Impact assessment of climate change and human activities on annual highest water level of Taihu Lake

The annual highest water level of Taihu Lake （Zm） is very significant for flood management in the Taihu Basin. This paper first describes the inter-annual and intra-annual traits of Zm from 1956 to 2000. Then, using the Mann-Kenall （MK） and Spearman （SP） nonparametric tests, the long-term change trends of area precipitation and pan evaporation in the Taihu Basin are determined. Meanwhile, using the Morlet wavelet transformation, the fluctuation patterns and change points of precipitation and pan evaporation are analyzed. Also, human activities in the Taihu Basin are described, including land use change and hydraulic project construction. Finally, the relationship between Zm, the water level of Taihu Lake 30 days prior to the day of Zm （Z0）, and the 30-day total precipitation and pan evaporation prior to the day of Zm （P and E0, respectively） is described based on multi-linear regression equations. The relative influence of climate change and human activities on the change of Zm is quantitatively ascertained. The results demonstrate that： （1） Zm was distinctly higher during the 1980-2000 period than during the 1956-1979 period, and the 30 days prior to the day of Zm are the key phase influencing Zm every year; （2） P increased significantly at a confidence level of 95% during the 1956-2000 period, while the reverse was true for E0; （3） The relationship between Zm, P and E0 distinctly changed after 1980; （4） Climate change and human activities together caused frequent occurrences of high Zm after 1980; （5） Climate change caused a substantially greater Zm difference between the 1956-1979 and 1980-2000 periods than human activities. Climate change, as represented by P and E0, was the dominant factor raising Zm, with a relative influence ratio of 83.6%, while human activities had a smaller influence ratio of 16.4%.

Impacts of climate change and human activities on water resources in the Ebinur Lake Basin, Northwest China

Changing climatic conditions and extensive human activities have influenced the global water cycle.In recent years,significant changes in climate and land use have degraded the watershed ecosystem of the Ebinur Lake Basin in Xinjiang,Northwest China.In this paper,variations of runoff,temperature,precipitation,reference evapotranspiration,lake area,socio-economic water usage,groundwater level and water quality in the Ebinur Lake Basin from 1961 to 2015 were systematically analyzed by the Mann-Kendall test methods(M-K)mutation test,the cumulative levelling method,the climate-sensitive method and land-use change index.In addition,we evaluated the effects of human activities on land use change and water quality.The results reveal that there was a significant increase in temperature and precipitation from 1961 to 2015,despite a decrease in reference evapotranspiration.The Wenquan station was not significantly affected by human activities as it is situated at a higher altitude.Runoff at this station increased significantly with climate warming.In contrast,runoff at the Jinghe station was severely affected by numerous human activities.Runoff decreased without obvious fluctuations.The contributions of climate change to runoff variation at the Jinghe and Wenquan stations were 46.87%and 58.94%,respectively;and the contributions of human activities were 53.13%and 41.06%,respectively.Land-use patterns in the basin have changed significantly between 1990 and 2015:urban and rural constructed lands,saline-alkali land,bare land,cultivated land,and forest land have expanded,while areas under grassland,lake,ice/snow and river/channel have declined.Human activities have dramatically intensified land degradation and desertification.From 1961 to 2015,both the inflow into the Ebinur Lake and the area of the lake have declined year by year;groundwater levels have dropped significantly,and the water quality has deteriorated during the study period.In the oasis irrigation area below the runoff pass,human activities mainly influenced the utilization mode and quantity of water resources.Changes in the hydrology and quantity of water resources were driven primarily by the continuous expansion of cultivated land and oasis,as well as the growth of population and the construction of hydraulic engineering projects.After 2015,the effects of some ecological protection projects were observed.However,there was no obvious sign of ecological improvement in the basin,and some environmental problems continue to persist.On this basis,this study recommends that the expansion of oasis should be limited according to the carrying capacity of the local water bodies.Moreover,in order to ensure the ecological security of the basin,it is necessary to determine the optimal oasis area for sustainable development and improve the efficiency of water resources exploitation and utilization.

Lake sediment records on climate change and human activities since the Holocene in Erhai catchment, Yunnan Province, China

According to high-resolution analyses on multi-proxy of sediment core from the Er- hai Lake, Yunnan Province, the sequence of climatic and environmental change since the Holo- cene has been reconstructed based on accurate dating. The results show that climate had tran- sited from cold-wet to warm-wet during ca. 12950-8399 aBP in this area, and the transition happened in ca. 10329 aBP. Due to the enhancing southwest Asian monsoon and increasing precipitation, the lake-level of the Erhai Lake began to rise after ca. 10329 a BP. Climate in the catchment was warm and wet during the mid-Holocene, and the warmest stage appeared in ca. 8399-6371 a BP. The lake-level descended in the mid-Holocene because of the decrease of effective moisture in the basin. Human activities appeared in ca. 6371 a BP, and the initial man- ner mainly focused on deforestation. Up to ca. 2139 a BP, due to the amount of immigration into this area, the cultivation was developed widely, which was followed by mining (coal mine).

Effects of climate change and human activity on lake shrinkage in Gonghe Basin of northeastern Tibetan Plateau during the past 60 years

Changes in the status of freshwater resources are a topic of major global, regional and local concern. This is especially so in the arid and semi-arid regions of China, where shortage of water resources plays a crucial role in limiting sustainable socioeconomic development, as well as in sustaining natural ecosystems. Recent climate change, as well as the effects of localized human activity, such as the use of water for irrigation agriculture, may have significant effects on the status of the water resources in the region. Here, we report the results of a study of changes in the areas of lakes in Gonghe Basin, northeastern Tibetan Plateau of China, over the last 60 years. The data were acquired from optical satellite images and demonstrate that the total water area of lakes in Gonghe Basin decreased significantly from the 1950s to 1980s. The cause is ascribed mainly to human activity including exploitation of farmland, against a background of increasing population; in addition, climatic data for the region demonstrate a minor drying trend during this period as the temperature increased slightly. After the construction of several reservoirs, significant amounts of water were redistributed to promote irrigation agriculture and we conclude that this caused a significant shrinkage of the natural lakes. However, both the area of farmland and the population size remained approximately constant after 1990. We conclude that the variation of the total area of lakes during the second period was mainly controlled by climatic factors （precipitation and temperature）. As the regional temperature reached a new high, the area of some of the lakes decreased sharply before finally maintaining a relatively steady state. We emphasize that anthropogenic climate change and human activity have both significantly influenced the status of water resources in the arid and semi-arid regions of China.

Shrinking and Drying up of Baiyangdian Lake Wetland:A Natural or Human Cause?

The shrinking and drying up of wetlands in arid and semiarid areas of China have been widely observed in the recent years, but there has been no consensus on whether the aggravation is caused by human activities or by global climate warming. For a better understanding of the cause, this study investigates the dynamic changes of Baiyangdian Lake wetland over the last 40 years. It is shown that since the 1980s, Baiyangdian Lake has suffered from an insufficient water input and shrunk considerably. By using SPSS 11.0, this study urines a detailed Analysis on the signifficance of the effects of the possible driving factors for the degradation. It is identified that the North China Plain has been warrnin~ up significantly in recent years, which causes a significant reduction in the precipitation and inflow to the lake. Although human disturbances such as the irrigation and storage of water in reservoirs do not play a decisive role, they accelerate the degradation and their effects should be minimized.

Lake evolution and its implication for environmental changes in China during 1950-2000

Lakes in China have undergone considerable environmental changes during the past 50 years, e.g. lake level, water area changes, as did in the past several thousands years. The enhanced human activities, such as land reclamation, application of chemical fertilizer, land use and cover, irrigation and industrialization in the catchment etc., have played an important role on the recent decades＇ changes of these lakes, although constrained to a great extent by the natural impact. Comparative study on variations of lake volume （water level, depth and area） in the eastern and western lake regions of China during 1950-2000 indicated that, lake volume in the eastern region had approximately undergone a two-stage change, i.e. a dramatic decrease from the 1950s to 1970s, and a continuous increase between the 1980s and 1990s; while, in the western region, lake volume had been decreasing nearly all the time. Further studies on some typical lakes concluded that, climatic change was a primary factor for the variations of lake volume during the past 50 years, although human activities showed important effect.

RELATIONSHIP BETWEEN QINGHAI LAKE LEVEL DESCENDING AND ARTIFICIAL WATER－CONSUMPTION

Qinghai Lake is the largest inland lake in China. It is a closed-drainage saline lake located at 3194m above sea level in the northeastern Qinghai-Xizang (Tibet) Plateau. Qinghai Lake region, about 36°15' -38°20' N and 97°50, - 101°20' E,is a closed basin

青海湖流域植被动态变化驱动力及空间粒度效应

基于Landsat遥感影像分析1986~2020年青海湖流域植被覆盖度时空变化特征,结合多元线性回归和地理探测器,考虑气候、地表及人类足迹的影响,阐明时间和空间尺度下植被覆盖度变化的机制,并探讨空间粒度对驱动因素及其相对贡献的影响.结果表明:(1)近35年来青海湖流域植被状况整体改善,表现为中等、中高覆盖度植被面积增加,其中环青海湖东北部及布哈河上游植被覆盖度呈显著增加趋势;(2)时间尺度上,流域平均植被覆盖度变化受气候暖湿化和生态恢复工程驱动;(3)空间尺度上,植被覆盖度变化由气候、地形、植被和土壤控制,解释力较大因素为气温(0.41),高程(0.34)和降水(0.30).气候、地形和人为因素对植被覆盖度的影响存在交互增强效应,气温、高程对交互效用具有控制作用,其中气温与距水系距离、降水和人类足迹的交互较为显著;(4)空间粒度对植被覆盖度空间变化驱动因素的贡献具有显著影响,考虑气候、地表和人为因素交互作用时青海湖流域植被覆盖度空间变化最佳研究粒度为6km.

1989-2021年蒙新高原湖泊时空特征及驱动力分析

内陆湖泊是水资源系统的重要组成部分,不仅在维系区域生态平衡方面具有重要意义,还可作为气候变化和人类活动的指示器。本研究基于Google Earth Engine(GEE)遥感云平台,以JRC(JRC Global Surface Water)水体数据为主要数据源,运用皮尔逊相关分析和时空地理加权回归模型等方法研究1989-2021年蒙新高原湖区湖泊数量和面积的时空动态变化特征,并定量分析蒙新高原湖泊变化的主要原因。结果表明:近33 a来,蒙新高原湖泊数量和面积整体上显著增加,小型湖泊(1~10 km^(2))的面积和数量占比最大且增加最为显著,其次是中型湖泊(10~100 km^(2))和大型湖泊(>100 km^(2))。在所有海拔带中,湖泊普遍呈现扩张的趋势,其中低海拔地区(DEM<1000 m)的湖泊扩张最为显著。与低海拔地区相比,高海拔地区(DEM≥1500 m)湖泊的变化受温度和降水影响显著,且在不同垂直地带上表现出一致性;湖区内14个流域的湖泊发生扩张,其中8个流域扩张显著,强烈的人类活动加之气候变化的影响,东部的额尔古纳河流域和内蒙古高原内陆河流域的湖泊明显萎缩。掌握蒙新高原湖泊时空变化特征及相关原因,可为我国干旱半干旱区乃至全球气候变化和水资源保护提供理论参考。

近40a流域气候变化与人类活动双重驱动下乌梁素海面积变化特征研究

湖泊面积变化是流域气候变化和人类活动的指示剂,明确湖泊面积时空动态过程是评估湖泊生态环境变化及其影响的基础。基于Landsat系列卫星影像,利用监督分类法提取1986—2021年乌梁素海面积;采用一元线性回归、M-K趋势、突变检验对乌梁素海流域的气温、降水量、相对湿度、潜在蒸散发进行了趋势、突变分析;收集流域人类活动数据,运用相关性和多元线性回归分析了气候变化和人类活动对湖泊面积变化的影响。结果表明:(1)乌梁素海面积从316.19 km^(2)波动增加到332.34 km^(2),增加了5.11%;流域气温显著上升、降水增加幅度小且不显著,相对湿度和潜在蒸散发呈增加趋势,流域气候整体变暖。(2)湖泊面积与气温、降水量呈正相关,与相对湿度、潜在蒸散发呈负相关,流域人口、国内生产总值、农作物播种面积与湖泊面积均呈显著正相关。(3)2002—2021年湖泊面积扩大,GDP贡献率为76.83%,人口贡献率为18.37%,潜在蒸散发贡献率为7.73%,湖泊面积变化受人类活动影响更大。

气候变化与人类活动对鄱阳湖水文情势的影响研究

进入21世纪以来,受气候变化与人类活动因素叠加影响,鄱阳湖退水时间提前、枯水期延长、水位降低等问题频发,呈现出常态化、趋势化特征,给鄱阳湖湖区生产生活带来巨大挑战。运用趋势检验及突变检验的方法分析鄱阳湖湖区1989~2020年5个水文站(星子、棠荫、康山、都昌和湖口)年均水位的变化趋势;耦合可细化人类活动影响的PCR-GLOBWB(PCRaster Global Water Balance)模型与可预测时间序列的LSTM长短期记忆神经网络模型,结合IHA/RVA法,量化气候变化与人类活动对鄱阳湖的影响。结果表明:受人类活动影响,鄱阳湖水位呈现下降趋势,在2003年鄱阳湖水位发生显著变异,同时,鄱阳湖水位整体改变度由低度改变上升到中度改变。以星子站为例,人类活动是鄱阳湖水文情势变化的主要驱动因素,贡献率达110.62%,气候变化对其贡献率仅为-10.62%。研究成果可为鄱阳湖的水资源科学管理调控提供依据。

近2600年来内蒙古居延海湖泊沉积记录的环境变迁

根据东居延海S1孔湖泊沉积柱状岩芯的多环境指标分析结果．将近2600年来湖泊沉积物记录的环境演化过程分为十个阶段．湖泊沉积记录的气候组合特点具有冷湿→暖湿（冷干）→暖干→冷湿的过程．现阶段处于暖干阶段，预测未来气候向偏湿方向变化．近2600年来自然的气候变化在居延海湖泊环境演化中居于主导地位，而人类活动只是在特定时段对湖泊环境产生较大影响．

近1800年来云南洱海流域气候变化与人类活动的湖泊沉积记录

对云南洱海湖泊岩芯沉积物进行了多环境指标 (年代学、色素、硅藻、有机碳稳定同位素、磁化率、化学元素 )的分析 ,建立了近 180 0年来云南洱海流域气候与环境变化的序列 ,气候演化具有暖干、冷湿交替的组合特点 ,一些特征气候阶段如中世纪温暖期、小冰期气候特征在洱海湖泊沉积记录中均有反映 .洱海湖泊沉积记录的气候暖干 -冷湿交替变化规律 ,反映了西南季风影响下的气候演化特征 .湖泊沉积记录中包含丰富的人类活动的信息 ,磁化率、元素Fe、色素与历史时期人类活动的强度变化过程具有较好的一致性 .多环境指标的综合分析方法 ,可以判识人类活动和气候变化的湖泊沉积响应 ,对高分辨率研究 2 0 0 0年时段湖泊沉积记录并合理解释环境指标变化具有重要意义 .

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.

气候变化和人类活动对鄱阳湖流域径流变化的影响研究

20个世纪60年代以来,鄱阳湖流域径流呈现出增加趋势,特别是1990年代流域径流增加显著,与该时期多次出现洪水灾害事件密切相关.运用Mann-Kendall检验法对1961—2000年流域径流序列进行突变分析,结果显示1992年附近是流域径流突变发生的拐点.基于径流对降雨和潜在蒸散发的敏感关系,以1961—1991年为基准期,定量分析了1992—2000年流域气候变化和人类活动对天然径流的影响分量.结果表明:相对于1961—1991年,1992—2000年多年平均径流量增加211.7mm,其中气候变化引起的增量为282.2mm,人类活动引起径流减小70.6mm,分别占多年平均径流变化量的133%和-33%.不同子流域间,气候变化和人类活动对径流的影响分量相差较大.气候变化因子中,流域降水量的增加,特别是夏季暴雨频率的增加,是引起1990年代鄱阳湖流域径流显著增大的主要原因,其次是蒸发量的长期下降.人类活动对鄱阳湖流域径流起着减流的作用,主要是由于流域内工农业的快速发展,大量水利工程设施的存在提高了水资源的利用程度;另一方面,1990年代流域水土流失状况的有效缓解,有助于增加流域的贮水能力,减小径流.

1990s以来气候变化和人类活动对洪湖流域径流影响的定量辨识

为针对性地提出洪湖流域水资源适应与应对气候变化和人类活动影响的措施,保护洪湖流域生态资源,促进其可持续发展,采取分布式水文模型SWAT定量辨识了1990s流域城镇快速发展以来气候变化和人类活动对洪湖流域地表径流的影响程度.结果表明:近20年来,人类活动是洪湖流域地表径流减少的主要原因,其影响量占径流减少量的63.72%,气候变化的影响占36.28%.但不同阶段人类活动与气候变化对流域径流影响的程度不同,1990s气候变化对流域径流的影响量高于人类活动,2000s气候变化对流域径流的影响量低于人类活动,近20年来的水土保持措施已经发挥了较好的径流调节和保水效益.

新疆博斯腾湖水质水量及其演化特征分析

于2008年8月对博斯腾湖进行了系统的水质和水量监测,并结合近50 a来气候水文资料,进行了博斯腾湖演化过程和阶段特征分析。结果表明,目前湖泊最大水深为13.9 m,湖泊面积928 km^2,蓄水量52.65×108m^3,湖水体矿化度平均1.48 g/L。近50 a来,博斯腾湖水质水量经历了3个明显的不同时期。1966年以前,湖泊处于1 048 m以上的高水位,矿化度低,湖泊受人类活动影响弱。第二个时期为1966-1996年,湖泊水位低,矿化度高,其中1987年湖泊水位处于历史低值而矿化度为最高。随后,湖泊水位明显上升、矿化度下降,湖泊扩展水体淡化。第三个时期为1996-2005年,湖泊水位处于历史高值段,矿化度有所下降但不明显。期间,人类活动对湖泊的影响显著,除流域农业用水影响外,城市和工业用水的影响也明显增加。最近几年,湖泊水位快速下降,并于2007年出现历史的低水位,湖泊矿化度也呈现升高趋势,鱼类种群和产量受人类强烈干预。另外,流域社会经济发展带来的城市化和工业化,也导致湖泊污染和富营养化,引起水质进一步恶化,湖泊面临新的生态环境压力。

湖北太白湖孢粉记录揭示的近1500年以来长江中下游地区的气候变化与人类活动

太白湖TN1孔总长153cm岩芯的孢粉组合与炭屑指标,揭示了近1500年以来太白湖流域的植被经历了7个阶段的变化,对引起植被发生这种变化的主导因素探讨认为,520-1310AD期间,植被变化主要受气候变化的控制,人类活动的影响相对较弱;1310-1710AD期间,人类活动对植被的影响强度增加,为以自然控制为主向人类活动驱动为主转化的过渡期;1710AD以来,植被变化以人类活动驱动为主,反映的气候信号相对较弱.在孢粉组合所反映的气候变化中,具有520-720AD、1050-1310AD和自1950AD以来的三个暖期和720-1050AD、1310-1710AD期间的两个冷期.

洞庭湖流域径流量对气候变化和人类活动的响应研究

为了定量化研究气候变化和人类活动对洞庭湖流域径流量变化的影响,采用累积距平分析和Mann-Kendall趋势检验对流域内4个水文站和16个气象站1985—2010年的水文及气象数据进行统计分析,并利用径流量变化定量分析方法,计算了气候变化和人类活动对径流的改变量及其贡献率。研究结果表明:降水量的下降和潜在蒸散发量的上升导致整个洞庭湖流域及湘江、资水、沅江、澧水4个子流域突变后相对于突变前径流量分别减少了28、15、130、112 mm和102 mm;洞庭湖流域径流量的减少主要受气候变化的影响,其贡献率为64%,人类活动虽然能增加径流,但是两者的叠加影响整体上仍使径流量减少。因此,洞庭湖流域的水文干旱是自然环境演化的结果,与全球气候变化的大格局息息相关。

东北松嫩平原区湖泊对气候变化响应的初步研究

以气候变暖为主要特点的气候变化已成为当前研究的焦点,气候变化和不同类型的生态系统之间的相互作用更是受到广泛关注.东北地区作为我国气候变化的一个敏感区,观测记录和多种模式预估显示该区气候变暖显著并将进一步增强,降水变化趋势则不明显或略有增加.东北松嫩平原湖泊群是我国湖泊密度最大的湖区之一,但近几十年来,该区湖泊生态环境不断恶化,其中气候因素最为受人关注.本文从以下几个角度综述了松嫩平原湖泊群对气候变化的响应:(1)湖泊面积和湖泊水位;(2)湖泊水质;(3)湖泊生态多样性.在此基础上,探讨了该区未来气候变化对湖泊的可能影响以及湖泊的演变趋势,也阐述了在这种自然背景下的人类活动对湖泊环境演变的影响.