The occurrence of microcystin-LR in Lake Chivero, Zimbabwe

Lake Chivero is a eutrophic reservoir, initially constructed to supply drinking water to the City of Harare, Zimbabwe. Blooms of blue‐green algae have been a problem in the lake for many years and concern has been expressed about the toxins produced by Microcystis spp. The concentrations of the toxin, microcystin‐LR, produced in cultures of Microcystis aeruginosa from Lake Chivero, were investigated from March–April 2003. Microcystin‐LR was found in algal cells cultured from the lake water in concentrations ranging between 18.02 and 22.48 µg L^?1, with a mean concentration of 19.86 µg L^?1. These concentrations are the highest recorded to date for the lake, raising concerns about the possible effects of the toxin on the health of people who are drinking the water. Based on these study results, there is a need to control eutrophication, reducing algal blooms in order to prevent their potentially detrimental effects from blue‐green algal toxins produced under such conditions.     

Enrichment and geoaccumulation of metals in the superficial sediments of Lake Chivero,Zimbabwe

Sediments act as a sink, being an integrator and an amplifier for metals in rivers, lakes and reservoirs. Thus, sediment quality has been recognized as an important indicator of aquatic pollution. The concentrations of aluminium (Al), calcium (Ca), iron (Fe), potassium (K), magnesium (Mg), manganese (Mn) and sodium (Na) were studied in the surface sediments of Lake Chivero, Zimbabwe, to determine metal accumulation, distribution, pollution status and to distinguish natural background metal levels from human pollution sources. Sediment samples were collected from 17 locations during a two‐year (2014–2015) monitoring period during the hot–dry, hot–wet and cool–dry seasons. The overall mean metal concentrations exhibited the following decreasing order: Fe > Al>Mn > Ca>K > Mg>Na. The Mn levels for all sites and seasons were above the severe effect level (SEL). The highest metal and enrichment factor (EF) values were observed for the hot–wet season, indicating the period when the reservoir received the highest metal pollution from its catchment. The Geochemical index (I_geo) values for Mn for all seasons indicated moderately to strong contamination in sediments. The pollution load index (PLI) for all seasons indicated low pollution levels. Sediment contamination was attributed to natural sources for Al, Na and K and anthropogenic sources for Fe, Ca, Mg and Mn. The levels of studied metals in the Lake Chivero sediments are comparable to other eutrophic lentic systems. The results of the present study provide baseline information necessary for developing future metal pollution control strategies for Lake Chivero and its catchment.     

Nutrient concentrations in the surface sediments of Lake Chivero,Zimbabwe: A shallow,hypereutrophic, subtropical artificial lake

A lake‐wide survey in Lake Chivero, Zimbabwe, was performed to (i) examine the spatial distribution of three sediment grain sizes; (ii) determine their nutrient concentrations; and (iii) analyse the relationships between the measured surface sediment variables in the three sediment grain sizes. The results of this study indicated sand, silt and mud sediments occupied about 24, 22 and 54%, respectively, of the lake area. All the measured physicochemical variables varied significantly among the three sediment grain sizes (P < 0.05, anova ). High values for pH, dissolved oxygen and NO₃ were observed in the sand sediments, while water depth, electrical conductivity, soluble reactive phosphorus, NH₄, total phosphorus, total nitrogen and total organic carbon were observed in the mud sediments. In the silt sediments, most measured variables showed intermediate values. Intervariable correlation indicated varied correlation patterns among the three sediment grain sizes. Information generated in this study is essential for an accurate delineation of the spatial extent of nutrient and contaminant distribution in the sediment of Lake Chivero and will facilitate the ability of lake managers to derive a comprehensive nutrient budget of the lake as a means of establishing realistic target conditions for lake restoration.     

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.     

博斯腾湖流域环境风险源指标体系研究

由于流域环境风险源识别和等级划分缺乏一套完整成熟的方法,在分析流域环境风险源风险度的基础上,从"驱动力—压力—状态"的框架模型出发,构建了博斯腾湖流域环境风险源识别指标体系,主要包括指标体系构建、评价指标选取和等级划分等内容,并采用多级灰色关联分析方法对博斯腾湖流域环境风险源进行风险源识别。研究结果表明:环境风险源识别区分度较高,识别指标体系合理,评估方法具有科学性和实用性,构建的环境风险源识别指标体系和采用的识别方法符合开展环境风险管理工作的要求,为环境风险源管理提供技术支持和决策信息。     

Ecosystem-based fisheries management is attainable,affordable, and should be viewed as a long-term commitment: Experiences from Lake Vättern,Sweden

Lake Vättern is Sweden’s second largest lake and faces multiple environmental challenges such as climate change, pollutants and invasive alien species. Since its foundation in 1957, the Lake Vättern Society of Water Conservation (LVSWC) has been a local actor aiming to manage a broad range of environmental issues concerning the lake and its catchment. Stakeholders can be members of LVSWC, which also organises a fisheries co-management group mainly dealing with fisheries issues. Ecosystem-based fisheries management (EBFM) is a widely desired framework shaped to focus on ecosystems, involve stakeholders, and address environmental issues in an adaptive, integrated and holistic manner while also including societal aspects. We have investigated how the management of Lake Vättern relates to 15 central principles for EBFM. The study found that LVSWC and the fisheries co-management group work along and towards the EBFM principles in a locally adapted way. Several environmental improvements have been observed concurrently with LVSWC activity, such as increased water clarity, and a strengthened stock of the Arctic char (Salvelinus alpinus). Long-term commitment by European, national and regional authorities was seen as essential to maintain and improve EBFM functions for Lake Vättern, to ensure continuity in the work, rather than having to depend on short projects. Becasue literature examples of EBFM in lakes are scarce worldwide, this study provides a unique example of the pursuit of EBFM in lake ecosystem management.     

Lake Chivero (Zimbabwe) and its climatic environment

The mean temperatures and mean maximum temperatures in Lake Chivero indicate a warming trend, which is not evident in mean minimum temperatures. The mean annual precipitation also exhibits a declining trend, as does the Manyame River flow trend. The relation between run‐off, river flow and precipitation indicate a discontinuous trend at a piecewise regression breakpoint of 998 mm precipitation. Above the breakpoint, the river flow is related exponentially with precipitation, while the run‐off relationship is linear, although with a low R² value. Below the breakpoint, both the run‐off and river flow exhibit a low variance accountability. Considered within the context of the IPCC findings of a subcontinent warming faster than the rest of the southern hemisphere, along with declining precipitation, these data suggest an uncertain water supply security for the City of Harare and its satellite settlements. The detectable warming of the lake, taken together with observations in Lake Kariba, also suggests an ecological shift that could be dominated by a shift to a permanent cyanobacteria‐dominated ecosystem, which is currently dominated by Microcystis and Anabaena species.     

太湖流域水环境综合整治与生态修复

在分析太湖流域流域性水环境污染、河湖生态退化现状及其成因的基础上,提出立足流域、破解区域,针对河网和湖泊生态系统的特征构建流域治理方案总体框架,并确定重点治理区域和相应的目标,以典型区域治理示范、指导流域水污染控制和水生态修复。     

洱海入湖河道综合整治规划研究

现阶段洱海流域综合治理任务艰巨,未能形成有效、完善的入湖河道综合治理体系,流域管理不能适应入湖河道治理及洱海保护的客观要求,入湖污染负荷尚未得到有效控制,流域水生态安全保障体系尚未建立。为此,开展了洱海入湖河道综合整治规划研究,从建立流域管理机制、构建完整防洪体系、打造清水通道、增加入湖清水量以及削减入湖污染物总量等方面,提出了建设洱海流域管理体制、流域截污治污体系、入湖河道生态治理、流域生态建设以及灌区高效节水减排等五大类工程,规划治理河道长度201.32 km,同时还规划新建286.04 km堤防或护岸工程,对35.92 km的河道进行清淤,对15.66 km河道的已建堤防进行修复。     

The ecological history of Lake Erie as recorded by the phytoplankton community

Lake Erie's water quality has fluctuated since European settlement due to cultural eutrophication and the effects of invasive species. Our attempts to understand the cause-and-effect linkages between observed ecosystem changes and various stressors are evolving. Non-indigenous species, pollutants, land-use and climate change that can alter a lake's physical and chemical environment can manifest rapid changes in community composition and abundance of phytoplankton. As such, for many decades researchers have used phytoplankton data from Lake Erie to track environmental changes. We provide a chronological account of previous and ongoing assessments of pelagic algae to summarize past and present environmental conditions of Lake Erie. This review necessarily focuses on diatom-based assessments as their preserved remains in sediments have been used to hind-cast human-induced impacts and recovery. Because of their uniqueness, this review summarizes where possible the long-term trends according to the western, central and eastern lake basins. Overall, this historical assessment summarizes a period of significant eutrophication throughout most of the 20th century, followed by water quality improvement due to nutrient reductions and establishment of filter-feeding dreissenids. Recent data suggest new issues associated with blooms of diatoms and blue-green algae. The challenges facing Lake Erie underline the need for continued monitoring and evaluation of historical records that will help us distinguish natural from anthropogenic changes, and to reveal the causes and extent of environmental insults in order to make management decisions.     

Lake Champlain Basin Program: Working together today for tomorrow

Lake Champlain is the sixth largest freshwater lake in the USA. Lake Champlain’s watershed is shared by Vermont and New York in the USA, and Quebec in Canada. The lake’s remarkable drainage area to surface area ratio is 19:1. More than 600 000 people live in the Lake Champlain basin and millions visit each year. The lake’s relatively healthy natural resources sustain a thriving economy. The three most challenging environmental issues facing the Lake Champlain basin are reducing phosphorus pollution, preventing toxic contaminants from entering the lake and managing invasive aquatic species that are not native that threaten native flora and fauna. To effectively address these issues, the Lake Champlain Basin Program (LCBP) believes that all decisions about the lake must be based on accurate, ongoing scientific research and that citizen involvement and inter‐jurisdictional cooperation is vital. The programme has worked hard to identify all citizens and organizations that have a stake in Lake Champlain and draw them into a cooperative, sustainable management process. A 1990 Act of Congress (Public Law 101‐596) established a coordinated framework to study and understand the diverse systems of Lake Champlain and its basin in order to develop a comprehensive management plan to protect and restore lake and watershed resources. A 31‐member multi‐stakeholder board was established to develop the plan, a process that took 5 years and included numerous public meetings. Today, a Steering Committee oversees the implementation of the plan and the activities of the LCBP.     

Poyang Lake basin: a successful, large-scale integrated basin management model for developing countries

Protection of water environment while developing socio-economy is a challenging task for lake regions of many developing countries. Poyang Lake is the largest fresh water lake in China, with its total drainage area of 160,000 km2. In spite of rapid development of socio-economy in Poyang Lake region in the past several decades, water in Poyang Lake is of good quality and is known as the "last pot of clear water" of the Yangtze River Basin in China. In this paper, the reasons of "last pot of clear water" of Poyang Lake were analysed to demonstrate how economic development and environmental protection can be coordinated. There are three main reasons for contributing to this coordinated development: 1) the unique geomorphologic features of Poyang Lake and the short water residence time; 2) the matching of the basin physical boundary with the administrative boundary; and 3) the implementation of "Mountain-River-Lake Program" (MRL), with the ecosystem concept of "mountain as source, river as connection flow, and lake as storage". In addition, a series of actions have been taken to coordinate development, utilisation, management and protection in the Poyang Lake basin. Our key experiences are: considering all basin components when focusing on lake environment protection is a guiding principle; raising the living standard of people through implementation of various eco-economic projects or models in the basin is the most important strategy; preventing soil and water erosion is critical for protecting water sources; and establishing an effective governance mechanism for basin management is essential. This successful, large-scale basin management model can be extended to any basin or lake regions of developing countries where both environmental protection and economic development are needed and coordinated.     

Management issues in the Lake Titicaca and Lake Poopo system: Importance of developing a water budget

Lake Titicaca is the largest freshwater lake in South America and the highest of the world’s large lakes. The Desaguadero River links Lake Titicaca to lakes Urur Uru and Poopo and, in wet years to the Coipasa Salt Marsh. Lake Titicaca is bordered by both Bolivia and Peru. The main international lake management problem for the Lake Titicaca/Desaguadero River/Lake Poopo system involves the use of water resources. The maximum usable flow in the Titicaca basin (only 20–25 m³ s^–1), is dramatically less than the estimated demand. Water transfer and irrigation projects will have to be strictly prioritized on the basis of environmental, social, economic and hydrological criteria. Establishing the overall volume and demand for water in the Titicaca system has been critical to making good management decisions. Agreements for the study and management of Lake Titicaca between Peru and Bolivia date back to 1955 when both countries signed a document declaring ‘the indivisible and exclusive joint ownership of both countries of the waters of the lake’. Over time, the two countries agreed to create a Binational Autonomous Authority that would have full autonomy for Titicaca–Desaguadero/Poopo system decisions related to implementing the master plan that they had developed. Although it is hard to quantify conservation success in large lake regions, water use projects are being prioritized, city wastewater pollution in the Bay of Puno is being reduced and ameliorated and a large biodiversity project through the Global Environment Facility is underway.     

关于衡水湖环境功能区划的研究

对衡水湖进行环境功能分区是解决引江水资源保护和利用的重要举措。本文通过大量的调查和研究，在选取了切合当地实际情况的环境功能区划方案的基础上，通过对衡水湖环境、社会和技术经济进行综合分析，利用层次分析法对备选方案进行遴选，确定了其最佳利用模式，可以为目前我国环境综合利用及管理提供有益的参考。     

石臼湖流域江苏段生态环境驱动因素分析

根据相关资料对石臼湖流域江苏段的土地利用和生态环境现状进行评价,结果表明:湖泊水质处于Ⅳ～Ⅴ类,营养化水平为富营养。粗放的经济发展模式、滞后的环保基础设施、过度的湖泊围垦以及低效的环境管理是石臼湖流域江苏段生态环境演化的驱动因子;提出以调整产业结构、削减污染负荷、优化流域环境管理、加快基础设施建设以及开展湖泊生态修复为重点的相应措施。     

Socio‐economic and institutional assessment of Malaysia's first biosphere reserve: Chini Lake

Despite being designated the first UNESCO Biosphere Reserve in Malaysia, the Chini Lake Basin experiences continuing management challenges attributable to existing sectoral management practices and differences in demands of multiple stakeholders. Accordingly, a socio‐economic survey and stakeholder consultative process were undertaken, involving relevant stakeholders in the lake basin. The consultative process involved: (a) identification and prioritization of relevant stakeholders; (b) assessment of their socio‐economic activities and perceptions; (c) organization of focus group discussions between basin stakeholders; and (d) development of management recommendations in collaboration with stakeholders. The results of this study indicated the local community's way of living has changed from traditional occupations to a wage economy. Overlapping functions and lack of communication were among the major identified challenges facing by Chini Lake. Multiple strategies were proposed to promote environmental protection and good governance of Chini Lake, including formation of special area plans and strengthening institutional arrangements to sustainably manage the Chini Lake catchment. An effective authority also is necessary to improve communication and coordination of programmes by the various basin agencies and communities.     

新疆博斯腾湖二维水质数学模型研究

博斯腾湖流域经济总产值占全州经济总量的80%以上,是巴州工农业生产的重要聚集区域。然而,随着流域社会经济的快速发展,流域污染物的产生量、入湖量和污水排放量日益增加,点源污染和面源污染逐年加剧,博斯腾湖已由淡水湖泊演变为微咸湖。因此,建立二维水质数学模型,分析矿化度变化规律,为博斯腾湖的环境管理及环境保护规划等提供科学依据。     

Nutrient management in Lake Erie: Evaluating stakeholder values,attitudes, and policy preferences

Harmful algal blooms (HABs) have impaired Lake Erie’s western basin water quality since the 1960s. Though scientists agree that eutrophication is a key driver of HABs in Lake Erie, the role of nitrogen is still the subject of debate. The problem is twofold: (1) uncertainty in the specific causes of HABs can lead to inappropriate management solutions, and (2) managing a cross-boundary watershed requires collaboration and agreement on apt solutions from multiple stakeholders as well as many U.S. states and Canadian provinces. In our study, we interviewed 29 stakeholders actively involved in western Lake Erie’s watershed. We analyzed the stakeholders’ values, attitudes, and policy preferences to understand their differences, similarities, and their effects on management decisions. We found that stakeholders agree on the urgency of the problem and the necessity for increased nutrient management in Lake Erie’s western basin. Furthermore, we found that stakeholders can be represented as distinct clusters based on their values, and these value-based clusters are associated with different policy preferences. The different opinions and preferences of these value clusters span across stakeholder sectors and may affect efforts toward policy change. Stakeholders often question the feasibility and effectiveness of existing policies and policy plans. The findings shed new light on the relationship between stakeholder type and environmental values, attitudes, and policy preferences. Collaboration on HABs in Lake Erie will require open lines of communication both to improve policy and to cultivate trust among the multiple parties in this diverse watershed.     

淀山湖跨省管理体制设计与建议

针对淀山湖水资源水环境管理的现状和存在问题,借鉴国内外跨界湖泊成功的管理经验,设计了建立淀山湖联席会议制度、扩大流域机构管理职能、成立淀山湖水污染防治办公室等3种淀山湖管理模式,分析了各种管理模式的特点,并比较其优劣。建议根据现阶段的实际情况,采取淀山湖联席会议制度,以尽快实现淀山湖水资源水环境的统一协调管理。