Lake Biwa: Have sustainable development objectives been met?

The need to control and manage the effects of urban, industrial and agricultural development on Lake Biwa, Japan's largest lake, led to the formation of the Lake Biwa Comprehensive Development Project (LBCDP). This article describes the nature and effects of the development, how the LBCDP was conceptualized, implemented and managed, and comments on its effectiveness. Although the basic objective of the project was to promote development of the Keihanshin region by providing additional water, other important objectives included the conservation of the natural environment, the promotion of public welfare, and the restoration of water quality. To achieve objectives on a sustainable basis, extensive political, legislative, social, technological and environmental matters needed comprehensive consideration. This article considers such matters in detail.     

鄱阳湖流域典型稻田水量平衡分析

为探索稻田田间水量平衡要素之间关系及其影响因素,通过在鄱阳湖流域赣抚平原灌区选取典型田块,结合江西省灌溉试验中心站系列灌溉试验资料,开展了稻田田埂渗流试验和田间水量平衡试验。田埂渗流试验表明,田埂侧向渗流速度为3.97 mm/d,侧向渗流占稻田蒸渗量49.2%,这一部分水将在下田块或下游区域得以重复利用;上框和双套环水位呈直线下降趋势,在田面低水层情况下(田面覆水30 mm),田面覆水深度对田间渗漏影响较小,田间渗漏(垂直入渗和侧向渗流)保持一个相对平稳状态。田间水量平衡试验表明,典型地块的灌水量和排水量明显小于有底测坑;在一季稻全生育期内,典型田块的侧向渗流在当地稻田渗漏量中占相当大比例,占全生育期耗水量的10.9%。     

从生活环境主义的立场解读琵琶湖流域的河川管理

为了解决伴随城市化发展、过度开发产生的河川环境污染问题,使人与河川和谐相处,以日本琵琶湖河川管理为实例,从社会学理论之一,即生活环境主义的立场出发,提出水利工程应该在考虑与河川生态系统共生的前提下进行可持续利用;在河川与流域管理中,注重恢复河川生物多样性,增加河川活力,实行管理部门与当地居民共同参与的方针。     

Present status of submerged macrophyte growth in Lake Biwa: Recent recovery following a summer decline in the water level

Whole‐lake areal distribution of submerged macrophyte growth in Lake Biwa was surveyed using aerial photographs in 1994 and 2000, when unusual declines in the water level of approximately 1 m occurred in the dry summers. The estimated total areas of the submerged macrophyte communities were 1441 ha for 1994 and 2825 ha for 2000. In the shallow and eutrophic southern basin, the bottom area covered by vegetation gradually increased year by year after 1994, and the ratio of this area to the total surface area of the basin in 2000 amounted to 52%. The dominant species were two natives, Hydrilla verticillata and Myriophyllum spicatum, and one exotic, Egeria densa. Changes in physical conditions and water quality associated with the decline in the water level, as well as the reactions of submerged plants to aquatic environments and ecosystem dynamics, are discussed.     

High-performance liquid chromatography-bioassay profiles of endocrine disrupters discharged from point and non-point pollution sources in Lake Biwa basin

Toxic pollution loading from both point and non‐point sources in Lake Biwa should be further reduced. In order to tackle toxicity problems, it is necessary to analyse characteristics of toxic pollution. We have developed a new profiling technique to display toxic distributions of endocrine disrupters in complex mixtures of environmental samples, using high‐performance liquid chromatography in combination with yeast bioassays. We have applied this technique to the major point and non‐point pollution sources in the Lake Biwa basin, that is, to municipal sewage‐treatment water (point) and road dust (non‐point). The dominant oestrogenic chemical in sewage‐treatment water was 17 β‐estradiol. The extracts from screened road dust showed arylhydrocarbon‐receptor binding activity (AhR–ligand activity), with much of this located in smaller particles of sifted dust. There were at least seven major AhR–ligand peaks in the road‐dust sample.     

太湖出入湖水质评价

１９８７年沿太湖历年巡测线进行了４次水文、水质同步监测，共有１３９条河道参加评价，有水文，水质监测项目３８个，评价中水质采用五级水标准，选用ｐＨ值等１８项指标和为评价参数，评价结果表明，入太湖水质污染主要以有机污染为主，出湖污染主要在江苏湖东段，占总量的６０％，因此，保护好太湖水质必须控制和减少入湖污染物量，加强污染源治理，限制污染行业发展。     

兴凯湖生态水位分析

基于兴凯湖1914~1957年水位过程线和水位-面积-库容曲线,通过计算兴凯湖多年平均和80%保证率水平年的来水量,并结合近期和远期需水量,进行水量平衡分析。结果表明,兴凯湖具有较大的调节功能,即使连续6年出现历史上水位从多年平均水位下降至历史最低水位,兴凯湖也能满足近期和远期水量需求。经分析、计算和推理,认为以1925年兴凯湖水位67.88 m为最低生态水位是合适的。     

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。     

环太湖出入湖水量影响因素分析及对策措施研究

在收集整理1986—2007年环太湖河道出入湖水量实测资料的基础上,利用面积包围法及相关法,以太湖流域水资源四级分区为统计单元对环太湖出入湖水量进行计算分析。结果表明:降雨、水资源调度及太湖直接取水户取水量变化为影响出入湖水量变化的主要因素。建议水行政相关部门建立健全水资源监控系统,并加快制定和实施太湖水量分配方案,加强取水许可监督工作。     

东平湖区高浓度污染水团的发生规律监测研究

为摸清汛期大汶河泄洪进入东平湖区的高浓度污染团的发生规律,减少和防止东平湖水污染事故的发生,根据1999～2001年环境监测资料,找出了主要污染指标是泥沙悬浮物、总氮和化学需氧量,查清了污染水团的发生原因、规律和特点,并提出了防治措施建议。     

梦湖水资源平衡分析

采用参证站连续水文资料,对无资料地区梦湖水资源进行平衡分析。为开发梦湖风景区,充分发挥梦湖在抚州市美化环境的作用,提高梦湖水资源的保证率提出了建议:湖区应进行防渗处理,雨、污分流,避免污水进入湖区等。     

基于大辽河上游水库来水与压盐流量关系的研究

根据大辽河上游水库的来水量,通过对营口境内历年灌区各提水站的实际提水量比较,经过分析从而得出压盐流量与水库来水之间的关系。其结论为：大辽河槽内必须保持淡水7000～9000万 m3,才能保证压盐流量至田庄台,两岸才能正常引水。水稻泡插期严重缺水年份,大辽河盐分太高,水库加大放流压盐效果明显。     

兴凯湖最低生态安全水位研究

基于兴凯湖1914～1957年水位过程变化线和水位～面积～库容曲线,通过计算兴凯湖多年平均和80%保证率水平年的来水量,并结合近期和远期需水量,对其进行了水量平衡分析.结果表明,兴凯湖具有较大的调节动能,即使连续6年出现历史上水位从多年平均水位下降至历史最低水位,兴凯湖也能满足近期和远期水量需求.经分析、计算和推理,认为以1925年兴凯湖水位67.88 m为最低生态水位是合适的.     

白洋淀水环境承载能力计算及保护措施探讨

通过对白洋淀水量、水质平衡分析,建立水质模型,对水环境承载能力进行计算,提出白洋淀水环境保护措施:加强污水灌溉和土地处理系统工程建设;建立湿地利用和污水净化工程;采取合理的水产养殖和水质控制技术措施。     

Development of a spatially resolved linked hydrodynamic and exposure model (LOTOX2) for PCBs in Lake Ontario

A linked hydrodynamic–hydrophobic organic chemical mass balance and food chain bioaccumulation model, LOTOX2, was developed to support the Lake Ontario Lakewide Management Plan (LaMP) for establishing contaminant load reduction strategies. This paper describes the development of LOTOX2, including the linkage with a relatively finer-scale hydrodynamic model (the Princeton Ocean Model, POM). An important component of this development was the reconstruction of PCB loading history (1930–2005), which was used to understand historic trends and to conduct model calibration/confirmation for total PCBs (tPCBs) in the lake water, sediments, and adult lake trout using data for the last 25 years. A separate mass balance was conducted for the radioisotope cesium-137 (¹³⁷Cs) in order to develop a sorbent mass balance model for the system. Following calibration and confirmation, a diagnostic application of the model showed that the lake is not yet at steady-state with current loads. It will take more than 50 years for tPCB concentration in lake trout to decrease to a steady-state value of about 0.4 ppm if year 2005 loads remain constant. If all external loads were instantaneously eliminated in 2005, it would take approximately 40 years for the adult lake trout tPCB concentration to reach 0.05 ppm (the uniform Great Lakes protocol value for unrestricted consumption) from its current level of 0.74 ppm.     

Modelling natural conditions and impacts of consumptive water use and sedimentation of Lake Abaya and Lake Chamo, Ethiopia

There is few available information regarding the water resource systems of Abaya Lake and Chamo Lake, which are found in the Southern Rift Valley Region of Ethiopia. This paper describes modelling of the water balance components of these lakes, as well as the impacts of water uses, and sediment transport and deposition in the lakes. The various parameters and data needed for the water balance model are derived on the basis of various surveys, analysis of data and modelling efforts. The watershed characteristics are derived using geographical information system, whereas the morphometry of the lakes is investigated by undertaking bathymetry surveys. The hydrometeorological components of this lake system also were investigated through the development of relevant database and information systems, by identifying regional relationships, and by a rainfall‐run‐off model. These information systems have subsequently been integrated to model the water balance of the two lakes, and simulating the in‐lake water levels. Several scenarios reflecting the natural conditions, water consumptive development possibilities, and sedimentation impacts have been investigated in this study. Based on the model simulation results, and on the computation of the life expectancies of the two lakes, it was found that sediment inflow and deposition significantly threaten their existence.     

Disrupted seasonal cycle of the warm-adapted and main zooplankter of Lake Biwa,Japan

The seasonal cycle is an important feature of life, leading to the succession of different species and allowing them to share a common environment. Disruption in the seasonal cycle of many species has been reported, but the source of disruption varies from species to species. Lacustrine zooplankton species are widely acknowledged to respond to climate-induced, thermal and trophic variations. Here, we discuss the case of a warm-adapted copepod in Lake Biwa (i.e., Eodiaptomus japonicus), which experienced changes in trophic status and thermal regime over four decades (1966–2010). We investigated the phenological response of E. japonicus to these changes over this period and aimed to identify the sources of the observed variations. The combined results of wavelet analysis and cluster analysis indicated that E. japonicus exhibited different seasonal cycles during the study period. The common unimodal seasonal cycle of the copepod was disrupted on several occasions during which it presented sometimes two or three modes. Wavelet coherence analysis revealed a strong stationary correlation with lake temperature for the total abundance, the clutch size, and the birth rate, but a transient correlation with the body size of females at the annual scale. No coherence was found with food proxies. Discriminant analysis between unimodal and plurimodal seasonal cycles highlighted the effect of low temperature and high predation in leading to plurimodal cycles. Our study emphasizes the need for considering the seasonality of both lower and higher trophic levels for understanding zooplankton phenology.