Seasonal dynamics of physico-chemical characteristics and biological responses of Lake Chilwa,Southern Africa

Lake Chilwa is shared by Malawi and Mozambique, it supports an important fishery and its watershed is undergoing rapid population growth and increasing utilization for agricultural production. It is a shallow, closed basin lake with extensive surrounding wetlands; and it has suffered several desiccation events in the last century. To better understand the current condition of the lake, we monitored a suite of physical, chemical and biological parameters at approximately monthly intervals over an annual cycle in 2004–2005. The limnology of the lake was extremely sensitive to seasonal changes in the lake's seasonal hydrological cycle. The physico-chemical parameters, temperature, electrical conductivity, and total suspended solids exhibited clear seasonal patterns driven by the highly seasonal rainfall and resultant lake levels. In response, phytoplankton and zooplankton abundance, as well as biologically dependent oxygen concentrations and pH, exhibited several maxima levels over the year. The peaks of phytoplankton and zooplankton were out of phase suggesting a lag in the zooplankton grazing in response to pulses in primary productivity. Chlorophyll concentrations can exceed 1 mg/L in surface waters indicative of hypereutrophic conditions, but they fell dramatically during zooplankton peaks. This hydrologically driven, shallow and mesohaline lake is a productive and critical resource to the region. Its management poses challenges arising from the dependence of its limnology and fishery on the lakes hydrology, catchment land use and climate variability.     

Determination of the status of stakeholder participation in the management of the Lake Malawi basin through application of Integrated Lake Basin Management

Lake Malawi is the southernmost of the Great Rift Valley Lakes of Africa and boasts the world's greatest freshwater fish biodiversity. Along with its basin, the lake provides many benefits to the country of Malawi. Settlements, agriculture and fishing are some of the major uses of the lake basin, making community involvement a necessary component of its management. With the use of key informant interviews, questionnaire survey, document review and site observations, this study demonstrates the applicability of the Integrated Lake Basin Management framework in the Lake Malawi Basin in regard to stakeholder participation. The main objective was to assess the participation of stakeholders, especially local communities, in the management of the lake basin. The framework applied in this study is discussed. The study findings indicate strong to very strong stakeholder participation, with notably high levels of awareness and women's involvement. Enhancing the understanding of the complex nature of lake basin issues, especially those related to the linkages between the water body and the basin, is a topic requiring further attention.     

Laurentian Great Lakes Hydrology and Lake Levels under the Transposed 1993 Mississippi River Flood Climate

The Laurentian Great Lakes are North America's largest water resource, and include six large water bodies (Lakes Superior, Michigan, Huron, Erie, Ontario, and Georgian Bay), Lake St. Clair, and their connecting channels. Because of the relatively small historical variability in system lake levels, there is a need for realistic climate scenarios to develop and test sensitivity and resilience of the system to extreme high lake levels. This is particularly important during the present high lake level regime that has been in place since the late 1960s. In this analysis, we use the unique climate conditions which resulted in the 1993 Mississippi River flooding as an analog to test the sensitivity of Great Lakes hydrology and water levels to a rare but actual climate event. The climate over the Upper Mississippi River basin was computationally shifted, corresponding to a conceptual shift of the Great Lakes basin 10̊ west and 2̊ south. We applied a system of hydrological models to the daily meteorological time series and determined daily runoff, lake evaporation, and net basin water supplies. The accumulated net basin supplies from May through October 1993 for the 1993 Mississippi River flooding scenario ranged from a 1% decrease for Lake Superior to a large increase for Lake Erie. Water levels for each lake were determined from a hydro-logic routing model of the system. Lakes Michigan, Huron, and Erie were most affected. The simulated rise in Lakes Michigan and Huron water levels far exceeded the historically recorded rise with both lakes either approaching or setting record high levels. This scenario demonstrates that an independent anomalous event, beginning with normal lake levels, could result in record high water levels within a 6- to 9-month period. This has not been demonstrated in the historical record or by other simulation studies.     

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。     

Framework for surface water quality management on a river basin scale: Case study of Lake Iseo, Northern Italy

River (DESERT) and lake (EVOLA) water quality models are used to simulate the influences of alternative water quality management scenarios on the quality of receiving surface waters in the Lake Iseo basin, Northern Italy. The scenarios are representative of the European Union Directive on Urban Waste Water Treatment (91/271/EEC) and of the regional authority’s objective to reduce the total phosphorus loads from point sources entering Lake Iseo and to restore the lake as close as it is practically possible to its former natural qualitative state. Application of DESERT shows that the regional ‘Water Clean Up Plan’ can achieve similar reductions in total phosphorus concentrations in the basin’s main river system, Oglio River, to the 91/271/EEC directive, but at notably lower economic costs. Application of EVOLA to Lake Iseo shows that it is not practical to achieve the regional authority’s objective of a specific total phosphorus concentration in the lake by 2016. Instead, the results show that a more realistic, but higher, total phosphorus concentration can be achieved by 2016. The results of both modelling exercises indicate the usefulness of DESERT and EVOLA for comparing and assessing water quality management scenarios and for revising the regional authority’s final objectives with regards to total phosphorus concentration in Lake Iseo, as well as the regional ‘Water Clean Up Plan’ for restoring and safeguarding the quality of the basin’s surface waters.     

Lake Champlain 2010: A summary of recent research and monitoring initiatives

Lake Champlain shares a geological history with the Great Lakes and, as part of the St. Lawrence drainage, also shares biological and ecological similarities. The complex bathymetry and extensive shoreline provide a variety of lacustrine habitats, from deep oligotrophic areas to shallow bays that are highly eutrophic. The large basin:lake ratio (19:1) makes Lake Champlain vulnerable to impacts associated with land use, and in some parts of the lake these impacts are further exacerbated by limited water exchange among lake segments due to both natural and anthropogenic barriers. Research in Lake Champlain and the surrounding basin has expanded considerably since the 1970s, with a particularly dramatic increase since the early 1990s. This special issue of the Journal of Great Lakes Research brings together 16 reports from recent research and monitoring efforts in Lake Champlain. The papers cover a variety of topics but primarily focus on lake hydrodynamics; historical and recent chemical changes in the lake; phosphorus loading; recent changes in populations of phytoplankton, zooplankton, and fishes; impacts of invasive species; recreational use; and the challenges of management decision-making in a lake that falls within the legal jurisdictions of two U.S. states, one Canadian province, two national governments, and the International Joint Commission. The papers provide not only evaluations of progress on some critical management issues but also valuable reference points for future research.     

Development of a system‐based water balance model to assess interrelated physical and anthropogenic constraints in lake and reservoir watersheds,applied to Coeur d'Alene Lake,Idaho, USA

This study presents a methodology for the development of a water balance model that uses publicly available data in a manner useful to water scientists and managers who manage complex lake and reservoir watersheds. The approach was applied to Coeur d'Alene Lake, a naturally occurring lake that is controlled by a dam located on its outlet (Spokane River) in North Idaho, USA. As in many other areas, the region surrounding Coeur d'Alene Lake has experienced high rates of population growth in recent years, and there is concern that, as consumptive water use increases, the lake will eventually not be able to be managed to simultaneously maintain the federally mandated minimum flow requirements in the Spokane River and also maintain the target summertime elevation of 2128 feet (648.6 m) for recreation and hydropower purposes. The complexity caused by the competing uses at Coeur d'Alene Lake makes it an excellent case study for similarly characterized watersheds. Both a natural flow model and regulated elevation model were developed, and sensitivity analysis was conducted on both models to evaluate which lake processes have the greatest effects on lake elevation, thereby requiring the most attention. A ‘low‐flow’ scenario was modelled to demonstrate the usefulness of the model and to inform Coeur d'Alene Lake regional stakeholders regarding the interrelationship between current water policy and the lake's physical behaviour under stressed conditions that could result from climate change. Model result indicates that, while lake elevation may be maintained at the summertime elevation of 2128 feet (648.6 m) under a low‐flow scenario, the outflows in the Spokane River start to approach the minimum flow requirements in the month of August. The developed approach is useful where publicly available data exist and allows for economic, yet rigorous, water resources systems evaluation without requiring significant field data collection.     

Tonle Sap Lake: Current status and important research directions for environmental management

Tonle Sap Lake (TSL) in Cambodia is the largest freshwater body in South‐East Asia and one of the most productive ecosystems in the world. The lake and its ecosystems are widely under threat, however, due to anthropogenic activities occurring inside and outside its basin (e.g., water infrastructure development; land use change), being poorly understood in most aspects. This study provides an updated review of the state of knowledge of the TSL ecosystem, as well as important research directions for sustainable lake environmental management of Tonle Sap Lake by focusing on four major topics, including climate change and hydrology, sediment dynamics, nutrient dynamics and primary and secondary production. The findings of this study suggest anthropogenic activities in the TSL basin, as well as the Mekong, in combination together with climate changes, are key contributing factors in the degradation of the TSL ecosystem. Insufficient accurate data, however, precludes quantitative assessment of such impacts, making it difficult to quantitatively assess and accurately understand the ecosystem process in the lake ecosystem. More efforts are recommended in regard to environmental monitoring in all sub‐basins around TSL, assessing seasonal changes in nutrient and sediment inputs corresponding to water level and flow changes, assessing cumulative impacts of water infrastructure and climate change on the ecosystem dynamics, and elucidation of ecosystem processes within the lake's internal system.     

Study of water quality distribution in Lake Biwa in consideration of runoff pollutant loads from its catchment basin.

Many strategies for water quality conservation in Lake Biwa are being carried out mainly by reducing runoff pollutant loads into the lake. But influence of the runoff load reduction on the water quality in Lake Biwa has not been clarified enough so far. This study is aimed at discussing methodology to estimate water quality distribution in Lake Biwa using runoff pollutant loads from its basin. The runoff loads from the basin are calculated by Macro Model with GIS database of the Lake Biwa basin, and the water quality distribution in the lake is estimated by the spline technique with the calculated runoff loads. As a result, it has been proved that the methodology has enough reproducibility to estimate the water quality distribution in Lake Biwa and is available to examine the water quality in the lake.     

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.     

Water quality estimation in consideration of pollutant runoff and internal production in Lake Biwa, Japan.

Lake Biwa is the largest lake in Japan, and water quality in the lake is heterogeneous. Therefore, it is important for water quality management that spatial distribution of water quality in the lake should be clearly understood. The objectives of this study are to show a methodology and to develop a simulation system to calculate COD distribution in Lake Biwa taking internal COD production into consideration. This study also aims to examine transition of COD in the lake using the simulation system. In the simulation system, runoff loads of COD from the Lake Biwa basin are calculated by Macro Model for each tributary. The external COD concentration in 233 inshore meshes of the Lake Biwa water surface was calculated using the runoff loads. The internal COD was calculated using relationships among limiting nutrients, chlorophyll-a and COD. Then, the spatial distribution of water quality in Lake Biwa was calculated both for the external and internal COD by spline technique. Simulations using the system were implemented for 1986-1998, and a clear difference in characteristics between a drought year and a flood year was shown. In the result, it was shown that the simulation system developed here was available to calculate COD distribution in Lake Biwa, and that it had the possibility to explain the recent phenomenon of COD increase in the lake.     

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.     

长江干流九江段与鄱阳湖不同季节的同位素特征

为了分析不同时期鄱阳湖与长江及其他各条河流的关系,初步探讨三峡水库运行对鄱阳湖水量的影响,对九江段长江干流、鄱阳湖地区河水、湖水进行了采样和氘氧稳定同位素分析。结果表明:水体同位素存在明显的时间和空间变化,可用于揭示湖泊与河流之间的关系。三峡补水调度过程能有效减少鄱阳湖春季的水量流失,4月份鄱阳湖流域已进入雨季,大量内河来水导致鄱阳湖水以较大的流量向长江补给;调洪削峰调度阶段,较高的长江水位对鄱阳湖存在一定的顶托作用,导致湖水难以排泄;三峡蓄水过程引起的长江水位降低加速了枯水期鄱阳湖水的流失。三峡水库的调度需要考虑到鄱阳湖流域水情,以免加重该流域丰水期的洪涝灾害和枯水期的水资源短缺。     

Influence of influent tributaries on water quality changes in Lake Mogan, Turkey

Lake Mogan, located in the steppes of central Anatolia, is a vital Turkish ecological system, in terms of its water resources, flora and fauna. The lake also is a unique recreational area for Ankara, the capital of Turkey. However, the lake is currently threatened by severe pollution, being under the risk of serious degradation because of (i) uncontrolled urbanization; (ii) point and non‐point source pollution; (iii) inefficient sewerage systems; (iv) sediment transportation and pollution via influent creeks to the lake; (v) uncontrolled soil erosion in its drainage basin; (vi) inappropriate flood control measures; and (vii) severe degradation of the natural wetlands within its drainage basin. This study evaluates the influence of its influent creeks on the water quality of Lake Mogan, mainly because the creeks are believed to be responsible for the major pollutant load reaching the lake, and because the extensive database documenting this situation has not previously been critically evaluated. Accordingly, this study reviews (i) change in the water quality of Lake Mogan between 1993 and 2002; (ii) the water quality classification of the major influent creeks feeding Lake Mogan; and (iii) the influence of the influent creeks on the water quality of the lake between 1993 and 2004.     

Analysing the extent (size and shape) of Lake Basaka expansion (Main Ethiopian Rift Valley) using remote sensing and GIS

This study attempted to estimate the extent of the expansion of the area of Lake Basaka over the past 50 years (1960 to 2010), using LANDSAT images, field observations, local information and topographic maps. The analysis revealed that the lake has exhibited a dramatic expansion over the past five decades. An increase in the lake water level by 7.6 m over this period resulted in flooding about 45.8 km² of surrounding areas and an incremental lake volume of about 280 Mm³. About 70% of the lake expansion was observed in the period between the 1970s and 1990s. This phenomenon coincides with the periods of remarkable land use/cover changes in the region. Furthermore, the beginning of the lake expansion coincided with the introduction of irrigated agriculture in the region, and construction of Koka Dam in the mid‐1960s in the upper Awash River Basin. This study suggests that the observed expansion trend, if it continues unabated, could result in certain socio‐economic and environmental consequences in the region in particular, and to Ethiopia in general. Groundwater inundation or salty water intrusion, for example, might occur in the area in the near future, thereby affecting the sustainability of regional irrigated agriculture. The lake has the potential to inundate the surrounding region (Matahara Sugar Estate; towns of Fantalle and Matahara) and might connect with the Awash River during the next 10–15 years. This would affect downstream irrigation developments in the Awash Basin and the livelihoods of people that depend on the basin’s water resources. The overall findings of this study emphasize the need to adopt mitigation measures before the lake expansion results in irreversible damage to the region or the basin.     

Management Options to Improve Water Quality in Lake Peipsi: Insights from Large Scale Models and Remote Sensing

Nutrient pollution causes frequent blooms of potentially harmful cyanobacteria in Lake Peipsi (Estonia/Russia). Although external nutrient loading has reduced since the 1990s, lake water quality has barely improved, and eutrophication is still considered a threat to lake biota and water usage. To understand the recovery dynamics of the lake it is necessary to analyse the effects of land use and lake management on water quality to develop mitigation strategies. Comprehensive analysis has thus far failed due to information gaps inherent to conventional monitoring strategies. We show how two large-scale hydrological models using Earth observation data provide spatial information on pollution and can help explain the causes of past and current lake eutrophication. WaterGAP3.2 provides valid estimates of present and probable future phosphorus concentration in the lake water, based on past hydrological conditions. WaterWorld models spatial potential water quality and a scenario of optimal pollution reduction. Remotely sensed optical water quality data can be used to analyse recent, spatial water quality dynamics. The spatial and temporal algae distributions and can help explain eutrophication causes at Lake Peipsi and its catchment, adding value to in situ monitoring and supporting river basin management with large scale data.

     

冰川亏损对哈拉湖流域湖泊水位波动的影响

青藏高原的内陆湖泊水位和冰川变化和其流域内冰川质量亏损对湖泊水位波动的影响及其贡献对水量平衡研究具有重要意义。以哈拉湖流域冰川为例,基于2000-2015年星载雷达测高资料和Landsat卫星多光谱遥感资料分别提取湖泊水位和面积变化;结合附近的托勒台站气象观测资料,进一步分析其水位波动变化原因和冰川亏损对湖泊水量贡献。结果表明:受年降水量和夏季降水量增加影响,哈拉湖水位呈增加趋势,但哈拉湖流域冰川亏损加速趋势不明显;与2000年相比,湖泊面积增加了(21.4±4.8)km~2,湖泊水位增加了(1.68±0.26)m,相应的湖泊水容量增加了(16.1±0.3)×10~8m~3水当量。流域冰川亏损量达对哈拉湖水量的贡献率为39.65%,降水量增加对湖泊水量贡献了22.82%。     

Better governance for integrated management of the Lake Biwa—Yodo River Basin

The present study discusses the efforts of the Union of Kansai Governments to resolve serious issues in the Lake Biwa—Yodo River Basin in Japan. It identifies many of the issues related to the basin on a ‘no man's land’ mindset of today's governmental framework, which has constrained both the will and the approach to remedy the associated problems. It also highlights better governance that not only encourages individual efforts, but also promotes collaboration and cooperation among the major stakeholders in the area, as important to developing acceptable solutions to relevant issues. The present study also recognizes objective scientific evidence as an effective driver for improving governance, being the basis for making informed decisions and highlighting the use of appropriate indicators to evaluate the conditions characterizing a specific location or the basin as a whole. The present study also describes the Union of Kansai Governments as a behind‐the‐scenes coordinator that gathers knowledge and intelligence on the basin, and works to integrate policies by getting basin stakeholders to gradually improve governance by repeating a cycle of: (a) recognizing the current situation; (b) identifying relevant issues to be addressed; (c) establishing a framework and policy for collaboration and corporation; and (d) taking necessary actions. To this end, the present study discusses the studies and efforts of the Union of Kansai Governments to develop and implement integrated management of this important interlinked lake–river water system in Japan.     

First insights into the diversity and ecology of non-biting midges (Diptera: Chironomidae) of the unique ancient Skadar Lake basin (Montenegro/Albania)

In the present study, based on faunistic information collected during 2014 and 2015, in association with physical–chemical conditions of the collection sites, the environmental factors influencing the composition and distribution of chironomid assemblages were investigated. In total, 164 Chironomidae taxa reported in this study extended the existing checklist with 152 taxa newly found in the Skadar Lake basin. The comparison based on the list of species from the six large, well-studied European lakes showed that Lake Constance (Switzerland/Germany/Austria) is the most species-rich waterbody with 174 taxa, followed by Lake Skadar with 164 taxa. For pupal exuviae, the most species-rich site was situated in the centre of the small lake (north-western part of the Skadar Lake). A Canonical Correspondence Analysis (CCA) revealed that shallow coastal parts of the lake are much richer in species than the open, deeper parts of the lake. This first investigation since 1979 of non-biting midge species (including imagines) diversity will help to monitor biodiversity of the basin and to understand how protection programs influence biodiversity within the lake basin.