Schistura sexnubes, a new diminutive river loach from the upper Mekong basin, Yunnan Province, China （Teleostei： Cypriniformes： Nemacheilidae）

An ichthyofaunistic survey of Mekong tributaries in Lincang Prefecture, Yunnan Province, China yielded a new species of nemacheilid loach, herein described as Schistura sexnubes species nova. The new species is readily distinguishable from its congeners by the following combination of characters： 8＋8 branched caudal fin rays, an incomplete lateral line, a dissociated caudal bar, a shallow caudal peduncle depth （7.6%-9.6% SL; respectively caudal peduncle 1.76-1.95 times longer than deep）, a diminutive size of less than 50 mm SL, and no sexual dimorphism. A dorsocephalic pattern consisting of a black, forward directed V-shaped formation located between the nares, and a white, ovoid blotch on the upper operculum serves as an autapomorphy.

A preliminary investigation of fossil wood from Lower Mekong Basin of Southeast Asia

Nine fossil wood samples from the Mesozoic bedrock and the Quaternary terrace deposits of the Lower Mekong Basin in Southeast Asia including Thailand,Laos and Cambodia were investigated in order to assist in developing a hypothesis about the Mekong River palaeocourses. Six of the samples were conifers assigned to Aga-thoxylon sp.,and three were dicots of cf. Pahudioxylon sp. and two unknown taxa( Dicotyloxylon sp.).The preservation of two dicotyledonous wood samples is insufficient for precise identification to family level,such that the samples are not suitable with respect to investigation of the river palaeocourse. However,these findings increase the systematic data of the fossil wood from the Mekong Basin. Further investigations of fossil wood from the Mekong Basin are in progress to gain a regional perspective on the plant communities and to form better reconstruction of the palaeoenvironment.

Evaluation of Transboundary Water Resource Development in Mekong River Basin: The Application of Analytic Hierarchy Process in the Context of Water Cooperation

Mekong River is one of the major international freshwater sources in the world. The Lower Mekong Basin (LMB) comprised of four downstream countries, including Thailand, Lao PDR, Cambodia, and Vietnam. The utilization of the basin’s water brings not only substantial benefits to the region ranging from hydropower to navigation, but also negative impacts caused by the unbalanced water using. The essential role of Mekong River requires all member nations to cooperate effectively for the sustainable development of the region. One of the most popular methods in the field of water resource management is a trustable tool called the Analytical Hierarchy Process (AHP). AHP is much appropriate for water resource policymaking. The literature, however, points out that there is no study to both structure the water using hierarchy and employ quantitative (objective) criteria to the AHP model in LMB case. With regard to water resource management, there are no previous studies applying AHP models to evaluating sustainable development of transboundary water resource in LMB case. This paper explores the evolution of water cooperation among Mekong countries and subsequently evaluates the water development scenarios in the LMB based on the water cooperation preferences of four LMB countries This study proposes a novel approach to analyzing, assessing water resource development scenarios characterized by sustainability indicators and to assisting in developing a suitable water policy in LMB according to the best cooperation scenario.

Achieving fish passage outcomes at irrigation infrastructure;a case study from the Lower Mekong Basin

Irrigation infrastructure expansion threatens the diversity of freshwater fish worldwide.Irrigation infrastructure creates migration barriers which can block access to important nursery,feeding and spawning habitat.Lao PDR is a landlocked country situated within the Lower Mekong River Basin where there is a substantial dependency on rice and fish for food,income and livelihoods.The country is experiencing an unprecedented boom in irrigation infrastructure investment,with modernisation programs being implemented in every province.Despite significant investment in infrastructure upgrades,and the potential impact on freshwater fish,little consideration has been given to fish passage solutions.In 2008,we commenced a fish passage program in Lao PDR.The intent of this case study is to outline the pivotal elements of the program of knowledge development and transfer,in the context of river connectivity and fisheries management in Lao PDR.We also highlight challenges in international research in development and lessons learned.

A Risk-Based Multi-Criteria Decision Analysis Approach to Evaluating Transboundary Water Development—The Case of Lower Mekong River Basin

The Lower Mekong River basin (LMB) covers the lower part of the Mekong river basin, including Laos, Thailand, Cambodia and Vietnam. Due to numerous pressures from high population growth and intensive hydropower development, the LMB has been facing significant challenges concerning its biodiversity and ecosystem. In 2017, Mekong River Commission (MRC), an intergovernmental organisation founded in 1995 among LMB countries, established the Council Study, which analysed the impacts of water development scenarios concerning the environmental, socioeconomic aspects of the LMB. This paper explores the nature of risks to the LMB water development and subsequently evaluates LMB’s water development scenarios described in the Council Study by using a multi-criteria decision analysis (MCDA) method. MCDA method has been widely applied in the field of water resource management in order to assist the decision-making process by systematically evaluating a certain number of alternatives against well-selected criteria through a preference rating scheme. By implementing a risk-based comprehensive assessment of the LMB transboundary water, this study provides insights into the impacts of the increasing risks to the ecosystem and human beings on the water development of the basin over time, which assists to change the awareness and the perspective toward humans’ risks and transboundary river ecosystem of decision-makers. This paper provides valuable recommendations for MRC to improve their policy concerning benefit-sharing scheme, water planning and risk mitigation strategies.

Hydrological Simulation Using TRMM and CHIRPS Precipitation Estimates in the Lower Lancang-Mekong River Basin

Satellite-based products with high spatial and temporal resolution provide useful precipitation information for data-sparse or ungauged large-scale watersheds. In the Lower Lancang-Mekong River Basin, rainfall stations are sparse and unevenly distributed, and the transboundary characteristic makes the collection of precipitation data more difficult, which has restricted hydrological processes simulation. In this study, daily precipitation data from four datasets(gauge observations, inverse distance weighted(IDW) data, Tropical Rainfall Measuring Mission(TRMM) estimates, and Climate Hazards Group InfraRed Precipitation with Stations(CHIRPS) estimates), were applied to drive the Soil and Water Assessment Tool(SWAT) model, and then their capability for hydrological simulation in the Lower Lancang-Mekong River Basin were examined. TRMM and CHIRPS data showed good performances on precipitation estimation in the Lower Lancang-Mekong River Basin, with the better performance for TRMM product. The Nash-Sutcliffe efficiency(NSE) values of gauge, IDW, TRMM, and CHIRPS simulations during the calibration period were 0.87, 0.86, 0.95, and 0.93 for monthly flow, respectively, and those for daily flow were 0.75, 0.77, 0.86, and 0.84, respectively. TRMM and CHIRPS data were superior to rain gauge and IDW data for driving the hydrological model, and TRMM data produced the best simulation performance. Satellite-based precipitation estimates could be suitable data sources when simulating hydrological processes for large data-poor or ungauged watersheds, especially in international river basins for which precipitation observations are difficult to collect. CHIRPS data provide long precipitation time series from 1981 to near present and thus could be used as an alternative precipitation input for hydrological simulation, especially for the period without TRMM data. For satellite-based precipitation products, the differences in the occurrence frequencies and amounts of precipitation with different intensities would affect simulation results of water balance components, which should be comprehensively considered in water resources estimation and planning.

The Pulses of the Mekong River Basin: Rivers and the Livelihoods of Farmers and Fishers

The transboundary Mekong River is shared by six SE Asia countries (China, Myanmar, Thailand, Lao PDR, Cambodia, and Vietnam). In this paper the livelihoods of farmers and fishers of Lao PDR, Cambodia and Vietnam are examined to assess impacts of Mekong River development and modernization projects on the rural peoples of the Mekong River and Delta. A high proportion of the 190 million rural people of the Mekong basin are dependent on the diverse and abundant resources of the Mekong River and its tributaries for food security and basic necessities, livelihoods, and cultural identities. Although rice farming and fisheries occupations are primary income sources, many livelihoods involve a diversity of on-farm and off-farm activities. Agricultural specialization and intensification and hydropower dam construction on the Mekong main stem and tributaries are altering traditional rural patterns of household food security, income, and cultural ways of living at an increasingly rapid pace. Rural transformation projects must better assess how these modernization efforts change the ecology of the Mekong River and in turn affect the capacity of rural people to adapt in ways that ensure food security and improve household livelihoods. It will be critical that development efforts recognize, value, and invest in rural people’s roles in producing a stable, affordable food system and managing the integrity of river ecosystems upon which future prosperity depends. Interventions are needed to prevent degradation of the Mekong Basin soil and water resources from large-scale agricultural intensification, water diversion and overbuilding of hydropower dams which are threats to small-scale land holdings and farmers and fishers capacities to provide daily food for their own consumption and to feed SE Asia’s growing urban populations.

Groundwater status and associated issues in the Mekong-Lancang River Basin： International collaborations to achieve sustainable groundwater resources

Groundwater is an important and readily available source of fresh water in the Mekong-Lancang River Basin. With a rapid population growth and increasing human activities, an increasing number of countries in the Mekong-Lancang River Basin are experiencing depleted and degraded groundwater supplies. In transboundary river basins, such as the Mekong-Lancang River, prioritizing the use of the shared aquifer by one riparian government may affect the opportunities of other riparian governments and lead to potential water conflicts between neighboring countries. To promote the sharing of strategies and information for the sustainable and equitable use of water resources of the shared basin, international collaborative workshops on groundwater resources have been organized for all Mekong-Lancang River countries. These workshops provide an opportunity to communicate and discuss nationally sensitive issues on groundwater by the associated countries, with topics covering multiple aspects of groundwater, such as the groundwater status in the basin, quality issues, water use conflicts, hydrological information gaps, management policies and capacity building for successful water resource management. Consensus has been reached by all countries on the importance of catchment-based groundwater management and the need for close communication among the countries. Strategies for managing transboundary aquifer issues must foster international collaboration based on the regional network, influence national networks and enhance the capacity to building maps and monitoring systems based on associated databases. The sustainability of water resources cannot be achieved without the integrated involvement and contributions by multiple countries and various stakeholders. Therefore, collaborative workshops provide a great opportunity to further our understanding of the hydrologic processes of the Mekong River Basin, share the benefits of the aquifer and provide a strategy and vision for sustainable water resource management in the Mekong-Lancang River countries.

FACILITATING REGIONAL SUSTAINABLE DEVELOPMENT THROUGH INTEGRATED MULTI-OBJECTIVE UTILIZATION, MANAGEMENT OF WATER RESOURCES IN THE LANCANG-MEKONG RIVER BASIN

The Lancnag Mekong River is the most important international river across China and Southeast Asia, If it is developed according to 'Great Mekong Subregional Cooperation Plan' [9] prepared by ADB, the area directly affected will be up to over 2.32 million km 2, the population over 220 million, and the natural environment, and socio-economic conditions within a large area will be greatly changed. 'Agreement on Cooperation for Sustainable Development of Mekong Basin' signed by the four riparian countries along the lower Mekong River on April 5, 1995 provides a new opportunity for sustainable development of the Basin. According to preliminary analysis, if the multipurpose utilization of the water resources is the target for carrying out integrated planning and management, and the efforts are made 1) to focus on energy exploitation on the Lancang River Mainstream and the tributaries of the lower Mekong River; 2) to build gated weirs at Tonle Sam; 3) to construct spillways at the Mekong Delta; 4) to facilitate flood dykes in big cities and on both banks of the mainstream which are concentrated with population and farmland and liable to be flooded, and 5) to strengthen networks for forecasting hydrological and meteorological conditions, then all problems such as power demand, irrigation, flood, salt water intrusion as well as acid water erosion to soil could be solved without constructing large cascaded stations and dams on the lower Mekong Mainstream. This will not only avoid input of great number of fund, large scale resettlement and land inundation, but also prevent aquatic organisms living in Mekong River from being injured due to dam construction, and promote the sustainable development of the Basin.

基于多维Copula函数的澜沧江-湄公河流域气象干旱特征分析

为全面揭示变化环境下澜湄流域多维气象干旱特征,采用标准化降水蒸散指数SPEI表征流域气象干旱,基于游程理论分别提取澜沧江段和湄公河段上、中、下游流域1901—1960年和1961—2021年两个时段的干旱事件,利用Copula函数分别构建两个时段不同子流域二维和三维干旱特征变量联合分布,计算不同干旱特征变量组合条件下的干旱联合发生概率,对比分析不同子流域多维气象干旱特征的时空变化。结果表明:时间上,1961—2021年各子流域平均干旱程度均较1901—1960年更严峻,尤其是极端干旱事件(单变量累积频率为25%、50%)的多维干旱联合发生概率增幅最大;空间上,1961—2021年,随着干旱历时、烈度和烈度峰值的增加,“或”情况下多维干旱联合发生概率最高值区自北向南转移,“且”情况下多维干旱联合发生概率最高值区自南向北转移。

东盟一体化背景下日本对湄公河国家援助:动因、路径与评估

不论是出于助力东南亚经济社会的发展、推动东盟经济一体化的积极性区域合作构想,还是基于与一体化水平更高的东盟合作实现经济与政治利益最大化的自身需求,日本对湄公河国家的援助都与东盟一体化进程呈现某种程度的相关趋向。这种相关性随着地区内外环境的变化发生适度调整,从而使援助的规模和形式呈现因时因势的起伏。总体看,东盟共同体背景下对湄公河地区的援助对于弥合地区发展差距、促进经济一体化起到了一定的正面作用;日本也得到了经济回报和政治外交收益。但援助与“民主、人权”等价值观外交理念相捆绑,并成为“印太”战略推进工具,将对东亚地区合作带来消极影响。

湄公河流域农业生态建设经验及其对中国长江经济带的启示

农业生态建设是实现农业可持续发展的必然之路,自20世纪80年代以来,“高投入、高能耗、高污染”农业发展模式导致土壤、水体污染,生态环境承载压力加大。加速转向高效节能、可持续的农业高质量发展迫在眉睫。本研究以湄公河流域国家为例,在分析湄公河流域国家农业生态建设发展现状的基础上,总结湄公河流域国家农业生态建设经验,对标中国长江经济带,提出农业生态建设的对策和建议。研究发现,湄公河流域国家农业生态建设的经验包括:以硬约束为支撑的缅甸农业生态建设、以合作社为抓手的泰国农业生态建设、因地制宜的老挝农业生态建设、越南数字化赋能农业生态建设、强化气候适应性为重点的柬埔寨农业生态建设。据此,本研究提出应完善顶层设计,加快长江经济带农业生态建设布局;强化新型经营主体带动作用,引导小农户参与农业生态建设;因地制宜,探索长江经济带不同区域的发展模式;发展数字化农业产业,打造智慧高效型农业生产模式;采取多样化措施来增强气候适应性,推动农业可持续发展。

气候变化影响下澜湄流域下游水稻生产用水量模拟与分析

农业用水是社会经济用水的主要行业,气候变化对农业用水的影响可能改变区域的水资源供需情势。以澜沧江-湄公河流域下游为研究区,基于ERA5-Land数据集和最新的CMIP6气候预测数据,选用SSP1-2.6、SSP2-4.5、SSP5-8.5三种排放情景,AquaCrop模型将非生产性土壤蒸发和生产性作物蒸腾分离,将水稻生长期内蒸腾总量作为水稻生产用水量,模拟了澜沧江-湄公河流域下游历史和未来时期水稻生产用水量,分析了水稻生产用水量的变化情况及其与温度、降水和CO_(2)浓度之间的相关关系。结果表明:澜沧江-湄公河流域下游水稻生产用水量在空间上表现为北多南少,总体呈现逐年减少趋势,且在SSP5-8.5情景下趋势更加明显。SSP5-8.5情景下的未来远期,澜沧江-湄公河流域下游水稻生产用水量将减少29.7%。与温度和降水相比,水稻生产用水量和CO_(2)浓度之间的相关性最强。SSP5-8.5情景下的未来远期,在泰国的相关系数为-0.875,其余国家各季度下的相关系数均小于-0.9。

区域治理视阈下的澜湄环保合作:进展、问题与对策

湄公河流域国家面临着陆地、海洋和空气等方面的环境问题,本身就有开展区域环境治理的需求。澜湄流域山水相连且同属发展中国家,在应对全球和地区环境问题上立场一致、责任相当,需求互补,双方的环保合作取得了积极的进展。但在双方的合作中还存在缺乏对环境的监测,中国环保的国际形象有待提升,中国民间对环保国际合作的参与度不高,中国还面临着来自外部大国和国际组织的竞争等问题。为了释放澜湄环保合作潜力,中国可从区域治理视阈出发,完善对区域环境的监测预警,着力提升自身国际形象,同湄公河国家开展环保联合执法,鼓励环保社会组织的参与,开展同流域国家的环保产业合作。

人类命运共同体视域下跨境水资源的研究进展与展望

基于CiteSpace可视化分析软件,对2013—2022年CNKI中跨境水资源相关文献进行了梳理,从整体跨境水资源与典型国际河流这两个层面分析了跨境水资源的研究进展和前沿动态。结果显示:人类命运共同体倡议提出后,跨境水资源研究经历了相对平稳和快速增长两个阶段;跨境水资源研究的核心作者主要是徐宗学、陈晓宏、何大明、周海炜等,这些学者之间已经形成了部分团队合作;河海大学商学院、中国科学院大学、武汉大学水资源与水电工程科学国家重点实验室等是跨境水资源的主要研究机构,各研究机构间合作较少;跨境水资源研究视角多元化,其中国际水法、水外交、水安全、水利益等是研究热点,国际河流中澜沧江和珠江流域是研究热点;跨境水资源研究最新进展主要体现在流域共同体建设上,并已提出构建澜湄流域水安全共同体;未来跨境水资源研究热点可能是利益共同体与生态共同体的构建、跨境水冲突的应对机制与补偿机制、结合地缘经济政治与粮食安全等领域的研究。

区域国别视域下泰国、越南湄公河流域地区秩序的竞构

区域国别研究是了解相关地区和国家发展的基础,也是共建“一带一路”高质量发展的必要支撑,因为除大国博弈之外,区域内国家自身发展战略的能动性也会影响区域秩序的演变。在湄公河流域地区,泰国、越南两国的竞争深刻影响了地区秩序的变革。泰国、越南两国在这一地区的竞争是一个长期过程,两国对地区秩序构建的理念经历了“曼陀罗体系与亚朝贡体系”“资本主义与社会主义”等不同历史阶段的竞争,双方均表现出主导湄公河流域地区秩序的意愿并付出了实际行动。泰国、越南两国在湄公河流域地区秩序维度的竞争既是政治理念差异的结果,也是在区域权力结构下地缘政治的表现。尽管存在域外大国不同程度的干预,泰国、越南的竞争直接影响了老挝和柬埔寨的国内政治进程,塑造了湄公河流域的地区秩序。而泰国、越南竞构下的湄公河流域地区秩序也成为冷战后不同行为体开展湄公河次区域合作的前提和基础。基于此,当前,区域国别研究需要突破大国作用的窠臼,重视区域内国家间的历史互动与实践,而中国与湄公河国家开展的次区域双边、多边合作也应重视这种区域内长期存在的互动关系。

Using Artificial Neural Network to Estimate Sediment Load in Ungauged Catchments of the Tonle Sap River Basin, Cambodia

Concern on alteration of sediment natural flow caused by developments of water resources system, has been addressed in many river basins around the world especially in developing and remote regions where sediment data are poorly gauged or ungauged. Since suspended sediment load (SSL) is predominant, the objectives of this research are to: 1) simulate monthly average SSL (SSLm) of four catchments using artificial neural network (ANN);2) assess the application of the calibrated ANN (Cal-ANN) models in three ungauged catchment representatives (UCR) before using them to predict SSLm of three actual ungauged catchments (AUC) in the Tonle Sap River Basin;and 3) estimate annual SSL (SSLA) of each AUC for the case of with and without dam-reservoirs. The model performance for total load (SSLT) prediction was also investigated because it is important for dam-reservoir management. For model simulation, ANN yielded very satisfactory results with determination coefficient (R2) ranging from 0.81 to 0.94 in calibration stage and 0.63 to 0.87 in validation stage. The Cal-ANN models also performed well in UCRs with R2 ranging from 0.59 to 0.64. From the result of this study, one can estimate SSLm and SSLT of ungauged catchments with an accuracy of 0.61 in term of R2 and 34.06% in term of absolute percentage bias, respectively. SSLA of the AUCs was found between 159,281 and 723,580 t/year. In combination with Brune’s method, the impact of dam-reservoirs could reduce SSLA between 47% and 68%. This result is key information for sustainable development of such infrastructures.

澜湄流域跨境水资源合作机制研究

跨境水资源合作对于澜湄国家命运共同体的建设意义重大,开展国际合作是化解当前跨境水资源合作难题的必然选择。由于国际硬法制定的繁杂性以及实施效果的不确定性,可以从国际软法入手,开展澜湄流域跨境水资源合作。澜湄流域水资源合作机制已经在机制构建、信息共享、科技文化交流等方面取得一系列成绩,但仍需要通过建立联合管理机构、扩大自身影响力、鼓励流域国共同参与、增加合作主体类型等来完善,以加快建设澜湄流域国家命运共同体的步伐,推动澜湄流域各国经济和社会的发展。

湄公河流域国家的制度重叠困境:基于泰国和越南的案例研究

21世纪以来,欧洲和东南亚国家均积极利用制度重叠策略解决特定议题领域的实际问题。欧盟国家在安全合作领域进行的制度重叠产生了正面的溢出效应,有助于欧洲一体化进程,但东南亚湄公河流域国家在水资源领域的制度重叠却使得该区域合作环境受到不利影响。有关这种差异的逻辑路径为,大国的地区竞争越激烈,地区国家越秉持“国家至上”理念,地区规范越强调共识与非正式性,地区国家针对于特定议题领域的制度重叠越容易产生负面溢出效应,令区域局势紧张,反之亦然。一方面,泰国原为解决水资源议题领域问题的区域合作制度被延展为澜沧江—湄公河合作,但美国秉持冷战思维,借机推出湄公河—美国伙伴关系进行竞争,地区合作环境由此受到消极影响;另一方面,受地区“国家至上”理念的驱动,再加之“东盟方式”提供的便利条件,泰国和越南两国根据自身利益设计并领导了“三河流域机制”和“四国机制”,以解决水资源领域的具体问题,并进一步争夺区域领导权,区域合作环境又一次因流域国家的制度重叠而恶化。不论是从结构层次还是区域层次来看,湄公河流域国家的制度重叠最终产生了负面溢出效应。泰国和越南两国在湄公河流域的制度参与现状清晰体现了湄公河流域国家的制度重叠困境,这为东南亚地区未来的制度发展提供了启示。在东南亚国家处理具体议题领域事项的过程中,东盟的内外“中心性”必须得到加强。

不同情境下公共流域水资源动态一体化调控——以澜湄流域为例

从一体化视角出发针对不同的水文情境分析公共流域水资源调控能够应对复杂多变的气候变化。文章采用DPSIR模型构建流域水资源系统分析框架,并构建其系统动力学模型组从供需方面分析流域水资源系统的因果关系。以澜沧江−湄公河流域(文中简称澜湄流域)为例,运用系统动力学模型探究流域现在和未来的水资源供需情况,结合不同水文情景进行仿真分析,分析其演化过程和调控机制。结果显示:不同水文情景下流域内的水资源供需矛盾存在较大差异,结构性措施主要影响水资源的供给,非结构性措施主要影响水资源的需求。两种类型措施单独实施时都能够缓解流域内水资源短缺的压力,但对于较为极端的水文情景,流域未来仍会面临水资源短缺的压力。当结构性措施和非结构性措施同时实施时,流域内水资源的供给具有较大韧性,即使在较为极端的水文条件下仍然能够调节流域的水资源供需平衡,有利于流域内水资源的长期可持续发展。研究结果揭示了一体化视角下澜湄流域在不同水文情境下水资源的调控效果,以及各种调控措施对水资源供需的影响,将为澜湄流域水资源系统调控的联合行动奠定了基础。