A water quality analysis system to evaluate the impact of agricultural activities on N outflow in river basins in Japan

We have developed a personal-computer-based water quality analysis system for river basins. The system estimates potential N outflow by model and calculates actual N outflow from monitoring data. For the former it uses the potential load factor method to estimate annual nitrogen load from various sources and runoff potential from each area of land in a basin. For the latter it analyzes water quality monitoring data in relation to meteorological data. We used the system to analyze N outflow in basins around Lake Kasumigaura and the Yahagi River in central Honshu, Japan. The land around Lake Kasumigaura is rather flat, and about 25% is periodically flooded for rice and lotus cultivation. The land around the Yahagi River is mountainous, and much less land is flooded. In the Yahagi River basin the actual N outflow agreed closely with the potential. However, the actual N outflow in the basin around Lake Kasumigaura was much less than the potential, suggesting that a large part of the N load is denitrified in flooded soils. This further indicates that a sequence of different land uses including flooded rice fields is an important factor determining N outflow in basins in Japan. On the basis of the above analyses, we incorporated a denitrification model into the system that enables us to estimate N balance in a designated basin;this system may be helpful in the formulation of scenarios of land use andsoil management for improving water quality.     

Water quality of rivers in the drainage basin of Lake Peipsi

Water quality and general regularities that have taken place in the water quality of rivers in the drainage basin of Lake Peipsi have been studied. The lake is located in the basin of the Narva River. Several changes of the water quality of the lake in 1970–1990, caused by increasing human impact, have been observed. The water quality of Lake Peipsi depends on its pollution load whereby the main part of the pollution reaches the lake via rivers. In 1985–1989 an extensive research programme of the lake and its drainage basin was carried out. In this paper a part of these results as well as recent changes in the water quality of the rivers of the Estonian side are studied. In the last years an improvement of the general state of rivers in the drainage basin of Lake Peipsi has taken place; the content of organic substances and nutrients in the inflows of Lake Peipsi and in the Narva River (lake outflow) is decreasing.     

Late- and postglacial history of lakes of the Karelian Isthmus

The Late Pleistocene and Holocene history of five lakes in the central part of Karelian Isthmus, south of the present Vuoksi River, are described on the basis of sediment stratigraphical investigations. Two of the Lakes, Michurinskoe (94 m a.s.l.) and Uzornoe (55 m a.s.l.) are situated in an upland area that remained dry land after the deglaciation even during the early high water stages of the Baltic Sea (Baltic Ice Lake until c. 10 000 yr BP and Ancylus Lake 9500–8800 BP). The low-lying central parts of the Isthmus were flooded by the outflow of Lake Ladoga that took place across this area until the formation of Neva River, c. 3 100 yr BP, and further by the waters of River Vuoksi that started flowing into the area from the NW c. 5000 yr BP as a new outlet of Lake Saimaa. The basins of the lakes Krasnoe and Vishnevskoe (both 16 m a.s.l.) became isolated when River Neva was formed and Lake Ladoga sank to its present level. Lake Rakovoe (12 m a.s.l.) was on the level of River Vuoksi up until the mid-19th century, when water level in the central stretch of the river was artificially lowered. Each of the lakes has been variously affected by hydrological and climatic changes and consequences of human activities, e.g. eutrophication due to intensified land use. As a consequence to artificial lowering, done in order to gain field and meadowland, the large, shallow Lake Rakovoe has been largely overgrown by macrophytic vegetation.     

云南省抚仙湖和杞麓湖流域土地利用变化对水质的影响

基于遥感技术和相关性分析方法对云南省2个典型高原湖泊抚仙湖和杞麓湖流域土地利用与湖泊水质关系进行了研究.结果表明:1989-2005年2个流域森林(灌丛)和建筑用地大量增长,荒地和农田有所减少,杞麓湖的污染程度比抚仙湖严重,2个湖泊的水质都呈下降趋势;湖滨200 m左右的缓冲带变化明显,且比流域其它土地利用变化对水质影响更大;城镇化和密集的农业耕作产生的面源污染是影响湖泊水质状况持续下降的重要因素,2个湖泊流域的土地利用结构不同也导致二者之间水质的差异.     

Synergistic changes in river-lake runoff systems in the Yangtze River basin and their driving force differences

Climate change and human activities simultaneously alter river–lake relationships. Determining the dynamics of river–lake runoff systems on multiple time scales and their differences in response to driving forces can provide insights into hydrological processes and water resource management. This study investigates the synergistic evolution of river–lake runoff systems in the middle and lower reaches of the Yangtze River basin (MLYR) using the cross-wavelet transform method. The effects of different driving force changes on river–lake runoff regimes are quantified based on the Budyko hypothesis, and an InVEST model is developed to assess the spatial and temporal patterns of habitat quality. The results indicate that during the variation period, the runoff distributions of the Yangtze River–Dongting Lake and Yangtze River–-Poyang Lake runoff systems are both skewed towards lower values in the flood seasons compared with those in the base period. The storage of lakes mitigates the extent of human disturbance to the mainstream hydrological regime, particularly under extremely low conditions. From 1960 to 2021, five significant resonance periods are indicated in the river–lake runoff system, and the phase–angle relationships indicate a positive phase coupling between the lake and mainstream hydrological regimes, with the lake lagging behind the mainstream; however, this interaction tends to weaken. In the mainstream and Dongting Lake basins, subsurface conditions are the dominant factor contributing to runoff variability, with contributions ranging from 50.9% to 72.6%; in the Poyang Lake basin, precipitation is the dominant factor, with a contribution of 50.6%; and in the Han River basin, changes in the potential evapotranspiration contribute to 50.6% of runoff variability. The proportion of high habitat quality in the MLYR is approximately 52%, the Dongting and Poyang Lake basins indicate a high habitat quality rating. However, frequent human activity is the main reason of conversion from higher habitats to lower ones, which may result in wetland habitat degradation.     

Stratification and mixing processes associated with hypoxia in a shallow lake (Lake Kasumigaura,Japan)

Limnology - Physical processes associated with hypoxia events in a shallow lake, Lake Kasumigaura, Japan, are investigated with long-term mooring observations at the middle of the lake basin....     

The densities of bacteria, picophytoplankton, heterotrophic nanoflagellates and ciliates in Lake Kasumigaura (Japan) monitored monthly since 1996

This data paper describes the densities of the bacterioplankton, picocyanobacteria, eukaryotic picoplankton, heterotrophic nanoflagellates and ciliates in the water of Lake Kasumigaura??a shallow, eutrophic lake that is the second largest in Japan. All of these planktonic organisms are components of a microbial loop and are countable using an epifluorescence microscope. These data represent the results of monthly collections from April 1996 through March 2010 at two sites on the lake, and this data set is unique among the available published data papers concerning lakes or plankton and continues to be freely available. The monitoring was performed as a component of the Lake Kasumigaura Long-term Environmental Monitoring program conducted by National Institute for Environmental Studies since 1977 and includes water quality, plankton, and benthos. The data have been used for ecological studies and for studies on the management of water quality.     

Conservation of the Lake Kasumigaura population of Nymphoides indica (L.) Kuntze based on genetic evaluation using microsatellite markers

We compared the genetic diversity of the Lake Kasumigaura population of Nymphoides indica with that of pond populations in Hyogo and Kagawa Prefectures, which are thought to maintain high genetic diversity, to elucidate the current genetic diversity and occurrence of distinctive alleles in the Lake Kasumigaura population. The genetic diversity, as measured by the mean number of alleles per polymorphic locus, effective number of alleles per locus, mean observed heterozygosity, mean expected heterozygosities, total gene diversity, and number of multilocus genotypes was lower in the Lake Kasumigaura population than in the Hyogo and Kagawa populations. In addition, the inbreeding coefficient suggests that random mating does not occur in the Lake Kasumigaura population. The degree of genetic differentiation between the Lake Kasumigaura population and the Hyogo and Kagawa populations suggests that the Lake Kasumigaura population is largely genetically distinct. We found five genotypes in the Lake Kasumigaura population that were absent from the Hyogo and Kagawa populations. These results demonstrate that the Lake Kasumigaura population is an important component of the overall genetic diversity of N. indica in Japan.     

Identifying potential areas for biofuel production and evaluating the environmental effects: a case study of the James River Basin in the Midwestern United States

Biofuels are now an important resource in the United States because of the Energy Independence and Security Act of 2007. Both increased corn growth for ethanol production and perennial dedicated energy crop growth for cellulosic feedstocks are potential sources to meet the rising demand for biofuels. However, these measures may cause adverse environmental consequences that are not yet fully understood. This study 1) evaluates the long‐term impacts of increased frequency of corn in the crop rotation system on water quantity and quality as well as soil fertility in the James River Basin and 2) identifies potential grasslands for cultivating bioenergy crops (e.g. switchgrass), estimating the water quality impacts. We selected the soil and water assessment tool, a physically based multidisciplinary model, as the modeling approach to simulate a series of biofuel production scenarios involving crop rotation and land cover changes. The model simulations with different crop rotation scenarios indicate that decreases in water yield and soil nitrate nitrogen (NO₃‐N) concentration along with an increase in NO₃‐N load to stream water could justify serious concerns regarding increased corn rotations in this basin. Simulations with land cover change scenarios helped us spatially classify the grasslands in terms of biomass productivity and nitrogen loads, and we further derived the relationship of biomass production targets and the resulting nitrogen loads against switchgrass planting acreages. The suggested economically efficient (planting acreage) and environmentally friendly (water quality) planting locations and acreages can be a valuable guide for cultivating switchgrass in this basin. This information, along with the projected environmental costs (i.e. reduced water yield and increased nitrogen load), can contribute to decision support tools for land managers to seek the sustainability of biofuel development in this region.     

东江湖流域水供给服务时空格局分析

与水相关的生态系统服务是生态学研究的热点问题。水供给服务对区域水循环和水量平衡具有至关重要的作用。东江湖流域是国家重点流域和水资源生态补偿试点,水供给服务是该流域生态系统服务保护的重中之重。基于In VEST模型,从流域、子流域两个尺度分析1995—2010年东江湖流域的水供给服务时空格局,并比较了不同土地覆被类型的水供给服务能力。结果表明:(1)1995—2010年,东江湖流域水供给量整体呈现先增加后减少的趋势,年均水供给量在1100—1600 mm之间,2000年的平均水供给量最多。(2)各年水供给量的空间分布格局相似,由湖区向四周递增。(3)平均水供给量较高的土地覆被类型为城镇建设用地、典型草地、灌丛、灌丛草地,在1600 mm左右。平均水供给量较低的土地覆被类型为河湖滩地、内陆水体、水田,在800 mm以下。(4)各个子流域平均水供给量大致在750—1700 mm之间。东北部子流域为水供给服务的高值地区。从水量平衡的角度而言,降水和实际蒸散发是决定生态系统水供给量的两个关键环节。东江湖流域水供给量的时空格局差异是气候和土地覆被共同作用的结果。研究能够为东江湖流域的水资源管理提供科学的参考依据,对东江湖流域生态系统服务功能的提升、生态环境质量的改善、社会经济的可持续发展具有重要的现实意义。     

北京市白河和潮河流域生态健康评价

选取北京市重要的饮用水源密云水库上游白河和潮河流域,结合北京山区流域生态现状,构建了涵盖水域生境结构、水生生物、生态压力和陆域生态格局与功能、生态压力5大类13项指标的评价指标体系,开展了流域生态健康评价。结果表明白河和潮河流域的健康状态整体处于良好等级,但水生生物和陆域生态格局状况相对较差。14个子流域的健康状况差异并不显著,琉璃河、白河下段、汤河上游的健康状况相对较好,潮河中下段和小汤河的健康状况相对较差。流域内不合理的畜禽养殖、岸边带种植及民俗旅游是导致流域生态健康退化的主要原因,建议加强污染负荷排放的控制和监管涉水活动对水生生境的干扰以改善流域健康状况,并重点关注可指示水生态系统早期退化的生物指数,以实现可持续性和适应性的流域管理,保障密云水库的水生态安全。     

Hypoxia tolerance of three native and three alien species of bitterling inhabiting Lake Kasumigaura,Japan

Differences in hypoxia tolerance among three native and three alien bitterling species were examined by means of field surveys and aquarium experiments. I caught fish in minnow traps and measured environmental factors such as dissolved oxygen and current velocity once a month between June and November 2006 at 30 points around Lake Kasumigaura, Japan. In addition, aquarium experiments were carried out to compare aquatic surface respiration thresholds among the bitterling species. Much more individuals of an alien species, Rhodeus ocellatus ocellatus, was caught at the least oxygen range than expected in the field, and showed the highest hypoxia tolerance in the laboratory experiments. Another alien bitterling, Acheilognathus rhombeus, also showed higher hypoxia tolerance than the three native bitterling species. Lake Kasumigaura is well known for eutrophication and water masses with low dissolved oxygen have often been observed there. Differences in hypoxia tolerance among bitterling species might have affected bitterling assemblage structure in Lake Kasumigaura, which is currently characterized by the dominance of R. o. ocellatus.     

Unravelling and forecasting algal population dynamics in two lakes different in morphometry and eutrophication by neural and evolutionary computation

Precious ecological information extracted from limnological long-term time series advances the theory on functioning and evolution of freshwater ecosystems. This paper presents results of applications of artificial neural networks (ANN) and evolutionary algorithms (EA) for ordination, clustering, forecasting and rule discovery of complex limnological time-series data of two distinctively different lakes. Ten years of data of the shallow and hypertrophic Lake Kasumigaura (Japan) are utilized in comparison with 13 years of data of the deep and mesotrophic Lake Soyang (Korea). Results demonstrate the potential that: (1) recurrent supervised ANN and EA facilitate 1-week-ahead forecasting of outbreaks of harmful algae or water quality changes, (2) EA discover explanatory rule sets for timing and abundance of harmful outbreaks algal populations, and (3) non-supervised ANN provide clusters to unravel ecological relationships regarding seasons, water quality ranges and long-term environmental changes.     

Effectiveness of best management practices in improving stream ecosystem quality

Implementation of best management practices (BMPs), such as improved manure storage, buffer strips, and grassed waterways, through government funded conservation programs is a common approach for mitigation of the impacts agricultural activities have on the surrounding environment. In this study, we tested the ability of these practices to meet the environmental goal of improved stream quality at a “micro-basin” scale in the Upper Thames River Watershed, southern Ontario, Canada. Micro-basins were first and second order basins, averaging 400 ha in area, representing gradients of land cover, geomorphology, and participation in conservation programs. At the outflow of each micro-basin the benthic macro-invertebrate community was sampled, water chemistry measurements completed, and habitat quality assessed. Results showed micro-basins with relatively high levels of BMP implementation consistently demonstrated improved stream ecosystem quality over the majority of micro-basins with low or no implementation. Streams in the Upper Thames River basin appeared to exhibit a threshold effect, where with several BMPs in the same basin an improvement in stream ecosystem quality is visible. In addition to the BMPs implemented through government funded conservation programs, the observed ecosystem improvements are probably due to increased environmental awareness and improved management by farmers. Handling editor: K. Martens     

Circulation and the nutrient budget in Myall Lakes

A two-dimensional model is used to study transport of material within Myall Lakes and is coupled to the ocean using a one-dimensional model of Lower Myall River. Runoff from the catchment is calculated from water levels and compares favourably with rainfall assuming an average runoff yield of 28% and a runoff coefficient of 47% for events above the 90th percentile. Most of the runoff enters Bombah Broadwater which is also the only basin connected to the ocean. Intermittent runoff events rapidly displace water from Bombah Broadwater into Boolambayte Lake and from Boolambayte Lake into Myall Lake. Displaced water is mixed within basins by wind-driven circulation within the time scale that levels fall as water drains from the lakes to the ocean. Only 7% of the nutrient load entering Bombah Broadwater becomes resident Myall Lake. About 40% of the nutrient load entering Boolambayte Lake becomes resident in Myall Lake. Median time scales for loss of conservative material entering each basin with the runoff are: 140 days for Bombah Broadwater, 118 days for Boolambayte Lake, and 535 days for Myall Lake. Salinity fluctuates greatly in Bombah Broadwater but is stable in Myall Lake. Material loss from Bombah Broadwater is characterized by many time scales associated with runoff from the catchment and low-frequency changes in ocean water level. Comparison of observed distributions of total nitrogen with simulations indicates that there are sources of total nitrogen in Boolambayte Lake and Myall Lake and sinks of total nitrogen in Bombah Broadwater. There appear to be sinks of total phosphorus throughout the Myall Lakes.     

基于遥感生态指数的新疆玛纳斯湖湿地生态变化评价

以2000、2006和2016年3期的Landsat遥感影像为基础数据源,结合前人研究成果和实地考察,借助RSEI指数,对玛纳斯湖湿地生态环境进行监测和评价。结果表明:利用主成分分析技术集成植被指数、湿度分量、地表温度和土壤指数建立的RSEI指数具有一定的适用性,可较好的对玛纳斯湖湿地生态环境质量状况及其时空变化进行监测和评价。2000、2006和2016年RSEI指数均值分别为0.227、0.183、0.234,对RSEI指数进行分级处理后,发现流域生态环境质量"较差"等级居于主导地位,"优"等级有所增加,湿地生态环境质量向好的方向发展。气候变化和人类活动共同作用于玛纳斯湖湿地产生的生态环境效应,日益增强的人类活动是湿地退化的主要原因,多年来粗放型的农业发展使玛纳斯河流域人口、经济与生态环境之间的关系严重失调。从优化水资源配置角度提出对主要源流流域水土资源大规模开发的同时,应重视尾闾湖泊湿地的生态价值与可持续发展。     

基于生态系统敏感性与生态功能重要性的高原湖泊分区保护研究——以达里湖流域为例

内蒙古高原湖泊流域是我国北方地区重要的涵养水源区域,发挥着防汛抗旱、气候调节、生物多样性维持等多种生态系统功能。近几十年来,全球气候变化加之人类活动加剧,导致内蒙古高原湖泊的数量和面积大幅减少,流域生态系统的损害日益明显,严重威胁到了周边地区的生态安全,保护与治理内蒙古高原湖泊流域已逐渐成为社会各界关注及迫切需要解决的问题。面向内蒙古高原湖泊流域保护和管理需求,以改善和提升流域生态环境质量和生态系统功能为目的,以内蒙古高原湖泊达里湖流域为研究对象,基于流域生态特性和主要生态环境问题,选取水土流失、土壤侵蚀及土地沙化敏感性3个指标评价了流域生态系统敏感性,从水源涵养、土壤保持和生境质量重要性3个方面评价了流域生态系统功能重要性,并在此基础上,通过GIS空间分析技术将流域分为极重要敏感区,一般重要敏感区和低重要敏感区。结合流域内达里诺尔国家级自然保护区的生态重要性与3个区域评价结果,从生态保护角度将流域分为禁止开发区、重点保护区、质量提升区与潜在威胁区4个区域,同时提出针对每个区域特点的保护与管理对策。研究结果对提高高原地区湖泊流域生态环境质量以及对流域实施科学有效的管理提供了科学依据,同时在促进区域乃至全球生态建设和可持续发展方面具有重要的理论与现实意义。     

水文变异条件下鄱阳湖流域的生态流量

受气候变化和人类活动综合影响,鄱阳湖流域水文状况发生变异。河流生态系统适应了变异前的水文状况,变异后势必会影响当地生态系统。基于此,采用8种变异检测方法对水文变异进行综合诊断,阐明水文变异原因。在此基础上,采用15种概率分布函数分别拟合5站各月变异前日流量序列,最终确定5站点各月最优分布函数及所对应的概率密度最大处的流量,即得河道内生态流量。研究表明:(1)抚河于1962年发生弱变异,赣江、修河于1968年发生中变异,信江、饶河于1991年发生弱变异;(2)变异后,赣江、信江、饶河、修河生态需水满足率平均上升11%,抚河生态需水满足率下降32%;(3)水文变异增加提高生态需水满足率,水利工程建设降低年均生态需水满足率、提高干季生态需水满足率。高森林覆盖率提高干季生态需水满足率,对年均生态需水满足率影响不明显。研究结果为鄱阳湖流域水资源管理及区域水资源规划与配置提供重要科学依据。     

广东省水质现状及驱动因素

水质现状评估及其驱动因素分析是实现水生态保护、水资源利用和水污染治理的关键,对于水生态系统的可持续发展具有重要意义。以广东省七大流域为研究区,基于2019-2020年间的溶解氧（DO）、透明度（SDD）、悬浮物（SPM）、叶绿素a （Chla）、氨氮（NH₃N）、总氮（TN）、总磷（TP）7个指标的水质监测数据,综合运用单因子指数法（SI）和综合水质指数（WQI）评价方法,分丰水期（N=66）和枯水期（N=54）评估研究区的水质现状,并探讨水质参数与地形、气象、社会经济和土地覆被类型等驱动因素之间的相关关系。SI评估结果显示广东七大流域主要以工业污水、农业面源等造成的Chla和TN浓度超标、部分水体富营养化严重为主,同时伴有溶解氧浓度偏低的问题;WQI评估结果显示研究区有57%以上的采样点属于中等以下水质。Chla、SPM、NH₃N和TP浓度具有显著的季节和驱动因素差异：丰水期的Chla和TP浓度低于枯水期,但SPM和NH₃N浓度高于枯水期。枯水期DO、TN和WQI的显著性影响因子为丰水期的1/3左右;这种季节差异可能是流域内降雨、营养盐负荷和土地覆被类型导致的复杂地表径流及面源污染所致。珠江三角洲河网区、粤西诸河、韩江下游以及粤东诸河练江流域的水质问题突出。未来水生态系统的可持续发展研究可以借助长时间序列、多频次、高分辨率的遥感监测手段和多种数值模拟方法以及常规水质评估模型,探讨气候变化、河岸带产业结构和流域土地利用方式对面源污染的影响,以进一步厘清降雨强度、三产结构和土地利用方式转变对区域水质变化的影响。     

岷江上游不同景观结构小流域水量平衡的比较

研究了1988～2002年岷江上游两个小流域（镇江关流域和黑水河流域）不同景观结构（土地覆盖、海拔、坡度、斑块密度、最大斑块指数等）对水量平衡的影响.基于两个流域土地覆盖类型、1988～2002年多年平均降水量和蒸散量的空间分布、两个流域土地覆盖类型同期多年平均径流深度的数据,得到不同土地覆盖类型的海拔、坡度、坡向与降雨、蒸散、径流的关系.结果表明,两个流域有林地海拔、坡度、坡向的不同导致其降水、蒸散降水比、径流降水比各异;两个流域草地水量平衡对景观格局的响应模式与有林地基本一致;由于黑水河流域的耕地分布在干旱河谷中,其蒸散量远远大于降水量,耕地本身的景观结构（坡向、坡度,斑块密度）并不对其水量平衡产生影响,这一点与镇江关完全不同.