Nutrient characteristics in the Yangtze River Estuary and the adjacent East China Sea before and after impoundment of the Three Gorges Dam

From November 2002 to 2006, five cruises were undertaken in the Yangtze River Estuary and the adjacent East China Sea to compare the nutrient concentrations, ratios and potential nutrient limitation of phytoplankton growth before and after impoundment (June 2003) of the Three Gorges Dam (TGD). Concentrations of dissolved inorganic nitrogen (DIN), soluble reactive phosphorus (SRP) and total nitrogen (TN) exhibited an increasing trend from 2002 to 2006. In contrast, total phosphorus (TP) concentration exhibited a decreasing trend. The mean concentrations of DIN, SRP, and TN in the total study area increased from 21.4 µM, 0.9 µM, and 41.8 µM in 2002 to 37.5 µM, 1.3 µM, and 82.2 µM in 2006, respectively, while TP decreased from 2.1 µM to 1.7 µM. The concentration of dissolved reactive silica (DRSi) had no major fluctuations and the differences were not significant. The mean concentration of DRSi in the total study area ranged from 52.5 to 92.3 µM. The Si:N ratio decreased significantly from 2.7 in 2002 to 1.3 in 2006, while TN:TP ratio increased from 22.1 to 80.3. The area of potential P limitation of phytoplankton growth expanded after 2003 and potential Si limitation appeared in 2005 and 2006. Potential P limitation mainly occurred in an area of salinity less than 30 after 2003, while potential Si limitation occurred where the salinity was greater than 30. By comparison with historical data, the concentrations of nitrate and SRP in this upper estuary during November 1980-2006 increased obviously after impoundment of TGD but DRSi decreased. Meanwhile, the ratios of N:P, Si:N and Si:P decreased obviously.     

三峡库区塔坪H2古滑坡台阶状复活变形的库水–降雨耦合作用机制

三峡水库蓄水以来,出现了大量大规模的老滑坡体复活现象。较多大型复活滑坡体的监测位移–时间曲线呈台阶状阶跃变化。此类滑坡的稳定状态识别难度较大,严重影响治理方案及治理时机的选择。以巫山曲尺塔坪H2滑坡为例,通过地质、位移监测及数值模拟方法,研究了此滑坡在实际降雨与库水涨落条件下渗流场、稳定性以及变形场演化规律。在汛期及库水位变动时期滑坡会发生变形,特别是库水位下降诱发滑坡前缘变形,并对后部坡体产生牵引作用。而降雨主要影响库水位变动带以上部分滑体的变形,并对前缘坡体产生推动作用。在周期性降雨和库水位涨落的循环作用下,滑坡体反复受到"推–拉"作用,导致滑坡的位移–时间曲线呈现台阶状阶跃特征。总体来说,库水位涨落是滑坡变形的主要因素,而降雨促进了滑坡变形进一步发展。     

库水位下降诱发的特大型顺层岩质滑坡变形特征与诱发机制

通过三峡库区旧县坪滑坡2016年6月?2018年8月的GNSS监测数据,采取多因素综合过程分析和定量分析手段,分析了滑坡变形在库水位7个不同变化过程下的响应特征和诱发机制.研究表明:(1)库水位下降是旧县坪滑坡位移变形的主要诱发因素,一般情况下,库水位下降速率越大,滑坡稳定性越差:库水位快速下降期间(＞0.4 m/d)...     

长江三峡区八字门滑坡稳定性分析与评价

在研究了三峡库区秭归县八字门滑坡的工程地质条件及滑坡体基本特征的基础上,介绍了该滑坡的结构及变形特征,从滑坡形成条件和诱发变形因素两方面分析了滑坡形成的原因及诱发坡体失稳的主要因素.在不同工况下及地震作用下对滑坡体进行稳定性计算,结果表明,在库水位变化和暴雨情况下滑坡处于不稳定状态,极有可能复活.     

Genesis and stability of the Zhoujiawan landslide,Three Gorges,China

The development of the Three Gorges project has resulted in the study of a number of landslides along the Yangtze River. This paper discusses three landslides in the Huanglashi group, some 66 km upstream of the Three Gorges dam. It describes the development and inter-relationship of these landslips, which occurred on the concave meander of the river where steep slopes were created by uniclinal shifting as incision took place. Finite element analysis was used to assess the most likely zone in which future failures will occur.      

Probabilistic stability analysis of Bazimen landslide with monitored rainfall data and water level fluctuations in Three Gorges Reservoir,China

Landslide is a common geological hazard in reservoir areas and may cause great damage to local residents’ life and property. It is widely accepted that rainfall and periodic variation of water level are the two main factors triggering reservoir landslides. In this study, the Bazimen landslide located in the Three Gorges Reservoir (TGR) was back-analyzed as a case study. Based on the statistical features of the last 3-year monitored data and field instrumentations, the landslide susceptibility in an annual cycle and four representative periods was investigated via the deterministic and probabilistic analysis, respectively. The results indicate that the fluctuation of the reservoir water level plays a pivotal role in inducing slope failures, for the minimum stability coefficient occurs at the rapid decline period of water level. The probabilistic analysis results reveal that the initial sliding surface is the most important area influencing the occurrence of landslide, compared with other parts in the landslide. The seepage calculations from probabilistic analysis imply that rainfall is a relatively inferior factor affecting slope stability. This study aims to provide preliminary guidance on risk management and early warning in the TGR area.     

适应水位变化的鸟类生境修复研究——以 三峡水库澎溪河大浪坝为例

蓄水后三峡水库消落带的剧烈水位变化与反季节水 淹，导致鸟类生境数量与质量的双重衰退，并引发鸟类群落组 成与空间分布的显著变化。针对适应水位变化并恢复鸟类多样 性这一三峡水库生物多样性保护的重要科学问题，选取澎溪河 大浪坝消落带为研究区域，基于栖息、觅食、繁殖及庇护等鸟 类生境综合需求，提出以“环境要素-生物要素-空间结构”协 同设计为核心的鸟类生境修复技术框架。对修复后大浪坝消落 带鸟类群落的结构及多样性变化进行评估，结果表明：鸟类生 境质量显著改善，在不同季节及水位条件下均能维持良好的鸟 类生境异质性，鸟类多样性得到持续提升。研究成果可为复杂 水位变化影响下大型水库消落带的鸟类生境修复与多样性提升 提供科学依据和可参考的技术范式。     

Significance of outward dipping strata in argillaceous limestones in the area of the Three Gorges reservoir,China

Re-location of the town of Fengjie due to the impounding of the Three Gorges reservoir involved some significant excavations into the valley slopes. It was noted that the mainly calcareous strata in gullies had a northerly dip while in the excavation the dips were sub-horizontal and even southerly, towards the Yangtze River. The paper discusses the process which leads to this change in dip in the superficial strata. This is particularly significant where orthogonal sub-vertical discontinuities are present such that gravitational effects result in blocks toppling out of the free face.     

三峡库区重庆段人居环境与经济协调发展研究

人居环境和经济发展是城市综 合系统中的两个重要因素,既相互促进, 又相互制约。本文采用定量分析方法探 讨库区人居环境与经济协调发展所面临 的问题。选取三峡库区重庆段8个区县 2004-2011年人居环境与经济发展的数 据资料,采用主成分分析法,计算人居环 境和经济发展指数,确定协调程度;再 通过横向对比,总结出库区人居环境与 经济协调发展的四种类型,并分析四种 类型的成因。在此基础上,对三峡库区 后续人居环境建设和经济协调发展策略 提出建议。     

三峡库区万州区膨胀性滑带土抗剪强度参数变化规律的试验研究

本文主要是以万州区近水平地层滑坡的滑带土为研究对象从影响滑带土抗剪强度参数的因素出发设计出切实可行的试验,全面系统地研究了粘粒含量、含水量和应力状态与抗剪强度参数的关系并对其机理进行详细的解释。可为万州区近水平地层滑坡以及具有膨胀性滑带土滑坡的稳定性评价和设计治理工程提供可靠的力学参数。     

2000—2020年三峡库区生态系统服务时空演变及驱动力研究

三峡库区生态环境变化是影响长江流域生态安全的关键因素。本文基于PSR模型建构生态系统服务“供给—调节—支持”的功能评价方法和“状态—压力”的驱动力识别要素体系,采用地理探测器和空间相关性分析方法,揭示了三峡库区生态系统服务功能在库首、库中、库尾的互构特征及驱动机理。研究表明：三峡库区蓄水初期对生态系统服务功能影响显著,不同区位的类聚作用逐年变强;生境面积比和土地利用强度是近20年影响库区生态系统服务功能的核心指标,地形位指数也凸显对山地城市生态系统服务功能的决定性作用;库首需关注景观多样性,库尾应处理好建设空间与生态空间的平衡关系。研究结果旨在为三峡库区生态修复与生态服务功能提升提供参考。     

新时期重庆三峡库区城乡统筹发展的规划思考

直辖十年,重庆提出了新的“一圈两翼”空间发展战略。并在2007年6月经国务院批准成为“统筹城乡综合配套改革试验区”。重庆三峡库区,在历经三峡工程开工以来的十多年建设后,又站在了新的发展起点上。文章在分析重庆三峡库区内涵变化的基础上,着眼于“一圈两翼”和“城乡统筹”发展战略,分析了重庆三峡库区在直辖十年后所面临的新的功能定住和新的发展态势,提出了重庆三峡库区城乡统筹发展的几点规划思考意见。     

Distribution of soil moisture and salinity in shelterbelts and its relationship with groundwater level in extreme arid area,northwest of China

Because of the shortage of water source in the extreme arid area, generally, there are several years of no irrigation on mature shelterbelts. In this study, the shelterbelt soil in different texture were compared based on distribution analysis of the soil moisture and salt levels of shelterbelts under large‐scale drip irrigation in Kalamiji Oasis in the lower reaches of Tarim River, Northwest China. The following conclusions were drawn. (1) In Kalamiji Oasis, the groundwater level declined at a rate of 0.5 m/a as a result of popularization of drip irrigation technology. (2) There was a larger heterogeneity in distribution for soil moisture in the sandy/loamy shelterbelt than in the clay shelterbelt. (3) Under non‐irrigation conditions, sandy/loamy shelterbelt has lower soil moisture and salinity, and clay shelterbelt has higher soil moisture and salinity. (4) The shelterbelt with the shallowest groundwater depth had highest soil moisture level, and the shelterbelt with the deepest groundwater level had the lowest soil moisture content. (5) In sandy and loamy shelterbelts, the shelterbelts with the shallowest groundwater depths had the lower salinity levels and the shelterbelts with the deepest groundwater depths had the highest salinity levels. (6) In clay shelterbelts, the shelterbelts with the shallowest groundwater depths had the highest salinity levels, and the shelterbelts with the deepest groundwater depths had the lowest salinity levels. Additionally, it is essential to implement irrigation at least once a year.     

Changing from intermittent to continuous water supply and its influence on service level benchmarks: a case study in the demonstration zone of Nagpur,India

A dearth in infrastructure and operations significantly reduces the expected benefits of safe drinking water provision. Intermittent water supplies are characterized by inefficient demand and supply management owing to operational inadequacies eventually causing physical deterioration of infrastructure and inconvenience to consumers, resulting in consumer dissatisfaction. Conversion from intermittent to continuous water supply was undertaken in a demonstration zone of Nagpur, India, with a population of about 150,000 people. Data related to the infrastructural, operational, managerial and financial capabilities were used to determine service level benchmarks (SLBs) — pre- and post-intervention — to quantify the improvement due to continuous water supply interventions. The post-intervention data analysis clearly indicated substantial improvement in post-intervention SLBs, consequently paving the way for the conversion of the water supply of the entire city to continuous mode.