Mass balance analysis and calculation of wind effects on heat fluxes and water temperature in a large lake

Modeling applications often ignore the water mass balance for hydrodynamic simulations in large lakes such as the Great Lakes. However, evaluation of the water budget can be of interest, especially when water surface calculations are important, and also as it relates to the heat budget. In this study Lake Ontario is modeled using the Environmental Fluid Dynamics Code for the heating seasons in 2008–2013, with calibration focused on 2008, for which more data are available. The model is used to test both water mass and heat budgets, and various interpolation schemes for meteorological data are tested to determine the degree of sensitivity of results to the interpolation method used. The water budget incorporates flow from major tributaries and precipitation/evaporation, and it is shown that these processes alone cannot provide a balance. Missing water quantities include direct runoff and flows from smaller, probably ungauged tributaries. In 2008 the calculated quantity is 1.61?×?10¹⁰?m³ during April to September, which is equivalent to a change in water surface level of 0.7?m and represents an average flow rate of 1018?m³/s, which is larger than the inflow of any tributary to the lake except the Niagara River. Latent and sensible heat flux calculations are highly affected by wind, and interpolation of wind data is found to impact model calculations of those quantities, though different interpolation schemes do not have a strong effect on surface water temperatures. In general, the natural neighbor interpolation method is preferred over inverse distance methods.     

Quasi-periodic decadal cycles in levels of lakes Michigan and Huron

While Great Lakes' seasonal water-level variations have been previously researched and well documented, few studies thus far addressed longer-term, decadal cycles contained in the 143-yr lake-level instrumental record. Paleo-reconstructions based on Lake Michigan's coastal features, however, hinted to an approximate 30-yr quasi-periodic lake-level variability. In the present study, spectral analysis of 1865–2007 Lakes Michigan/Huron historic levels revealed 8 and 12-yr period oscillations; these time scales match those of large-scale climatic signals previously found in the North Atlantic. While the existing paleodata are inadequate to the task of asserting significance of the 30-yr signal, it is suggested here that this cycle is due to intermodulation of the two near-decadal signals. Furthermore, water budget analysis argues that the North Atlantic decadal climate modes translate to the lake levels primarily through precipitation and its associated runoff.     

Patterns in the crustacean zooplankton community in Lake Winnipeg,Manitoba: Response to long-term environmental change

Changes in the crustacean zooplankton community composition and abundance in Lake Winnipeg (1969–2006) provide a rare opportunity to examine their response to environmental changes in the largest naturally eutrophic lake on the Canadian prairies. Since 1929, zooplankton species composition in Lake Winnipeg has changed little except for the addition of the invasive cladoceran, Eubosmina coregoni in 1994. The dominant taxa in the lake in summer include: Leptodiaptomus ashlandi, Acanthocyclops vernalis, Diacyclops thomasi, Daphnia retrocurva, Daphnia mendotae, Diaphanosoma birgei, Eubosmina coregoni, and Bosmina longirostris. Climate-accelerated nutrient loading to southern Lake Winnipeg over the last two decades has led to increased phytoplankton abundance and higher frequency of cyanobacterial blooms especially in its northern basin. Crustacean zooplankton have likewise increased especially in the North Basin, but less so in the more nutrient rich South Basin, possibly as a consequence of higher densities of pelagic planktivorous fish and light-limited primary production compared with the more transparent North basin (Brunskill et al., 1979, 1980). Calanoid copepods play a larger role in the South basin food web in contrast to cyclopoid copepods and Cladocera in the North basin. The study begins to fill the recognized gap in understanding of Lake Winnipeg's food web structure and provides a baseline for evaluating ongoing changes in the zooplankton community with the arrival of new non-indigenous taxa, e.g. Bythotrephes longimanus and Dreissena polymorpha. It reinforces previous work demonstrating that zooplankton provide valuable indices toward evaluating the health of an ecosystem.     

Lake Ontario’s nearshore zooplankton: Community composition changes and comparisons to the offshore

In large lake systems the nearshore habitat is an intermediate zone between the shoreline and offshore, is an important nursery for larval fish, and is highlighted as an area in need of research in the Laurentian Great Lakes. In this study, we used two long-term monitoring programs to characterize the nearshore zooplankton community composition using seasonal data (May – October) and to compare the nearshore and offshore zooplankton community composition changes over time (1998 – 2019) to determine if the changes were synchronized. In the nearshore, we found the highest zooplankton biomass during the late summer/early fall (August 27th – Oct 6th), compared to mid-summer (July 1st – Aug 26th) and late spring (May 20th – June 30th). In the summer, the nearshore zooplankton community was dominated by cladocerans while copepods dominated the offshore community. From 1998 to 2019, both nearshore and offshore copepods shifted from a cyclopoid to a calanoid-dominated state, but the details of this change were different. For example, taxon-specific analysis revealed that despite reduced cyclopoids in both habitats, Mesocyclops edax increased in the nearshore. Additionally, taxon-specific analysis suggested the changes occurred an average of three years earlier in the nearshore. Using Analysis of Similarity, the nearshore and offshore summer zooplankton community compositions became increasingly distinct over time. Results from this study highlight the uniqueness of the nearshore in large lake systems, the importance of seasonal and long-term monitoring, and the potential of the nearshore as an early indicator of offshore changes.     

Links between type E botulism outbreaks, lake levels, and surface water temperatures in Lake Michigan, 1963-2008

Relationships between large-scale environmental factors and the incidence of type E avian botulism outbreaks in Lake Michigan were examined from 1963 to 2008. Avian botulism outbreaks most frequently occurred in years with low mean annual water levels, and lake levels were significantly lower in outbreak years than in non-outbreak years. Mean surface water temperatures in northern Lake Michigan during the period when type E outbreaks tend to occur (July through September) were significantly higher in outbreak years than in non-outbreak years. Trends in fish populations did not strongly correlate with botulism outbreaks, although botulism outbreaks in the 1960s coincided with high alewife abundance, and recent botulism outbreaks coincided with rapidly increasing round goby abundance. Botulism outbreaks occurred cyclically, and the frequency of outbreaks did not increase over the period of record. Climate change scenarios for the Great Lakes predict lower water levels and warmer water temperatures. As a consequence, the frequency and magnitude of type E botulism outbreaks in the Great Lakes may increase.     

Invertebrate communities of former southern moravian floodplains (Czechoslovakia) and impacts of regulation

The natural hydrobiological conditions of southern Moravian floodplains have been drastically altered by regulation of the lower Dyje river and its tributaries. Natural floodplains were characterized by temporary pools and swamps, each inhabited by a typical community of aquatic invertebrates, and permanent water bodies (rivers and abandoned channels). Some aquatic taxa migrated onto ‘terrestrial’ localities during flood periods. Following regulation, floods were eliminated and most of the wet floodplain habitats disappeared, together with their typical species. The results of faunistic studies carried out in different permanent and temporary water bodies of the floodplains are reviewed. Altogether 188 taxa of planktonic and 206 taxa of benthic and semiplanktonic animals have been recorded. Of the planktonic community, rotifers (96 taxa) and copepods (41 taxa) have very favourable conditions for their development, especially in the spring. The main season for cladocera (53 taxa) development (summer) is less favourable due to the short duration of flooding (in flooded meadows) or poor oxygen conditions (in temporary pools with a high content of decaying organic matter). Among the zoobenthos, mainly facultative aquatic macroinvertebrates (larvae of insects) appear in these localities.     

Evidence from field measurements and satellite imaging of impact of Earth rotation on Lake Iseo chemistry

During an initial field survey in 2012, we observed an unexpected asymmetry of dissolved oxygen distribution between the western and eastern side in northern Lake Iseo. Motivated by this apparent anomaly, we conducted a detailed field investigation, and we used a physical model of the northern part of the lake to understand the influences that might affect the distribution of material in the northern section of the lake. These investigations suggested that the Earth's rotation has significant influence on the inflow of the lake's two main tributaries. In order to further crosscheck the validity of these results, we conducted a careful analysis at a synoptic scale using images acquired during thermally unstratified periods by Landsat-8 and Sentinel-2 satellites. We retrieved and post-processed a large set of images, providing conclusive evidence of the role exerted by the Earth's rotation on pollutant transport in Lake Iseo and of the greater environmental vulnerability of the north-west shore of this lake, where important settlements are located. Our study confirms the necessity for three-dimensional hydrodynamic models including Coriolis effect in order to effectively predict local impacts of inflows on nearshore water quality of medium-sized elongated lakes of similar scale to Lake Iseo.     

Near-inertial wave driven dissolved oxygen transfer through the thermocline of a large lake

The offshore regions of large temperate lakes are characterized by strong summer temperature stratification that limits vertical mass flux, and enables near-inertial internal wave motions. Here, we investigate the contribution of near-inertial baroclinic velocity shear on enhancing the vertical transport of dissolved oxygen (DO) through the thermocline of the central basin of Lake Erie. The lake is prone to severe annual hypoxia in the hypolimnion and also has strong near-inertial Poincaré wave activity. Using field measurements, analytical arguments and a numerical model under idealized conditions, we show that the near-inertial waves drive baroclinic shear instabilities that enhance the vertical turbulent diffusivity and reduce the rate of DO depletion in the hypolimnion by up to 12% over the entire basin. Results from modeling large-spatial variability in the enhanced thermocline flux to match the distribution of near-inertial wave energy density, indicate that the observed oxygen budgets will vary as a function of location of sampling.     

Large lakes in climate models: A Great Lakes case study on the usability of CMIP5

Large lakes have an impact on regional weather. In addition, they can be both sensitive to and influence regional climate changes. In the climate models that are used to investigate future climate changes, lakes are greatly simplified and sometimes absent. At the regional scale, this can have strong implications for the quality of the model information about the future. Through our work with climate information users in the Laurentian Great Lakes region, we have found that basic credibility of the information requires the underlying climate models simulate lake-atmosphere-land interactions. We are not aware of efforts within the scientific community to make known how individual large lakes are represented in models and how those representations translate to the quality of the data for particular regions. We share our framework for identifying how the Laurentian Great Lakes are represented in the Coupled Model Intercomparison Project (CMIP) version 5 climate models. We found that most CMIP5 models do not simulate the Great Lakes in a way that captures their impact on the regional climate, which is a credibility issue for their projections. We provide a perspective on the usability of CMIP5 for practitioners in the Great Lakes region and offer recommendations for alternative options.     

大直径压力输水管道增设大倾角阀门施工技术

大直径压力输水管道增设阀门在输水管道运行管理中被广泛应用,传统施工技术通过焊接将法兰与原管道进行连接,但在实际操作中,有时会面临诸如增设的阀门尺寸与原输水管道尺寸不匹配（尤其是原输水管道安装年限较久的情形）、原输水管道倾斜角度过大、作业空间狭小、安装困难等问题,从而导致焊接、安装等施工质量不易保证。为解决以上问题,经过调查与试验,通过利用切割原管道的弃料制作连接原管道与增设阀门的伸缩变径、合理利用现场常规起重设备——汽车式起重机、手拉葫芦等,成功创新了大直径压力输水管道增设大倾角阀门施工技术,在实际应用中取得了良好的效果。     

Changes in mid-summer water temperature and clarity across the Great Lakes between 1968 and 2002

In recent decades, three important events have likely played a role in changing the water temperature and clarity of the Laurentian Great Lakes: 1) warmer climate, 2) reduced phosphorus loading, and 3) invasion by European Dreissenid mussels. This paper compiled environmental data from government agencies monitoring the middle and lower portions of the Great Lakes basin (lakes Huron, Erie and Ontario) to document changes in aquatic environments between 1968 and 2002. Over this 34-year period, mean annual air temperature increased at an average rate of 0.037 °C/y, resulting in a 1.3 °C increase. Surface water temperature during August has been rising at annual rates of 0.084 °C (Lake Huron) and 0.048 °C (Lake Ontario) resulting in increases of 2.9 °C and 1.6 °C, respectively. In Lake Erie, the trend was also positive, but it was smaller and not significant. Water clarity, measured here by August Secchi depth, increased in all lakes. Secchi depth increased 1.7 m in Lake Huron, 3.1 m in Lake Ontario and 2.4 m in Lake Erie. Prior to the invasion of Dreissenid mussels, increases in Secchi depth were significant (p < 0.05) in lakes Erie and Ontario, suggesting that phosphorus abatement aided water clarity. After Dreissenid mussel invasion, significant increases in Secchi depth were detected in lakes Ontario and Huron.     

温度变化对人工湿地净化城市湖泊水体影响研究

以西安市兴庆湖为研究对象,对湖泊的水质进行了水平潜流和自由表面流净化的实验研究。在相同的水力负荷、水深等条件下,分析了温度变化对城市湖泊中的有机物、氮、磷等主要污染物的净化效果的影响。实验结果表明,随着水体温度的降低,湿地对各污染物的去除率呈现减少的趋势。     

再论洪泽湖的治理与改造

洪泽湖是我国第四大淡水湖，是一典型的过水性湖泊，无论是洪水（水灾）或是枯水（旱灾）均应当引起同等重要的关注，泄与蓄要兼顾兼施，必须从资源水利的角度来审视和研讨洪泽湖的治理和改造，因此，开辟了海水道是治理淮河与洪泽湖的根本举措，蓄泄兼施，淮水在湖外分流；清淤掘底，增加蓄水量；整治湖口，淮河洪水畅流入湖，防治污染，保护水环境。     

平原水网地区湖泊群退圩还湖规划研究——以里下河射阳湖为例

江苏省里下河腹部湖泊湖荡地区湖泊群约41个,面积695 km2,主要以圩区形式存在,基本丧失湖泊的功能。目前涉湖市县随着社会、经济、生态发展纷纷提出退圩还湖需求,本文以射阳湖为试点进行平原水网地区湖泊群的退圩还湖规划研究,提出退圩排泥场的安置、湖泊岸线调整、功能区重新划分,进行退圩后防洪、环境、生态、经济效益分析,为其他类似湖泊退圩还湖提供参考。     

汈汊湖生态水位确定方法研究

湖泊的适宜生态水位是进行湖泊规划设计、湖泊保护范围确定等工作的重要依据。本文以湖北省汈汊湖为例,通过选取频率分析法、湖泊形态分析法、生物空间法、最低水位法、水环境模拟法5种不同的生态水位确定方法,开展了湖泊生态水位确定方法的比较研究。研究结果表明,湖泊生态水位计算结果与每种方法的理论和假设密切相关,5种方法计算的汈汊湖生态水位结果介于22.86~24.20m之间。     

Lakes in Bavaria: Concepts for protection and on-going, sustained utilization

The paper outlines the nature of lakes in Bavaria, Germany, and discusses their uses, development, protection and conservation. Interdisciplinary regional concepts are also considered as is integrated planning of an area of artificial lakes.