The late Quaternary evolution of the Negro River, Amazon, Brazil: Implications for island and floodplain formation in large anabranching tropical systems

The Rio Negro has responded significantly in the Late Pleistocene and Holocene to lagged environmental changes largely associated with activity during the last glacial in the Amazon basin. On the basis of geological structure, the Rio Negro can be divided into six distinct reaches that each reflects very marked differential processes and geomorphological styles. No deposits of the Upper Pleniglacial were recognized in the field. The oldest recognizable Late Pleistocene alluvial unit is the Upper Terrace of Middle Pleniglacial age (ca. 65–25 ka) (reach I), tentatively correlated with the oldest terrace identified on the left bank of reach III. At that time, the river was mainly an aggradational bed load system carrying abundant quartz sand, a product of more seasonal conditions in the upper catchment. The late glacial (14–10 ka) is represented by a lower finer-grained terrace along the upper basin (reach I), which was recognized in the Tiquié, Curicuriarí, and Vaupes rivers. At that time, the river carried abundant suspended load as a response to climatic changes associated with deglaciation.Since about 14 ka, the river has behaved as a progradational system, infilling in downstream series a sequence of structurally controlled sedimentary basins or ‘compartments,’ creating alluvial floodplains and associated anabranching channel systems. Reach II was the first to be filled, then reach III, both accumulating mainly sand. Fine deposits increase downstream in reach III and become predominant in some anabranch islands of the distal reach. The lowermost reaches of the Negro (V and VI) have been greatly affected by a rising base level and associated backwater effect from aggradation of the Amazon during late glacial and recent times. Reach V has acted almost entirely as a fine sediment trap. The remarkable Anavilhanas archipelago is the product of Holocene deposition in the upper part of this sedimentary basin; however, suspended sediment load declined about 1.5 ka, prior to the lower part of this basin becoming infilled.The progradational behavior of the Rio Negro, filling tectonic basins as successive sediment traps with sand in the upper basins and fines in the downstream ones, illustrates how a large river system responses to profound changes in Late Quaternary base level and sediment supply. The most stable equilibrium conditions have been achieved in the Holocene in reaches IIb and IIIa, where an anabranching channel and erosional–relictual island system relatively efficiently convey water and sediment downstream. Reaches IIIb and V never achieved equilibrium conditions during the Holocene, characterised as they are today with incomplete floodplains and open water.     

黄河下游河道改道的地理变化特征(英文)

The changing pattern of the Lower Yellow River (LYR) obtained from the traditional studies, which mainly did literal analysis based on historical documents related to the LYR are too macroscopic and absent of intuitiveness. This paper integrates all the records in historical documents related to course shift, flood and overflow of the last 3000 years and stores them in a GIS database. Then, all the data will be visualized in the form of map, which is helpful to show and understand the rules those events conform more intuitively and accurately. Taking these data as foundation, this study summarizes characteristics of the LYR’s courses and influence scope, and classifies them both into three types; divides the flow directions of the LYR’s courses into two periods, and proposes its changing pattern; concludes the characteristic of diversion points of courses shift events; calculates the velocity of courses shifts, gradient and sinuosity, and analyzes their changing patterns. Finally, this study classifies factors that may influence the occurrence of a course shift into two types: the internal factors, such as sediment rate, gradient and sinuosity of the river, and the external factors, such as precipitation and human activities.     

GIS支持的澜沧江下游区泥石流爆发危险性评价

澜疮江下游区是我国泥石流灾害相对频发的地区之一，在分析泥石流形成发育影响因素的基础上，指出澜沧江下游区泥石流的爆发主要受沟道坡度，植被覆盖度／土地利用和降水等环境因素影响，据此，构建了泥石流爆发危险性评价数据库，知识库和危险性评价数字环境模型，在ARC／INFO，GIS的支持下，提取了坡度，植被盖度和降雨量等主要泥石流危险性评价指标。依据知识库对各类因子进行了分级和赋权，对澜沧江下游区泥石流爆发危险性进行了区划。     

闽江下游全新世孢粉记录的植被与环境变化

为了揭示闽江下游闽侯盆地第四纪沉积环境演变与人类活动历史,对闽江下游闽侯盆地庄边山遗址附近的FZ5钻孔进行了孢粉、硅藻分析。结果表明：闽侯盆地全新世海侵初始发生时间约为9 000 cal. a B.P.,至7 500 cal. a B.P.达到最大海侵范围,晚全新世海退的发生时间在闽侯盆地大约为1 900 cal. a B.P.。孢粉分析证实了当地早中全新世温暖的亚热带气候以及浓密的常绿阔叶林植被。在7 500―1 900 cal. a B.P.之间无论植被覆盖还是气候环境均比较稳定,高海平面时期的适宜气候以及海湾环境也有利于当地以渔猎经济方式为主的新石器文化（昙石山文化）的兴起和发展。自1 900 cal. a B.P.以后,孢粉组合突变为以先锋植物芒萁属（Dicranopteris）、禾本科（Poaceae）、松属（Pinus）等类型为主,揭示了当地植被受到人类农业刀耕火种的影响而发生显著变化。高含量的禾本科花粉（含一定数量的水稻）仅在剖面上部明显增加这一事实,证实了闽侯和福州一带水稻种植的大面积发展始于距今1 900 a前后。     

Impacts of climate change and agricultural activities on water quality in the Lower Kaidu River Basin,China

In the context of climate change and over-exploitation of water resources, water shortage and water pollution in arid regions have become major constraints to local sustainable development. In this study, we established a Soil and Water Assessment Tool (SWAT) model for simulating non-point source (NPS) pollution in the irrigation area of the lower reaches of the Kaidu River Basin, based on spatial and attribute data (2010–2014). Four climate change scenarios (2040–2044) and two agricultural management scenarios were input into the SWAT model to quantify the effects of climate change and agricultural management on solvents and solutes of pollutants in the study area. The simulation results show that compared to the reference period (2010–2014), with a decline in streamflow from the Kaidu River, the average annual irrigation water consumption is expected to decrease by 3.84x10⁸ m³ or 8.87% during the period of 2040–2044. Meanwhile, the average annual total nitrogen (TN) and total phosphorus (TP) in agricultural drainage canals will also increase by 10.50% and 30.06%, respectively. Through the implementation of agricultural management measures, the TN and TP in farmland drainage can be reduced by 14.49% and 16.03%, respectively, reaching 661.56 t and 12.99 t, accordingly, and the increasing water efficiency can save irrigation water consumption by 4.41 x10⁸ m³ or 4.77%. The results indicate that although the water environment in the irrigation area in the lower reaches of the Kaidu River Basin is deteriorating, the situation can be improved by implementing appropriate agricultural production methods. The quantitative analysis results of NPS pollutants in the irrigation area under different scenarios provide a scientific basis for water environmental management in the Kaidu River Basin.

     

黄河下游主槽断面形态对水沙变化响应过程的模拟

准确把握环境变化下前期水沙条件对当前河床形态调整的影响,建立非平衡态河床形态调整的模拟方法,对深化河床非平衡调整过程的认识至关重要。基于黄河下游花园口—利津河段1965—2015年的水沙和沿程82个大断面数据,首先统计分析了不同河段主槽断面形态参数（面积、河宽、水深和河相系数）的调整过程及其对水沙变化的响应规律;进而以水沙因子作为主槽断面形态调整的主控因素,采用滞后响应模型的多步递推模式,建立了其对前期水沙条件变化的滞后响应模型。结果表明,各河段面积、河宽和水深经历了减小—增加—减小—增加的变化过程,并且其与4 a滑动平均流量和含沙量之间分别呈正相关和负相关;而河相系数孙口以上段整体减小,孙口以下段呈增加—减小—增加—减小的变化过程,除花高段1965—1999年外,其与流量呈负相关,与含沙量呈正相关。滞后响应模型在黄河下游主槽断面形态对前期水沙条件响应过程的应用表明,各参数模型计算值与实测值符合程度均较高,模型能够很好地模拟主槽断面形态对水沙变化的响应调整过程,模型计算结果显示主槽断面形态调整受当年在内的前8 a水沙条件的累积影响,当年和前7 a水沙条件对当前断面形态的影响权重分别约为30%和70%。本文模型有助于深化前期水沙条件对当前河床形态调整影响机理的认识,并为未来不同水沙情形下主槽断面形态的预测提供了有效计算方法。     

Integrated hydrologic modeling in the inland Heihe River Basin, Northwest China

As a typical inland river basin in arid Northwest China, having distinct hydrological characteristics and severe and representative water problems, the Heihe River Basin (HRB) has attracted considerable research interest worldwide and in 2007 became a pilot basin of the G-WADI network of UNESCO/IHP. Many research programs have been conducted in the HRB since the 1980s, producing rich knowledge and data about the basin, which will be very helpful to further studies. This paper reviews research efforts related to hydrologic modeling and ongoing model integration studies performed in the HRB in recent years. Recently, an observation network covering the whole area and a Web-based data-sharing system have been established which can greatly improve data acquisition. This paper tabulates modeling activities in past years, including model applications, model modifications and enhancements, and model coupling efforts. Also described is a preliminary modeling integration tool designed to quickly build new models, which has been developed for hydrologic modeling purposes. Challenges and issues confronted in current studies are discussed, pointing toward key research directions in the future.     

海河流域水资源短缺风险研究

本文对海河流域水平衡和水资源短缺风险进行评价。文章采用研究时段为1994-2007年,作者首先研究了海河流域的水量平衡问题,并提出了流域非用水消耗量的概念和计算方法,经过分析,计算得出海河流域多年平均非用水消耗量为5.91×109m3。通过建立水资源短缺风险的评价方法,得出海河流域1994-2007年处于缺水量较多、缺水风险较高的时期,计算出缺水风险率、恢复性指标、稳定性指标和脆弱性指标分别为0.786、0、0.154和0.173。在考虑社会系统应对措施的条件下,水资源短缺风险将会显著下降。考虑南水北调工程对于该地区的影响,分别考虑在50%和75%两种来水水平年下,如果南水北调工程一期（2014年）的来水量为5×109m3,未来该地区的水资源短缺风险会从0.229-0.297下降到0.152-0.234。     

Geomorphological explanation of the long profile of the Lower Mississippi River

Concavity in the long profile of rivers has traditionally been explained through the concept of grade, in which the slope declines downstream as a response to changing discharge, bed material size and sediment transport. Applying this concept to particular river systems has, however, proved problematic. The long profile reflects spatially-distributed form–process feedbacks between all aspects of channel morphology operating at a range of poorly defined time- and space-scales, and in the presence of natural controls. In many river systems, process–form dynamics are further complicated by engineering interventions which add additional extrinsic controls and constrain the range of intrinsic dynamics. In this paper, the 1974–75 long profile of the Lower Mississippi River is examined at three scales: the regional; the reach; and the sub-reach (pool–crossing) scales. A combination of curve-fitting, zonation algorithms, and empirical classification techniques are used to show that, although the long profile of the Lower Mississippi River is concave at the largest scale, the profile is characterised by discontinuities, shorter trends and zonal variations in the amplitude and wavelength of pool–crossing morphology. These characteristics are a response to morphological and bed material changes relating to a range of physical (geological, tectonic, tributary input) and engineering controls. Despite its apparent simplicity and correspondence to a ‘graded’ condition, the long profile of the Lower Mississippi River is actually a complex and scale-dependent morphological property. At best, the concave river profile is, therefore, a property which emerges from several scales of process–form interaction; at worst, it is no more than an artefact arising from the application of over-simplified curve-fitting techniques. Disclosure of the nature of the long profile thus requires the application of a variety of analytical techniques, as well as geomorphological explanations which are themselves scale-dependent and which consider the interaction of natural processes and the history of engineering intervention.     

塔里木河下游垦区绿洲生态系统服务的价值

生态系统服务价值的评估研究是生态学结合社会发展所面临的环境挑战而出现的一个新的研究热点 ,是建立绿色国民经济核算体系的基础工作。以Constanza等对全球各类生态系统服务单位公顷价值的平均估算结果 ,根据对 1986年、1990和 2 0 0 0年的塔里木河 (以下简称塔河 )流域 1 10万的陆地卫星TM图像解译数据为基础 ,在分析塔河下游土地利用与植被覆盖变化的同时 ,对塔河下游以塔里木垦区为主的人工及部分天然绿洲区生态系统服务的价值予以估算 ,结果表明 :按当前价计算 ,研究区生态系统服务的年价值 1986年为 77.84× 10 6＄ ,相当于6 4 6 .0 72× 10 6元人民币 ;1990年为 10 5 .93× 10 6＄ ,相当于 879.2 19× 10 6元人民币 ;2 0 0 0年为 183.77× 10 6＄ ,相当于 15 2 5 .2 91× 10 6元人民币。由于缺乏对盐碱荒地、居民点用地、沙丘 /戈壁等的相关研究信息 ;因此 ,该结果是对研究区生态系统服务总价值的保守估计。     

遥感与地理信息系统技术在长江下游江岸稳定性评价中的应用

应用多时相遥感动态分析方法对长江南京以下河段近四十多年来江岸变迁进行调查,并建成江岸变迁图形数据库。对多期航道水深测量资料进行动态分析,建成航道水深数据库。应用地理信息系统技术,研究河床时空演变规律,结合沿江地质地貌,护岸工程等消息,对长江下游江岸稳定性进行评价。     

石羊河中下游流域植被的演替历史

以参考历史文献、实地调查和访问当地居民的方法,研究了石羊河中下游流域的植被演替。结果表明,该流域2000多年前为湖泊、沼泽和平原景观,后来由于气候和水文演化、人类活动加强和干旱加剧,导致湖泊与河流逐渐消失、绿洲因水系的变迁而向东南移动、早期的绿洲农田逐渐沙漠化,也使植被从水生、沼泽、草甸植物向沙旱生、强旱生、超旱生方向演替,物种大量消失,已演化成现在的沙漠、戈壁与绿洲景观。目前, 该流域红崖山水库以南的一些河道中尚有常年流水,河漫滩和湿地中还有水生、沼泽、草甸和中生植物种类,物种相对丰富;而水库以北的古河床及广大荒漠区植被稀疏,且多为沙旱生和强旱生植物种类,生物多样性低,稳定性差,沙漠化过程加强。要恢复流域植被、遏制土地沙漠化,应当采用调水、引水和节约用水的方法,加强绿洲保护,使地下水位恢复至植物可吸收利用状态。     

Simulating cross-sectional geometry of the main channel in response to changes in water and sediment in Lower Yellow River

Journal of Geographical Sciences - To understand the non-equilibrium morphological adjustment of a river in response to environmental changes, it is essential to (i) accurately identify how past...     

历史时期黄河下游的淤积、决口改道及其与人类活动的关系

黄河是世界闻名的多沙性河流,历史时期就不断淤积、决口改道,且淤积速度不断加快,决口改道的频率也在不断增加。黄河下游地上河的发展和演变是自然因素和人类活动综合作用的结果。历史时期流域内人口的增加、耕作方式的改变及其对植被造成的破坏都对中游地区侵蚀的加剧、来沙的增加,以及下游地区河道的淤积及决口改道的发生带来不同程度的影响。     

鸭绿江下游江心洲资源与鸟类保护

鸭绿江下游有江心洲53个,其中中方有13个。江心洲是鸟类南北迁徙的脚踏石,是许多动物繁殖的斑块,是城市重要的景观资源,同时也是中朝两国间的重要战略资源。中方许多大型岛屿都已被开发成工业园区、住宅、高尔夫球场或旅游度假村,旅游开发使岛上原有高耸、茂密的植被遭到破坏,相关珍稀鸟类消失,公众利益变成私有财产,暂时的经济税收取代了长久的生态价值。建议加强江心洲及相关各类资源的保护,实施森林岛屿的生态重建和修复,注重存在价值及非消耗性利用,树立保护即利用的辩证唯物主义资源价值观,使江心洲成为镶嵌在鸭绿江上的绿色宝石。     

塔里木河下游地下水位对植被的影响

对塔里木河下游断流河道2000~2002年9个地下水监测断面和18个植被样地的实地监测资料分析表明,地下水埋深对天然植被的组成、分布及长势有直接关系。地下水位的不断下降和土壤含水率大大丧失是引起塔里木河下游植被退化的主导因子。塔里木河下游的四次输水对其下游地下水位抬升起到了积极作用,河道附近地下水位呈逐级抬升过程,横向影响范围达1000 m左右,纵向上,表现为上段地下水抬升幅度较大 (达84%),下段抬升幅度较小 (6%)。随着地下水位的抬升,天然植被的响应范围由第一次输水后的200~250 m,扩展到第四次输水的800 m。     

黄河下游河道治理及滩区问题研究

从防灾观点出发, 从河道的水动力学特性入手, 研究决定黄河下游河道水动力学特性的因素, 找到河道水 动力学特性和影响因子之间的关系。在此基础上, 从水流运动和泥沙输移之间的关系出发, 分析黄河下游河道的泥 沙运动特性, 对于黄河下游河道的演化特性作了探讨, 对于治理黄河提出了建议。和黄河下游河道紧密联系的下游 滩区问题, 不仅仅是一个自然科学的问题, 而且是和社会、经济、环境、资源等问题相关的一个综合性问题, 本文从 可持续发展的角度出发, 给出了解决滩区问题的建议。     

Response of bankfull discharge to discharge and sediment load in the Lower Yellow River

This paper presents a study on the response of bankfull discharge to incoming discharge and sediment load based on long-term hydrological and bankfull discharge data measured on the lower reaches of the Yellow River. The analysis indicated that the bankfull discharge was a function of the preceding 5 to 6 years' flow regimes, revealing that bankfull channel dimensions were a result of the accumulative effect of several consecutive years' flow discharge and sediment load conditions. In other words, the mean relaxation time was about 5 to 6 years for channel adjustment. Theoretical methods for the prediction of bankfull discharge were developed, in which the response time or the relaxation time was fully considered. Testing of the methods using data observed at five hydrologic stations in the lower reaches of the Yellow River from 1960 to 2003 showed that the proposed methods can predict the variation of bankfull discharge in response to changes in the incoming discharge and sediment load. The proposed methods hold promise for predicting the magnitude and trend of channel response to other rivers undergoing aggradation or degradation from changes in hydrologic or sediment regime.     

黑河流域水资源承载力分析计算与对策

根据干旱区水资源开发利用阶段可用水资源的计算方法和内陆河流域社会经济发展及其需水预测,分析计算了黑河流域中游地区的水资源承载力。结果表明,当完成水资源开发利用第二阶段,可用水资源在首先保证未来50 a内流域中游地区人口、环境和工业等部门发展的需水后,农业灌溉用水的总量将还有所增加,水资源不会成为社会经济发展的制约因素,可以使绿洲和农业走可持续发展道路。但东干流中游张掖盆地,因要在下世纪初完成分水指标,在下世纪的前20 a农业灌溉用水有缺口,但只要加大农业节水力度,在此期间提前完成农业节水目标的60%,就能顺利渡过今后20 a的社会经济快速发展时期。如果在2050年能按计划完成流域社会经济发展的预测目标,则届时流域人均国内生产总值将超过一万美元,可以达到世界中等发达国家的水平。     

Environmental factors and pattern of riparian vegetation along the downstream sections of the Lower Ogun River,Nigeria

The River Continuum Concept (RCC) is an existing theory regarding the distribution of plant communities along riverbanks. This study is concerned with the pattern of riparian vegetation along the Lower Ogun River (LOR) in relation to the observed downstream variation of various environmental factors (bank height, width, gradient, distance, cross‐sectional area and particle size). The LOR transits between undisturbed and disturbed sections. Forty‐eight cross sections were established at bankfull stage along the river channel stretch of about 90 km. Environmental variables distribution were determined using standard field procedures. Gradient was estimated from a 1:50 000 topographical map. At each corridor along the study sites, a 0.1 ha sampling site was chosen, in which 10 transects of 100 m² were demarcated. In all, 332 individuals stratified under 80 species were recorded across the transects. The study revealed that total species richness (TSR) downstream decreases exponentially. TSR is significantly correlated with channel width, suggesting that hydraulic variable contributes more to the variation in TSR. The downstream total environmental factors revealed that width is inversely significant with downstream distance, suggesting that the river channel is narrower downstream. This affects plant life form distribution downstream and confirms why there is appearance of anthropogenic induced species downstream as against those in the upper course.