A biodiversity evaluation framework for restoration of aquatic macrophyte communities in shallow lakes driven by hydrological process management     

Shuhan Li  Tao Sun  Wei Yang  Baoshan Cui  Xinan Yin 《水文研究》2021,35(1):e13983

Macrophyte community diversity and composition respond to ecosystem conservation and local environmental factors. In this study, we developed a multidimensional diversity framework for macrophyte communities, including the taxonomic and functional alpha and beta diversity. We used the framework to explore the relationships among water level regimes and these diversity parameters in a case study of China's Baiyangdian Lake. Analysis of indicators of hydrologic alteration divided the water level from 1959 to 2019 into four regimes (dry, <6.42 m; low, 6.42–7.23 m; medium, 7.23–8.19 m; high, >8.19 m). Alpha and beta diversity were significantly higher in the medium regime than in the low and high regimes. Redundancy analysis indicated that the maximum water depth significantly affected taxonomic alpha diversity, and total nitrogen (TN) and chemical oxygen demand (COD) concentration significantly affected functional alpha diversity, respectively. Mantel tests showed that TN, Secchi depth (SD), and water depth in the high water level regime significantly increased the total beta diversity and turnover components. TN was the main factor that increased total taxonomic beta diversity. Water level regime mainly influenced interspecific relationships by changing the TN and COD concentration. The water level should be maintained between the medium and high water level regimes to promote restoration of the macrophyte community and improve ecosystem stability. The biodiversity evaluation framework would provide a deeper insight into the hydrological process management for restoration of aquatic macrophyte communities in shallow lakes.  相似文献   

A two-layer model for studying 2D dissolved pollutant runoff over impermeable surfaces     

Taotao Zhang  Yang Xiao  Dongfang Liang  Hongwu Tang  Junzeng Xu  Saiyu Yuan  Nairu Wang  Bin Luan 《水文研究》2021,35(5):e14152

Dissolved pollutants in stormwater are a main contributor to water pollution in urban environments. However, many existing transport models are semi-empirical and only consider one-dimensional flows, which limit their predictive capacity. Combining the shallow water and the advection–diffusion equations, a two-dimensional physically based model is developed for dissolved pollutant transport by adopting the concept of a ‘control layer’. A series of laboratory experiments has been conducted to validate the proposed model, taking into account the effects of buildings and intermittent rainfalls. The predictions are found to be in good agreement with experimental observations, which supports the assumption that the depth of the control layer is constant. Based on the validated model, a parametric study is conducted, focusing on the characteristics of the pollutant distribution and transport rate over the depth. The hyetograph, including the intensity, duration and intermittency, of rainfall event has a significant influence on the pollutant transport rates. The depth of the control layer, rainfall intensity, surface roughness and area length are dominant factors that affect the dissolved pollutant transport. Finally, several perspectives of the new pollutant transport model are discussed. This study contributes to an in-depth understanding of the dissolved pollutant transport processes on impermeable surfaces and urban stormwater management.  相似文献   

Investigation of inner-basin variation: Impact of large reservoirs on water regimes of downstream water bodies     

Xue Dai  Zhongbo Yu  Guishan Yang  Chong-Yu Xu  Rongrong Wan 《水文研究》2021,35(5):e14241

Large dams and reservoirs alter not only the natural flow regimes of streams and rivers but also their flooding cycles and flood magnitudes. Although the effect of dams and reservoirs has been reported for some vulnerable locations, the understanding of the inner-basin variation with respect to the effects remains limited. In this study, we analyse the Three Gorges Dam (TGD) built on the Changjiang mainstream (Yangtze River) to investigate the dam effect variations in the system of interconnected water bodies located downstream. We investigated the effect of flow alterations along the downstream river network using discharge time series at different gauging stations. The river–lake interactions (referring to the interactions between the Changjiang mainstream and its tributary lakes i.e. the Dongting and Poyang lakes) and their roles in modifying the TGD effect intensity were also investigated in the large-scale river–lake system. The results show that the water storage of the tributary lakes decreased after the activation of the TGD. Severe droughts occurred in the lakes, weakening their ability to recharge the Changjiang mainstream. As a consequence, the effect of the TGD on the Changjiang flow increase during the dry season diminished quickly downstream of the dam, whereas its impact on the flow decrease during the wet season gradually exacerbated along the mainstream, especially at sites located downstream of the lake outlets. Therefore, when assessing dam-induced hydrological changes, special attention should be paid to the changes in the storage of tributary lakes and the associated effects in the mainstream. This is of high importance for managing the water resource trade-offs between different water bodies in dam-affected riverine systems.  相似文献   

An experimental investigation of the effects of thawed soil depth on rill flow velocity     

Xiaofeng Gao  Xiaonan Shi  Tingwu Lei  Huaqing Liu  Jiahui Yang 《水文研究》2021,35(2):e14043

Water flow velocity is an important hydraulic variable in hydrological and soil erosion models, and is greatly affected by freezing and thawing of the surface soil layer in cold high-altitude regions. The accurate measurement of rill flow velocity when impacted by the thawing process is critical to simulate runoff and sediment transport processes. In this study, an electrolyte tracer modelling method was used to measure rill flow velocity along a meadow soil slope at different thaw depths under simulated rainfall. Rill flow velocity was measured using four thawed soil depths (0, 1, 2 and 10 cm), four slope gradients (5°, 10°, 15° and 20°) and four rainfall intensities (30, 60, 90 and 120 mm·h⁻¹). The results showed that the increase in thawed soil depth caused a decrease in rill flow velocity, whereby the rate of this decrease was also diminishing. Whilst the rill flow velocity was positively correlated with slope gradient and rainfall intensity, the response of rill flow velocity to these influencing factors varied with thawed soil depth. The mechanism by which thawed soil depth influenced rill flow velocity was attributed to the consumption of runoff energy, slope surface roughness, and the headcut effect. Rill flow velocity was modelled by thawed soil depth, slope gradient and rainfall intensity using an empirical function. This function predicted values that were in good agreement with the measured data. These results provide the foundation for a better understanding of the effect of thawed soil depth on slope hydrology, erosion and the parameterization scheme for hydrological and soil erosion models.  相似文献   

Geochemical evidence of ions’ sources and influences of meteorological factors on hydrochemistry of glacier snow meltwater in the source region of the Yangtze River     

Zong-Jie  Li  Jin-Zhu  Ma  Hai-Chao  Yu  Huan  Yang  Ling-Ling  Song  Zong-Xing  Li  Juan  Gui 《Environmental Earth Sciences》2020,79(10):1-17

The risk management of cascade reservoir systems (CRSs) is a major public challenge, and the establishment of risk criteria is critical to solving this iss  相似文献   

琼东南盆地华光凹陷天然气水合物稳定带厚度的影响因素     

刘杰  杨睿  邬黛黛  金光荣  张辉 《海洋学报》2019,41(8):13-25

为了探讨琼东南盆地华光凹陷海底天然气水合物稳定带的分布规律，定量研究了静水压力、底水温度、地温梯度和气源组分对水合物稳定带的影响程度。在此基础上，分析了华光凹陷现今甲烷水合物稳定带的厚度分布。最后，综合各因素的历史演化过程，初步探讨了华光凹陷1.05 Ma BP以来天然气水合物稳定带的演化。结果表明:(1)气源组分和海底温度的变化对研究区内水合物稳定带的影响较大；水合物稳定带厚度与海底温度呈良好的线性负相关性。(2)水深超过600 m的海域具备形成天然气水合物的温压条件；超过600 m水深的海域水合物稳定带厚度大部分超过 100 m，其中西北部稳定带的最大厚度超过300 m，是有利的水合物勘探区。(3)华光凹陷1.05 Ma BP以来天然气水合物稳定带厚度经历了快速增厚–窄幅变化–快速减薄和恢复的过程。麻坑群与水合物稳定变化敏感区在空间上具有较好的叠合关系。结合前人的研究成果，推测其形成与天然气水合物的分解释放有关。  相似文献   

东昆仑金水口地区格林威尔期超高温麻粒岩   总被引：1，自引：1，他引：0  

何凡  宋述光 《岩石学报》2020,36(4):1030-1040

格林威尔期构造事件是了解罗迪尼亚超大陆形成的关键。本文报道了东昆仑造山带东段金水口地区古生代花岗岩中新发现二辉麻粒岩包体,其峰期变质矿物组合为单斜辉石+紫苏辉石+钙长石+石英+磁铁矿。通过锆石U-Pb测年,我们确定二辉麻粒岩样品的峰期变质年龄为995±34Ma,并受到泥盆纪(～417Ma)构造热事件的叠加改造。利用单斜辉石-斜方辉石温压计估算出该区二辉麻粒岩变质峰期温度867～1079℃,压力46～89kbar,属于低压超高温变质的温压范围,可能形成于高地温梯度的岛弧环境。该二辉麻粒岩是首次在东昆仑地区发现的格林威尔期超高温麻粒岩,代表罗迪尼亚超大陆汇聚过程中低压高温变质的产物。该发现对了解东昆仑造山带前寒武纪基底的构造属性和起源有重要意义。  相似文献   

基于波形特征的露天钼矿微震事件的识别分析——以卓资山钼矿为例     

赵艳红  包金哲  王树波  翟浩  魏建民  杨智升  张晖  赵铁锁  苏日亚  王磊  王鑫  贾昕晔  刘芳 《震灾防御技术》2019,14(3):662-676

基于前人研究成果以及现场的实测结果，采用卓资山露天钼矿微震监测项目产出资料，提取了5类微震事件的波形特征和时频特征。波形特征显示:微地震的振幅、辐射均匀性和频率变化特征表明微地震是由于岩层受到单力偶和剪切力作用破裂而产生；爆破具有P波初动方向向上、S波不易识别的特点，包含“初震段、主震段、尾波段”三段变化形态；小型边坡滑坡波事件属楔体滑坡，是由多个“加速—缓冲—终止”构成，波形是由包络线呈“V”字形的多组脉冲波列组成；机械开采震动事件具有自振能量不变、脉冲幅度相差很大、持续时间间隔不确定的特点；运输车辆波形振幅具有形态“弱—强—弱”、等频率、包络线呈多段纺锤形的特征。时频空间分布可以分为相对独立、界限分明的两类:一类包含微地震、爆破、机械开采、小型边坡滑坡事件，另一类只包含车辆运输事件。  相似文献   

1960-2015年青海三江源地区降水时空特征   总被引：5，自引：0，他引：5  

刘晓琼  吴泽洲  刘彦随  赵新正  芮旸  张健 《地理学报》2019,74(9):1803-1820

青海三江源地区是中国生态系统最为敏感和脆弱的地区,其降水特别是生长季降水的波动,是影响本区及江河中下游水资源安全、生态系统可持续发展的关键因素。综合线性趋势、Mann-Kendall检验、BG分割算法、R/S、EEMD等多方法细致辨识了1960-2015年研究区降水量序列的时空特征。结果显示：① 三江源降水量总体呈现弱增趋势,21世纪以来降水量显著增加,各子源区气候倾向率不尽相同;② 年、季降水量自东南向西北递减,澜沧江源区夏季降水和黄河源区秋季降水呈弱减趋势,雨量弱减区在空间上呈斑块状分布;③ 年、季降水量年代际变化和增湿率的空间差异较明显,春夏季降水气候倾向率与经纬度、海拔的复相关性显著高于冬季;④ 20世纪90年代中后期,各子源区降水总体显现增强信号,并于2002年前后发生突变;⑤ 年际和低值年代际显著周期是造成降水量变动的主要因素;⑥ 除澜沧江源区夏季降水趋于减少外,其他年、季降水量变化呈现增幅不一的转湿趋势;⑦ 横向比较各子源区可见,长江源区降水变化更能表征高原气候变化。研究结果显示,研究区降水时空序列变化具有明显的区域和季节差异性特征,与以往类似研究存在些许差异,可见为有效提高气候序列演变过程及突变诊断的准确性,仍需进一步融合多方法实施集成分析。  相似文献   

新疆西天山查岗诺尔铁矿床环带石榴子石和绿帘石的发现及意义   总被引：1，自引：0，他引：1  

冯浩轩  申萍  李昌昊  武阳  石福品  李文广 《矿床地质》2020,39(5):805-824

查岗诺尔铁矿是新疆西天山阿吾拉勒铁矿带内的重要大型铁矿床之一。矿体赋存在下石炭统大哈拉军山组安山质火山岩中，与普遍发育的石榴子石化、阳起石化和绿帘石化时空关系密切。石榴子石和绿帘石分属不同热液成矿阶段，它们均发育丰富的环带结构，具体表现为明显地颜色、干涉色、背散射图像及成分（FeO、Al₂O₃、SiO₂、MnO、TiO₂）等差异性。石榴子石具有2个世代、3个类型。早世代石榴子石（Grt1和Grt2）产于块状石榴子石-磁铁矿蚀变岩，呈褐黄色，粒度较细，发育核-边结构，呈非均质性，显示异常干涉色，其核部（Grt1-c）均匀相对富钙铝榴石（Gro_51-53And_41-43Spr_4-8），而边部（Grt1-r）发育振荡成分环带，总体相对富钙铁榴石（Gro_18-35And_60-77Spr_4-6）；Grt2核部（Grt2-c）呈均质性，为钙铁榴石（And_99-100Spr_0-1），边部显异常干涉色，发育振荡成分环带，为钙铝铁榴石（Gro_34-54And_38-61Spr_6-9）。晚世代的石榴子石（Grt3）以细脉状或角砾胶结物形式分布，呈红褐色，自形粗粒结构，显非均质性，发育振荡成分环带，端员组分总体以钙铁榴石为主，次为钙铝榴石（Gro_27-43And_50-68Spr_3-8）。石榴子石结构和元素含量变化表明，早期石榴子石形成于弱氧化-氧化、中性-碱性流体体系，其中向边部生长过程，由于新注入流体以及周期性压力汇聚和释放，体系的氧逸度、pH值呈振荡变化；晚期石榴子石形成于弱氧化、弱碱性、动荡的开放流体环境。绿帘石发育3个世代（Ep1、Ep2和Ep3）。Ep1发育核-边结构，核部（Ep1-c）均匀无环带，X_Fe值（X_Fe=Fe³⁺/（Al+Fe³⁺），原子比值）为0.19~0.21，w（MnO）为0.05%~0.18%，w（TiO₂）为0.10%~0.12%，生长边（Ep1-r）多发育振荡环带，X_Fe值为0.26~0.29，w（MnO）为0.01%~0.14%，w（TiO₂）为0.19%~0.26%。Ep2沿Ep1-r边缘生长，不均匀且经历了溶解-再沉淀过程，X_Fe值为0.15~0.20，w（MnO）为0.42%~1.19%，w（TiO₂）为0.02%~0.07%。Ep3呈柱状或不规则粒状交代Ep2、贴近或穿切Ep1-r生长，较均匀、无环带结构，X_Fe值为0.28~0.37，w（MnO）为0.12%~0.77%，w（TiO₂）为0.02%~0.10%。绿帘石成分变化表明，从Ep1-c到Ep1-r，到Ep2，再到Ep3，流体体系氧逸度经历了先增加，后降低，再升高的变化过程。同时，流体成分也在变化，先从相对贫Ti和Mn向相对富Ti贫Mn演化，而后又变为富Mn贫Ti。因此，在热液磁铁矿矿化阶段，查岗诺尔铁矿的成矿热液的物理-化学环境是不断变化的。研究显示，石榴子石和绿帘石结构和成分研究可以刻画热液成矿系统的流体演化历史。  相似文献