The Potential Link Between El Nino and Water Hyacinth Blooms in Winam Gulf of Lake Victoria, East Africa: Evidence from Satellite Imagery

This study evaluates the link between the occurrence of El Nino events in East Africa and water hyacinth blooms in Winam Gulf of Lake Victoria using remote sensing technology. A time-series of the Normalized Difference Vegetation Index (NDVI) analyzed from data acquired by the multispectral Aqua/Terra sensors aboard the Moderate Resolution Imaging Spectroradiometer (MODIS) satellite are used to monitor areal extent and density of the aquatic plants. We related the NDVI derived from MODIS imagery to data on El Ni?o South Oscillation (ENSO) events that were obtained from NOAA and rainfall data from the study site. Our results from the 11-year time-series data show a statistically significant positive correlation (R = 0.6, P = 0.021) between the occurrence of El Ni?o events and water hyacinth blooms in Winam Gulf. The proliferation of water hyacinth rafts in Winam Gulf may be a response to dramatic environmental and water quality changes in Lake Victoria. The patterns of impact of ENSO events and rainfall show spatial and temporal variation patterns in the region, depending on the time and space evolution of each individual ENSO event that could explain the differences in general patterns of water hyacinth cover in Lake Victoria during different El Ni?o events. Although the problems eutrophication and water hyacinth are severe in the Winam Gulf of Lake Victoria some of the solutions to the problem are located several hundreds of kilometers away in the rich agricultural farmlands of the Lake Victoria catchment area. These include better land management practices and strategies aimed at limiting pollution and soil erosion within the lake’s drainage basin.     

Spatial-temporal dynamics of water hyacinth, Eichhornia crassipes (Mart.) and other macrophytes and their impact on fisheries in Lake Victoria,Kenya

Invasive aquatic macrophytes in Lake Victoria including water hyacinth (Eichhornia crassipes) exhibit periodic cyclical patterns of decline and proliferation with attendant ecological and economic impacts. This study aimed to monitor the extent of macrophytes and other invasive weeds on Lake Victoria to establish their impact on fisheries. The study employed a combination of remote sensing and geographical information system (GIS) techniques to estimate the coverage of water hyacinth and other invasive macrophytes. Data on fish landings and their respective market values were acquired from the Electronic Fish Market Information Service (EFMIS) database, which is hosted by the Kenya Marine and Fisheries Research Institute (KMFRI). Analysis of consistent temporal satellite data showed that the weeds frequently cover sheltered bays and river mouths. These areas of Winam Gulf had higher coverage (average 5000?ha) of macrophytes than the open waters (<200?ha). The proliferation of the invasive weeds showed fluctuations over the study period reaching the highest peak between September and November 2016. Other aquatic plants that have invaded the littoral areas of Lake Victoria include Egeria densa, Ceratophyllum demersum and Potamogeton spp. Increased coverage of macrophytes was found to be correlated inversely with the commercially important tilapia Oreochromis niloticus, but not with other species. The study concludes that there is a need for sustained monitoring of the invasive macrophytes alongside ecosystem modelling studies using the available time series data to clearly identify the ecological factors that drive water hyacinth dynamics and predict more precisely its impact on the fishery.     

Management issues in the Lake Victoria watershed

Lake Victoria is the largest lake in Africa (68 800 km²) and is the eighth largest lake in the world by volume. The three East African countries of Tanzania, Uganda and Kenya share Lake Victoria and its resources. The total annual catch of fish from the lake ranges between 400 × 10⁶ kg and 500 × 10⁶ kg, bringing these riparian countries a combined annual income of approximately US$250 000–500 000 from exports alone. Approximately 30 million people live in the riparian region and the catchment, with about 2 million of these depending directly or indirectly on fishing activities. Tragically, Lake Victoria’s extremely diverse fauna was decimated in only 30 years following the introduction of non‐native Nile perch in the early 1960s. An estimated 200 endemic cichlid species became extinct. Dramatic increases in overfishing, pollution from various sources, effects of noxious water weeds and other associated problems threaten the sustainability of the lake’s resources and the economies of the riparian governments and peoples. Regulations governing Lake Victoria’s resources are different in each country. The laws concerning treatment of effluents from point sources in the three countries are not harmonized, neither are implementation or enforcement provisions. The governments of Kenya, Uganda and Tanzania have begun to put in place regional mechanisms to address the lake’s many problems including the creation of a permanent regional international institution through the establishment of the Lake Victoria Fisheries Organization (LVFO). A strategic vision document and action plans have been developed. Efforts are being made at local, national and regional levels to control the water hyacinth, including manual pulling, mechanical harvesting and introduction of weevils that weaken hyacinth root systems. To address the problem of overfishing, fishermen committees at landing beaches have been put in place. Each country has committed to take all necessary measures including legislation to implement the decisions of the LVFO governing bodies. All three countries have agreed to adopt and enforce legislation and regulations prohibiting the introduction of non‐indigenous species to the lake and to enforce existing regulations regarding fisheries. A Global Environment Facility project which provides funding to the Lake Victoria Fisheries Organization addresses land use management, catchment forestation, fisheries research and management, water hyacinth control, industrial effluent treatment and municipal waste treatment.     

Farmers’ preferences towards water hyacinth control: A contingent valuation study

Lake Tana is the most important freshwater lake in Ethiopia. Besides pressures on water quality resulting from urbanization and deforestation, the invasion of the exotic water hyacinth (Eichhornia crassipes) poses new threats to the ecosystem. Water hyacinth, endemic to South America, is widely considered as the world’s worst aquatic invasive weed. In 2011, the weed appeared on the northern shores of Lake Tana, expanding in south-eastern direction. The lake area affected by water hyacinth was last estimated in 2015 at 34,500 ha, which equals 16% of the total lake surface. In this research, the benefits of water hyacinth control and eradication for the rural population inhabiting the northern and north-eastern villages bordering Lake Tana, are investigated. In the area, the population largely depends on farming and fishing. An assessment of the total economic benefit of eradication was conducted. The stakeholder-centered approach led to measuring the willingness to contribute in labor and cash terms. Results showed smallholders in the study are willing to contribute over half-a-million euros annually. Costs of management actions can be weighed to the benefits, where further research is needed on the impact on other stakeholder groups. Moreover, wetland management should advance to explore multiple pathways in an integrated approach: water hyacinth control, water hyacinth utilization and sustainable waste water management.     

Common water hyacinth (Pontederia crassipes) invades Lakes Edward,George, and Kazinga Channel: A call for immediate action

Common water hyacinth, Pontederia (former Eichhornia) crassipes is a notorious aquatic invasive species. In African Great Lakes, the species is known for deleterious social, economic, and environmental impacts in lakes such as Victoria, Kyoga, Albert, Malawi, Tanganyika, Tana, and Naivasha. We report invasion and establishment of the species in Lake Edward, Kazinga Channel and possibly in Lake George. Lake Edward is one of the African Great Lakes. Common water hyacinth was observed at multiple locations on Lake Edward and Kazinga Channel. Presence of ‘mats’ of the weed with flowers is a sign of successful establishment. We observed free floating Common water hyacinth plants, indicating that the invasion is spreading. The invasion and establishment of the weed threatens a fishery of significant importance to rural livelihoods, fish species of conservation importance and tourism among others. At the current extent of invasion, mechanical removal and use of water hyacinth weevils, if expedited, could be adequate for stopping the expansion of the invasive weed. We recommend immediate action by government agencies responsible for the management of fisheries and protected areas to control the weed.     

Trends in health risks from water-related diseases and cyanotoxins in Ugandan portion of Lake Victoria basin

Studies to examine the prevalence of water‐related diseases, cyanobacteria toxins and other health risks at landing beaches in the Ugandan portion of the Lake Victoria basin were carried out. Based on surveillance studies and other data sources in the region, water samples were analysed for indications of faecal contamination. The coliform numbers were generally high for most sampling sites, indicating significant water contamination. The wet seasons exhibited significantly higher coliform counts than the dry seasons for all lakeshore sample sites. This seasonal variation in coliform counts correlated positively with the incidence of waterborne diseases, which are typically higher in the wet season. The water supply for domestic consumption for the Lake Victoria riparian communities is mainly the lake itself. The most prevalent diseases associated with the landing sites include malaria, dysentery, diarrhoea and bilharzia. Malaria was most prevalent, followed by dysentery, in all the studied districts. Many people in the catchment dispose of faecal wastes in lakeshore area bushes, or in polythene bags, contaminating water sources with faecal material, and resulting in waterborne diseases. The vulnerability of lakeside communities to water‐related diseases is further aggravated by low accessibility to health facilities and personnel. Further, cyanobacteria (potentially toxic to humans and animals) dominate other algal species in Lake Victoria, contributing >50% of the algal biomass. Algal blooms occurred frequently in Murchison Bay, a source of drinking water for the city of Kampala and surrounding urban centres. Algal blooms can cause unpleasant odours and tastes in domestic water supplies, clog pump and machinery filters, increase chlorine demands for water disinfection, and necessitate more complex and expensive treatment processes. The findings of this study suggest improved water quality, changes in sanitation and hygiene behaviour could significantly reduce the prevalence of water‐related diseases and cyanotoxins in the Ugandan portion of the Lake Victoria basin.     

Experiences and lessons learned from interventions in the Lake Victoria Basin: The Lake Victoria Environmental Management Project

The Lake Victoria basin has experienced a myriad of environmental changes leading to its degradation, and necessitating various interventions to be implemented. The purpose of this study was to review early development initiatives, past and ongoing interventions in order to document experiences and lessons learned from them. The methods used in this study include review of published articles, project reports, and personal opinions of experts and project implementers in the lake basin. There are numerous threats to the lake basin, the major ones being poor land use and agricultural practices, catchment deforestation, destruction of wetlands, pollution loading, fishing malpractices and invasion by exotic aquatic weeds. These threats have resulted in rampant land and wetland degradation, leading to poor water quality and consequent water loss, a decline in the diversity of the commercial fisheries, and the lake’s biodiversity in general, unsustainable use of natural resources, increased poor human health and food insecurity, with high levels of poverty among the riparian communities. Initiatives for socio‐economic development within the lake basin began as early as the turn of the 20th century, while intervention studies started as early as the 1920s. Current lake management intervention projects, such as the Lake Victoria Environmental Management Project (LVEMP), undertaken by the riparian states of the East African Community, have invested heavily in the lake basin, with the goal of addressing the above‐noted threats to the lake. Some pilot projects undertaken through the LVEMP include: (i) water quality and quantity monitoring; (ii) industrial and municipal management; (iii) fisheries studies; (iv) water hyacinth control; (v) wetlands; (vi) land use; (vii) catchment afforestation; and (viii) micro‐projects to alleviate poverty, to cite a few examples. Phase 1 of the LVEMP was a major effort in the history of the lake basin; hence, its critical examination. To this end, this study highlights, in chronological order, the experiences, achievements, challenges and lessons learned with regard to Phase 1 of the LVEMP.     

Interactive management of transboundary waters on the external European Union border.

The paper addresses issues specific to planning of water protection measures in transboundary water basins located on the external European Union border. The case study of the Lake Peipsi/Chudskoe, a large transboundary lake shared by Estonia and Russia, is used to demonstrate issues of management of transboundary waters on the Eastern European fringe. The author emphasizes the importance of managing transboundary water basins located on the EU external borders interactively, i.e., through regular communication and consultation among water experts, decision-makers and stakeholders involved in managing waters on transboundary, national and subbasin levels, and discusses difficulties in, and opportunities for, the interactive management of transboundary waters on the EU external borders.     

Exotic introductions to the fishery of Lake Victoria: What are the management options?

Lake Victoria is Africa's most important source of inland fishery production, exhibiting annual catches of ≈ 400 000 mt. The predatory Nile perch, Lates niloticus, and the herbivorous tilapiines, Oreochromis niloticus, Oreochromis leucostictus, Tilapia zillii and Tilapia rendalii, were introduced in Lake Victoria in the 1950s and 1960s. Nile perch were introduced to convert the abundant, but bony, haplochromines to fish flesh, while the tilapiines were introduced to boost the declining fishery. Since that time, the fisheries of Lake Victoria have undergone dramatic social and ecological changes. The catches increased tremendously, changing the fishery from artisanal to commercial, in turn increasing fisher income and employment opportunities. However, there was a decline and, in some cases, the disappearance of many indigenous fish species, especially the haplochromine cichlids. This reduction was attributed to overexploitation, predation, and competition and hybridization with the introduced species. The decline of the native fish species has had impacts on the trophic and ecological status of the lake. Nile perch now dominate the formerly complex food web. The loss of phytoplanktivorous haplochromines has contributed to an increase in algal blooms, reduction in water quality and occasional fish kills. Water hyacinth, Eichhornia crassipes, invaded Lake Victoria in 1988, with high rates of infestation in shallow waters and bays, which are breeding and nursery grounds for most fish species. Catches of Nile perch decreased following the infestation, while those of Nile tilapia, lung fish (Protopterus aethiopicus) and mud fish (Clarias gariepinus) increased. Haplochromines species also showed some signs of recovery. In view of all these changes, the future of the Lake Victoria fishery is uncertain.     

太湖湖盆取土的环境影响和管理

根据太湖湖盆取土区的自然地理和水环境,论述了湖盆取土对湖体生态将造成较大冲击,强调湖盆取土论证和环境影响评价,取土后的生态修复和补偿措施是取土湖区生态环境保护的关键。最后给出生态维护技术原则和建议。     

Advances in eutrophication science within Lake of the Woods,a complex transboundary lake – Forward to the special section

Outside of the five Great Lakes, Lake of the Woods (LoW) is the largest transboundary lake shared by Canada and the United States. Over the last two decades, an international consortium of researchers has advanced our understanding of eutrophication science in this complex watershed. This introductory paper outlines eleven research articles included in this special section, within three main themes pertinent to LoW: external phosphorus sources to LoW and internal phosphorus loading, lake and watershed modeling, and new insights into cyanobacterial and harmful algal blooms (cHABs). We conclude with a roadmap to guide future transboundary water quality management in LoW, including remaining research gaps and future monitoring needs.     

鄱阳湖水利枢纽工程关键技术研究

本文针对鄱阳湖水利枢纽工程修建后将发挥的作用和可能产生的影响,采用现场调研、实测资料分析和数学模型计算等研究手段,从鄱阳湖流域水资源演变趋势及开发利用状况,三峡水库运用对长江中下游河道冲淤变化及江湖关系的影响,枢纽工程对水资源、防洪、湖区水环境和鱼类的影响,枢纽工程合适的下闸蓄水时期和蓄水位,工程闸门型式及鱼道建设等方面进行了研究,试图为鄱阳湖水利枢纽工程项目立项和规划设计提供科技支撑。     

Assessing the Assessments: Improving Methodologies for Impact Assessment in Transboundary Watercourses

Transboundary impact assessment (TIA) has become an important environmental management tool, particularly where a project may have transboundary impacts. With the growing practice of TIA, it becomes important to consider the accuracy of the transboundary impact assessments that are being conducted. If TIA is a planning tool designed to provide a basis for making an informed decision, does it actually provide the necessary information? This paper summarizes lessons learned in pilot testing a methodology to assess the accuracy of TIAs.     

南水北调东线工程运行对南四湖水环境影响评价

在综合分析南水北调东线工程对南四湖水环境影响基础上,将层次分析法改进,结合模糊评价方法,量化评价指标,突出体现了这种方法在定性指标量化方面显示的优势。南水北调东线工程对南四湖的水环境影响评价最终结果是0.640,说明调水工程会对南四湖水生态环境产生一定正面影响。     

An overview of the current status of Lake Victoria fishery: Opportunities, challenges and management strategies

Lake Victoria is African's most important source of inland fishery production, exhibiting an annual catch of ≈500 000 mt. The lake moderates local climate, serves as a means of transport, and a source of human food and raw material for the fishmeal industry. The introduction of Nile perch transformed the fisheries from a locally based artisanal fishery to a national and international capital investment industry. The fisheries produce an annual income of $US 600 million, providing employment opportunities for over 3 million people. Although the benefits of transforming the fishery of Lake Victoria appear to be quite remarkable, the negative impacts of this development are even more dramatic. Several challenges face the lake fishery, including environmental degradation, the introduction of exotic species, overfishing, and a fish export ban. Nutrients inputs into the lake have resulted in eutrophication and increased algal blooms. Deteriorated water quality and increased anoxia have caused the displacement and decline of some fish species. Exotic tilapiines have hybridized, displacing the indigenous fish species. Nile perch predation has caused the disappearance of once abundant native fish species. The once complex food web is now dominated by Nile perch. Unhygienic fishing methods have led to several fish export bans, while water hyacinth invasion in the lake has affected water quality, fishing and transportation possibilities. The current top‐down management and use of different regulations by the riparian states have been a major drawback to sustainable management of the lake. There is a need for a paradigm shift, in which the lake is considered to be one ecosystem and relevant stakeholders are involved in the decision‐making process.     

Environmental consequences of Menik Ganga diversion

Kirindi Oya Irrigation and Settlement Project is one of the main activities of the Southern Development Programme in Sri Lanka. The project has been in operation for the past five years though the reservoir constructed has not filled to the expected level. During this period it has met with a number of problems due to shortage of water. In an attempt to obtain sufficient water, a new proposal is being considered to divert water from another river, the Menik Ganga, into this reservoir. A feasibility study funded by ADB has recently been completed but does not include an environmental impact assessment. However, because of increasing public involvement it has been decided to do a socio‐economic study with an environmental component. This article attempts to deliberate the environmental consequences of the proposed project.     

“引江济太”工程对鄱阳湖水利枢纽工程的启示

为更好的推进鄱阳湖水利枢纽工程各项工作,通过对太湖流域“引江济太”工程实地考察学习,总结了该工程改善太湖水资源与生态环境方面的成功经验和做法,为鄱阳湖水利枢纽工程带来启示,并进一步阐明了工程建设的科学意义和必要性,为更好的开展工程建设提供参考。     

Wetland use and impact on Lake Victoria, Kenya region

This article reports on a study of wetland use and impact on Lake Victoria conducted in March and April 1995. A field survey and interviews were used to study wetland use and their impact on Lake Victoria. This article identifies management issues and establishes a broad vision for the future. It also addresses the need to balance the competing demands for wetland use and development with the need to conserve a healthy and functional Lake Victoria. Investment proposals are made that would minimize destruction of the wetlands and negative impacts on the lake. General recommendations for planning and management issues, as well as suggestions of specific research needs that should form the basis of action and investment initiatives, are given.     

河湖清淤工程环境影响评价要点分析——以太湖输水主通道清淤工程为例

为深入了解河湖清淤工程对区域自然生态环境的影响,在对此类工程一般性环境影响特征分析识别的基础上,通过太湖输水主通道清淤工程这一典型案例,从工程分析、环境质量现状调查、环境影响预测方法、主评价结论5个方面对该工程环境影响评价工作点进行分析。结果表明,河湖清淤工程环境影响评价点与工程特征、环境特征密不可分,环境保护目标的分布及其敏感程度应当作为优先因素加以考虑,此外还应重点关注施工期间排泥场恶臭对大气环境影响、清淤活动对地表水环境及生态环境影响问题。     

Managing the wicked problem of Devils Lake flooding along the US–Canada border

ABSTRACT

The flooding of Devils Lake, North Dakota, is a multi-decade, multi-billion-dollar, and yet unsolved water management issue along the US–Canada border. In this study, we define this situation as a ‘wicked problem’ and suggest a ‘green paradiplomacy’–based framework that fosters multiactor, multiscale collaboration across jurisdictions as a management strategy. We interviewed stakeholders and combined their perceptions with currently employed management strategies to assess the potential for green paradiplomacy to address the Devils Lake problem. This study may encourage further discussion of green paradiplomacy as a strategy to manage other transboundary watershed problems along the US–Canada border and elsewhere.