THE RELATIONSHIP BETWEEN INLAND LAKES EVOLUTION AND CLIMATIC FLUCTUATION IN ARID ZONE

The evolution of the inland lakes in arid and semi-arid zones is accorded with the climatic fluctuation. The humid climate is in harmony with the higher water level and greater lake water quantity budget while arid climate is in correspondence with the lower water level and little water budget. Based on the analysis of the lake fluctuation and lake budget change, with the aid of the data of geom’orphology, palynology, sedimentology and chronology, It is found that the climate experienced a warm and humid period during 7000-3500 yr. B. P. and showed a drying and warming trend in the last century in the Central Asia.

Monitoring variations of inland lakes in the arid region of Central Asia

Inland lakes are the major surface water resource in the arid regions of Central Asia. Therefore, the surface area changes in inland lakes have been a sensitive indicator of climate changes and human activ- ities, and have often been the focus of ecological and environmental research. This study aimed to monitor the changes in surface area of nine major lakes over a 32-year period. The water body was extracted from MSS images from the mid-1970s, TM images from the early 1990s, ETM ＋ images in the late 1990s, and TM images in 2007. The results indicated that the total surface area of these nine lakes had decreased over time to 50.38% of the area, from 91402.06km^2 in 1975 to 46049.23 km^2 in 2007. As the surface area of lakes in the western part of Central Asia was larger than that in the eastern part, the shrinking trend of lake area was more significant in the west than in the east. There was a varied reduction of closed lakes in flat regions. The most substantial decrease was in the surface area of closed lakes in flat regions. Most significantly, the area of the Aral Sea was reduced by 75.7% from its original area in 1975. The area of alpine lakes remained relatively stable; the change in surface area was less than 0.7% during the period 1975-2007. The area change in opened lakes with outlets was notably different from the other two types. The area of Zaysan had increased sharply by 5.85%, and that of Bosten had decreased by 9.1%. Sasykkol had hardly any changes in this period. Due to global climate wanning, vapor transfer to the south via westerly winds had been blocked, resulting in a decrease of much-needed precipitation in the western parts of Turkmenistan, Uzbekistan, and Kazakhstan between 1970 and 2000. The decrease in precipitation and the increase in water consumption for agricultural irrigation resulted in the decrease of fiver runoff. Consequently, thearea of inland lakes in Central Asia shrank over the past 32 years.

Characterization of saline soil for the halophytes of largest inland saline wetland of India using geospatial technology

About 23%of the surface area and 44%of the volume of all the lakes are occupied by saline lakes in the world.Importantly,agricultural diversion,illegal encroachment,pollution,and invasive species could cause these lakes to dry up completely or partially by 2025.Illegal saltpan encroachment is causing Sambhar,India’s largest saline lake,to shrink by 4.23%every decade.This study aims to characterize the soil parameters where halophytes are growing.A literature survey was conducted for halophytes and soil characteristics.The study area was divided into four zones for stratified random sampling.Soil sampling was conducted in February 2021.The soil indicators for halophyte selected were pH,electrical conductivity,moisture,salinity,organic carbon,and organic matter.The obtained results were interpolated in the geospatial platform for soil characteristic mapping.It is found that no research is conducted on halophytes of the lake.Studies on soil are also inconsistent and only six common parameters could be identified.Results show that the pH ranged 9.37-7.66,electrical conductivity was 16.1-0.38,moisture 23.37%-1.2%,organic carbon 3.29%-0.15%,organic matter 5.6%-0.2%,and salinity 8.86%-0.72%.Though these results show improved condition as compared to last few years,in long term,the lake is desiccating.During the UN Decade of Ecosystem Restoration(2021-2030),if these causes are not addressed,the ecosystem may completely dry up.

Climate effects on an inland alpine lake in Xinjiang, China over the past 40 years

Inland lakes are important water resources in arid and semiarid regions. Understanding climate effects on these lakes is critical to accurately evaluate the dynamic changes of water resources. This study focused on the changes in Sayram Lake of Xinjiang, China, and addressed the effects of climate fluctuations on the inland lake based on long-term sequenced remote sensing images and meteorological data from the past 40 years. A geo- graphic information system （GIS） method was used to obtain the hypsometry of the basin area of Sayram Lake, and estimation methods for evaporation from rising temperature and water levels from increasing precipitation were proposed. Results showed that： （1）Areal values of Sayram Lake have increased over the past 40 years. （2） Both temperature and precipitation have increased with average increases of more than 1.8~C and 82 mm, respectively. Variation of the water levels in the lake was consistent with local climate changes, and the areal values show linear relationships with local temperature and precipitation data. （3） According to the hypsometry data of the basin area, the estimated lake water levels increased by 2.8 m, and the water volume increased by 12.9×108 m3 over the past 40 years. The increasing area of Sayram Lake correlated with local and regional climatic changes because it is hardly affected by human activities.

Sulfate Attack on Concrete in an Inland Salt Lake Environment

Several cracks were found on the surface of the concrete foundations that support the steel towers of the Luohe （漯河）-Huaiyung （淮阳） high-voltage electricity transmission line that is 20 years old and situated in an inland salt lake environment in North China. To analyze the deterioration mechanism that led to this condition, field investigations were carried out and several tests were conducted on the soil and the affected concrete, including XRD （X-ray diffraction）, electric probe analysis, and chemical analysis. The results show that the concentration of sulfates is very high （0. 39% wt. -0.67% wt. ） in both the surrounding soil and the material around the coarse aggregates inside the concrete. Hence, sulfate attack could be one of the main causes of concrete deterioration. The percentage of sulfates in the surface layer of the concrete was higher than that in the inner layers of the concrete. The sulfates penetrate into the concrete and react with the hydrates of cement to form ettringite （AFt）, which leads to increase in the volume and cracking of the concrete.

A TECHNOLOGY OF PALEOPRECIPITATION RESTORATION BASED ON CHANGES OF INLAND LAKE LEVEL——WITH REFERENCE TO THE DAIHAI LAKE IN INNER MONGOLIA

The Daihai Lake,situated in the south of the Inner Mongolia Plateau, is a rift inland lake with a drainage area of 2621.6 km^2 and an annual average precipitation (AAP) of 436.8mm. Remarkable changes of the Daihai Lake have taken place since the Holocene.

基于Sentinel-2影像东北秋季典型湖泊大气校正方法适用性评价

本文利用6S(Second Simulation of a Satellite Signal in the Solar Spectrum)、Acolite DSF(Dark spectrum fitting)、C2RCC(Case 2 Regional Coast Color)、SeaDas(SeaWiFS Data Analysis System)、Sen2Cor(Sentinel 2 Correction)、Polymer(Polynomial based algorithm applied to MERIS)和iCOR(Image correction for atmospheric effects)7种大气校正算法,结合松花湖、月亮泡、小兴凯湖实测遥感反射率数据对“哨兵-2号”(Sentinel-2)数据进行大气校正研究,验证算法性能。整体校正结果显示,相较于实测遥感反射率,上述7种大气校正算法均在可见光波段(400~800 nm)呈现不同程度的低估。除C2RCC算法外,其余6种算法校正后的遥感反射率与实测光谱曲线变化趋势基本吻合,其中Sen2Cor算法与iCOR算法性能最佳,Polymer算法性能最差;在单波段校正精度对比中,Sen2Cor和iCOR算法几乎所有波段的均方根误差和平均绝对百分比误差都低于其余5种算法。Sen2Cor算法在560 nm、665 nm和705 nm处校正精度优于其余6种算法,iCOR算法在443 nm和740 nm处有良好的表现,在490 nm处6S算法校正精度最高,拥有最低的均方根误差(0.0059 sr^(−1))和平均绝对百分比误差(21.40%)。结果表明,这7种大气校正算法均可以在一定程度上去除大气影响,增加影像的可用性,Sen2Cor算法和iCOR算法更适用于本文所研究水体或相似水体。

Response of Glacier and Lake Covariations to Climate Change in Mapam Yumco Basin on Tibetan Plateau during 1974-2003

The study of spatial and temporal covariances of glaciers and lakes would help us to understand the impact of climate change within a basin in Tibet. This study focuses on glacier and lake variations in the Mapam Yumco （玛旁雍错） basin （covering 7 786.44 km^2） by integrating series of spatial data from topographic maps and digital satellite images at four different times： 1974, 1990, 1999, and 2003. The results indicate that： （1） decreased lakes, retreated glaciers, enlarged lakes and advanced glaciers co-exist in the basin during the last 30 years; （2） glacier recession was accelerated in recent years due to the warmer climate; （3） lake areas in the basin are both reduced and enlarged by an accelerated speed with more water supplies from speeding melt glaciers or frozen ground in the last three decades.

Growth of the Sayram Lake and retreat of its water-supplying glaciers in the Tianshan Mountains from 1972 to 2011

Inland lakes and alpine glaciers are important constituents of water resources in arid and semiarid regions. Understanding their variations is critical for both an accurate evaluation of the dynamic changes of water resources and the retrieval of climatic information. On the basis of earlier researches, this study investigated the growth of the Sayram Lake and the retreat of its water-supplying glaciers in the Tianshan Mountains using long-term sequenced remote sensing images. Our results show that over the past 40 years, the surface area and the water level of the lake has increased by 12.0±0.3 km2 and 2.8 m, respectively, and the area of its water-supplying glaciers has decreased continuously since the early 1970s with a total reduction of about–2.13±0.03 km2. Our study has indicative significance to the research of regional climate change.

基于CiteSpace的三维荧光光谱技术对内陆水体中溶解性有机质研究的进展

采用文献计量学方法厘清国内外三维荧光光谱技术对内陆水体中溶解性有机质(DOM)的研究现状、热点和发展趋势。利用CiteSpace知识图谱分析工具,以CNKI和WoS核心合集为数据源,从年发文量、发文作者、发文国家、关键词聚类以及突显等方面进行可视化分析,并对三维荧光光谱技术研究内陆水体中的DOM及其数据分析方法与解析技术进行综述。结果表明该领域年发文量呈上升趋势且以外文文献量增长较快为主要特征,中国是发文量最多的国家,国际化交流合作程度高且已形成较为稳定的研究团体,研究潜力充足。国内外利用三维荧光光谱技术对内陆水体中DOM的研究主要集中在易受人类活动影响或富营养化严重的水域,包括富营养化水体与沉积物中溶解性有机质,有色溶解性有机质和消毒副产物的研究,以及涉及溶解性有机质与重金属相互作用、全球气候变化响应、生物利用性等方面。除了采用常规的数据分析方法外,综合运用三维荧光光谱与吸收光谱、质谱等技术相结合,从分子水平解析内陆水体中DOM的组成和来源特征是该领域未来的重要研究热点与趋势。

Variations in Optical Scattering and Backscattering by Organic and Inorganic Particulates in Chinese Lakes of Taihu, Chaohu and Dianchi

This study presents an investigation of the scattering and backscattering properties of the particulates in three Chinese inland lakes(the Taihu Lake, the Chaohu Lake and the Dianchi Lake) based on in situ measurements taken at 119 sites. We modeled the particulate scattering spectra using a wavelength-dependent power-law function, finding that the power-law exponents in the Taihu Lake and the Chaohu Lake differ from those in the Dianchi Lake but are similar to the values in the U.S. coastal waters. In contrast to the open ocean, the backscattering properties in the three lakes can not be determined only from chlorophyll-a concentration. The backscattering ratio spectra exhibit a wavelength dependence feature in all three lakes, generally decreasing with the increasing wavelength. Analysis results of the correlations between the backscattering ratio and the individual water quality parameters clearly show that there are distinctive relations among the three lakes, attributed primarily to different compositions of optically active materials in the three lakes. Analysis of the mass-specific scattering and backscattering coefficients shows that the coefficients at wavelength 532 nm in the Taihu Lake and Chaohu Lake are similar, but they are apparently different from those in the Dianchi Lake. Lastly, Model I multiple linear regressions were adopted to partition the mass-specific cross-sections for scattering and backscattering into organic and inorganic cross-sections to further interpret the scattering and backscattering properties. The relative contribution of organic and inorganic particulates to scattering and backscattering is clearly different among the three lakes. The scattering and backscattering properties of the particulates in the three inland lakes vary significantly based on our collected data. The results indicated that the existing semi-analytical water quality retrieval models of the Taihu Lake can not be applied perfectly to the Chaohu Lake and the Dianchi Lake.

WATER QUALITY STUDIES IN MALAYSIAN DISUSED MAN MADE LAKES FOR SUITABILITY OF AN AQUACULTURE PROJECT

A study has been conducted on the status of water quality in two disused man made lakes, which have potential for cage aquaculture project. This study highlights the quality of water analyzed with reference to various physical-chemical parameters in two selected lakes and their suitability for fish farming. A number of parameters were measured including the amount of NH_ 3 -N, NO_ 3 -N, NO_ 2 -N and total phosphorus while in-situ measurement including DO, pH, temperature, conductivity, TDS and Secchi disk visibility. Beside the physical-chemical of water, the location, morphometry and climate conditions were also investigated. The chemical data analyzed for six months indicated that Lake A and Lake B are characterized by relatively high DO, slightly neutral pH and low TSS. The concentration of NH_ 3 -N and NO_ 2 -N was very low (0.058 mg/L and 0.04 mg/L, respectively) and total phosphorus was usually in low concentration and sometimes would seem negligible. Besides, NO_ 3 -N occurred in slightly higher concentration ( 1.75 mg/L ). Results obtained indicated that the study site has high potentiality for development of inland fisheries practices.

Greenhouse gas emissions from Daihai Lake,China:Should eutrophication and salinity promote carbon emission dynamics?

Greenhouse gases(GHGs)emitted or absorbed by lakes are an important component of the global carbon cycle.However,few studies have focused on the GHG dynamics of eutrophic saline lakes,thus preventing a comprehensive understanding of the carbon cycle.Here,we conducted four sampling analyses using a floating chamber in Daihai Lake,a eutrophication saline lake in Inner Mongolia Autonomous Region,China,to explore its carbon dioxide(CO_(2))and methane(CH_(4))emissions.The mean CO_(2)emission flux(FCO_(2))and CH_(4)emission flux(FCH_(4))were 17.54±14.54 mmol/m^(2)/day and 0.50±0.50 mmol/m^(2)/day,respectively.The results indicated that Daihai Lake was a source of CO_(2)and CH_(4),and GHG emissions exhibited temporal variability.The mean CO_(2)partial pressure(p CO_(2))and CH_(4)partial pressure(p CH_(4))were 561.35±109.59μatm and 17.02±13.45μatm,which were supersaturated relative to the atmosphere.The regression and correlation analysis showed that the main influencing factors of p CO_(2)were wind speed,dissolved oxygen(DO),total nitrogen(TN)and Chlorophyll a(Chl.a),whereas the main influencing factors of p CH_(4)were water temperature(WT),Chl.a,nitrate nitrogen(NO_(3)^(-)-N),TN,dissolved organic carbon(DOC)and water depth.Salinity regulated carbon mineralization and organic matter decomposition,and it was an important influencing factor of p CO_(2)and p CH_(4).Additionally,the trophic level index(TLI)significantly increased p CH_(4).Our study elucidated that salinity and eutrophication play an important role in the dynamic changes of GHG emissions.However,research on eutrophic saline lakes needs to be strengthened.

合成孔径雷达高度计应用研究进展

【目的】合成孔径雷达高度计采用延迟-多普勒技术有效提高观测精度,使得卫星测高技术可以应用于地形复杂区域。为探究合成孔径雷达高度计的应用进展,【方法】对合成孔径雷达高度计的发展进行概述,列举了目前主要载荷合成孔径雷达高度计的测高卫星,并对测高原理以及数据处理方法进行描述,针对合成孔径雷达高度计在海洋、冰川、内陆湖泊区域以及高程数据产品制作的应用进行重点分析。【结果】针对当前合成孔径雷达高度计应用现状,总结出合成孔径雷达高度计存在时空分辨率受限、数据精度检验代价较大、长序列数据短缺的问题,并提出多源数据协同、三维领域拓展以及数据处理方法优化的发展方向。【结论】合成孔径雷达高度计目前对海洋、冰川及内陆湖泊的高程监测方面已具有较强的应用能力,随着卫星观测密度的增加及数据优化处理方法的改进,合成孔径雷达高度计在高程监测、地形反演、水量监测等方面将具有更加广泛的应用,为探究地球水资源变化提供科学依据。

Sentinel-2和ICESat-2密集时序数据反演浅平型内陆湖泊水量变化

干旱区内陆尾闾湖泊由于湖盆地形浅平、岸线复杂等特点,采用传统的水位-面积关系法难以反演高精度的水量变化信息。本文提出了一种基于密集时序ICESat-2和Sentinel-2数据反演浅平型内陆湖泊湖盆地形和重建水量时序的方法。本文方法利用浅平型湖泊季节性变化显著的特性,筛选和计算不同时期湖盆内非水面区域的所有ICESat-2激光光子点的高程信息,并根据水面等高的特性内插得到Sentinel-2不同时相水面线的高程信息,在此基础上通过这些加密的高程点构建高精度湖盆地形信息,并结合水面时序重建湖泊的水量变化。以新疆塔里木河尾闾台特玛湖为试验区,基于132期Sentinel-2卫星影像和28个时相的ICESat-2激光脉冲数据,重建了2016—2022年的湖泊水量时序。结果表明,本文方法获取的湖盆地形高程中误差为0.103 m,可为无资料浅平型湖泊水量信息的时序重建提供一种思路。

内陆盐湖环境输电线路沿线软弱盐渍土工程特性及工程对策探讨

察尔汗地区有多条输电线路穿越盐湖工业采矿区,而输电线路沿线软弱盐渍土特有的工程特性和塔基附近复杂的影响因素对输电线路勘察、设计、施工及后期安全运维有重大影响。本文以察尔汗盐湖软弱盐渍土区输电线路工程建设为研究重点,在已有研究资料和现场岩土勘察成果基础上,总结软弱盐渍土的工程特性,分析盐湖软弱盐渍土区铁塔基础稳定影响因素,最后对输电线路建设的工程对策给出建议,以期为内陆盐湖软弱盐渍土地区输电线路工程建设提供参考。

基于压缩感知的波形净化及在波形重跟踪中的应用

受“陆地污染”效应影响,利用卫星测高技术对内陆湖泊水域进行波形重跟踪的精度较低,针对该问题,提出一种基于压缩感知(Compressive Sensing,CS)的波形净化技术用于实现对“陆地污染”引起的异常波峰数据检测及重构,进而结合优化的重跟踪算法进行波形重跟踪改进,提升对内陆水域的测高精度。基于内陆湖泊水文站数据开展验证实验,结果表明,利用净化后的波形进行重跟踪可以明显提升测高精度,相对于传统阈值法和伦敦大学学院法(UCL)精度分别提升28.3%和25.6%,具有较高的应用前景。

内河洪水对龙赛湖蓄滞洪区蓄洪容积影响特点的计算分析

蓄滞洪区的有效蓄洪容积是蓄滞洪区在分洪运用时实际能够蓄纳洪水的容积,是制定蓄滞洪区调度预案、实时优化调度方案的重要依据,内河洪水的调度将会占用蓄滞洪区内湖泊、圩垸及洼地的蓄洪容积,从而使有效蓄洪容积减少。选取汉北河龙赛湖蓄滞洪区,计算分析了不同频率内河洪水调度占用湖泊、圩垸及洼地蓄洪容积的变化特点,调蓄内河洪水后蓄滞洪区有效蓄洪容积的变化规律及影响,结果表明:①对于同时包括湖泊、圩垸和洼地的蓄滞洪区,调蓄内河洪水占用湖泊蓄洪容积显著大于占用圩垸及洼地蓄洪容积,内河洪水越大,占用湖泊与圩垸及洼地蓄洪容积的差别就越大。龙赛湖蓄滞洪区内河发生5年至50年一遇洪水时,在被占用蓄洪容积总量中,占用湖泊容积的比例达到97.9%~98.1%。②调蓄内河洪水减小蓄滞洪区有效容积随内河洪水频率的不同而改变,内河洪水越大,蓄滞洪区有效蓄洪的减小就越显著,龙赛湖蓄滞洪区内河发生50年一遇洪水时,有效蓄洪容积减小了约13.5%,而在发生5年一遇洪水时,有效蓄洪容积仅减小了7.81%。③当内河发生洪水并可能遭遇干流洪水时,蓄滞洪区有效蓄洪容积的减小将对干流防洪调度产生较为明显影响,应根据来水情况实时计算确定蓄滞洪区有效蓄洪容积,实时优化或调整调度方案,提前转移人员和财产。

1975-2007年中亚干旱区内陆湖泊面积变化遥感分析

中亚干旱区内陆湖泊的湖面变化反映了气候波动和人类活动对流域水文过程的影响.本文以中亚干旱区平原区尾闾湖泊、吞吐湖泊和高山湖泊三类典型内陆湖泊为研究对象,利用1975-2007年Landsat遥感影像,基于归一化水体指数提取湖泊水域边界信息,分析近30年来内陆湖泊湖面变化特征.结果表明,近30年来,研究区内有超过一半的内陆湖泊急剧萎缩,湖泊总面积从1975年的91402.06km2减小到2007年的46049.23km2,减小了49.62%.其中,平原区尾闾湖泊面积减小最为显著;吞吐湖泊主要受出口河流水资源利用方式不同,湖面变化较为复杂,既有扩张也有萎缩;高山湖泊主要受气候波动影响,水面变化相对稳定.在中亚区域气候变暖的背景下,不同类型湖泊面积的变化也反映出干旱区人类活动对区域水资源时空分配的影响.

利用卫星测高资料监测长江中下游湖泊水位变化

利用Envisat 1卫星的GDRs数据,根据适当的数据编辑准则,进行了必要的地球物理改正之后,研究分析了长江中下游鄱阳湖、洞庭湖、太湖、巢湖的水位变化及其与气候环境的关系,为长江流域水位变化与气候变化的长期性研究提供了一种有效的手段和方法。