Assessing the Assessments: Case Study of an Emergency Action Plan for the Control of Water Hyacinth in Lake Victoria

This study evaluates the impact assessment methodologies used by Uganda's Water Hyacinth Control Programme in Lake Victoria, a domestic project with transboundary implications. The Control Programme sought to reduce infestations of water hyacinth (Eichhornia crassipes), an aquatic weed native to South America, through the use of integrated chemical, mechanical and biological methods. The environmental impact assessment for the project was conducted by Aquatics Unlimited, with support from the United States Agency for International Development. Although the case study involves a domestic impact assessment, it raised transboundary concerns. One of the major outcomes of the assessment was recognition of the need for informed involvement of the other riparian countries, Kenya and Tanzania, in the assessment process to ensure a regional effort among all three East African Community Partner States to control water hyacinth and other invasive weeds in Lake Victoria.     

Lake Victoria fisheries: Outlook and management

The past subsistence of the Lake Victoria fishery was dominated by rich, diverse haplochromine cichlids. This multispecies fishery has undergone a decline over the past four decades, evolving into a commercial fishery consisting mainly of Nile perch (Lates niloticus), Nile tilapia (Oreochromis niloticus) and cyprinid (Rastrineobola argentea species). To better understand Lake Victoria fisheries, studies dating as far back as the 1920s have been carried out to assess the status of the fish stocks. These past studies indicated the lake fisheries were declining because of numerous major challenges, including intense fishing, invasive species, loss of biodiversity, ecological alterations, climate change, inadequate information to inform management and unharmonized policies. Numerous policies and regulations have been developed and implemented over the years to address these issues and manage the fisheries sustainably. Most of the interventions have been sectorial, disjointed and unharmonized and have not reduced the declining fish catch rates. With reestablishment of the East Africa Community (EAC) with several institutions in 1994, the Lake Victoria riparian states initiated an ecosystem approach to manage the Lake Victoria fishery resources in a sustainable manner. This study reviews the development of the Lake Victoria fisheries, outlines major past and present management challenges and provides a set of new strategies to manage the lake's fisheries resources, with emphasis on an ecosystem approach.     

The application of geospatial analyses to support an integrated study into the ecological character and sustainable use of Lake Chilwa

Wetlands, which occupy a considerable proportion of Malawi, are an important resource for the rural-poor. In regions of low and erratic rainfall, they provide important opportunities for agriculture and fisheries and are often vital for food security. However, overutilization and some farming practices can result in environmental degradation and the loss of valuable ecosystem services. The Lake Chilwa wetland, a complex aquatic ecosystem comprising a shallow open water lake surrounded by marsh and floodplain grassland, is one of the most important wetlands in Malawi. Most of the 1 million people who live in the vicinity of the lake derive their livelihoods from the wetland. Increases in population in recent decades have increased the pressures on the wetland. In light of continued population growth, it is anticipated that some levels of resource use may be difficult to sustain in the long-term. Consequently, planning the use of wetland resources is a priority if the diverse benefits that local communities presently receive are to be sustained. Baseline wetland information is needed to determine appropriate sustainable management plans, as well as to identify limits to resilience. However, for many wetlands in southern and eastern Africa, these data are lacking, or not available to those who need them. This paper provides an overview of the distribution and characteristics of wetlands in Malawi. Using Lake Chilwa as an example, it illustrates how Earth Observation data, in combination with hydrometric and botanical data, can be used to provide information crucial for sustainable wetland management.     

Environmental Monitoring of Spatio-temporal Changes Using Remote Sensing and GIS in a Mediterranean Wetland of Northern Greece

Loss and degradation of terrestrial and aquatic habitats and degraded water quality are major environmental concerns worldwide. Especially wetlands are sensitive ecosystems that are subject to stress from human activities. Remote sensing techniques have been primarily used to generate information on land cover/use changes. Geographical Information Systems (GIS) and remote sensing can be used to provide a rapid or a large-scale understanding of lake change and in developing lake management strategies. The principal objectives of this study are to monitor and assess the spatial and temporal changes in land cover/use by using GIS, and to determine the main environmental factors affecting these changes. This paper presents a case study for the application of integrated remote sensing and GIS data for the classification and monitoring of the spatial and temporal changes in land use types. The study was conducted in a small natural wetland of Lake Cheimaditida, located in the East Mediterranean region of Northern Greece. Data analysis was conducted using GIS software. During the past several decades Lake Cheimaditida wetland has been influenced by many anthropogenic activities. The variables chosen for the assessment included condition of wetland and lake areas, present extent of wetlands relative to historic area, cover of natural habitat, wetland disturbances, etc. These variables address catchments properties that are important for maintaining and improving wetland habitats and water quality and assessment of trends useful for environmental monitoring. Land cover/land use patterns were assessed and compared using aerial photographs taken in 1945, 1969, 1982, and 1996. Over this period, reed beds enormously increased by 1,655.19%, while open-water areas and peat lands decreased by 74.05 and 99.5%, respectively. The significance of the changes in land cover distribution within the Lake Cheimaditida wetland are discussed in relation to the historical pattern of reed beds colonization, the importance of Phragmites australis in the process and the implications for strategic management of freshwater wetland resources.     

Stimulating a Great Lakes coastal wetland seed bank using portable cofferdams: implications for habitat rehabilitation

Coastal wetland seed banks exposed by low lake levels or through management actions fuel the reestablishment of emergent plant assemblages (i.e., wetland habitat) critical to Great Lakes aquatic biota. This project explored the effectiveness of using portable, water-filled cofferdams as a management tool to promote the natural growth of emergent vegetation from the seed bank in a Lake Erie coastal wetland. A series of dams stretching approximately 450 m was installed temporarily to isolate hydrologically a 10-ha corner of the Crane Creek wetland complex from Lake Erie. The test area was dewatered in 2004 to mimic a low-water year, and vegetation sampling characterized the wetland seed bank response at low, middle, and high elevations in areas open to and protected from bird and mammal herbivory. The nearly two-month drawdown stimulated a rapid seed-bank-driven response by 45 plant taxa. Herbivory had little effect on plant species richness, regardless of the location along an elevation gradient. Inundation contributed to the replacement of immature emergent plant species with submersed aquatic species after the dams failed and were removed prematurely. This study revealed a number of important issues that must be considered for effective long-term implementation of portable cofferdam technology to stimulate wetland seed banks, including duration of dewatering, product size, source of clean water, replacement of damaged dams, and regular maintenance. This technology is a potentially important tool in the arsenal used by resource managers seeking to rehabilitate the functions and values of Great Lakes coastal wetland habitats.     

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.     

引调水工程对调蓄湖泊生态环境的影响分析

引调水工程利用天然湖泊调蓄,将引起调蓄湖泊水文情势、水质发生一定变化,对与湖泊水环境关系密切的水生生物、湖滨植被、湿地鸟类产生影响.以金沙江某提水工程方案比选阶段利用拉市海调蓄方案为例,采用图形叠置法、类比分析法、生态机理法等方法,分析工程运行对拉市海水生生物、湖滨植被、湿地鸟类的影响,为引调水工程对调蓄湖泊的生态环境...     

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.     

Empirical modeling of chlorophyll a from MODIS satellite imagery for trophic status monitoring of Lake Victoria in East Africa

We detail our attempts at empirical modeling of MODIS derived Chlorophyll a (Chl a) distribution on Lake Victoria in East Africa and consequently its trophic status. This was motivated by the need for Lake Victoria specific algorithms, as the current satellite based standard algorithms overestimate derived Chl a. In situ Chl a data was hence collected in three field campaigns in November 2014, March 2015 and July 2015. In situ reflectances were collected during the July campaign only. We first developed models from in situ reflectances and in situ Chl a, which when applied to MODIS bands performed dismally (R² = 0.03). We then proceeded to derive empirical models by directly comparing MODIS bands with in situ Chl a based on data collected in November 2014 and July 2015. The March 2015 dataset couldn’t be used due to cloud cover hence no matchups could be obtained. The best model derived (R² = 0.88) was based on the ratio 488 nm/645 nm, and was then used to determine the trophic status of Lake Victoria using Carlson’s Chl a Trophic State Index (TSI). The results show that large areas of the lake are mesotrophic with eutrophic displays closer to the shores. The modeled TSI was then validated against in situ TSI derived from the March dataset and posted an 80% matchup. One of the main challenges, however is the prevalence of cloud cover, which hinders synoptic mapping of the lake. That notwithstanding, the study demonstrates the potential of earth observation in providing accurate TSI information for improved management of Lake Victoria.     

星海湖湿地综合整治中生态规划与景观设计的思考

通过对近几年星海湖滨水湿地整治建设过程中景观和生态两个方面的问题进行分析思考,总结成功经验和教训,探求一种城市滨水湿地型景观开发与生态保护的新思路、新途径。     

Management issues of the Lake Peipsi/Chudskoe region

Lake Peipsi is the fourth largest lake in Europe and the largest international lake in Europe. Lake Peipsi is shallow, eutrophic, biologically very productive and is bordered by many wetland areas along its coasts. Large peat deposits in the Lake Peipsi basin are protected under national legislation. The lake is most important as a resource for recreation and fisheries. The fish stock in Lake Peipsi is one of the richest in Europe. The most critical environmental issues for the Peipsi watershed are eutrophication and unregulated fishing in the lake. During the Soviet period, large collective farms dramatically accelerated eutrophication. Despite the drop in fertilizer use during the last 10 years and a decrease in the number of domestic animals in the watershed, the impact of the earlier agricultural pollution is still significant. Untreated sewage has also been dumped in the Narva River tributary as a result of an international dispute concerning water supply and wastewater treatment. People living in the Lake Peipsi region have faced traumatic changes as a result of the re‐establishment of the border between Russia and Estonia in 1992. The establishment of an international border on the waters of the lake has resulted in fishermen losing access to many of their traditional fishing areas. Political and economic transformations of the last 10 years have seriously interrupted information exchange between different institutions and organizations concerned with the health of the lake. The Centre for Transboundary Cooperation facilitates international communication and cooperation between the Estonian and Russian governments and promotes public participation in environmental, social and economic development and decision‐making. The centre is in the process of guiding the development of a watershed management plan for the Lake Peipsi watershed and a vision for watershed development that is truly sustainable.     

基于稳定碳同位素比的植物水分利用效率分析——以鄱阳湖湿地为例

植物水分利用效率是表征植物生长状态的一个综合性生理生态指标,对植物水分利用效率的研究有助于揭示变化条件下植物对环境的适应能力。通过在鄱阳湖湿地上布设的3个断面,测定了典型植物样品的稳定碳同位素比δ~(13)C以及断面土壤组成,探究了植物水分利用效率的变化规律。研究结果表明:鄱阳湖湿地植物的δ~(13)C值差异较为明显,变化范围为-14.302‰~-33.134‰,δ~(13)C值的大小可以作为鄱阳湖湿地植物水分利用效率的表征指标;植物类型和土壤水分含量是影响植物水分利用效率的重要因素;鄱阳湖湿地内南荻的δ~(13)C值最大,属C4植物,具有较高的水分利用效率,在水分胁迫条件下更容易生存下来,从而发育为鄱阳湖地区的优势植物种群。研究结论对变化环境下鄱阳湖湿地植被的演变趋势研究具有一定的参考价值。     

Investigation of aquaculture dynamics at a Ramsar site,using earth observation systems in conjunction with a socio‐economic assessment

This study presents a comprehensive site‐scale analysis conducted within the global wetland inventory and mapping (GWIM) project. GWIM was developed and promoted by the International Water Management Institute (IWMI) through global partnerships to investigate wetland analyses at multiple scales. The present study investigates the complexity of an inland freshwater wetland system, presenting a conceptual framework for mapping and monitoring the dynamics of Lake Kolleru (a wetland of international importance, as defined by the Ramsar Convention), utilizing a geospatial platform. Illustrating the pace of land use changes leading to the progressive elimination of the wetland ecosystem of freshwater Lake Kolleru, this study also highlights the impacts of such changes on the socio‐economic system. A comprehensive temporal analysis (1977–2007) provided a structural base to schematically analyse the dynamics of biophysical and ecological changes to the wetland by effectively using a spectrum of remote sensing data. The present status and changing trends in ecological dimensions of Lake Kolleru were illustrated, utilizing information from spatial analyses, complimented with socio‐economic assessment. Attention is drawn to the potential of utilizing earth resources systems in exploring space–time interactions in freshwater ecosystems heavily modified through aquaculture interventions. Further, the spatial derivatives are meant as reference material for local authorities and decision‐makers to rehabilitate the economic livelihood activities to the social community dependent on the lake ecosystem. The disseminated message emphasizes the applicability of geospatial tools to enhance the efficacy of the decision‐making process by facilitating regular monitoring of ecosystem dynamics and providing updated information on wetland patterns and uses.     

Institutional Evolution in Lake Okeechobee Management in Florida: Characteristics,Impacts, and Limitations

The management of Lake Okeechobee in Florida has undergone significant changes in the last decade. Socio-political, environmental and demographic factors have driven changes in the environmental and water policy, which in turn have led to wide-ranging institutional changes and a shift toward multiobjective planning and implementation in the Lake management. This article describes the changes in the philosophy and practice of water resources management in South Florida hydrologic system, of which Lake Okeechobee is a crucial component. The impacts of the changes on management goals and decision processes are illustrated through a case study of the use of climate information in Lake management. The article concludes with a brief examination of the implications of the institutional changes, including greater public participation, for the long-term sustainability of the social-ecological system in South Florida.     

Variations in the contents of heavy metals in arable soils of a major urban wetland inlet drainage system of Lake Victoria,Uganda

Little is known about the effects of urbanization on the chemical quality of soils in suburban wetland inlet drainage systems to the Uganda side of Lake Victoria, on which food crops are extensively grown. It is feared that pollution in the soils might eventually enter food chains through such crops being consumed by urban populations unaware of their occurrence. Soil samples were collected from cultivated areas of a major wetland drainage system (Nakivubo Channel), at Kampala, Ubanda, near Lake Victoria and from a rural control wetland site (Senge). The soil from this site had similar properties as those from the urban test site (i.e., soil texture; porosity; humus content). Analysis of heavy metals with atomic absorption spectrophotometry (AAS) yielded the following soil concentration ranges: manganese (190–780), cadmium (<0.001–1.0), zinc (6.0–10.0) and lead (10–20 mg kg^?1) dry weight for the control site, and 450–900, 1.0–2.0, 131–185, 40–60 mg kg^?1 dry weight, respectively, for the urban wetland, indicative of relatively heavy metal pollution in the suburban drainage system. Heavy metal levels in cocoyam (Colocasia Esculenta) and sugarcane (Saccharum Officinarum) grown on both wetland soils also were evaluated via AAS with a modified wet‐acid‐digestion technique. The results highlighted high cadium and lead levels (P ≤ 0.0003) in the crops from urban wetland cultivation. Cadmium and lead concentrations in cocoyam from urban wetland soils exceeded those from the control site by 0.17 and 3.54 mg kg^?1, respectively. The corresponding results for sugarcane indicated a similar increase of 0.56 and 2.14 mg kg^?1 of juice extract. Cadmium and lead levels in both urban wetland crops were higher than the maximum permissible limits of the Codex Alimentarius Commission, indicating that these concentrations pose potential health risks to urban consumers, and call for early counter‐measures to combat urban pollution entering the lake.     

Analysis of the technical efficiency of Nile perch (Lates niloticus) fishers in the Tanzanian portion of Lake Victoria: A stochastic frontier analysis

The Nile perch fishery sector in Tanzania is important for enhancing the livelihoods and food security for the majority of people living near the Tanzanian portion of Lake Victoria. Despite continued government efforts and other institutions, including the Food and Agriculture Organization (FAO), Lake Victoria Fisheries Organization (LVFO), European Union and World Bank regarding the management of Lake Victoria, the Nile perch fishers have remained relative inefficient in regard to improving their fish catches. The Nile perch small‐scale fisheries sector in particular faces a challenge regarding how to improve production performance while, at the same time, ensuring a sustainable level of fisheries resources. This reality necessitates the measurement and analysis of artisan fishers’ technical efficiency. Accordingly, the present study analyses Nile perch fishers technical efficiency, using a stochastic production frontier (SPF) model based on the sample of 268 Nile perch fishers in the Tanzanian portion of Lake Victoria. The translog stochastic frontier model results indicate the technical efficiency of Nile perch fishers range between 61% and 80%, with an overall average technical efficiency of 75%. This finding implies that, based on existing fishery resources, the current quantity of Nile perch catch can be improved efficiently by 25%, a reality highlighting mismanagement of the lake's fishery resources. The quantity of bait and petrol and the number of hooks used per trip are the most important fishing inputs, indicating a positive Nile perch fishing output–input elasticity. To address the Nile perch fisher inefficiency, it is important to provide subsidized inputs such as outboard engines and mesh gillnets. Provision of access to affordable credits will enable fishers to purchase less destructive fishing inputs and improve the current structure of fishery organizations.     

Development of a fish‐based index of biotic integrity (FIBI) for monitoring riverine ecosystems in the Lake Victoria drainage Basin,Kenya

The long term monitoring of aquatic ecosystems based on chemical analysis is expensive resulting in a lack of time series data for management purposes thus necessitating the need for new cost effective methodologies. This study developed a fish‐based index of biotic integrity (FIBI) for monitoring environmental conditions in riverine ecosystems within the Lake Victoria Basin, Kenya. The fish fauna in the basin is poorly studied, less diverse and ecologically specialized than the temperate fauna that provided the origins of the Index of Biotic Integrity. Fish samples were collected by electrofishing from 24 sites during baseflow periods in February, March and July 2004. Validation data were collected from 7 sites with varying levels of degradation. Fish samples were identified, counted and grouped into different trophic groups, relative tolerance to pollution, habitat guild and whether exotic or native to riverine environment. Thirty‐three candidate metrics were evaluated for responsiveness to habitat quality and twelve were selected for inclusion in the final index. The index classified 6 of the 7 validation sites according to their levels of degradation. As a bioassessment tool, the index was useful in laying the basis for long‐term monitoring of rivers in the Lake Victoria drainage basin. Copyright © 2010 John Wiley & Sons, Ltd.