Spatio-temporal trends and causes of variations in runoff and sediment load of the Jinsha River in China

The Jinsha River Basin is an important basin for hydropower in China and it is also the main runoff and sediment source area for the Yangtze River,which greatly influence the runoff and sediment in the Three Gorges Reservoir.This study aims to characterize the spatial distribution,inter-annual variation of runoff and sediment load in the Jinsha River Basin,and to analyze the contribution of rainfall and human activities to the runoff and sediment load changes.The monitoring data on runoff,sediment load and precipitation were collected from 11hydrological stations in the Jinsha River Basin from1966 to 2016.The data observed at the outlet of the basin showed that 71.4%of the runoff is from the upper reaches of the Jinsha River Basin and the Yalong River,while 63.3%of the sediment is from the lower reaches(excluding the Yalong River).There is no significant increase in runoff on temporal scale in the Jinsha River Basin,while it has an abrupt change in runoff in both upstream and midstream in 1985,and an abrupt change in downstream in 1980 and2013.The sediment load demonstrated a significantincreasing trend in the upstream,no significant reducing trend in the midstream,but significant reducing trend in the downstream.The sediment load in upstream showed abrupt change in 1987,in midstream in 1978 and 2014,in downstream in 2012.Rainfall dominated runoff variation,contributing more than 59.0%of the total variation,while human activity,including reservoirs construction,the implementation of soil and water conservation projects,is the major factor to sediment load variation,contributing more than 87.0%of the total variation.     

Three Gorges Dam controls sediment coarsening of the mud patch on the inner East China Sea shelf

The well-known Three Gorges Dam(TGD) within the Yangtze catchment launched its operation in 2003. The effect of the TGD operation on the sediment size on the East China Sea shelf is rarely known. High resolution(0.5 cm sampling) grain size analysis and 137 Cs and 210 Pb dating of the DH8-1 core were conducted with core collected from the distal part of a main sink for the modern Yangtze sediment entering the sea, the Min-Zhe Coastal Mud Deposits(MZCMD) on the inner East China Sea shelf. The 137 Cs dating results show that the core DH8-1 formed during 1946–2012 with a mean deposition rate of 0.65 cm yr~(-1), indicating that the 0.5 cm sampling for grain size analysis in this local area could reflect environmental changes generally on a one-year time scale. The mean grain size of DH8-1 core sediment that deposited after 2003 is significantly larger than that deposited during 1988–2002. After ruling out other possible factors, we infer that the sediment coarsening of DH8-1 core after 2003 is attributed to the TGD operation which causes the erosion of the Yangtze subaqueous delta. Specifically, the TGD operation significantly intensifies the declining trend of the Yangtze sediment loads to the sea despite no decreased water discharge, which results in extensive erosion of the Yangtze subaqueous delta. The relatively coarse sediment of the subaqueous delta is eroded and resuspended by ocean dynamics and then transported by coastal current, finally depositing on the MZCMD area. In addition, the general sediment fining of core DH8-1 that deposited during 1988–2002, comparing with 1946–1987, is mainly caused by dam construction and soil and water conservation within the Yangtze catchment. Our findings are helpful for better understanding the effects of such a huge dam as the TGD on a sediment sink like the MZCMD of such a large river as the Yangtze River.     

Long-term impact of extra sediment on notches and incised meanders in the Hoshe River, Taiwan

The extra sediment load induced by typhoons and rainstorms in the Heshe River,Taiwan,are the principal reason for severe sediment-related disasters.The total sediment load during Typhoon Morakot in 2009 was 31 × 106m3,accounting for 95% of the annual sediment discharge.Large amounts of sediment load entered the Hoshe River,causing the braiding index(BI) to increase.Subsequently,the BI became positively correlated with the channel width in the Hoshe River.The specific typhoon and rainstorm events decreased after Typhoon Morakot,the sediment input decreased,inducing the fluvial morphology of the braided river to develop into a meandering river.The extra sediment load induced the deposition depth to increase and produce a headward deposition in the main channel and its tributaries.In addition,the river bend and the topographical notch restrained the sediment from moving downstream and being stored locally,indirectly increasing the erosion density of the river banks from 2.5 to 10.5 times.     

Modelling the Effects of Land-use Change on Runoff and Sediment Yield in the Weicheng River Watershed,Southwest China

As a major sediment area in the upper Yangtze River, Jialing River basin experienced substantial land-use changes, many water conservancy projects were constructed from the 1980 s onward to promote water and soil conservation. The water and sediment yield at the watershed outlet was strongly affected by these water conservation works, including ponds and reservoirs, which should be considered in the modelling. In this study, based on the observed data of the Weicheng River catchment, the relationships between precipitation, runoff, vegetation, topography and sediment yield were analyzed, a distributed runoff and sediment yield model(WSTD-SED) was developed, and the hydrological processes of different land-use scenarios were simulated by using the model. The main results are summarized as follows: 1) there is an alternating characteristic in river channels and reservoirs in the Jialing River hilly area, with scour occurring in wet years and deposit occurring in dry years. 2) Most of the sediment deposited in river channels and reservoirs is carried off by the largest flood in the year. 3) The model yielded plausible results for runoff and sediment yield dynamics without the need of calibration, and the WSTD-SED model could be usedto obtain qualitative estimates on the effects of land use change scenarios. 4) The modelling results suggest that a 10% increase in cropland(dry land) reforestation results in a 0.7% decrease in runoff and 1.5% decrease in sediment yield.     

Heavy Minerals in Shelf Sediments off Fujian-Zhejiang Coast of the East China Sea: Their Provenance and Geological Application

To examine the composition and source variations of heavy minerals in the Fujian-Zhejiang mud belt(FZMB) over the past few hundred years, heavy minerals in 150 surficial sediment samples and two sediments cores collected from the southern FZMB were identified and analyzed. The results show that the mineral assemblage of hornblende-magnetite-epidote-chlorite is dominant in the study area. Based on the heavy mineral contents, the study area is divided into two mineral zones, namely a near-shore muddy sediment zone(zone Ⅰ) and an offshore mixed sediment zone(zone Ⅱ). The sediments from zone Ⅰ contains relatively abundant metallic minerals with proximal sediments from the Oujiang River and the Minjiang River as the primary component. The sediment from zone Ⅱ has relatively low content for minerals from the near-shore materials and is significantly affected by the Oujiang River sediments, and by the flaky minerals from the Yangtze River to a certain extent. The characteristics of heavy minerals in the cores may be affected by a variety of factors. Before the 20th century, under the influence of strong East Asian winter monsoon(EAWM), the sandy sediment in FZMB is significantly affected by the Oujiang River and the Yangtze River sediments, and relatively unaffected by near-shore terrigenous matter. In the 20th century, as the intensity of the Zhejiang-Fujian Coastal Current(ZFCC) decreased, the influence of the Minjiang coastal sand enhanced. Since the 1980s, as the collective effect of relatively weak EAWM and frequent storm surges and typhoons, the impact of the Minjiang River sediments on the FZMB sediments has increased considerably.     

秭归盆地东缘断裂构造觅踪——再论仙女山断裂带北延过长江问题

文章在概略介绍仙女山断裂带所处的大地构造位置、展布特征、组合关系基础上,用详实的材料,逐一分析了荒口—腰店子、腰店子—将军垭、将军垭—卜庄河及尹家湾—黄垭畔、黄垭畔—贾家店长江南北两岸各段的断裂构造形迹特征、力学性质和交切关系。认为仙女山断裂带已北延过长江,并建议对断裂的应力传递方式和可能出现的史前地震进行深入研究。     

Principal Denudation Processes and Their Contribution to Fluvial Suspended Sediment Yields in the Upper Yangtze River Basin and Volga River Basin

This paper synthesized the principal land denudation processes and their role in determining riverine suspended sediment yields(SSY) in two typical geographical environments of the Upper Yangtze River Basin in China and the Volga River Basin in Eastern Europe. In the Upper Yangtze River Basin, natural factors including topography, climate,lithology and tectonic activity are responsible for the spatial variation in the magnitude of denudation rates.Human disturbances have contributed to the temporal changes of soil erosion and fluvial SSY during the past decades. On one hand, land use change caused by deforestation and land reclamation has played an important role in the acceleration of sediment production from the central hilly area and lower Jinsha catchment; On the other hand, diverse soil conservation practices(e.g., reforestation,terracing) have contributed to a reduction of soil erosion and sediment production since the late 1980 s.It was difficult to explicitly decouple the effect of mitigation measures in the Lower Jinsha River Basindue to the complexity associated with sediment redistribution within river channels(active channel migration and significant sedimentation). The whole basin can be subdivided into seven sub-regions according to the different proportional inputs of principal denudation processes to riverine SSY. In the Volga River Basin, anthropogenic sheet, rill and gully erosion are the predominant denudation processes in the southern region, while channel bank and bed erosion constitutes the main source of riverine suspended sediment flux in the northern part of the basin. Distribution of cultivated lands significantly determined the intensity of denudation processes.Local relief characteristics also considerably influence soil erosion rates and SSY in the southern Volga River Basin. Lithology, soil cover and climate conditions determined the spatial distribution of sheet, rill and gully erosion intensity, but they play a secondary role in SSY spatial variation.     

Dynamics of loose granular flow and its subsequent deposition in a narrow mountainous river

A large amount of loose debris materials were deposited on the slope of mountainous areas after the 2008 Ms 8.0 Wenchuan earthquake. During and after the earthquake, these loose debris deposits collapsed and slide into valleys or rivers, changing river sediment supply condition and channel morphology. To investigate the mechanisms of granular flow and deposition, the dynamics of slope failure and sediment transportation in typical mountainous rivers of different intersection angles were analyzed with a coupling model of Computational Fluid Dynamics and Discrete Element Method(CFD-DEM). The numerical results show that the change of intersection angle between the granular flow flume and the river channel can affect the deposit geometry and the fluid flow field significantly. As the intersection angle increases, the granular velocity perpendicular to the river channel increases, while the granular velocity parallel to the river channel decreases gradually. Compared to the test of dry granular flow, the CFD-DEM coupling tests show much higher granular velocity and larger volume of sediments entrained in the river. Due to the river flow, particles located at the edge of the deposition will move downstream gradually and the main section of sediments deposition moves from the center to the edge of the river channel. As a result, sediment supply in the downstream river will distribute unevenly. Under the erosion of fluid flow, the proportion of fine particles increases, while the proportion of coarse particles decreases gradually in the sediment deposition. The build-up of accumulated sediment mass will cause a significant increase in water level in the river channel, thus creating serious flooding hazard in mountainous rivers.     

长江三角洲城市化地区植被初级生产力的时空变化研究

城市化过程对植被初级生产具有重要影响。以往研究主要集中于城市用地扩张对植被初级生产力的直接影响分析,而较少关注其间接效果。本文以长江三角洲地区为例,分别从地区尺度和城市尺度分别分析了2000-2013年植被初级生产力的时空变化,探讨了其与气温、降水量及城市建成区绿化覆盖率的关系。研究表明：地区尺度上,2000-2013年长江三角洲植被初级生产力呈现不断增加,其中城市建成区植被初级生产力呈现显著增加的趋势（P<0.05）;城市尺度上,城市建成区内植被初级生产力主要呈现增加的趋势,而其外围缓冲区内则与此相反。在当前气候变化背景下,这可能与城市建成区绿化覆盖率不断增加,及快速的城市扩张有关。     

黄河大柳树坝址岩体破坏机制动力模拟试验分析

黄河黑山峡大柳树坝址区存在大范围的岩体松动破坏现象，其主要特征是岩体应力释放，结构面张开，密度显著下降。为进一步研究岩体松动的成因机制，在详细调查区域地质背景条件及区域地震动力作用基础之上，提出了地震动力作用与岩体松动现象的内在联系。通过动力模拟试验进一步证明大柳树坝址区存在的大深度、大范围岩体松动与历史上该地区发生的强烈地震具有密切关系。因此在目前的工程地质条件下，一旦发生较大强度的地震活动，坝址区所遭受的破坏程度会更大，对拟建的水利工程设施将产生严重威胁。     

Sources of sediment in tidal fl ats off Zhejiang coast,southeast China

The growth of tidal fl ats off Zhejiang coasts in southwestern China has provided substantial areas for local agriculture and construction activities. To evaluate modern and future development of tidal fl ats in the region, a good understanding of sediment sources is necessary. Previous research has concluded that the Changjiang(Yangtze) River is the dominant supplier of sediments to this part of the southeast Chinese coast, despite the fact that sediment delivery from this source has been decreased markedly in the past two decades. In this study, we investigated the sources of tidal fl at sediments, and the magnetic and geochemical properties of recent tidal fl at sediments along the Zhejiang coast were compared with those discharged from rivers. Magnetic and geochemical properties of the tidal fl at samples reveal statistically distinct sediment provenance groups. The magnetic and geochemical scatter plots show that the suspended sediment samples are naturally divided into two diff erent groups, one including the Changjiang River and Qiantang River material, and the other including the Jiaojiang, Oujiang, and Feiyun Rivers that located in the central and southern parts of the study areas. At last, a binary source of tidal fl at sediments along the Zhejiang coast was determined, with the substantial majority originating from local rivers, while a much smaller proportion emanates from the Changjiang River to the north. We conclude that the sediment contribution of the Changjiang River to tidal fl at development in the region has been markedly overestimated, with important implications for management.     

137Cs finger printing technique for erosion and sedimentation studies

137 Cs is an artificial radionuclide with a half-life of 30.2 years,which was released into the environment as a byproduct of atmospheric testing of nuclear weapons during the period of 1950s to 1970s with a peak deposition in 1963.137 Cs fallout was strongly and rapidly adsorbed by soil particles when it deposited on the ground mostly with precipitation.Its following movements will associate with the adsorbed particles.137 Cs tracing technique has been widely used in soil erosion and sedimentation studies since 1980s.This paper introduces the basis of the technique and shows several case studies of assessment of soil erosion rates,investigation of sediment sources and dating of reservoir deposits by using the technique in the Loess Plateau and the Upper Yangtze River Basin.     

三峡水库建成后对长江河床演变影响的预测与对策

本文重点讨论了长江三峡水利枢纽建成后,水动力条件大大改变,必然会引起水库上、中、下游河床发生一系列的变化。如注入水库的各条支流,由于河流基准面被大大抬高,都会形成河口拦门沙和水下三角洲。分析了因入库河流基准面抬高,自然会引起水库上游河床的摆动变形。以及水库蓄水后,由于波浪、水流对库岸的侵蚀塑造作用和水库运营调蓄时,会产生动水压力和静水压力的变化,以及风浪的侵蚀、掏蚀,必然会大大引起库岸变形;对水库库区附近淹没、侵没和渗漏的影响;水库建成后,水库运营清水下泄时,由于含沙量大大减少,水的动能加大,任何水库都会引起其下游河道冲刷及河床变形,河床会发生演变,所以,三峡水库的河床也会有一个新的调整周期。     

Characteristics of Heavy Minerals and Quantitative Provenance Identification of Sediments from the Muddy Area Outside the Oujiang Estuary Since 5.8 kyr

The heavy mineral compositions of the sediments in core D04 with a length of 20.2 m from the muddy area outside the Oujiang Estuary along the coast of Zhejiang-Fujian Provinces have been analyzed. Core D04 can be divided into three units: DU1(0–7.4 m), DU2(7.4–11.4 m) and DU3(11.4–20.2 m). The results showed that the heavy minerals are authigenic pyrite(65.6%)– hornblende(16.0%) – epidote(4.6%) assemblages. The core sediments are mainly composed of clayey silt, which belongs to the clinoform deposit formed since 5.8 kyr, indicating a weak hydrodynamic environment. The deposition rates changed in the trend of high-low-high upward. Quantitative analysis shows that the core sediments were mainly from the suspended sediments of the Changjiang(Yangtze) River, accounting for 79.2%, with only 10.0% from Oujiang, and 10.8% from other provenance. The Oujiang-derived sediments were gradually increased from the bottom unit DU3(3.1%) to the top unit DU1(17.8%), but the Changjiang-derived sediments were gradually decreased. The source changes are closely related to the development of Yangtze River Delta and Wenzhou Bay, climate changes and human activities. During the period of 2.1–3.7 kyr, the sediment supply was greatly reduced due to the poor reclamation capacity of the river basins, resulting in a low deposition rate. Since 2 kyr, the enhancement of human activities in the Yangtze River Basin and the Oujiang River Basin led to more soils to be eroded and transported to the study area. Due to the short distance of the site of core D04 from the Oujiang River mouth, the study area received more Oujiang-derived sediments when upper unit(DU1) deposited than the lower units(DU2 and DU3).     

The Sources and Transport Patterns of Modern Sediments in Hangzhou Bay: Evidence from Clay Minerals

Clay mineral compositions of 199 offshore surface sediment samples collected from the Hangzhou Bay have been analyzed. The clay minerals in the sediments from the Hangzhou Bay are dominated by illite(58.7%, on average), followed by chlorite(20.3%), kaolinite(16.9%) and smectite(4.1%). Two provinces were classified by Q-mode cluster analysis. Class Ⅰ with relatively low amounts of illite and smectite is widely distributed in the Hangzhou Bay, especially concentrated in the top and mouth of the bay, and the northern and southern nearshore areas. Class Ⅱ with comparatively high amounts of illite and smectite is mainly concentrated in the central part of the bay with the water depth of 8–10 m. By comparing clay mineral compositions with the neighbouring regions, we can find that the sediments in the Hangzhou Bay are mainly influenced by the resuspension and repeated deposition of particles from the Yangtze River due to the strong dynamic environment. In particular, the clay fraction of Class Ⅰ is mainly supplied by the Yangtze River, while the sediments of Class Ⅱ are mixture of the clay minerals carried by the Yangtze River and Qiantang River. In general, the distributions of clay minerals in the northern bay are affected by Yangtze River runoff, coastal current and flood tide together, and in the southern they are mainly affected by the Qiantang River runoff and ebb tide.     

QUANTITATIVE MODELING OF SUSPENDED SEDIMENT IN MIDDLE CHANGJIANG RIVER FROM MODIS

1INTRODUCTIONThe quality of water is traditionally determined by col-lectingwatersamplesandanalyzingthesamplesin a lab-oratory. However, sampling is very much hard sledding,time-consuming, slow and expensive, and easily in thecontrol of weather conditions, and does not include allwater areas. Satellite estimates of water quality havefound widespread application. Remote sensing instru-ments have been applied in water quality monitoringwith varying success (DANA and RICHARD, 1999;RUDD…     

Multi-Time Scale Analysis of Runoff at the Yangtze Estuary Based on the Morlet Wavelet Transform Method

Runoff series of the Yangtze River presents an intricate variation tendency under the reinforced influence of human activities.The Morlet Wavelet Transform method has been applied to analyze the annual runoff data from 1950 to 2011 at the Yangtze River Estuary.It can clearly reveal the multi-time scales structure,break point,change and distribution of periodic variation in the different time scales of the runoff series.The main conclusions are that：1） Repeated periodic oscillations accompanied by an extremely large fluctuation are presented in the runoff series with an obvious difference between wet and dry years,and the major periods of the time series are about 3,8,16 and 23 years respectively.Among them,the presented maximum periodic oscillation is 23 years scale.2） In the 23-year time scale,the wet periods are 1950-1958,1969-1980 and 1992-2003,and the dry periods are 1959-1968,1981-1991 and 2004-2011.3） It can be predicted from the view of long time scales that the low annual runoff will likely occur in the near future.     

Clay mineral distribution in surface sediments of the South China Sea and its significance for in sediment sources and transport

Clay minerals of surface sediments in the South China Sea (SCS) are analyzed with X-ray diffraction, and their transport is explored with a grain size trend analysis (GSTA) model. Results show that clay mineral types in various sedimentary environments have different sediment sources and transport routes. Sediments in the northern SCS (north of 20°N) between the southwest of Taiwan Island and the outer mouth of the Pearl River have high contents of illite and chlorite, which are derived mainly from sediments on Taiwan Island and/or the Yangtze River. Sediments from the Pearl River are characterized by high kaolinite and low smectite content, and most are distributed in the area between the mouth of the Pearl River and northeast of Hainan Island and transported vertically from the continental shelf to the slope. Characterized by high illite content, sediments from Kalimantan Island are transported toward the Nansha Trough. Sediments from Luzon Island are related with volcanic materials, and are transported westwards according to smectite distribution. On the Sunda Shelf, sediments from the Mekong River are transported southeast in the north while sediments from the Indonesian islands are transported northward in the south. Ascertaining surface sediment sources and their transport routes will not only improve understanding of modern transportation and depositional processes, but also aid paleoenvironmental and paleoclimatic analysis of the SCS.     

地理空间信息的M-R曲线扩展分析

分形理论在地理空间信息的复杂性分析中具有广泛的应用前景,但是强调完全自相似为基础的单一分形维数,难以描述复杂变化的地理目标特征。本文研究表明,与分形维数相比,M-R曲线所包含的更丰富的地理空间特征信息使之成为更值得关注的分形分析对象。在此基础上,本文初步阐述了M-R曲线的性质与地理空间意义,并进一步探讨了M-R曲线的扩展分析方法,包括M-R曲线的函数拟合与分维谱分析。最后以小比例尺地图中河流数据为例,分析了我国长江、黄河两大河流的空间形态特征及其规律。实验表明,在小尺度范围内长江具有更丰富的细节变化,黄河则在更大的尺度上表现出复杂性。     

南阳伏牛山自然风景区的旅游价值

伏牛山是河南省的著名山脉 ,是我国亚热带向北暖温带的过渡带 ,是长江、黄河、淮河三大水系的分水岭 ,是华北地台和扬子地台的结合部。这里动、植物资源丰富 ,自然景观优美迷人 ,开发以旅游观光 ,生态示范 ,休闲度假、科普探险为一体的生态旅游区非常理想 ,是河南省近期重点开发的两条旅游线之一。文章从地质资源等方面详细介绍了伏牛山的概况 ,全面分析了伏牛山特殊的旅游价值和开发优势 ,提出了伏牛山生态旅游开发的基本思路 ,为伏牛山的系列开发提供了较好的科学依据。