Inter‐annual changes of alpine inland lake water storage on the Tibetan Plateau: Detection and analysis by integrating satellite altimetry and optical imagery

The effects of climate change have a substantial influence on the extremely vulnerable hydrologic environment of the Tibetan Plateau. The estimation of alpine inland lake water storage variations is essential to modeling the alpine hydrologic process and evaluating water resources. Due to a lack of historical hydrologic observations in this remote and inaccessible region, such estimations also fill a gap in studies on the continuous inter‐annual and seasonal changes in the inland lake water budget. Using Lake Siling Co as a case study, we derived a time‐series of lake surface extents from MODIS imagery, and scarce lake water level data from the satellite altimetry of two sensors (ICESat/GLAS and ENVISAT RA‐2) between 2001 and 2011. Then, based on the fact that the rise in lake water levels is tightly dependent on the expansion of the lake extent, we established an empirical model to simulate a continuous lake water level dataset corresponding to the lake area data during the lake's unfreezing period. Consequently, from three dimensions, the lake surface area, water level and water storage variations consistently revealed that Lake Siling Co exhibited a dramatic trend to expand, particularly from 2001 to 2006. Based on the statistical model and lake area measurements from Landsat images since 1972, the extrapolated lake water level and water storage indicate that the lake has maintained a continual expansion process and that the cumulative water storage variations during 1999–2011 account for 66.84% of the total lake water budget (26.87 km³) from 1972 to 2011. Copyright © 2013 John Wiley & Sons, Ltd.     

GLEAM和MOD16蒸散发产品在青藏高原中东南湖泊流域的适用性评价

GLEAM(Global Land Evapotranspiration Amsterdam Model)和MOD16(MODIS Global Evapotranspiration Project)全球蒸散发产品已经得到了广泛的检验和应用,但由于观测资料缺乏,尚缺少对高原地区的检验。本文以青藏高原然乌湖流域、羊卓雍错流域、纳木错流域、色林错流域和塔若错流域为检验区域,利用流域水量平衡法,采用相关系数、相对误差、均方根误差和Kling-Gupta系数,对这两种蒸散产品开展了精度验证与评价。结果表明:GLEAM蒸散发产品在然乌湖、色林错和塔若错流域整体存在低估现象,在羊卓雍错和纳木错流域存在轻微高估现象,而MOD 16产品仅在色林错流域有轻微低估现象,在其他湖泊流域均表现为高估;GLEAM和MOD16蒸散发产品在5个湖泊流域年降水量较少的年份均存在高估的现象,在湿润年份则为低估;GLEAM产品在然乌湖流域、羊卓雍错流域和色林错流域的验证结果相对较好,而MOD16产品在纳木错流域和塔若错流域的验证精度相对较高;总体而言,在年尺度和多年平均尺度下,GLEAM蒸散发产品在青藏高原中东南湖泊流域...     

洞庭湖水面面积与城陵矶水位之间的绳套关系

洞庭湖是我国第二大淡水湖,与长江连通,在防洪抗旱和湿地生态保护等方面具有重要的现实意义.采用Terra/MODIS L1B遥感数据,提取了2000-2012年洞庭湖水面面积,结合同期城陵矶水位观测数据,建立了城陵矶水位与洞庭湖水面面积的绳套关系曲线.分析结果表明:2000-2012年间,洞庭湖水面面积呈现总体减少的趋势;在季节上表现为规律性的涨落,具有明显的涨(4-6月)-丰(7-9月)-退(10-12月)-枯(1-3月)的水文特征;在空间格局上表现为由湖体中心向外扩张,随后由外向湖体中心逐渐收缩的变化过程;洞庭湖水面面积与城陵矶水位之间具有较高的相关性,但不同时期的相关系数存在一定的差异:枯水期二者相关性较低,丰水期相关性最高,涨水期和退水期相关性较高;这种差异与各个时期的主导因素不同有关,长江来水对枯水期、丰水期的绳套关系影响较大,其中东洞庭湖最为明显;不论丰水年(2002年)或干旱年(2011年),洞庭湖水面面积变化与城陵矶水位之间的相关性均较高.研究结果对于深入认识江湖关系的宏观复杂性、长江中下游地区以及洞庭湖水域洪涝灾害的预防和治理都具有积极的意义.     

Sturmeinfluß auf das Tiefenwasser des Zürichsees im Winter

Summary During the period of partial circulation in the Lake of Zurich at the end of 1949 and the beginning of 1950, winds blowing in general up the lake led to an accumulation of surface water rich in oxygen in the lee half and a windward drift in the lower layers of water poor in oxygen. At the beginning of February 1950 the lake was, although homothermal, only mixed to a depth of about 80 m because of the increased specific gravity of the deep water (meromictic condition). During February strong and continued winds blew up the lake; these produced gradient currents which forced oxygen-poor bottom water (lying originally at 100 to 140 m depth) to the windward end where it welled up to the 55 m level. Over a horizontal distance of 12 km this represented a rise in level of this layer of sometimes more than 50 m. Subsequent oscillations of the water masses continued for several weeks; but nothing certain can be stated about possible affects of later winds in maintaining the oscillation, as only the winds in February were constant in character and blowing along the longitudinal axis of the lake. Such movements of bottom water caused by wind are important for the aeration of the lake, for the fishery and for an assessment of the lake's condition.      

Factors affecting seasonal patterns in epilimnion zooplankton community in one of the largest man-made lakes in Africa (Lake Nasser, Egypt)

The objective of the study was to determine which factors regulate zooplankton organisms along Lake Nasser. Temperature, pH, DO, conductivity, turbidity, nutrients, and zooplankton abundance were measured. Twenty-three species of zooplankton were recorded in Lake Nasser included in Copepoda, Cladocera and Rotifera. Copepoda represented the main bulk of the community. The lowest standing stock of zooplankton was noticed during spring due to the highest fish predation during this season associated with the lowest turbidity. Big difference in temperature in Lake Nasser along the year round is considered as a controlling factor related to range of tolerance of species. The oscillation of the lake water level and the different factors affect the standing stock of zooplankton in the lake. Thus, continuous monitoring of Lake Nasser biota should be undertaken to follow the changes in the ecosystem.     

Wind-induced hydrodynamic changes impact on sediment resuspension for large,shallow Lake Taihu,China

The internal sediment release is a key factor controlling eutrophication processes in large,shallow lakes.Sediment resuspension is associated with the wave and current induced shear stress in large,shallow lakes.The current study investigated the wind field impacts on sediment resuspension from the bottom at Meiliang Bay of large,shallow Lake Taihu.The impacts of the wind field on the wave,current,and wave-current combined shear stresses were calculated.The critical wind speed range was 4–6 m/s after which wave and current shear stress started to increase abruptly,and onshore wind directions were found to be mainly responsible for greater shear stress at the bottom of Lake Taihu.A second order polynomial fitting correlation was found between wave(R^2 0.4756)and current(R^2 0.4466)shear stresses with wind speed.Wave shear stress accounted for 92.5% of the total shear stress at Meiliang Bay.The critical wave shear stress and critical total shear stress were 0.13 N/m^2 for sediment resuspension whereas the current shear stress was 0.019 N/m^2 after which suspended sediment concentrations(SSC)increased abruptly.A second order polynomial fitting correlation was found between wave(R^2 0.739),current(R^2 0.6264),and total shear stress(R^2 0.7394)with SSC concentrations at Meiliang Bay of Lake Taihu.The sediment resuspension rate was 120 to 738 g/m^2/d during 4–6 m/s onshore winds while offshore winds contributed ≥ 200 g/m^2/d.The study results reveal the driving mechanism for understanding the role of the wind field in sediment resuspension while considering wind speed and direction as control parameters to define wave and current shear stresses.     

西洞庭湖沉水植物分布格局对环境因子及水文情势差异的响应

沉水植物是湖泊生态系统的重要组成部分,其生产力和分布格局受环境因子特别是水文情势决定.洞庭湖是长江流域重要的大型通江湖泊,近年来受人为干扰和气候变化影响,水文节律与水质等环境因子发生改变,导致沉水植物出现衰退现象,急需开展科学恢复,因此有必要对洞庭湖沉水植物深入研究.本研究选取西洞庭湖为研究区域,于2018年和2019年夏季调查了12处典型生境、98个样点的沉水植物与水深、透明度等11个环境因子,采用独立样本T检验和冗余分析方法对沉水植物与环境因子的关系进行分析,对比年际水文情势变化的影响.结果表明：1）西洞庭湖沉水植物主要在水深较浅、水质更优、水体更为稳定的半阻隔子湖和自由连通的湖湾区分布,在河道及水位波动较大的区域分布较少,有、无沉水植物分布样点间存在显著差异的环境因子为水深、透明度、底泥总磷和pH;2）在有沉水植物分布的样点,沉水植物生物量与pH、水深和水体总磷呈显著相关关系;3）自然连通的季节性淹没湖泊沉水植物生物量在2018年高于2019年,可能与2019年5—8月沉水植物关键生长期出现的涨水过程有关,持续的高水位对沉水植物的生长产生了不利影响.维持自然水文节律、湖泊生境异质性与自由连通性、健康的水质等是恢复西洞庭沉水植物的关键,建议在水深低于3 m、营养盐浓度适中、流速及风浪较小的湖湾区或半阻隔湖泊开展沉水植物恢复.     

Three-dimensional numerical modeling of cohesive sediment transport and wind wave impact in a shallow oxbow lake

It was observed that in some closed inland lakes sediment transport was dominated by wind-induced currents, and the sediment resuspension was primarily driven by wind-induced waves. This paper presents the development and application of a three-dimensional numerical model for simulating cohesive sediment transport in water bodies where wind-induced currents and waves are important. In the model, the bottom shear stresses induced by currents and waves were calculated, and the processes of resuspension (erosion), deposition, settling, etc. were considered. This model was first verified by a simple test case consisting of the movement of a non-conservative tracer in a prismatic channel with uniform flow, and the model output agreed well with the analytical solution. Then it was applied to Deep Hollow Lake, a small oxbow lake in Mississippi. Simulated sediment concentrations were compared with available field observations, with generally good agreement. The transport and resuspension processes of cohesive sediment due to wind-induced current and wave in Deep Hollow Lake were also discussed.     

近2000年淮河流域地理环境的变化与洪灾——淮河中游的洪灾与洪泽湖的变化

近2000年来淮河流域的洪涝灾害十分频繁。作者认为淮河中游的洪涝灾害与洪泽湖的演变有非常密切的关系。洪泽湖本是人工筑堤蓄水而形成的。湖区水位的上升与湖底淤高,势必会引起淮河中游发展溯源加积和洪水位的上升。估计鲁台子-蚌埠河段平均每公里河长加积了约3400×10～4t泥沙,由此造成泄洪不畅,加剧了洪害。     

巢湖快速变化风浪场及其环境效应

浅水湖泊风浪过程对于湖泊生态系统具有重要的意义.基于巢湖风场、风浪和水环境参数同步高频观测结果,详细分析了快速变化风场下的风浪快速变化特征及其对湖泊水环境的影响特征.浅水湖泊风浪的有效波高和平均波周期均随风速的快速变化有较好的同步响应规律.在风速快速衰减阶段,相较有效波高,波周期有更好的稳定性.湖泊水体pH、水温、溶解氧会快速响应风浪的变化,随着风浪强度增强,对水体浊度、总磷浓度以及藻密度和生物量的扰动影响逐渐呈现.强烈的风浪扰动引起水体浊度变化的滞后时间可达3 d.快速变化的风浪场下,风浪的强烈扰动会改变水体固有的理化参数分布特征,扰动藻类常规的水体分布规律,风浪强度是造成差异的主要因子.     

从沉积物特征谈太湖的演变

通过太湖湖底淤泥层中的微体古生物及其物理化学分析,在西太潮W1孔发现多门类海相化石。海相化石出现的时间约在1100—5000aB.P.之间。据此提出西太湖在全新世期间曾遭受海侵,因而支持了太湖形成于泻湖的说法,同时,还提出海水进入太湖的时间,比以往学者推测的早2000多年。     

太湖诱变剂污染调查分析

应用蚕豆根尖细胞微核试验监测太湖水污染,结果表明太湖诱变剂污染轻,分布面积小,限于西北湖区,污染分布及程度受水位状况影响较大。微核指标和其他理化性质指标互为补充,被用于评价太湖水质,并就太湖水湖保护及污染控制提出了若干建议     

鄱阳湖拟建水利枢纽工程对洪泛区地下水动力的影响及其生态意义

洪泛湿地是位于水生系统和陆生系统之间的过渡带,在河流和陆地之间的水文生态方面起着纽带作用,受气候变化和人类活动的叠加影响,其水文过程改变很大程度上影响了湿地生态系统循环、结构和功能的稳定。本文以鄱阳湖洪泛区湿地为研究区,应用湖泊水动力和洪泛区地下水数值模型,评估鄱阳湖拟建水利枢纽工程对洪泛区地下水系统的影响。模拟结果表明,拟建水利枢纽工程将会遵循调度方案使得湖泊水位明显提高,但同时导致洪泛区地下水位的整体抬升,且东部主湖区附近的地下水位受到的影响（约1～3 m）要明显强于洪泛区其它区域（约小于1 m）。地下水位的变化同时导致不同典型时期洪泛区地下水流速的减小及地下水流向的改变,表现为枢纽建设后地下水流向的逆转和流速基本小于0.1 m/d。鄱阳湖涨水-丰水期总体为湖水补给洪泛区地下水模式,枯水-退水期主要为地下水补给湖水模式,但水利枢纽可能导致洪泛区地下水系统水均衡状态发生转变,影响了地下水系统的补给和排泄状态,最终形成了长期稳定的湖泊补给地下水的作用模式。从地下水-生态系统响应变化的角度分析,拟建水利枢纽建设引起的地下水位上升,可能会给湿地生物地球化学元素的迁移转化、植被群落的演变与退...     

Quantitative comparison of river inflows to a rapidly expanding lake in central Tibetan Plateau

The recent rapid expansion of inland lakes on the Tibetan Plateau (TP) are a good indicator of the consequences of climate change. Quantifying the hydrological cycle of the lake basin is fundamentally important to understand the causes of lake growth. However, the hydrological processes of the TP interior are very complex and difficult to investigate because of the lack of observations. This is especially true for estimating the lake changes when run‐off inflows are affected by small lakes located in the flow routes within drainage areas. We used an integrated hydrological model, in combination with glacier melt and lake retention models, to analyse the run‐off inflows to Lake Siling Co, the largest endorheic lake in Tibet. It includes four subdrainage basins: Zhajiazangbu, Zhagenzangbu, Alizangbu, and Boquzangbu. Lake Siling Co was characterized by considerable increases during warm season from 1981 to 2012, due to the increased run‐off from Zhajiazangbu accounting for about 51–62% of the total run‐off inflows. Moreover, the dramatic increases exhibited during cold seasons were related to the increased retention water released from the small lakes within Zhagenzangbu and Alizangbu. Of the studied subdrainage basins, Boquzangbu contributed the least during both warm and cold seasons. On average, the annual amount of evaporation from lakes within the drainage area was about 2 times greater than that of glacier melt run‐off. Our results suggest that the retention effects of lakes on river inflows should receive more attention, because understanding these effects is potentially crucial to improved understanding of lake variations in the TP.     

Modeling of turbidity dynamics caused by wind-induced waves and current in the Taihu Lake

A simple turbidity model was developed with a sound physical basis based on in situ high-frequency observations of short-term, strong wind-induced sediment suspension in Taihu Lake, China. The validation results show that the model could successfully simulate turbidity caused by strong wind events, despite the relatively poor simulation accuracy for high values of turbidity caused by the entrainment of cyanobacteria by turbulence. The in situ observations and model simulation results indicate that the wind waves were within a narrow spectral band, with spectral energy mainly distributed within the 0.28–0.75 Hz band on opposite sides of the peak frequency. These high-frequency and low-energy wind waves are sensitive to depth filtering. However, the average depth of the lake is only 1.9 m, and wind waves still represent the main force of sediment suspension at the sediment-water interface. Moreover, lake currents were of significance to the maintenance of background turbidity in calm waves or ripples and in the determination of critical shear stress. By considering the spatial distribution of hydrodynamics and sediment, the model can be used to simulate the turbidity of the entire lake as well as boundary conditions for three-dimensional numerical models.     

Sediment mobility and bed armoring in the St Clair River: insights from hydrodynamic modeling

The lake levels in Lake Michigan‐Huron have recently fallen to near historical lows, as has the elevation difference between Lake Michigan‐Huron compared to Lake Erie. This decline in lake levels has the potential to cause detrimental impacts on the lake ecosystems, together with social and economic impacts on communities in the entire Great Lakes region. Results from past work suggest that morphological changes in the St Clair River, which is the only natural outlet for Lake Michigan‐Huron, could be an appreciable factor in the recent trends of lake level decline. A key research question is whether bed erosion within the river has caused an increase in water conveyance, therefore, contributed to the falling lake level. In this paper, a numerical modeling approach with field data is used to investigate the possibility of sediment movement in the St Clair River and assess the likelihood of morphological change under the current flow regime. A two‐dimensional numerical model was used to study flow structure, bed shear stress, and sediment mobility/armoring over a range of flow discharges. Boundary conditions for the numerical model were provided by detailed field measurements that included high‐resolution bathymetry and three‐dimensional flow velocities. The results indicate that, without considering other effects, under the current range of flow conditions, the shear stresses produced by the river flow are too low to transport most of the coarse bed sediment within the reach and are too low to cause substantial bed erosion or bed scour. However, the detailed maps of the bed show mobile bedforms in the upper St Clair River that are indicative of sediment transport. Relatively high shear stresses near a constriction at the upstream end of the river and at channel bends could cause local scour and deposition. Ship‐induced propeller wake erosion also is a likely cause of sediment movement in the entire reach. Other factors that may promote sediment movement, such as ice cover and dredging in the lower river, require further investigation. Copyright © 2012 John Wiley & Sons, Ltd.     

Paleomagnetic Logs: A Tool for Dating Lake Erie's Past

An examination of the lithology, paleomagnetic and Mossbauer Effect Spectroscopy (MES) log data and ¹⁴C determinations of cores taken from three small basins located in western Lake Erie, in conjunction with data obtained from earlier studies, has been used to re-evaluate the postglacial history of the area. After the re-advance of the Laurentide Ice Sheet into the Huron basin and the eastern part of the Erie basin during the Port Huron stadial about 13,000 yrs B.P., lacustrine clay was deposited across much of the western Erie basin in a lake ponded against the glacial ice front to the east. However, by 12,000 yrs B.P. as the ice front retreated, the waters from the Huron basin bypassed Lake Erie, first by the Kirkfield outlet to Lake Ontario, and later by the Fossmill and North Bay outlets to the Ottawa River. This resulted in the draining of water from most of the western Erie basin. Extensive swamps choked with plants formed in the small basin areas, and the surrounding low-lying former lake bottom was subjected to subaerial weathering. It would appear that by about 9,500 yrs B.P. there was an increase in surface run off into these basins and the swamps evolved into shallow, relatively warm-water lakes in which calcareous-rich clay was deposited. Isostatic rebound of the northeastern outlets of the Huron basin led to a gradual tilting of the basin and a progressive migration of the southern shoreline of Lake Huron (Lake Stanley phase) to the southwest. By about 5000 yrs B.P. the water level in the southern Huron basin had been raised sufficiently to re-open the Port Huron outlet into the Erie basin. This resulted in a substantial rise in the lake level in the Erie basin, terminated the deposition of calcareous-rich clay in the small basins, and led to the deposition of normal lacustrine sediments in the modern phase of Lake Erie.     

Active fault and water loading are important factors in triggering earthquake activity around Aswan Lake

Aswan Lake started impounding in 1964 and reached the highest water level so far in 1978 with a capacity of 133.8 km³, thus forming the second largest man-made lake in the world. An earthquake of magnitude 5.3 (Ms) took place on 14 November 1981 along the most active part of the E-W Kalabsha fault beneath the Kalabsha bay (the largest bay of the lake). This earthquake was followed by a tremendous number of smaller events that continue till now. A radio-telemetry network of 13 seismic short period stations and a piezometer network of six wells were established around the northern part of the lake.Epicenters were found to cluster around active faults near the lake. The space-time distribution and the relation of the seismicity with the lake water level fluctuations were studied. Six years after flooding the eastern segment of the Kalabsha fault, strong seismicity began following the main shock of 14 November 1981. It occurred four days after the reservoir had reached its seasonal max level. The effect of the North African drought (1982 to present) is clearly seen in the reservoir water level. As it decreased and left the most active fault segments uncovered, the activity (Gebel Marawa area) decreased sharply. Also, the shallow activity was found to be more sensitive to rapid discharging than to the filling. This study indicates that geology, topography, lineations in seismicity, offsets in the faults, changes in fault trends and focal mechanisms are closely related. No relation was found between earthquake activity and both-ground water table fluctuations and water temperatures measured in wells located around the Kalabsha area.     

1973-2018年青海湖岸线动态变化

青海湖独特的地理位置使得其不仅对环湖周边区域气候起着天然调节器的作用,而且还拥有丰富的湖岸线资源,准确、及时地掌握青海湖岸线动态变化对保护沿湖生态环境有重要意义.因此本文基于1973-2018年Landsat MSS/TM/OLI遥感影像和1961-2017年实测水位资料,对青海湖岸线动态变化及对鸟类栖息地的影响进行研究,同时结合面积、水位及气象数据讨论了影响岸线变化的主要因素.研究表明：1）近45年来青海湖岸线发生变化最大的区域是东岸的沙岛,西岸的鸟岛、铁布卡湾及北岸沙柳河入口区域.尤其自2004年以来,鸟岛地区岸线后退距离最大（5.52 km）,鸟类栖息地扩张约97.94 km²,为鸟类提供了较好的栖息环境.（2）1973-2018年青海湖岸线长度以0.88 km/a的速率逐渐延长.1997年之前岸线长度呈较为平稳的上升趋势,1997-2004年呈波动下降趋势,2004年之后呈剧烈波动增加趋势,岸线曲折性也表现出相同的变化趋势.（3）总体上岸线长度和曲折性受水位和面积的影响并不显著,但在不同的水位情况下,二者对青海湖动态变化做出不同的响应.尤其当水位小于3193.3 m或面积小于4249.3 km²时,岸线曲折性会随着水位和面积变化呈现相同的变化趋势,而水位高于3193.3 m时,岸线曲折性一直在增加,且水位上升速率越大则曲折性年际变化越大.（4）1973-2004年间青海湖水位下降和土地沙漠化是造成湖岸线变化的直接成因,人类活动及草场退化加速了湖泊岸线的变迁.2004年之后,随着青海湖水位回升与面积扩张,岸线逐渐后退,尤其在2017-2018年岸线后退距离最大.     

基于水平衡模型的呼伦湖湖泊水量变化

针对北方寒旱区呼伦湖水位下降、水面萎缩的现象,根据气候特征,利用月水量平衡模型探究湖泊水文过程并揭示其变化规律.在此基础上,利用不同气候条件下各水平衡项对于湖泊水位的影响程度确定水位升降的直接原因.基于1963-1980年间水位的实测数据,根据水量平衡原理及其他辅助计算判断出湖泊与周边区域存在着地下水的交换,且具有一定的规律性,即历年11月至次年3月期间的累积降雪融化渗入土壤中形成浅层径流补给湖泊,而7、8月份湖泊补给周边草原.基于以上规律,根据周边坡面汇流、地下水与湖泊交换量的年内变化特征,利用水平衡方程式推算湖泊1981-2008年逐月水位变化,并与其他研究成果比较,吻合度较高.不同气候条件下,径流量对于湖泊水位的影响程度最为突出,是水位变化的主控因子.