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.     

Is the destabilisation of lake peipsi ecosystem caused by increased phosphorus loading or decreased nitrogen loading?

Lake Peipsi (3555 km2, mean depth 7.1 m) located on the border of Estonia and Russia is the largest transboundary lake in Europe. L. Peipsi consists of three parts. The shared largest northern part L. Peipsi s.s. (2611 km2, 8.3 m) and the southern L. Pihkva (708 km2, 3.8 m) which belongs mainly to Russia are connected by the river-shaped L. L?mmij?rv (236 km2, 2.5 m). The catchment area (44,245 km2 without lake area) is shared between Estonia (33.3%), Russia (58.6%) and Latvia (8%). Intensive eutrophication of L. Peipsi started in the 1970s. The biomass of N2-fixing cyanobacteria was low at heavy nutrient loading in the 1980s. After the collapse of soviet-type agriculture in the early 1990s, the loading of nitrogen sharply decreased. A certain improvement of L. Peipsi s.s. was noticed at the beginning of the 1990s together with the temporary reduction of phosphorus loading from Estonian catchment while in recent years a destabilisation of the ecosystem has been observed. This deterioration has been expressed mainly as intensive blue-green blooms and fish-kills in summer. Reappearance of blooms has been explained by the decrease in N/P loading ratio due to reduced N discharge while in some periods increased phosphorus loading could have supported this trend.     

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.

     

武汉市后官湖水环境演变特征及其影响因素分析

水环境精细化管理背景下湖泊水质演变特征分析对湖泊水环境整治规划有着重要意义。根据后官湖2010～2018年水质监测数据,采用单因子评价法和综合营养状态评价法从年份、月份、季度、水期等4个时间角度分析了后官湖水质浓度、水质类别和富营养化演变特征。结果显示:2010～2018年后官湖总磷、总氮浓度呈上升趋势,高锰酸盐指数、氨氮呈下降趋势;2015年以来,后官湖水质为Ⅳ类,超标因子为总氮、总磷,受农业种植、城镇生活污水影响最大;湖泊呈中营养化状态,且综合营养状态指数有增加趋势;四季中,除春季水质达标外,其余季节均超标;多年月平均水质除4～6月达标外,其余月份均超标。后官湖湖边与湖心的水质差别较小,说明后官湖属于均匀混合型湖泊。月均降雨量、气温和水位等水文气象指标与水质浓度指标的相关分析表明:降雨量、气温与总氮、溶解氧浓度呈显著负相关关系,其余指标浓度与水文气象无相关关系。     

Statistical modelling of riverine nutrient sources and retention in the Lake Peipsi drainage basin.

Implementation of the Water Framework Directive calls for methodologies and tools to quantify nutrient losses from diffuse sources at a river basin district scale. Here, we examine the possibility of using a statistical model for source apportionment and retention of nutrients in a large transboundary drainage basin (44,000 km2). The model approach uses non-linear regression for simultaneous estimation of e.g. source strength, i.e. export coefficients to surface waters, for the different specified land-use or soil categories and retention coefficients for pollutants in a drainage basin. The model was tested on data from 26 water quality stations with corresponding sub-basin data, i.e., land cover, point sources and atmospheric deposition, from the Estonian part of the Lake Peipsi drainage basin. The model showed that it was statistically possible to derive reliable export coefficients (i.e. unit-area loads) for nitrogen on agricultural land and forests. Moreover, it was shown with simple empirical functions that lake retention was approximately 30-35% for both nitrogen and phosphorus and that the riverine retention was low for both nitrogen and phosphorus (approx. 10%). Results show that the MESAW model is a simple and powerful tool for simultaneous estimation of sources and retention of nutrient loads in a river basin.     

St. Clair-Detroit River system: Phosphorus mass balance and implications for Lake Erie load reduction,monitoring, and climate change

To support the 2012 Great Lakes Water Quality Agreement on reducing Lake Erie's phosphorus inputs, we integrated US and Canadian data to update and extend total phosphorus (TP) loads into and out of the St. Clair-Detroit River System for 1998–2016. The most significant changes were decreased loads from Lake Huron caused by mussel-induced oligotrophication of the lake, and decreased loads from upgraded Great Lakes Water Authority sewage treatment facilities in Detroit. By comparing Lake St. Clair inputs and outputs, we demonstrated that on average the lake retains 20% of its TP inputs. We also identified for the first time that loads from resuspended Lake Huron sediment were likely not always detected in US and Canadian monitoring programs due to mismatches in sampling and resuspension event frequencies, substantially underestimating the load. This additional load increased over time due to climate-induced decreases in Lake Huron ice cover and increases in winter storm frequencies. Given this more complete load inventory, we estimated that to reach a 40% reduction in the Detroit River TP load to Lake Erie, accounting for the missed load, point and non-point sources other than that coming from Lake Huron and the atmosphere would have to be reduced by at least 50%. We also discuss the implications of discontinuous monitoring efforts.     

Strategy of water pollution prevention in Taihu Lake and its effects analysis

Taihu Lake, the third largest freshwater lake in China, is located in the Chanjiang Delta of the Yangtze River. Its waters are used by agriculture, industry and as major drinking water for several cities including Shanghai and Wuxi. The lake also is important for tourism, aquaculture and flood control. Taihu Lake and its surrounding areas are facing three major water-related threats: deteriorating water quality with inflow and runoff from its watershed; flooding during the rainy seasons; and water shortages during drier months. Noxious algae blooms are occurring with increasing frequency and water quality continues to decline. Remedial actions implemented to date have been ineffective. This paper proposes that the problems could be remedied by constructing a by-pass channel (BPC), which would divert low-quality water from the lake during low precipitation periods and allow better quality water to flow into the lake during high flow periods. This remedial action would simultaneously deal with the deteriorating water quality of Lake Taihu and maintain its water level at a desired level. A preliminary assessment of this strategy shows that, if the BPC were implemented, the water quality of Taihu Lake would be improved significantly in few years, the flood disaster would be greatly mitigated, and the water shortage problem in the basin would be alleviated.     

Fish and fishing in Lake Peipsi (Estonia/Russia) since 1851: Similarities and differences between historical and modern times

The first survey data on the fisheries in Lake Peipsi were collected by natural scientist Karl Ernst von Baer as a result of the world's first special fishery expedition in 1851–1852. In the current study, all available numerical datasets on fishing in Lake Peipsi from 1851 to 2018 have been drawn together in order to analyse the long-term changes in the lake’s fish assemblages. As the study indicates, the overexploitation, catching of juvenile fish and predator–prey imbalance have been common problems associated with fisheries in Lake Peipsi for the last two centuries. Similar to many inland waterbodies worldwide, total catch of fish from Lake Peipsi has decreased about four times since the mid-19th century, and the catch of lake (dwarf) smelt, a previously dominant species, has periodically fluctuated with long-term gradual reduction. The decline of cool-water fish, such as vendace, burbot and Peipsi whitefish during the last two centuries, and the domination of Eurasian perch, common bream and pike-perch in the catches of the last 20 years mark considerable structural shifts in fish assemblages. Of the multiple stressors (e.g., nutrient enrichment, increased water temperature, overfishing) triggering shifts in fish assemblages, the impact of climate warming, especially extreme weather events such as heatwaves, seems to be the strongest during the last three decades. However, none of the fish species have completely disappeared from the lake during the last century although the share of cool-water fish in the total catch has declined about tenfold since the 1930s.     

Circulation and mixing in Sodus Bay due to water exchange with Lake Ontario

Embayments on large lakes may be affected by water exchange with the lake that, in turn, impact water quality in the embayment. In this study we examine the influence of hydrodynamic factors that may play a role in controlling water quality in Sodus Bay, the largest enclosed embayment on the U.S. shoreline of Lake Ontario. The motivation for this study was the occurrence of a blue-green algal (cyanobacterial) bloom in 2010, and the need to understand the factors that influence this and other water quality issues. A hydrodynamic model with high spatial and temporal resolution was applied and calibrated to field data collected in a detailed sampling program in 2013. The model, along with field data collected over several additional years, was then used to develop a comprehensive understanding of the hydrodynamic impacts on physical conditions in the bay. A primary result of this process is a determination of the importance of flow exchange between Lake Ontario and Sodus Bay, particularly during lake upwelling periods that cause colder water to enter the bay as an underflow. Hydrodynamic features identified to have played a potential role in the bloom formation of 2010 include a lake upwelling event, strong stratification, and relatively warm conditions throughout much of the summer. Lack of continuous monitoring in 2010 precludes a specific comparison of the model and data when the bloom formed, but the model clearly shows conditions that would have led to a bloom, assuming other preconditions were in place. The customized hydrodynamic model provides opportunities for future ecological modeling, hypothesis development, and what-if scenario testing. This study reinforces the importance of hydrodynamic interactions between lakes and embayments, and their impacts on water quality.     

Water quality assessment of a tropical coastal lake system using multivariate cluster,principal component and factor analysis

Statistical techniques represent a reliable tool for classifying, modelling and interpreting surface water quality monitoring data, particularly for lakes. The complexity associated with the analysis of a large number of measured variables, however, is a major problem in water quality assessments. Multivariate analysis, such as cluster analysis and factor analysis (FA), was utilized in this study for the analysis of water quality data (including water discharges and 28 water quality parameters) for Akkulam–Veli Lake, a tropical coastal lake system in Kerala, India. This lake is partially divided into two sub‐systems, namely Veli Lake and Akkulam Lake. Akkulam Lake exhibits freshwater characteristics, in contrast to Veli Lake, which exhibits saline water characteristics because of its close proximity to the sea. Thus, studying this lake provides insights into water quality variations in both a freshwater and saline water lake in a tropical region. Water quality patterns and variations in Akkulam–Vela Lake over three seasons, including pre‐monsoon (PRM), monsoon (MON) and post‐monsoon (POM), also were studied, utilizing multivariate techniques. The organic pollution factor played a significant role on lake water quality during PRM. The influence of organic pollution tends to decrease during MON and POM, a particular situation faced by urban lakes in tropical regions. Polluted stretches in a lake system during different seasons can easily be ascertained by hierarchical cluster analysis. Further, the factors affecting a lake system as a whole, as well as for a particular sampling site, can easily be identified by FA. Improved water quality can be observed during POM. Akkulam and Vela lakes exhibit a wide variation in water quality during all seasons, a finding that corroborates a water flow obstruction from Akkulam Lake to Veli Lake because of the bund existing between the two lakes. The location of the bund is identified as the major reason for different hydrochemical processes in A–V Lake.     

镇江金山湖水体污染源解析

分析了2012年金山湖各监测段的水质情况,并对金山湖水体污染源进行解析。结果表明,运粮河入流水质较差,金山湖TN值超标;降雨地表径流是金山湖的第一大污染源,并且城镇地表径流所产生的污染物的负荷及浓度要远高于农田地表径流;由于截污工程的实施,工业生产废水与城镇生活污水对污染的贡献率较低。     

模糊数学方法在鄱阳湖水质评价中的应用

针对鄱阳湖水质情况,采用了14个具有代表性的监测站点的监测资料,利用模糊数学法对其水质变化情况进行了现状分析及趋势预测.结果表明:应用模糊数学方法能够更客观地反映水体环境的质量状况.同时发现,鄱阳湖的入、出湖及湖区水质整体优良,且有好转趋势;污染物进入湖泊南面后经过稀释、降解,下游水质好于上游;湖泊主要污染物为氨氮、总磷;污染较为严重的站点为乐安河口.     

Chloride and total phosphorus budgets for Lake Nipissing,headwater of Lake Huron,Ontario, Canada

Anthropogenic sources of total phosphorus (TP) and chloride (Cl^?) to lakes and rivers have been issues of concern for many decades in the Great Lakes Basin with northern Boreal Shield headwater tributaries less well studied. In the Sturgeon River – Lake Nipissing – French River basin, a headwater basin of Georgian Bay, Lake Huron, water quality monitoring of major inflows to Lake Nipissing, the third largest inland lake located entirely within Ontario, is only available from the mid-1960s to the 1990s. During the period of 2015–2018, we conducted monthly water quality surveys of major and minor inflows for two water years and have generated the first chloride (Cl^?) and total phosphorus (TP) elemental budgets for the lake. Review of available long-term concentration data indicate decreasing TP concentrations by decade in major inflows, but select inflows continue to exhibit concentrations above provincial objectives, including inflows from agricultural areas that are no longer part of provincial monitoring programs. Some inflows also show high average Cl^? concentrations with potential influences (e.g., road salt, agricultural activities) to stream water quality throughout the year. Water and elemental budgets indicate that while specific runoff (l/s/km²) is quite similar across contributing catchments, yields of Cl^? and TP (kg/ha/yr) are disproportionately higher in catchments with urban and agricultural activities. While uncertainties in the water balance and elemental yields remain, this first effort to quantify annual elemental budgets of Lake Nipissing highlights the need to develop community-based, spatially distributed water quality surveying for long-term ecosystem monitoring and future planning.     

Watershed management in the Lake Ohrid region of Albania and Macedonia

Lake Ohrid is the oldest lake in Europe and one of the oldest lakes in the world, formed 4–10 million years ago. Lake Ohrid serves as a refuge for numerous freshwater organisms from the tertiary period, whose close relatives can be found only as fossils. A breeding programme that artificially hatches the native and endemic trout supports the natural recruitment of lake Ohrid trout and since 1935 the lake has been stocked with more than 600 million young trout. The critical transboundary issue for Lake Ohrid water quality is phosphorus pollution. The current phosphorus load of the lake is estimated at 150 ton per year and needs to be reduced to 50 ton per year to keep the mean concentration of phosphorus below 7 mg m^–3 in the lake water. In 1996, a Memorandum of Understanding between the Macedonian and Albanian governments was signed and a binational Lake Ohrid Management Board was established, with substantial funding by the Global Environmental Facility. Both governments agreed to undertake appropriate legal, institutional, investment and technical measures to protect Lake Ohrid. The Lake Ohrid Conservation Project has four main goals: (i) to develop the institutional legal and regulatory framework for environmental management in the Lake Ohrid watershed; (ii) to establish a comprehensive binational monitoring programme, (iii) to mobilize and secure commitments from all the stakeholders in the watershed who will need to take measures to prevent degradation of the lake; and (iv) to increase public awareness and participation. Harmonizing Albanian and Macedonian laws and regulations may be the Lake Ohrid Conservation Project’s greatest challenge, particularly on fisheries and wastewater treatment issues.     

淀山湖富营养化防治与生态修复技术研究

淀山湖是上海市最大的天然淡水湖泊,也是黄浦江上游的重要水源保护地．其水质、水量状况对上海市饮用水水源安全具有重要作用。近年,淀山湖水体质量不断下降,尤其是2007年,淀山湖各区域出现了不同程度的蓝藻暴发。基于此背景,在对淀山湖进行前期调查的基础上,提出建设试验工程．通过试验工程的实施形成一套可供修复淀山湖富营养化防治的技术体系,为大规模实施相关工程提供科学依据和技术支持。     

冬季节制闸调控对巢湖水质影响评估

厘清湖泊大型节制闸工程冬季不同调控对湖泊水质时空分布格局变化的影响,对于科学提升湖泊水环境质量、保障供水安全和提高工程综合效益具有重大意义。利用巢湖数字流场平台,以 2020 年冬季巢湖高水位为背景,模拟了巢湖闸稳定泄流、分时段泄流和综合泄流三种调控方案下巢湖总氮、总磷、氨氮和藻类生物量的响应特征和后续效应。结果表明：不同泄流方案可降低巢湖全湖氨氮和西半湖总氮、总磷浓度,但会造成中东部湖区总氮和总磷浓度,以及全湖藻类生物量的上升;稳定泄流方案影响最为明显,该方案下全湖氨氮浓度平均下降 4.13%,藻类生物量平均上升 6.59%。开闸泄流有利于缩减湖体氮、磷、藻的总存量,有利于后期较大水时巢湖总磷、总氮浓度的控制。     

First results of the restoration of Lake Geerplas

In 1986 lake restoration was started in the Langeraar lakes, three small connected lakes in the western part of The Netherlands. In one of the lakes, Lake Geerplas, both the internal and external phosphorus load to the lake was reduced. Water quality parameters have been monitored six years after the measures were taken, in both Lake Geerplas and in one of the other Langeraar lakes. Water quality improved in Lake Geerplas during four years, indicated by decreased phosphorus concentrations and turbidity. At the end of the third fourth summer, phosphorus concentrations increased rapidly, presumably due to excessive phosphorus release from the lake sediment. Phytoplankton biomass and phytoplankton composition changed as well. In the sixth year phosphorus concentrations decreased slowly without any additional measures taken. Chlorophyll-a concentrations and turbidity are at the same level now as shortly after the measures were taken. At this moment, the effects of the measures are evaluated and additional measures are considered. Though the changes in water quality variables during the years are clearly related, the driving forces are not yet identified.     

镜泊湖水质及富营养化现状调查

为了解镜泊湖水质及富营养化情况,于2007年4~7月,每月取水样一次,分别监测透明度、COD、TN、TP等水质指标,依据地表水水域环境功能和保护目标,按功能高低依次划分为5类,进行水质分析。结果表明:湖水的透明度较低,COD偏高,pH值小于7,略显酸性,TN、TP较高,其中TN含量严重超标;镜泊湖水质类别属于Ⅴ类,水质较差,属严重富营养化。     

重庆双龙湖富营养化限制性因素确定试验研究

双龙湖是浅水型城市湖泊,一度为重富营养化湖泊。综合治理后水体仍处于中-富营养化。探求富营养化限制性因素对于防治双龙湖富营养化、维护双龙湖水质至关重要。本文通过双龙湖藻类增长潜力试验研究,确定双龙湖富营养化限制性因素是磷,这对于采取适宜管理措施修复水体、保持水质具有重要意义,为湖泊治理、水环境保持提供科学依据。     

查干湖湿地富营养化变化趋势分析及其防治措施探讨

湿地被称为地球之"肾",在生态系统中具有重要不可替代的作用。总氮及总磷含量过高是导致水库、湖泊发生富营养化的主要因素,因此预防氮磷含量增高是减少湖泊富营养化发生的有效途径。作者通过对查干湖湿地近十年水质监测资料统计分析,找出氮磷含量的变化趋势以及湖泊富营养化变化趋势,针对氮磷含量过高原因,提出切实可行治理措施和建议,为有关政府决策部门提供了科学可靠依据。