风场和吞吐流对洪泽湖流场的影响分析

采用MIKE21建立洪泽湖二维水动力数学模型,通过对模型参数的率定,使得模型的计算结果能较好地与实测值相符合,进而研究了不同风场和吞吐流条件下的洪泽湖水动力特性,比较了2013年洪泽湖在5、10 m/s风速和无风条件下的流场。结果表明:风速会改变流场强度的大小而不会改变流场结构;同时,风场的作用会影响洪泽湖的出流能力,湖区流速随风速的增加呈减小的趋势。吞吐流是影响洪泽湖流场的主要因素,采用2007洪水年进行模拟时,进出口湖区流场会发生明显改变。洪泽湖的溧河洼区和成子湖区流场结构主要由风场决定,而南部湖区和东部湖区流场结构由风场和吞吐流共同决定,且以吞吐流为主。研究结果可以为洪泽湖物质输移规律研究提供理论基础。     

新型防洪减灾措施在洞庭湖中的模拟应用研究

为提高洞庭湖的防洪能力及增强其枯水期供水能力,提出了适用于洞庭湖区的新型防洪减灾措施——“河湖分离”方案。通过采用数值模拟方法,以洞庭湖1996年型洪水为例,探讨了“河湖分离”方案对洞庭湖区防洪效果的影响,并统计分析了在应用该方案后洞庭湖1996-2014年的蓄水能力。结果表明：洞庭湖实施“河湖分离方案”后,若遇1996年型洪水,湖内有效防洪库容可由1996年的20.91×10⁸ m³增加至119.01×10⁸ m³,从而增强了洞庭湖的削峰能力。通过统计分析发现,洞庭湖具有很大的蓄水潜力,即使在年极端干旱年份（比如2006及2011年）,“河湖分离”方案仍能使得洞庭湖的可用蓄水量超过18.0×10⁸ m³,这说明“河湖分离”方案能有效地缓解洞庭湖区季节性缺水的状况。     

改进综合水质指数法的乌伦古湖水质空间特征

湖泊水质状况是识别湖泊变化、评价湖泊健康的重要指标,关系流域生态环境安全。以典型干旱内陆湖泊———乌伦古湖为研究对象,采用改进综合水质指数法(WPASEQI)并结合GIS技术对乌伦古湖湖区(吉力湖、布伦托海)2017年水质状况及空间分布规律进行研究。结果表明:(1)乌伦古湖水质类别及状况为Ⅲ类、轻度污染,其中,吉力湖水质类别为Ⅱ类,布伦托海水质类别为Ⅲ类,水质空间分布特征表现出越靠近湖中心东部区域,以及越远离进水口区域水质污染越严重的基本规律;(2)乌伦古湖水质污染关键超标因子为COD、COD_(Mn)、TN、TP、氟化物,其空间分布特征表现为,COD、COD_(Mn)与氟化物指标浓度空间分布规律大致相似,呈现出吉力湖优于布伦托海、进水口优于湖心区的空间分布特征;TN、TP指标浓度变化差异较小,大体呈现出进水口优于湖心区、布伦托海西部优于东部的特征;(3)富营养物、有机物以及无机物是乌伦古湖水质主要污染来源,气候变化与人类活动是导致湖泊水质进一步恶化的驱动力。     

新型渠道清淤技术与设备研究

国家重点水利工程南水北调工程、东调南下工程、引黄济青续建工程等建成后,部分干线渠道除调水外还要承担排涝泄洪的任务,泥沙淤积在所难免。根据南水北调东线工程混凝土衬砌输水渠道清淤,研制了一种通过吸泥系统、泥浆输送系统完成清淤疏浚任务的高度自动化的潜水疏浚机,可以接收岸上人员的指令或者自主判断水下淤泥的分布情形,并以此决定在水下的行走方式,实现转弯、避碍,控制自身在水中的方位。这种小型清淤设备可以应用于渠道、湖泊、航道的环保清淤、水库清淤、沉砂池清淤、河道治理等。同时这种清淤设备还能做到在水下清淤疏浚过程中不引起环境的二次污染,不造成断流,具有高效、节能、方便操作、劳动强度小,适应作业范围宽及低成本等优点。     

南水北调东线工程运行对南四湖水环境影响评价

在综合分析南水北调东线工程对南四湖水环境影响基础上,将层次分析法改进,结合模糊评价方法,量化评价指标,突出体现了这种方法在定性指标量化方面显示的优势。南水北调东线工程对南四湖的水环境影响评价最终结果是0.640,说明调水工程会对南四湖水生态环境产生一定正面影响。     

Comparative spatial metal concentrations and partitioning in bottom sediments of two tropical freshwater lake basins,Kenya

Metal concentrations in the water, sediments and biota in alkaline, near neutral water tropical freshwater lake basins were determined and a comparative analysis made on the spatial and accumulated trace metal concentrations, and geochemical partitioning of iron (Fe), manganese (Mn), copper (Cu), chromium (Cr), zinc (Zn), nickel (Ni), cadmium (Cd) and lead (Pb) in bottom lake sediments. Variable accumulated levels were found in the analysed sediments and aquatic biological tissues. Metal partitioning data in the present study from the two areas exhibits similar trends in magnitude. The residual fractions retained relatively higher amounts of metals. Relatively higher contents of Pb, Cr and Cu were found in Lake Victoria sediments. Cd, Ni, Mn and Pb are of concern because a higher percentage of these metals were retained in the more bioavailable fractions in Lake Naivasha. Total levels of sediment mercury were comparable for the two lake basins. Metals were found in significant levels in the tissues of aquatic organisms, highlighting the potential risks to other levels within the aquatic food chain. Although the exposure risk was not evaluated, it is important to continue monitoring these elements in fish, as sediments were found to contain considerable quantities of the metals. Numerous sediment extraction techniques data applied for evaluating metal partitioning in sediments cannot be compared because of the use of different methods. Nevertheless, the information is still useful in differentiating and understanding pollution loads from natural versus anthropogenic sources and their associated risks.     

Modeling runoff from an agricultural watershed of western catchment of Chilika lake through ArcSWAT

Chilika lake is the biggest lagoon in the Indian Eastern coast and is a source of livelihood for peoples of the coastal region surrounding it mainly through fisheries. However, the deposition of sediments in the lake carried through runoff water from its drainage basins may alter this wetland ecosystem in future. Implementation of appropriate soil water conservation measures may reduce the sediment load in runoff water and thus may protect this lagoon ecosystem. Keeping in view these concerns, runoff water from a selected watershed of western catchment of Chilika lagoon was modeled through ArcSWAT with a purpose to estimate future runoff potential from western catchment. Effective hydraulic conductivity of main channel, base flow alpha factor, curve number corresponding to antecedent moisture content II, and roughness coefficient of main channel were found most sensitive parameters in decreasing order. Nash–Sutcliffe coefficient of predicted monthly runoff was 0.72 and 0.88 during calibration and validation period, respectively whereas root mean squared error of predicted monthly runoff was 54.5 and 66.1 mm, respectively. Modeling results indicated that about 60% of rainfall is partitioned to runoff water, which carry significant amount of sediment load and contributes to Chilika lake.     

简述乌伦古湖入湖水量及湖水位情势分析

由于乌伦古河河川径流具有连续枯水年且枯水时段长的特点,且乌伦古河在连续枯水年份出现断流是一种不可抗拒的自然因素,需要在流域综合规划指导下,具体研究吉力湖和布伦托海入湖水量及水位变化情势,尽可能恢复乌伦古河流域原有生态,保障洄游性鱼类所需要的流量要求,显著减少布伦托海湖水向吉力湖倒灌发生的时间和倒灌水量,使乌伦古湖和周边生态系统有所好转。     

Relative demand by double-crested cormorants and anglers for fish production from lakes on Manitoulin Island,Lake Huron

The magnitude of angler harvest (kg·ha^− 1·yr^− 1) and cormorant consumption (kg·ha^− 1·yr^− 1) were compared for a set of lakes (N = 11) on Manitoulin Island. Empirical models relating total phosphorus to total fish production as well as production to body mass were used to scope the possible range of fish production and to partition production among small, medium and large size segments of fish populations, respectively. Medium (66–112 g) and large (> 200 g) size segments were defined as size categories targeted by cormorants (stomach diet analysis) and anglers (creel interviews), respectively. Angling effort and cormorant density were estimated from aerial surveys of the lake set during the open water season and for anglers during the winter ice-fishing season. Results showed that anglers harvested almost all large fish production, assuming the mean total fish production model, and 43% of large fish production under the more optimistic upper 80% prediction limit of total fish production. Cormorant consumption of medium fish production was less (39% using mean regression model; 15% using upper 80% prediction model) than angler consumption of large fish production. Anglers therefore imposed more population stress on their preferred sizes of fish than cormorants imposed on their preferred sizes of fish. Population stress was increased when cormorant consumption of medium size fish was discounted from contributing to large fish production. Angler harvest near (or above) sustainable yield levels will be exacerbated and appear as a fish collapse when cormorants consume fish production destined for fish size segments preferred by anglers.     

Shifting status and distribution of range margin chorus frog (Pseudacris) populations in eastern Great Lakes watersheds

Contiguous with their range across major rivers into Canada, two different species of chorus frogs are now thought to inhabit the Great Lakes watersheds of New York. Pseudacris triseriata is found along the western Lake Ontario and Lake Erie plains while P. maculata (tentatively a new frog species in NY) inhabits the lowlands of eastern Lake Ontario and the St. Lawrence River. Both species are on their extreme range margins in NY. In 2010 we detected distributional declines of both putative chorus frog species based on a broad survey following standardized occupancy detection protocols. Causes are unclear but could relate to reforestation and urbanization of formerly more extensive agricultural lands, climate change, pathogenic fungal outbreaks and/or the contaminant effects of intensive agriculture. On the other hand, the prior overestimation of ranges because of misidentification may have inflated earlier perceived distributions (positive survey bias) because false positives are problematical for this cryptic frog. At broad geographical scales, chorus frog (meta)populations are highly dynamic and are likely shifting their ranges in response to rapidly changing overall environmental conditions in the northeastern U.S. and Canada.