Amazon, Congo, and Mekong 
45  10  Hecht et al. (2019) Hydropower dams of the Mekong River Basin: a review of their hydrological impacts 
42 10.28 26 0.01 1.12 Fan et al. (2015) Environmental consequences of damming the mainstream Lancang-Mekong River: a review 
#2 46 18.53 36 0.02 1.51 Ziv et al. (2012) Trading-off fish biodiversity, food security, and hydropower in the Mekong River Basin 
41 16.50 31 0.02 1.34 Lauri et al. (2012) Future changes in Mekong River hydrology: impact of climate change and reservoir operation on discharge 
37 8.94 50 0.04 1.45 Arias et al. (2014a) Impacts of hydropower and climate change on drivers of ecological productivity of Southeast Asia's most important wetland 
31 13.71 25 0.03 1.51 Grumbine & Xu (2011) Mekong hydropower development 
#3 27 12.61  1.05 MRC (2010) State of Basin Report (SoBR) 
16 8.44 17 0.01 1.06 Kummu & Varis (2007) Sediment-related impacts due to upstream reservoir trapping, the Lower Mekong River 
14 7.76 21 0.07 1.74 Lu & Siew (2006) Water discharge and sediment flux changes over the past decades in the Lower Mekong River: possible impacts of the Chinese dams 
12 6.81 17 0.01 1.1 Fu et al. (2008) Sedimentation in the Manwan reservoir in the Upper Mekong and its downstream impacts 
#4 28 4.03 11  Berg et al. (2001) Arsenic contamination of groundwater and drinking water in Vietnam: a human health threat 
17 3.94 14 0.01 1.04 Smedley & Kinniburgh (2002) A review of the source, behaviour, and distribution of arsenic in natural waters 
16   JICA (2001) The study on groundwater development in central Cambodia 
14   Kinniburgh & Kosmus (2002) Arsenic contamination in groundwater: some analytical considerations 
#5 27 9.83 41 0.04 1.43 Grumbine et al. (2012) Mekong hydropower: drivers of change and governance challenges 
15 7.64 21 0.01 1.05 Orr et al. (2012) Dams on the Mekong River: lost fish protein and the implications for land and water resources 
10  11 0.01 Mirumachi (2015) Transboundary water politics in the developing world 
 20 0.01 Keskinen et al. (2015) Water-Energy-Food Nexus in a transboundary river basin: the case of Tonle Sap Lake, Mekong River Basin 
#6 12 7.07 0.01 1.06 Phan et al. (2009) Current status of farming practices of striped catfish, Pangasianodon hypophthalmus in the Mekong Delta, Vietnam 
 16 0.03 Kummu & Sarkkula (2008) Impact of the Mekong River flow alteration on the Tonle Sap flood pulse 
  MRC (2005) Overview of the hydrology of the Mekong Basin 
 10 0.01 Nhan et al. (2007) Integrated freshwater aquaculture, crop, and livestock production in the Mekong Delta, Vietnam: determinants and the role of the pond 
#7 25 8.78 24 0.05 1.55 Kuenzer et al. (2013b) Flood mapping and flood dynamics of the Mekong Delta: ENVISAT-ASAR-WSM based time series analyses 
21 5.79 12  1.01 Gorelick et al. (2017) Google Earth Engine: planetary-scale geospatial analysis for everyone 
12  21 0.02 Kontgis et al. (2015) Mapping rice paddy extent and intensification in the Vietnamese Mekong River Delta with dense time stacks of Landsat data 
10  15  Mosleh et al. (2015) Application of remote sensors in mapping rice area and forecasting its production: a review 
#9 19 7.78 Toan et al. (2013) Pesticide management and their residues in sediments and surface and drinking water in the Mekong Delta, Vietnam 
 19 0.01 Kuenzer & Renaud (2012) Climate and environmental change in river deltas globally: expected impacts, resilience, and adaptation 
 10 0.01 Berg & Tam (2012) Use of pesticides and attitude to pest management strategies among rice and rice-fish farmers in the Mekong Delta, Vietnam 
 13 0.01 Auerbach et al. (2015) Flood risk of natural and embanked landscapes on the Ganges-Brahmaputra tidal delta plain 

The most-cited references in the Vietnamese Mekong Delta (Clu#0) are Smajgl_2015 on comprehensive adaptation measures to sea-level rise (Smajgl et al., 2015), Hoang_2016 on the evaluation of hydrological impacts of climate change in Mekong Region (Hoang et al., 2016), and Anthony_2015 on the linkage of the large-scale shoreline erosion and land loss with the sediment retention by dams, large-scale commercial sand mining in the river and delta channels and land subsidence caused by groundwater exploitation (Anthony et al., 2015). The article Manh_2015 that combined the comprehensive impact of hydropower development, climate change, and sea level rise on sediment dynamics had the highest betweenness centrality value of 0.04 and sigma value of 1.27 within Clu#0. The reference with the highest degree value within Clu#0 was Darby_2016 that proposed changes in tropical-cyclone climatology but not upstream reservoir trapping altered the trends in fluvial suspended sediment loads.

The first four most-cited references in the Mekong River Basin (Clu#1) are all hydropower development-related research, including Rasanen_2017 on river discharge change, Winemiller_2016 on biodiversity, and two review papers, Hecht_2019 and Fan_2015, that comprehensively summarized the hydrological impact and environmental consequences of hydropower dams of the Mekong River Basin, respectively. The Clu#2 was mainly composed of references related to but not limited to hydropower development including Ziv_2012 on tradeoff among fish biodiversity, food security, and hydropower, Lauri_2012 and Arias_2014 on integrated influence of climate change and hydropower. The dominant references in Clu#3 are Kummu_2007, Lu_2006, and Fu_2008 that all focused on the impact of upstream reservoir especially Manwan Reservoir on sediment with the State of Basin Report (SoBR) published by Mekong River Commission (MRC) in 2010 as its most-cited reference.

Different from the former largest four clusters, the stars in the arsenic contamination (Clu#4), Berg_2001 and JICA_2001, are two of the earliest research achievements on arsenic contamination of groundwater in Vietnam and Central Cambodia, respectively. The publication time of the top-ranked references in Clu#4 was relatively earlier compared with other clusters and concentrated during 2001–2002. For Clu#5 labeled as Water-Energy-Food Nexus, its research focus shifts from purely discussing the positive and negative effects of dam construction to how to tradeoff hydropower development, food security, and water security in the context of hydropower development in the Lower Mekong. The most-cited papers, Grumbine_2012 and Orr_2012, discussed the drivers of dam construction in the Lower Mekong Basin and its potentially huge impact on local fisheries. The book Mirumachi_2015 proposed the Transboundary Waters Interaction NexuS (TWINS) framework to examine the coexistence of conflict and cooperation among riparian countries that share international transboundary rivers, Keskinen_2015 applied the Water-Energy-Food Nexus theory in the Tonle Sap Lake, the most important wetland in the Mekong Basin. The top-cited reference of stripped catfish cluster (Clu#6) is Phan_2009 which traced the catfish farming history and current harvesting and marketing procedures of the farming community in the Mekong Delta. The Nhan_2007 on integrated freshwater aquaculture, crop, and livestock production ranked fourth in Clu#6 in addition to MRC_2005 on hydrological overview report and Kummu_2008 on flood pulse changes caused by dams in the Tonle Sap Region. Clu#7 labeled as cropping pattern is mainly about the application of remote sensing technology in mapping flood (Kuenzer_2013), rice paddy extent (Kontgis_2015), and forecasting rice production (Mosleh_2015). The last one of the nine largest clusters is a vulnerability indicator, with the core paper of Toan_2013 which systematically investigated the pesticide residues in sediments, surface, and drinking water in the Mekong Delta. Climate and environmental change (Kuenzer_2012) and flood disaster (Auerbach_2015) are also components of vulnerability.

Most-coverage citers as research front

The coverage value is the number of references in the cluster that the citing article cited. In this paper, the articles with the most-coverage values were used to indicate the research front. The most frequent citers to each of the nine largest DCA clusters are listed in Table 3.

Table 3

Titles of the most frequent citers to each of the nine largest DCA clusters.

CluCoverageAuthor (Year)Title
#0 37 Hecht et al. (2019)  Hydropower dams of the Mekong River Basin: a review of their hydrological impacts 
27 Pokhrel et al. (2018)  A review of the integrated effects of changing climate, land use, and dams on Mekong River hydrology 
22 Shin et al. (2020)  High resolution modeling of river-floodplain-reservoir inundation dynamics in the Mekong River Basin 
21 Arias et al. (2019)  Maintaining perspective of ongoing environmental change in the Mekong floodplains 
#1 29 Hecht et al. (2019)  Hydropower dams of the Mekong River Basin: a review of their hydrological impacts 
19 Pokhrel et al. (2018)  A review of the integrated effects of changing climate, land use, and dams on Mekong River hydrology 
17 Shin et al. (2020)  High resolution modeling of river-floodplain-reservoir inundation dynamics in the Mekong River Basin 
16 Arias et al. (2019)  Maintaining perspective of ongoing environmental change in the Mekong floodplains 
#2 22 Arias et al. (2014a)  Impacts of hydropower and climate change on drivers of ecological productivity of Southeast Asia's most important wetland 
21 Arias et al. (2014b)  Dams on Mekong tributaries as significant contributors of hydrological alterations to the Tonle Sap floodplain in Cambodia 
21 Cochrane et al. (2014)  Historical impact of water infrastructure on water levels of the Mekong River and the Tonle Sap system 
20 Keskinen et al. (2016)  The Water-Energy-Food Nexus and the transboundary context: insights from large Asian rivers 
#3 11 Lebel et al. (2010)  The role of social learning in adaptiveness: insights from water management 
10 Bearden (2012)  Following the proper channels: tributaries in the Mekong legal regime 
10 Xue et al. (2011)  Changes in hydrology and sediment delivery of the Mekong River in the last 50 years: connection to damming, monsoon, and ENSO 
10 Johnston & Kummu (2012)  Water resource models in the Mekong Basin: a review 
#4 16 Lado et al. (2008)  Modelling arsenic hazard in Cambodia: a geostatistical approach using ancillary data 
16 Kocar et al. (2008)  Integrated biogeochemical and hydrologic processes driving arsenic release from shallow sediments to groundwaters of the Mekong Delta 
14 Winkel et al. (2008)  Predicting groundwater arsenic contamination in Southeast Asia from surface parameters 
14 Buschmann & Berg (2009)  Impact of sulfate reduction on the scale of arsenic contamination in groundwater of the Mekong, Bengal and Red River deltas 
#5 16 Keskinen et al. (2016)  The Water-Energy-Food Nexus and the transboundary context: insights from large Asian rivers 
16 Middleton et al. (2015)  The rise and implications of the Water-Energy-Food Nexus in Southeast Asia through an environmental justice lens 
12 Middleton & Dore (2015)  Transboundary water and electricity governance in mainland Southeast Asia: linkages, disjunctures and implications 
Keskinen et al. (2015)  Water-Energy-Food Nexus in a transboundary river basin: the case of Tonle Sap Lake, Mekong River Basin 
#6 10 Ahmed & Garnett (2011)  Integrated rice-fish farming in Bangladesh: meeting the challenges of food security 
De Silva & Phuong (2011)  Striped catfish farming in the Mekong Delta, Vietnam: a tumultuous path to a global success 
Ahmed et al. (2011)  Socioeconomic aspects of rice-fish farming in Bangladesh: opportunities, challenges and production efficiency 
Dudgeon (2011)  Asian river fishes in the Anthropocene: threats and conservation challenges in an era of rapid environmental change 
#7 13 Rudiyanto et al. (2019)  Automated near-real-time mapping and monitoring of rice extent, cropping patterns, and growth stages in Southeast Asia using Sentinel-1 time series on a Google Earth Engine platform 
10 Minh et al. (2019)  Monitoring and mapping of rice cropping pattern in flooding area in the Vietnamese Mekong Delta using Sentinel-1a data: a case of a Giang province 
Clauss et al. (2018)  Estimating rice production in the Mekong Delta, Vietnam, utilizing time series of Sentinel-1 SAR data 
Fikriyah et al. (2019)  Discriminating transplanted and direct seeded rice using Sentinel-1 intensity data 
#9 10 Sebesvari et al. (2016)  A review of vulnerability indicators for deltaic social-ecological systems 
Kuenzer et al. (2013a)  Understanding the impact of hydropower developments in the context of upstream–downstream relations in the Mekong River Basin 
Kuenzer et al. (2013b)  Flood mapping and flood dynamics of the Mekong Delta: ENVISAT-ASAR-WSM-based time-series analyses 
Szabo et al. (2016)  Population dynamics, delta vulnerability and environmental change: comparison of the Mekong, Ganges-Brahmaputra and Amazon Delta regions 
CluCoverageAuthor (Year)Title
#0 37 Hecht et al. (2019)  Hydropower dams of the Mekong River Basin: a review of their hydrological impacts 
27 Pokhrel et al. (2018)  A review of the integrated effects of changing climate, land use, and dams on Mekong River hydrology 
22 Shin et al. (2020)  High resolution modeling of river-floodplain-reservoir inundation dynamics in the Mekong River Basin 
21 Arias et al. (2019)  Maintaining perspective of ongoing environmental change in the Mekong floodplains 
#1 29 Hecht et al. (2019)  Hydropower dams of the Mekong River Basin: a review of their hydrological impacts 
19 Pokhrel et al. (2018)  A review of the integrated effects of changing climate, land use, and dams on Mekong River hydrology 
17 Shin et al. (2020)  High resolution modeling of river-floodplain-reservoir inundation dynamics in the Mekong River Basin 
16 Arias et al. (2019)  Maintaining perspective of ongoing environmental change in the Mekong floodplains 
#2 22 Arias et al. (2014a)  Impacts of hydropower and climate change on drivers of ecological productivity of Southeast Asia's most important wetland 
21 Arias et al. (2014b)  Dams on Mekong tributaries as significant contributors of hydrological alterations to the Tonle Sap floodplain in Cambodia 
21 Cochrane et al. (2014)  Historical impact of water infrastructure on water levels of the Mekong River and the Tonle Sap system 
20 Keskinen et al. (2016)  The Water-Energy-Food Nexus and the transboundary context: insights from large Asian rivers 
#3 11 Lebel et al. (2010)  The role of social learning in adaptiveness: insights from water management 
10 Bearden (2012)  Following the proper channels: tributaries in the Mekong legal regime 
10 Xue et al. (2011)  Changes in hydrology and sediment delivery of the Mekong River in the last 50 years: connection to damming, monsoon, and ENSO 
10 Johnston & Kummu (2012)  Water resource models in the Mekong Basin: a review 
#4 16 Lado et al. (2008)  Modelling arsenic hazard in Cambodia: a geostatistical approach using ancillary data 
16 Kocar et al. (2008)  Integrated biogeochemical and hydrologic processes driving arsenic release from shallow sediments to groundwaters of the Mekong Delta 
14 Winkel et al. (2008)  Predicting groundwater arsenic contamination in Southeast Asia from surface parameters 
14 Buschmann & Berg (2009)  Impact of sulfate reduction on the scale of arsenic contamination in groundwater of the Mekong, Bengal and Red River deltas 
#5 16 Keskinen et al. (2016)  The Water-Energy-Food Nexus and the transboundary context: insights from large Asian rivers 
16 Middleton et al. (2015)  The rise and implications of the Water-Energy-Food Nexus in Southeast Asia through an environmental justice lens 
12 Middleton & Dore (2015)  Transboundary water and electricity governance in mainland Southeast Asia: linkages, disjunctures and implications 
Keskinen et al. (2015)  Water-Energy-Food Nexus in a transboundary river basin: the case of Tonle Sap Lake, Mekong River Basin 
#6 10 Ahmed & Garnett (2011)  Integrated rice-fish farming in Bangladesh: meeting the challenges of food security 
De Silva & Phuong (2011)  Striped catfish farming in the Mekong Delta, Vietnam: a tumultuous path to a global success 
Ahmed et al. (2011)  Socioeconomic aspects of rice-fish farming in Bangladesh: opportunities, challenges and production efficiency 
Dudgeon (2011)  Asian river fishes in the Anthropocene: threats and conservation challenges in an era of rapid environmental change 
#7 13 Rudiyanto et al. (2019)  Automated near-real-time mapping and monitoring of rice extent, cropping patterns, and growth stages in Southeast Asia using Sentinel-1 time series on a Google Earth Engine platform 
10 Minh et al. (2019)  Monitoring and mapping of rice cropping pattern in flooding area in the Vietnamese Mekong Delta using Sentinel-1a data: a case of a Giang province 
Clauss et al. (2018)  Estimating rice production in the Mekong Delta, Vietnam, utilizing time series of Sentinel-1 SAR data 
Fikriyah et al. (2019)  Discriminating transplanted and direct seeded rice using Sentinel-1 intensity data 
#9 10 Sebesvari et al. (2016)  A review of vulnerability indicators for deltaic social-ecological systems 
Kuenzer et al. (2013a)  Understanding the impact of hydropower developments in the context of upstream–downstream relations in the Mekong River Basin 
Kuenzer et al. (2013b)  Flood mapping and flood dynamics of the Mekong Delta: ENVISAT-ASAR-WSM-based time-series analyses 
Szabo et al. (2016)  Population dynamics, delta vulnerability and environmental change: comparison of the Mekong, Ganges-Brahmaputra and Amazon Delta regions 

For the largest Clu#1 and Clu#2, the first four citers are exactly the same, including three review articles (Hecht_2019, Pokhrel_2018, and Arias_2019) and one numerical simulation paper (Shin_2020). The three review papers are all about the impact of hydropower development and dam construction on the Mekong River and its interaction with other driving factors such as climate change and land use conversion on hydrology regime and environmental conditions. The numerical simulation paper used a new model of river hydrodynamic-reservoir operation to comprehensively evaluate and verify the impact of dam and climate change on the flood dynamics of the Mekong River Basin on a finer scale, finding that with 2010 as the dividing line, the dam has little impact on the flood dynamics of the alluvial plain before 2009, and after 2010 its impact has been increased significantly due to doubled reservoir capacity contributed by newly built dams, and the impact of dams on the downstream is largely determined by the reservoirs' operation strategy.

Both of the two most frequently cited literatures of Clu#2 were written by Mauricio E. Arias of the University of Canterbury, New Zealand, who studied the Tonle Sap River floodplain, the most important wetland in Southeast Asia, from the perspective of natural environment change and human activities. Another document with high citation frequency is about the long-term impact of local water conservancy infrastructure on the water level of Mekong River and Tonle Sap Lake system, which is co-authored by Thomas A. Cocharane, and Mauricio E. Arias and Thanapon Piman. These three documents were all published in 2014 and were written by scholars from the University of Canterbury, New Zealand, showing that this institution is leading the research frontier in this field. In addition, the study on Water-Energy-Food Nexus (Keskinen Marko_2016) is a new research trend in the flood pulse-affected areas, especially the flood plain of Tonle Sap Lake.

Lebel_2010 on social learning and Bearden_2012 on legal system were the publications that cited the most literatures within Clu#3, followed by Xue_2011 on the relationship between changes in hydrology and sediment load in the Lower Mekong, and dam construction, monsoon climate and El Niño Southern Oscillation (ENSO). Scholars argue that it is necessary to strengthen interactive learning, build trust, and mutual understanding among social communities to establish community adaptability, and promote the construction of legal systems to adapt and alleviate the impact of earlier dam construction and dam operation on the downstream, as well as analyze the impact of dams from a broader, comprehensive and more objective standpoint. These most frequent citers of Clu#3 were concentrated in the years 2010–2012, indicating that the study on the impact of dam construction, particularly the dams on the Upper Mekong (Lancang River), and the mitigation and adaptation to the dam construction has reached a general consensus or that some newer and more important issues have piqued the interest and enthusiasm scholars in the field around 2010.

Similar to Clu#3, Clu#4 also has relatively concentrated publication years of frequent citing literature, which indicates that the research on arsenic pollution of groundwater in the Mekong River Basin has made important breakthroughs in 2008–2009. Rodriguez_2008 and Winkel_2008 simulated and predicted arsenic pollution, respectively, and Kocar_2008 studied the mechanism of arsenic release from sediment to groundwater driven by biogeochemical and hydrological processes. Buschmann_2009 analyzed the effect of sulfate reduction on the scale of arsenic pollution in groundwater, and basically made clear the scope, degree, geographical causes of arsenic pollution in the Mekong River Basin, especially in some arsenic pollution study areas in Cambodia and Vietnam, as well as the possible effects of long-term arsenic intake on human body.

Study on the Water-Energy-Food Nexus is the research frontier of Clu#5, with Carl Middleton and Marko Keskinen are the most representative scholars in this field, and their representative works were published in 2015–2016. Integrated rice-fish farming and striped catfish farming are research hotspots of Clu#6, which were concentrated in 2011. Integrated rice-fish farming was one of the most important ways and means to cope with food security challenges and improve comprehensive production efficiency at that time. In Clu#7, Rudiyanto 2019, Minh_2019, Clauss_2019, and Fikriyah_2019, the top 4 citing documents in terms of citing frequency, are all related to the application of remote sensing satellites. From the publication year of the above citing documents, it can be seen that the research in this field is still developing rapidly. Sebesvari_2016, the most citing core paper in Clu#9, provided a structured review of potential vulnerability indicators for delta socio-ecological assessments and proposes a socio-ecological system-centric framework for research on risk and vulnerability.

Dynamics of major research topics

The average age of top 10 core papers in a cluster was used to estimate the time of cluster formation (Figure 5). And the average years of publication that cite the references in the cluster was used to indicate the frontier research time of this cluster. Therefore, the time span τ between research front and its intellectual base can be estimated as the difference between their average year of publication.
formula
Fig. 5

Time span of the top 9 largest clusters.

Fig. 5

Time span of the top 9 largest clusters.

Close modal

In terms of time span, Clu#4 has the longest time span of 7.8 years, while the time spans between the research front and knowledge intellectual of all the other clusters are less than 4.5 years. Of which, Clu#2 and Clu#6 have the shortest time spans of 2.7 and 2.6 years, respectively. In addition to the time span, the average year of intellectual base and research front of Clu#4 are significantly earlier than those of other clusters. The average publication year of references cited that constitute the knowledge basis for arsenic contamination (Clu#4) is 2001.8, and the average year of publication of its heavyweight cutting-edge outputs is 2008.6. The second earlier formed intellectual bases formed are Clu#3 (2008.3) and Clu#6 (2008.6), and the average years of knowledge base formation of other clusters are all after 2013, among which Clu#1 has the most recent formation year of 2016.3. In terms of the average years of research frontiers, in addition to Clu#4 being the earliest to obtain research frontiers, the frontier studies of Clu#6, Clu#3, and Clu#2 were also formed in 2010.2, 2010.7, and 2013.8. Clu#7 and Clu#1 and Clu#0, which are the largest clusters, are still in the process of research, and the average years of frontier studies are 2018.1, 2018.6, and 2019.1, respectively.

Key articles and important findings of different topics

For a visually salient feature in co-citation networks, Chen (2004) proposed to use landmark nodes, hub nodes, and pivot nodes to indicate highly cited articles, high-degree articles, and high-betweenness-centrality articles, respectively. For the indicator of high citations, we conducted study on both the citing papers and the cited references. And for high-degree and high-betweenness-centrality articles, only the cited references were studied based on the analysis of co-citation network. Consistent with the above analysis, within the 1,776 articles, 5 of the 7 articles with LCSs higher than 60 were published between 2006 and 2008, and half of the 24 articles with GCSs greater than 100 were published during the 3 years (Figure 6), which once again illustrates the importance of the research results of the 3 years to the entire Mekong water research field. The top 4 articles with highest LCS were Kummu & Varis_2007 (Kummu & Varis, 2007), Lauri_2012 (Lauri et al., 2012), Lu & Siew_2006 (Lu & Siew, 2006), and Kummu & Sarkkula_2008 (Kummu & Sarkkula, 2008), which are all about the influence of the construction and operation of hydropower stations on the hydrological regime, sediment transport, and ecological environment in the lower reaches, which has always been a hot spot in the study of Mekong water and the focus of the international community. Matti Kummu is not only the first author and collaborator of the two highest LCS scores, and his papers on the construction of reservoirs in the Upper Mekong River on the flood pulses of the lower Tonle Sap Lake ranked fourth in LCS scores, three of the first four papers with the highest LCSs were written or co-authored by Matti Kummu of Aalto University in Finland. It was followed by four high-LCS papers, Hoa_2007, Wassmann_2004, Smajgl_2015, and Sakamoto_2007, all of which focused on the Mekong Delta in Vietnam. Hoa_2007 studied the combined influences of local man-made structures, sea level rise, and dams upstream in the river catchment on the Vietnamese Mekong Delta (VMD; Hoa Le et al., 2007), Wassmann_2004 focused on the effects of rising sea level, especially in flood season, on VMD rice production (Wassmann et al., 2004). Sakamoto_2007 retrieved the annual flood range of the Mekong Delta in Cambodia and Vietnam based on MODIS time-series images, and also initiated the application of remote sensing technology in the flood range monitoring.
Fig. 6

Bubble plot of the top 50 citing articles with highest LCS based on GCS and LCS, the size of bubble indicates the ratio of LCS to GCS.

Fig. 6

Bubble plot of the top 50 citing articles with highest LCS based on GCS and LCS, the size of bubble indicates the ratio of LCS to GCS.

Close modal

Of the top 50 articles with highest LCS, Polizzotto_2008 and Berg_2007 have the highest GCS of 399 and 321, both of which are all about groundwater arsenic pollution in the Mekong River Basin, especially in the Mekong Delta of Cambodia and Vietnam. The article with the highest GCS is a study on arsenic pollution in the Mekong Delta of Cambodia published in the journal Nature by Matthew L. Pollizzotoo in 2008, proposing that arsenic in groundwater comes from sediments of near-surface, river-derived sources and will return to rivers again through subsurface aquifers on a 100-year time scale and the release and transport of arsenic is very sensitive to continuous anthropogenic disturbance including groundwater extraction, changes in agricultural practices, sediment excavation, and construction of dykes and dams (Polizzotto et al., 2008), which is also the only article with LCS/GCS ratio less than 20%. Other arsenic-related research outputs, such as Berg_2007, Buschmann_2008, and Buschmann_2007 ranked 2nd, 5th, and 6th, respectively, in GCS, while their ratios of LCS and GCS are 21.2, 25.0, and 20.3%, respectively, indicating that a considerable part of the citations come from the contributions of scholars in other fields.

From the perspective of bubble size, the larger the bubble indicates that the higher the LCS/GCS ratio, and the more the research content represented by the bubble focuses on the water issue of the Mekong Basin itself, and the smaller the bubble, it means that scholars in other fields are also widely citing research results derived from this field, indicating the scalability and generalizability of the research outputs. In addition to the arsenic contamination studies mentioned above, Sakamoto_2006 and Sakamoto_2007 on mapping the spatial distribution and flood extent of rice cropping system in Cambodia and VMD based on MODIS time-series data also have the low LCS/GCS ratios. It is worth noting that Sneddon & Fox_2006 on water politics in the Mekong River and Bakker_1999 on the hydropower politics have also been widely cited in studies outside the region.

The document with the highest betweenness centrality of 0.10 is Eastham_2008 funded by AusAID on climate change's influence on Mekong River Basin water resources (Eastham et al., 2008), and Buschmann_2008 on the contamination of drinking water in the Mekong Delta floodplains especially arsenic and manganese contamination and their potential threats to human health (Buschmann et al., 2008). Kummu_2008 (Kummu & Sarkkula, 2008) and Lu_2006 (Lu & Siew, 2006) have the second highest betweenness centrality values of 0.07, which links the water discharge variation with Tonle Sap flood pulse and upstream dam construction, respectively, Lu_2006 is one of the earliest papers that linked changes in flow and sediment flux in the Lower Mekong River with the operation of the Manwan Dam upstream in China, which divided the 1962–2000 period into pre-dam and after-dam stages taking the operation of Manwan dam in 1992 as the critical time node, and proposed the river flow and sediment flux in the downstream decreased significantly after the impounding of Manwan dam. Subsequently, Kummu_2007 and Fu_2008 also studied the sediment interception capacity of Manwan Dam and its possible impact on the downstream, and their research results were widely cited by scholars in the field. There were two other papers with a betweenness centrality greater than 0.05, Kuenzer et al. (2013b) mapped the flood dynamics of the Mekong Delta based on time-series analysis of ENVISAT data, and Delgado_2012 studied the correlationship between Western Pacific monsoon and discharge of Mekong River, and proposed the possibility of predicting floods in the Mekong Delta based on the correlation analysis between the Pacific sea surface temperature and monsoon variance (Delgado et al., 2012).

Different from the literatures with high betweenness centrality mainly concentrated in 2008, the literatures with the highest burstness strength mainly concentrated in 2010–2012, and with the exception of Berg_2007 on the sources of groundwater arsenic pollution in the Mekong Delta, the remaining articles, Ziv_2012, Lauri_2012, Grumbine_2011, and Kummu_2010 are all members of Clu#2 (Figure 7), indicating that the study of the Tonle Sap Lake and the flood pulse has received close attentions from scholars in the short term. The paper with the strongest citation burstness is Ziv_2012, with a burstness strength of 18.53, which examined how to balance fish biodiversity, food security, and hydropower development in the Mekong Basin, especially the 78 tributary dams that not subject to PNPCA of 1995 Mekong Agreement (Ziv et al., 2012). Followed by Lauri_2012, with the burstness strength of 16.50, a comparative study on the cumulative impacts of climate change and reservoir operation on the hydrology regime and fishery of the Mekong River, and research results showed that the operation of planned hydropower plants may have a greater impact on the hydrology regime than climate change over the next 20–30 years, especially during the dry season. Climate change, on the other hand, will increase uncertainty in estimating the impact of reservoir operations (Lauri et al., 2012). The citation burstness strength of Grumbine_2011 and Kummu_2010 are 13.71 and 13.5, respectively, both of which are studies about the impacts of Mekong hydropower development, especially dam construction in China on Lower Mekong. Grumbine_2011 believed that although the cascade would provide substantial power, it would likely reduce biodiversity and ecosystem service values and undercut the livelihood and food security in the LMB (Grumbine & Xu, 2011), Kummu_2010 even directly put forward the conclusion that if the entire cascade of eight dams in China are completed, the sediment interception efficiency will increase to 78–81%, and more than 50% of the sediment will be intercepted every year (Kummu et al., 2010). When we look at the time distribution of the citation of the top documents with the strongest citation burstness in detail (Figure 7(c)), it can be found that a large number of citations took place between 2014 and 2017, with 2014 and 2017 being the years of intensive citations. We speculate that this may be related to the construction progress of hydropower dam in the Lancang River, with the gradual completion and operation of the two largest hydropower stations in China, Xiaowan Hydropower Station (2012) and Nuozhadu Hydropower Station (2014), the controversy over the possible negative impact of China's construction of hydropower stations in the Upper Mekong River on the Lower Mekong has gradually decreased, and the actual monitoring data has been used to cite or refute previous speculations and simulations (Li et al., 2017; Rasanen et al., 2017).
Fig. 7

The key articles with visually salient feature in co-citation networks (a) scatter plot between degree centrality and frequency of citations of different clusters formed in document co-citation network; (b) scatter plot between betweenness centrality and citation burstness of cited documents in different clusters, the bubble size indicates the Sigma value, the bigger the bubble, the higher the Sigma value; (c) the citation number variation of the top 5 documents with the strongest citation burstness.

Fig. 7

The key articles with visually salient feature in co-citation networks (a) scatter plot between degree centrality and frequency of citations of different clusters formed in document co-citation network; (b) scatter plot between betweenness centrality and citation burstness of cited documents in different clusters, the bubble size indicates the Sigma value, the bigger the bubble, the higher the Sigma value; (c) the citation number variation of the top 5 documents with the strongest citation burstness.

Close modal

The calculation results of Sigma values suggested that Eastham_2008 on climate change impact on Mekong River Basin water resources has the highest Sigma value of 2.56, Buschmann_2008 that links the arsenic contamination of groundwater with human health risk ranked the second highest Sigma value, Kummu & Sarkkula_2008 that links the flow variation caused by hydropower dam construction, large-scale irrigation plan, and the rapid urban development in the upper stream with ecosystem productivity of the Tonle Sap Lake Plain (Kummu & Sarkkula, 2008), and Lu & Siew_2006 that attribute changes in flow and sediment fluxes in the Lower Mekong River over the past few decades to Chinese dam construction also have the higher Sigma values of 1.74.

However, neither the centrality measure that indicates the role of the bridge nor the citation burstness indicator that measures the novelty of the study were mainly scored by members of Clu#2, and no transformative findings were identified from the members of the two largest clusters, Clu#0 on the Vietnamese Mekong Delta and Clu#1 on the whole Lancang-Mekong River Basin.

The water-related research process in the Mekong Region can be divided into seed stage (before 1994), budding stage (1995–2002), fluctuation stage (2003–2010), stabilization stage (2010–2016), and rapid growth stage (2017–present), which among the 12 identified clusters, the topic of Vietnamese Mekong Delta has the most research results, followed by the Lancang-Mekong River Basin. Their knowledge bases were both formed after 2015, showing their exuberant vitality, and it can be predicted that the research achievements in these two fields will continue to grow rapidly in the future. Clu#4 (Arsenic pollution/risk assessment) has the longest time span between the research frontier and its knowledge base, and articles with the highest GCSs and lowest LCS/GCS ratios are all members of Clu#4, indicating that the arsenic pollution of groundwater in the Mekong Region has been studied for a long time, and its research results have provided support for research in other fields or regions.

During 2009–2010, both the number of articles published and articles with high LCSs declined significantly, which could be related to the progress of widespread controversy and multi-party gaming over the hydropower development and dam construction. The first and highest peak in terms of LCS and GCS is in 2008, and the articles with the top highest betweenness centralities, Eastham_2008, Buschmann_2008, and Kummu_2008 were also concentrated around 2008, suggesting the periodical achievements and consensus were achieved in some fields during this period.

All relevant data are included in the paper or its Supplementary Information.

The authors declare there is no conflict.

Ahmed
N.
,
Zander
K. K.
&
Garnett
S. T.
(
2011
).
Socioeconomic aspects of rice-fish farming in Bangladesh: opportunities, challenges and production efficiency
.
Australian Journal of Agricultural and Resource Economics
55
(
2
),
199
219
.
Anthony
E. J.
,
Brunier
G.
,
Besset
M.
,
Goichot
M.
,
Dussouillez
P.
&
Nguyen
V. L.
(
2015
).
Linking rapid erosion of the Mekong River delta to human activities
.
Scientific Reports
5
(
1
),
14745
.
Arias
M. E.
,
Cochrane
T. A.
,
Kummu
M.
,
Lauri
H.
,
Holtgrieve
G. W.
,
Koponen
J.
&
Piman
T.
(
2014a
).
Impacts of hydropower and climate change on drivers of ecological productivity of Southeast Asia's most important wetland
.
Ecological Modelling
272
,
252
263
.
Arias
M. E.
,
Piman
T.
,
Lauri
H.
,
Cochrane
T. A.
&
Kummu
M.
(
2014b
).
Dams on Mekong tributaries as significant contributors of hydrological alterations to the Tonle Sap floodplain in Cambodia
.
Hydrology and Earth System Sciences
18
(
12
),
5303
5315
.
Arias
M. E.
,
Holtgrieve
G. W.
,
Ngor
P. B.
,
Dang
T. D.
&
Piman
T.
(
2019
).
Maintaining perspective of ongoing environmental change in the Mekong floodplains
.
Current Opinion in Environmental Sustainability
37
,
1
7
.
Auerbach
L. W.
,
Goodbred
S. L.
Jr
,
Mondal
D. R.
,
Wilson
C. A.
,
Ahmed
K. R.
,
Roy
K.
,
Steckler
M. S.
,
Small
C.
,
Gilligan
J. M.
&
Ackerly
B. A.
(
2015
).
Flood risk of natural and embanked landscapes on the Ganges–Brahmaputra tidal delta plain
.
Nature Climate Change
5
(
2
),
153
157
.
Berg
M.
,
Tran
H. C.
,
Nguyen
T. C.
,
Pham
H. V.
,
Schertenleib
R.
&
Giger
W.
(
2001
).
Arsenic contamination of groundwater and drinking water in Vietnam: a human health threat
.
Environmental Science & Technology
35
(
13
),
2621
2626
.
Burt
R. S.
(
1992
).
Structural Holes: The Social Structure of Competition
.
Harvard University Press
,
Cambridge
.
Buschmann
J.
,
Berg
M.
,
Stengel
C.
,
Winkel
L.
,
Sampson
M. L.
,
Trang
P. T. K.
&
Viet
P. H.
(
2008
).
Contamination of drinking water resources in the Mekong Delta floodplains: arsenic and other trace metals pose serious health risks to population
.
Environment International
34
(
6
),
756
764
.
Chen
C.
(
2004
).
Searching for intellectual turning points: progressive knowledge domain visualization
.
Proceedings of the National Academy of Sciences
101
(
suppl_1
),
5303
5310
.
Chen
C.
(
2006
).
Citespace II: detecting and visualizing emerging trends and transient patterns in scientific literature
.
Journal of the American Society for Information Science and Technology
57
(
3
),
359
377
.
Chen
C.
,
Ibekwe-SanJuan
F.
&
Hou
J.
(
2010
).
The structure and dynamics of cocitation clusters: a multiple-perspective cocitation analysis
.
Journal of the American Society for Information Science and Technology
61
(
7
),
1386
1409
.
Clauss
K.
,
Ottinger
M.
,
Leinenkugel
P.
&
Kuenzer
P.
(
2018
).
Estimating rice production in the Mekong Delta, Vietnam, utilizing time series of Sentinel-1 SAR data
.
International Journal of Applied Earth Observation and Geoinformation
73
,
574
585
.
Cochrane
T. A.
,
Arias
M. E.
&
Piman
T.
(
2014
).
Historical impact of water infrastructure on water levels of the Mekong River and the Tonle Sap system
.
Hydrology and Earth System Sciences
18
(
11
),
4529
4541
.
Delgado
J. M.
,
Merz
B.
&
Apel
H.
(
2012
).
A climate-flood link for the lower Mekong River
.
Hydrology and Earth System Sciences
16
(
5
),
1533
1541
.
Dore
J.
,
Lebel
L.
&
Molle
F.
(
2012
).
A framework for analysing transboundary water governance complexes, illustrated in the Mekong Region
.
Journal of Hydrology
466–467
,
23
36
.
Eastham
J.
,
Mpelasoka
F. S.
,
Mainuddin
M.
,
Ticehurst
C.
,
Dyce
P.
,
Hodgson
G.
,
Ali
R.
&
Kirby
M.
(
2008
).
Mekong River Basin water resources assessment: impacts of climate change
.
Water for a Healthy Country National Research Flagship. Commonwealth Scientific and Industrial Research Organization, Canberra.
Fan
H.
,
He
D. M.
&
Wang
H. L.
(
2015
).
Environmental consequences of damming the mainstream Lancang-Mekong River: a review
.
Earth-Science Reviews
146
,
77
91
.
Fikriyah
V. N.
,
Darvishzadeh
R.
,
Laborte
A.
,
Khan
N. I.
&
Nelson
A.
(
2019
).
Discriminating transplanted and direct seeded rice using Sentinel-1 intensity data
.
International Journal of Applied Earth Observation and Geoinformation
76
,
143
153
.
Fu
K. D.
,
He
D. M.
&
Lu
X. X.
(
2008
).
Sedimentation in the Manwan reservoir in the Upper Mekong and its downstream impacts
.
Quaternary International
186
,
91
99
.
Garfield
E.
,
Paris
S. W.
&
Stock
W. G.
(
2006
).
HistCite: a software tool for informetric analysis of citation linkage
.
Information
57
(
8
),
391
400
.
Gorelick
N.
,
Hancher
M.
,
Dixon
M.
,
Ilyushchenko
S.
,
Thau
D.
&
Moore
R.
(
2017
).
Google Earth Engine: planetary-scale geospatial analysis for everyone
.
Remote Sensing of Environment
202
,
18
27
.
Grumbine
R. E.
&
Xu
J.
(
2011
).
Mekong hydropower development
.
Science
332
(
6026
),
178
.
Grumbine
R. E.
,
Dore
J.
&
Xu
J.
(
2012
).
Mekong hydropower: drivers of change and governance challenges
.
Frontiers in Ecology and the Environment
10
(
2
),
91
98
.
Hecht
J. S.
,
Lacombe
G.
,
Arias
M. E.
,
Dang
T. D.
&
Piman
T.
(
2019
).
Hydropower dams of the Mekong River basin: a review of their hydrological impacts
.
Journal of Hydrology
568
,
285
300
.
Hoa Le
T. V.
,
Nguyen
H. N.
,
Wolanski
E.
,
Tran
T. C.
&
& Haruyama
S.
(
2007
).
The combined impact on the flooding in Vietnam's Mekong River delta of local man-made structures, sea level rise, and dams upstream in the river catchment
.
Estuarine, Coastal and Shelf Science
71
(
1
),
110
116
.
Hoang
L. P.
,
Lauri
H.
,
Kummu
M.
,
Koponen
J.
,
van Vliet
M. T. H.
,
Supit
I.
,
Leemans
R.
,
Kabat
P.
&
Ludwig
F.
(
2016
).
Mekong River flow and hydrological extremes under climate change
.
Hydrology and Earth System Sciences
20
(
7
),
3027
3041
.
JICA
(
2001
).
The Study on Groundwater Development in Central Cambodia
.
Japan International Cooperation Agency
,
Tokyo
.
Johnston
R.
&
Kummu
M.
(
2012
).
Water resource models in the Mekong Basin: a review
.
Water Resources Management
26
(
2
),
429
455
.
Keskinen
M.
,
Guillaume
J. H. A.
,
Kattelus
M.
,
Porkka
M.
,
Rasanen
T. A.
&
Varis
O.
(
2016
).
The Water-Energy-Food Nexus and the transboundary context: insights from large Asian Rivers
.
Water
8
(
5
),
25
.
Kleinberg
J.
(
2003
).
Bursty and hierarchical structure in streams
.
Data Mining and Knowledge Discovery
7
(
4
),
373
397
.
Kocar
B. D.
,
Polizzotto
M. L.
,
Benner
S. G.
,
Ying
S. C.
,
Ung
M.
,
Ouch
K.
,
Samreth
S.
,
Suy
B.
,
Phan
K.
,
Sampson
M.
&
Fendorf
S.
(
2008
).
Integrated biogeochemical and hydrologic processes driving arsenic release from shallow sediments to groundwaters of the Mekong Delta
.
Applied Geochemistry
23
(
11
),
3059
3071
.
Kuenzer
C.
,
Renaud
F. G.
, (
2012
). In
Mekong Delta System: Interdisciplinary Analyses of a River Delta
.
Renaud
F. G.
&
Kuenzer
C.
(eds).
Springer
,
New York
, pp.
7
46
.
Kuenzer
C.
,
Campbell
I.
,
Roch
M.
,
Leinenkugel
P.
,
Tuan
V. Q.
&
Dech
S.
(
2013a
).
Understanding the impact of hydropower developments in the context of upstream-downstream relations in the Mekong River Basin
.
Sustainability Science
8
(
4
),
565
584
.
Kuenzer
C.
,
Guo
H. D.
,
Huth
J.
,
Leinenkugel
P.
,
Li
X. W.
&
Dech
S.
(
2013b
).
Flood mapping and flood dynamics of the Mekong Delta: ENVISAT-ASAR-WSM based time series analyses
.
Remote Sensing
5
(
2
),
687
715
.
Kummu
M.
&
Varis
O.
(
2007
).
Sediment-related impacts due to upstream reservoir trapping, the Lower Mekong River
.
Geomorphology
85
(
3–4
),
275
293
.
Kummu
M.
,
Lu
X. X.
,
Wang
J. J.
&
Varis
O.
(
2010
).
Basin-wide sediment trapping efficiency of emerging reservoirs along the Mekong
.
Geomorphology
119
(
3
),
181
197
.
Lado
L. R.
,
Polya
D.
,
Winkel
L.
,
Berg
M.
&
Hegan
A.
(
2008
).
Modelling arsenic hazard in Cambodia: a geostatistical approach using ancillary data
.
Applied Geochemistry
23
(
11
),
3010
3018
.
Lauri
H.
,
de Moel
H.
,
Ward
P. J.
,
Rasanen
T. A.
,
Keskinen
M.
&
Kummu
M.
(
2012
).
Future changes in Mekong River hydrology: impact of climate change and reservoir operation on discharge
.
Hydrology and Earth System Sciences
16
(
12
),
4603
4619
.
Lebel
L.
,
Grothmann
T.
&
Siebenhuner
B.
(
2010
).
The role of social learning in adaptiveness: insights from water management
.
International Environmental Agreements: Politics Law and Economics
10
(
4
),
333
353
.
Li
D. N.
,
Long
D.
,
Zhao
J. S.
,
Lu
H.
&
Hong
Y.
(
2017
).
Observed changes in flow regimes in the Mekong River Basin
.
Journal of Hydrology
551
,
217
232
.
Manh
N. V.
,
Dung
N. V.
,
Hung
N. N.
,
Kummu
M.
,
Merz
B.
&
Apel
H.
(
2015
).
Future sediment dynamics in the Mekong Delta floodplains: impacts of hydropower development, climate change and sea level rise
.
Global and Planetary Change
127
,
22
33
.
Middleton
C.
&
Dore
J.
(
2015
).
Transboundary water and electricity governance in mainland Southeast Asia: linkages, disjunctures and implications
.
International Journal of Water Governance
3
(
1
),
93
119
.
Middleton
C.
,
Allouche
J.
,
Gyawali
D.
&
Allen
S.
(
2015
).
The rise and implications of the Water-Energy-Food Nexus in Southeast Asia through an environmental justice lens
.
Water Alternatives – An Interdisciplinary Journal on Water Politics and Development
8
(
1
),
627
654
.
Minh
H. V.
,
Avtar
R.
,
Mohan
G.
,
Misra
P.
&
Kurasaki
M.
(
2019
).
Monitoring and mapping of rice cropping pattern in flooding area in the Vietnamese Mekong Delta using Sentinel-1A data: a case of an Giang Province
.
ISPRS International Journal of Geo-Information
8
(
211
),
1
22
.
Mirumachi
N.
(
2015
).
Transboundary Water Politics in the Developing World
.
Routledge
,
London
.
MRC
(
2005
).
Overview of the Hydrology of the Mekong Basin
, p.
73
.
Mekong River Commission
,
Vientiane
.
MRC
(
2010
).
State of the Basin Report
.
Mekong River Commission
,
Vientiane
.
Nhan
D. K.
,
Phong
L. T.
,
Verdegem
M. J. C.
,
Duong
L. T.
,
Bosma
R. H.
&
Little
D. C.
(
2007
).
Integrated freshwater aquaculture, crop and livestock production in the Mekong Delta, Vietnam: determinants and the role of the pond
.
Agricultural Systems
94
(
2
),
445
458
.
Orr
S.
,
Pittock
J.
,
Chapagain
A.
&
Dumaresq
D.
(
2012
).
Dams on the Mekong River: lost fish protein and the implications for land and water resources
.
Global Environmental Change: Human and Policy Dimensions
22
(
4
),
925
932
.
Phan
L. T.
,
Bui
T. M.
,
Nguyen
T. T. T.
,
Gooley
G. J.
,
Ingram
B. A.
,
Nguyen
H. V.
,
Nguyen
P. T.
&
De Silva
S. S.
(
2009
).
Current status of farming practices of striped catfish, Pangasianodon hypophthalmus in the Mekong Delta, Vietnam
.
Aquaculture
296
(
3–4
),
227
236
.
Pokhrel
Y.
,
Burbano
M.
,
Roush
J.
,
Kang
H.
,
Sridhar
V.
&
Hyndman
D. W.
(
2018
).
A review of the integrated effects of changing climate, land use, and dams on Mekong River hydrology
.
Water
10
(
3
),
25
.
Polizzotto
M. L.
,
Kocar
B. D.
,
Benner
S. G.
,
Sampson
M.
&
Fendorf
S.
(
2008
).
Near-surface wetland sediments as a source of arsenic release to ground water in Asia
.
Nature
454
(
7203
),
505
U505
.
Rasanen
T. A.
,
Someth
P.
,
Lauri
H.
,
Koponen
J.
,
Sarkkula
J.
&
Kummu
M.
(
2017
).
Observed river discharge changes due to hydropower operations in the Upper Mekong Basin
.
Journal of Hydrology
545
,
28
41
.
Sebesvari
Z.
,
Renaud
F. G.
,
Haas
S.
,
Tessler
Z.
,
Hagenlocher
M.
,
Kloos
J.
,
Szabo
S.
,
Tejedor
A.
&
Kuenzer
C.
(
2016
).
A review of vulnerability indicators for deltaic social-ecological systems
.
Sustainability Science
11
(
4
),
575
590
.
Shin
S.
,
Pokhrel
Y.
,
Yamazaki
D.
,
Huang
X. D.
,
Torbick
N.
,
Qi
J. G.
,
Pattanakiat
S.
,
Thanh
N. D.
&
Tuan
N. D.
(
2020
).
High resolution modeling of river-floodplain-reservoir inundation dynamics in the Mekong River Basin
.
Water Resources Research
56
(
5
),
23
.
Smajgl
A.
,
Toan
T. Q.
,
Nhan
D. K.
,
Ward
J.
,
Trung
N. H.
,
Tri
L. Q.
,
Tri
V. P. D.
&
Vu
P. T.
(
2015
).
Responding to rising sea levels in the Mekong Delta
.
Nature Climate Change
5
(
2
),
167
U167
.
Smedley
P. L.
&
Kinniburgh
D. G.
(
2002
).
A review of the source, behaviour and distribution of arsenic in natural waters
.
Applied Geochemistry
17
(
5
),
517
568
.
Szabo
S.
,
Brondizio
E.
,
Renaud
F. G.
,
Hetrick
S.
,
Nicholls
R. J.
,
Matthews
Z.
,
Tessler
Z.
,
Tejedor
A.
,
Sebesvari
Z.
,
Foufoula-Georgiou
E.
,
da Costa
S.
&
Dearing
J. A.
(
2016
).
Population dynamics, delta vulnerability and environmental change: comparison of the Mekong, Ganges-Brahmaputra and Amazon delta regions
.
Sustainability Science
11
(
4
),
539
554
.
Toan
P. V.
,
Sebesvari
Z.
,
Blasing
M.
,
Rosendahl
I.
&
Renaud
F. G.
(
2013
).
Pesticide management and their residues in sediments and surface and drinking water in the Mekong Delta, Vietnam
.
Science of the Total Environment
452
,
28
39
.
Wassmann
R.
,
Hien
N. X.
,
Hoanh
C. T.
&
Tuong
T. P.
(
2004
).
Sea level rise affecting the Vietnamese Mekong Delta: water elevation in the flood season and implications for rice production
.
Climatic Change
66
(
1
),
89
107
.
Winemiller
K. O.
,
McIntyre
P. B.
,
Castello
L.
,
Fluet-Chouinard
E.
,
Giarrizzo
T.
,
Nam
S.
,
Baird
I. G.
,
Darwall
W.
,
Lujan
N. K.
,
Harrison
I.
,
Stiassny
M. L. J.
,
Silvano
R. A. M.
,
Fitzgerald
D. B.
,
Pelicice
F. M.
,
Agostinho
A. A.
,
Gomes
L. C.
,
Albert
J. S.
,
Baran
E.
,
Petrere
M.
,
Zarfl
C.
,
Mulligan
M.
,
Sullivan
J. P.
,
Arantes
C. C.
,
Sousa
L. M.
,
Koning
A. A.
,
Hoeinghaus
D. J.
,
Sabaj
M.
,
Lundberg
J. G.
,
Armbruster
J.
,
Thieme
M. L.
,
Petry
P.
,
Zuanon
J.
,
Vilara
G. T.
,
Snoeks
J.
,
Ou
C.
,
Rainboth
W.
,
Pavanelli
C. S.
,
Akama
A.
,
Soesbergen
A. v.
&
Sáenz
L.
(
2016
).
Balancing hydropower and biodiversity in the Amazon, Congo, and Mekong
.
Science
351
(
6269
),
128
.
Winkel
L.
,
Berg
M.
,
Amini
M.
,
Hug
J.
&
Johnson
C. A.
(
2008
).
Predicting groundwater arsenic contamination in Southeast Asia from surface parameters
.
Nature Geoscience
1
(
8
),
536
542
.
Ziv
G.
,
Baran
E.
,
Nam
S.
,
Rodríguez-Iturbe
I.
&
Levin
S. A.
(
2012
).
Trading-off fish biodiversity, food security, and hydropower in the Mekong River Basin
.
Proceedings of the National Academy of Sciences
109
(
15
),
5609
.
This is an Open Access article distributed under the terms of the Creative Commons Attribution Licence (CC BY 4.0), which permits copying, adaptation and redistribution, provided the original work is properly cited (http://creativecommons.org/licenses/by/4.0/).