Variation Characteristics of Main Climate Factors in the Upstream of Wei River in Recent 39 Years

Wei River is an important river which affects the industrial and agricultural production,people's life in Guanzhong district of Shaanxi and the east of Gansu.To study the variation characteristics of main climate factors in recent 39 years in the upstream of Wei River,we analyzed the variation characteristics of climate factors by using the data in 11 meteorological stations in the upstream basin of Wei River during 1971-2009.The results showed that the precipitation presented the decline trend in the basin,and the temperature rose in 0.3 ℃/10 a trend.The temperature increase trend was 0.4 ℃/10 a in winter,spring and wasn't obvious in summer,autumn.The potential evapotranspiration presented the yearly increase trend in recent years.The precipitation decreased,and the temperature rose.Moreover,the potential evapotranspiration strengthened.It wasn't favorable for the healthy run of ecological system in the upstream,downstream basins and aggravated the shortage degree of water resources.

Detrital Zircon Ages of Hanjiang River:Constraints on Evolution of Northern Yangtze Craton,South China

Clastic sedimentary rocks are natural samples of the exposed continental crust over large areas. The Hanjiang （汉江） River drains the northern Yangtze craton, including the South Qinling （秦岭） belt and the northern parts of the Yangtze craton. Detrital zircons from this river thus provide an ideal sample for studying the formation and evolution of the northern Yangtze craton. Here we report laser ablation inductively coupled plasma mass spectrometer U-Pb ages of 122 detrital zircons from one sand sample of the Hanjiang River. The 110 concordant zircons reveal four major age groups of 768, 444, 212, and 124 Ma, which well correlate with known magmatic events in the northern Yangtze craton. A minor group is present at 1 536 Ma, which is less known in the study area. Only seven zircons have ages of 〉1 750 Ma. Our results show that the Early Paleozoic, Late Triassic, and Early Cretaceous are important episodes of zircon growth and crustal growth/reworking in addition to the previously documented Neoproterozoic event. Our results suggest very limited exposures of Paleoproterozoic and Archean rocks in the northern parts of the Yangtze craton.

Cosmogenic 26Al/10Be Burial Dating of the Birth of the Present Hanjiang River

Objective Structural lows and major rift systems provide the basis for the creation of large rivers.The uplift of the Qinling and Daba Mountains structural belts and Tibetan Plateau would have provided the basis for the origin and northwest–southeast flow of the ancient Hanjiang River(Lu et al.,2018).After a long-term evolution,the present pattern of Hanjiang River has been formed.Five to six river terraces in the Hanzhong and Yunxian basins along the flanks of Hanjiang River valleys had been identified and some terraces had been dated by using optically stimulated luminescence(OSL),paleomagnetic,and electron spin resonance(ESR)dating methods,and correlating the pedostratigraphy and magnetic susceptibility with the Luochuan loess section by our team(Sun et al.,2016,2017).These terraces are composed of fluvial deposits overlaid with eolian deposits,and record the evolution history of the Hanjiang River.(Fig.1).This study is aimed to deduce the birth time of the present Hanjiang River by using 26Al/10Be burial dating method to date the highest fluvial terraces of the Hanjiang River.

THE DRIVING FORCES OF LAND USE/COVER CHANGE INTHE UPSTREAM AREA OF THE NENJIANG RIVER

ABSTRACT: Based on the Landsat 5 and Landsat 7 TM images, the land use/cover change was detected in the upstream area of the Nenjiang River between 1995 and 2000. With the spatial analysis techniques of GIS, the maps of land use degree and its change within this period were produced. To identify the causes of changes, elevation and slope were regarded as the main natural influencing factors and were transformed from coverage format to grid format within GIS. The Thiesson polygon method was used to the spatial allocation of socio-economic factors including human population, livestock numbers, mechanizing power of farming and the nearest distance from the changed pixel to the trunk stream and to main settlements, thereby the spatial relationship between land use degree change and socio-economic factor variation was analyzed. According to results of the spatial correlation, the determinants of changes in land use/cover, i. e. elevation, slope, population density change, livestock increase were extracted quantitatively in this area. At last, the spatial multi-linear regression model of land use degree change was developed as follows: △ La = 11. 037-4. 512 * eleva-tion-0. 298 * slope + 0. 292 *△ population + 2. 596 *△ livestock.

Comparative Assessment of the Upstream and Downstream Water Qualities of River Tano in Ghana

River Tano, located in the Brong Ahafo region of Ghana, has a number of socio-ecological functions. Anthropogenic activities such as farming, washing, and discharge of industrial effluents into the river pose serious threat to human health. In view of this, water quality campaign was carried out for a period of 12 months by taking samples from the source and the downstream end of the river and analysing for some physico-chemical parameters. The results showed that most of the physico-chemical parameters such as pH, fluoride, nitrite, manganese and temperature were not within the regulatory safe limit. Although the levels of total alkalinity, total iron, ammonia and phosphate kept fluctuating along the course of the river, the difference were not statistically significant apart from fluoride and phosphate which showed significant difference between the upstream and downstream levels. This may be attributed to anthropogenic activities such as farming and washing in the river which implies that human activities have impacted slightly on the water quality. It is recommended that the relevant stakeholders should come together to enforce the environmental laws regarding protection of water bodies and do continuous monitoring for early detection of any change in quality of the River Tano.

Torrent risk zonation in the Upstream Red River Basin based on GIS

This paper explores the methodology for compiling the torrent hazard and risk zonation map by means of GIS technique for the Red River Basin in Yunnan province of China, where is prone to torrent. Based on a 1：250,000 scale digital map, six factors including slope angle, rainstorm days, buffer of river channels, maximum runoff discharge of standard area, debris flow distribution density and flood disaster history were analyzed and superimposed to create the torrent risk evaluation map. Population density, farmland percentage, house property, and GDP as indexes accounting for torrent hazards were analyzed in terms of vulnerability mapping. Torrent risk zonation by means of GIS was overlaid on the two data layers of hazard and vulnerability. Then each grid unit with a resolution of 500 m- 500 m was divided into four categories of the risk： extremely high, high, moderate and low. Finally the same level risk was combined into a confirmed zone, which represents torrent risk of the study area. The risk evaluation result in the upper Red River Basin shows that the extremely high risk area of 13,150 km^2 takes up 17.9% of the total inundated area, the high risk area of 33,783 km^2 is 45.9%, the moderate risk area of 18,563 km^2 is 25.2% and the low risk area of 8115 km^2 is 11.0%.

GLOBAL WARMING EFFECTS ON THE HANJIANG RIVER HYDROLOGICAL REGIMES

The paper, based on a semi-conceptual hydrological model, analysed global warming effects on the Hanjiang River hydrological regimes and water resources, including soil moisture, evaporation, runoff and the transferable water quantity from the Danjiangkou Reservoir according to Middle Route of China's South-to-North Water Transfer Project.

The Greening Situation and Developing Countermeasures along the Han River——Taking Chaozhou Downtown Part as an Example

Hanjiang is the main river in Chaozhou. The urban sections on both sides of it are large-scale landscape zones which combine the natural landscape and the cultural landscape. Aiming at better manifesting the geographical features and pro-moting the sustainable development of the ecological environment on both sides of the Hanjiang River, the research, with the reach between the Jinshan River and the Hanjiang River as an example, pointed out the existing problems and put forward some constructive suggestions based on a thorough survey on the plant species and the rationality of plant configuration and the afforstation managements, in order to provide reference for the decision-maker of the further planning and construction of this area.

Impacts of water and soil erosion in upstream watershed of Nenjiang River

Making a brief analysis of the water and soil loss present situation in Daxing＇anling area which locates to the upstream region of Nenjiang River, and giving the water and soil loss of this area that have been made near 20 years, as well as the factors of the water and soil loss. According to the factors corresponding prevention measure and forecast model have been put forward, make a brief introduction to this model in this article. It is helpful to improve the local soil conservation and sustainable development.

Impact of Tidal River Management (TRM) for Water Logging: A Geospatial Case Study on Coastal Zone of Bangladesh

Bangladesh is a floodplain dominated country. Coastal delta areas of Bangladesh convey multiple impacts of climate change worth-hit. Most of the rivers carry a huge amount of sediment from upstream piedmont area. The river bed rises due to insufficient upstream water supply. Similarly, the deposited sedimentation creates a large number of sandbars inside the river. That’s why, water logging and siltation turn into a serious problem in the south-western region of Bangladesh, especially in Satkhira, Khulna and Jessore district. In the middle of September, 2011 the Tidal River Management (TRM) project approved at the study site for four years to develop the water logging problem with basic consideration of silt management. In this circumstance, this study focused on the consequences of the TRM on water logging in the coastal area of Bangladesh. Primary and secondary data have been used. Geospatial analyses have been used following the NDWI in Arc GIS for water logging area detestation using Landsat Enhance Thematic Mapper (ETM) and Landsat Operational land Image (OLI) satellite images. The geo-spatial analysis denoted, about 5090 acres of agricultural land and about 729 acres of homestead land have been water logged during TRM implementation period.

基于BHM-EcoFlow模型的汉江中下游河段水文-生态响应关系研究

河流水文-生态响应关系是确定生态流量阈值的科学基础。针对当前河流水文-生态响应关系研究中生态数据不足且生态建模难度大的问题,建立了基于贝叶斯层次分析法的BHM-EcoFlow(Bayesian hierarchical modelling-ecological flow)模型,该模型将河流不同河段及同一河段不同站点间的先验知识与实测数据相结合,可有效利用短系列数据,实现河流水文-生态响应关系的模拟。采用汉江中下游干流2011年的水文、生态数据,模拟了浮游植物细胞密度与流量、混合层温度间的关系,计算了不同流量条件下各河段的浮游植物密度。结果表明:BHM-EcoFlow模型提高了短系列数据的可用性,对汉江中下游干流的水文-生态响应关系具有良好的识别能力,为确定生态流量提供了科学依据。

Reconstructing the extraordinary palaeoflood events during 3200-2800 a BP in the upper reaches of Hanjiang River Valley, China

Palaeoflood hydrology study is a leading subject in global change study. Through field investigation in the upper reaches of Hanjiang River, palaeoflood slackwater deposits （SWD） were found in the bedrock gorges of the Yunxi reach. The results of field observation, laboratory analysis including particle-size distribution and magnetic susceptibility, and com- parison with modern flood deposits, the SWD were identified as the most typical Holocene palaeoflood deposits of the Hanjiang River. By using stratig;aphic correlation and OSL dating method, the palaeoflood event was dated to be 3200-2800 a BP at the turn from the middle to late Holocene. According to the palaeoflood peak stage and hydraulic parameters, the peak discharges of the palaeoflood were reconstructed as 48,830-51,710 m3/s by using the slope-area method. At same time, the flood peak discharges of 1983, 2005 and 2010 severe floods were reconstructed with the same method and hydraulic parameters in the same cross section. The error between the reconstructed and gauged discharges was 1.99%-4.21%. This showed that the reconstructed palaeoflood peak discharges were reliable. The flood peak discharge-frequency relationship at 10,000-year time scale was established by a com- bination of the gauged flood, historical flood and palaeoflood hydrological data. These results are very important for hydraulic engineering and flood mitigation on the Hanjiang River.

Differential Geochemical Features of Clinopyroxene from the Floodplain Sediments in Yangtze and Hanjiang Rivers and Its Implication for Detrital Source Identification

The evolution history of the Yangtze River attracted increasing attention in recent years. Comparison of the properties of the floodplain sediments between the upper and lower reaches of the Three Gorges is of significance to identify the material detrital sources for the Yangtze River Basin. Clinopyroxene （Cpx） is the typical mineral widely distributed in the sediments of the Yangtze River Ba- sin. Cpx was extracted from the fine sediments with the grain size ranging from 0.063 to 0.125 mm in the upper and lower reaches of the Three Gorges. The sediments, from which the Cpx was extracted, were taken from the floodplains of the catchments of both the Yangtze River and the Hanjiang River, as well as from the surface of the Zhoulao Core drilled in the center of the Jianghan Basin where the two rivers flow through. Geochemistry of these Cpx was investigated, concerning the contents of major elements measured by electron probe microanalysis （EPMA） and the contents of trace elements analyzed by laser ablation inductively coupled plasma-mass spectrometry （LA-ICP-MS）. The Cpx in the Yangtze River contains titaniferous augite which is sourced from the Panzhihua-Xichang region in South Sichuan Province, whereas the Cpx in the Hanjiang River is mainly from the surroundings without any titanif- erous augite. The REE analysis infers that the titaniferous augite is the diagnostic mineral of the upper Yangtze River, and thus could be used as a tracer mineral to identify the detrital sources for the sedi- ments formed during the evolution of the Yangtze River. The Cpx from the surface sediments of the Jianghan Plain （Zhoulao Core） shows comparable geochemical nature with that of the Yangtze River, but is different in geochemistry from that of the Hanjiang River, implying that the modern sediments in the Jianghan Plain are mainly sourced from the upper Yangtze River.

Geochemical characterization of loess-paleosol sequences:Comparison between the upper reaches of the Hanjiang and Weihe river valleys,China

This paper aims to compare the geochemical characteristics of loess-paleosol sequences in the upper reaches of the Hanjiang and Weihe river valleyswhich are located in the semi-humid temperate zone and humid subtropical zonerespectively. The Mituosi（MTS） profile in the upper reaches of the Hanjiang River valley and the Yaohecun（YHC） profile in the Weihe River valley were selected for this comparative research. The stratigraphic characteristicscompositionchemical weathering intensityleaching rates of Ca and Namobility of major elementsand transport features of Na and Fe were analyzed with respect to depth and compared between the two profiles. This study reached the following conclusions.（1） The composition of the loess-paleosol sequences in two regions are quite similar to the average composition of the upper continental crust（UCC）indicating that the loess in the two regions came from multiple sources and was mixed well. Thereforethe loess in the two regions is considered aeolian loess.（2） Compared with the loess-paleosol sequence in the Weihe River valleythe loess-paleosol sequence in the upper reaches of the Hanjiang River valley features a darker color; a higher chemical index of alteration（CIA） value; higher leaching rates of Na and Ca; higher migration ratio（relative to K） of AlSiMgand Na; and lower migration ratio of Fe and Ca. This evidence indicates that the loess-paleosol sequence in the humid subtropical environment experienced stronger chemical weathering intensity than the loess-paleosol sequence in the semi-humid temperate zone.（3） Both the YHC profile and MTS profile record a period of climate deterioration at 6000–5000 a BP. The period punctuated the mid-Holocene Climatic Optimum（8500–3100 a BP） in the study area.

Spatio-temporal variations of the flood mitigation service of ecosystem under different climate scenarios in the Upper Reaches of Hanjiang River Basin, China

Extreme rainstorm and the subsequent flood increasingly threaten the security of human society and ecological environment with aggravation of global climate change and anthropogenic activity in recent years. Therefore, the research on flood mitigation service(FMS) of ecosystem should be paid more attention to mitigate the risk. In this paper, we assessed FMS in the Upper Reaches of Hanjiang River(URHR), China from 2000 to 2014 using the Soil Conservation Service Curve Number(SCS-CN) model, and further simulated the future FMS under two climate scenarios(in 2020 and 2030). The results reveal that the FMS presented a fluctuating rising trend in the URHR from 2000 to 2014. The FMS in southern URHR was higher than that of northern URHR, and the change rate of FMS in the upstream of URHR(western URHR) was higher than the downstream of URHR(eastern URHR). The future FMS under scenarios of Medium-High Emissions(A2) and Medium-Low Emissions(B2) will decrease consistently. As land use/land cover changes in the URHR are negligible, we concluded that the change in FMS was mainly driven by climate change, such as storm and runoff. Our study highlights that climate scenarios analysis should be incorporated into the assessment of hydrologic-related services to facilitate regional water resources management.

Increasing probability of concurrent drought between the water intake and receiving regions of the Hanjiang to Weihe River Water Diversion Project,China

Water diversion projects are an effective measure to mitigate water shortages in water-limited areas.Understanding the risk of such projects increasing concurrent drought between the water intake and receiving regions is essential for sustainable water management.This study calculates concurrent drought probability between the water intake and receiving regions of the Hanjiang to Weihe River Water Diversion Project using Standardized Precipitation Index and Copula functions.Results showed an increasing trend in drought probability across both the water intake and receiving regions from 2.67%and 8.38%to 12.47%and 14.18%,respectively,during 1969-2018.The return period of concurrent drought decreased from 111.11 to 13.05 years,indicating larger risk of simultaneous drought between the two regions.Projections from CMIP6 suggested that under the SSP 2-4.5 and 5-8.5 scenarios,concurrent drought probability would increase by 2.40%and 7.72%in 2019-2050 compared to that in 1969-1990,respectively.Although increases in precipitation during 2019-2050 could potentially alleviate drought conditions relative to those during 1991-2018,high precipitation variability adds to the uncertainty about future concurrent drought.These findings provide a basis for better understanding concurrent drought and its impact on water diversion projects in a changing climate,and facilitate the establishment of adaptation countermeasures to ensure sustainable water availability.

A study on the relationship between vegetation pattern and environment in the upstream of Minjiang River,China

The vegetation pattern in the upstream of Minjiang River,and its relationship with environment factors,such as landscape position(elevation,slope,aspect),precipitation and temperature and soil are analyzed in this paper.The data used in this paper were based on the landscape map derived from 1994 TM imagery.The results were as follows:1)dominant landscape types were forest,shrub land and grassland,which were very similar in terms of area ratio(32.87%,31.85%and 28.44%,respectively);2)the patch shape of conifer forest and mixed forest was complicated while that of broad-leaved forest and cultivated land was simple;3)the fragmentation of conifer forest and mixed forest was serious in contrast with low fragmentation of broad-leaved forest and cultivated land;and 4)closed scrub and grassland had a high contagion and good connectivity while mixed forest had a lower contagion and bad connectivity.In addition,the vegetation distribution pattern of upstream of Minjiang River was closely related with elevation and temperature,but the relationship between vegetation and precipitation was not statistically significant.

Three Gorges Project——key to harness and develop Yangtze River

The upper Yangtze upstream ofYichang with a drainage area of1,000,000 km^2 brings an average annualrunoff to Yichang by 450 km^3 of river water,the drastic variation and uneven distributionof which often causes severe floods for fer-tile alluvial plains of middle and lower Yang-

气候变暖背景下汉江流域降水和气温时空变化特征

为探究气候变暖背景下汉江流域降水和气温的时空发展规律,基于汉江流域及其周边地区29个气象站点逐日降水(P_(re))、最高气温(T_(max))、最低气温(T_(min))和平均气温(T_(ave))的观测资料,利用线性拟合、Mann-Kendall突变检验和空间插值等方法,分析1960~2019年汉江流域降水和气温的时空变化特征,以及对变暖停滞现象(Hiatus)的响应。结果表明:①在全球变暖背景下,汉江流域气候表现出降水不显著减少(p>0.05)、气温显著上升(p<0.05)的暖干化趋势。1960~2019年汉江流域P_(re)变化幅度夏季(0.582 mm/a)>秋季(-0.477 mm/a)>春季(-0.403 mm/a)>全年(-0.184 mm/a)>冬季(0.125 mm/a);全年升温幅度呈T_(min)(0.028℃/a)>T_(max)(0.025℃/a)>T_(ave)(0.022℃/a),四季T_(max)、T_(min)和T_(ave)一致呈上升趋势,多数升温趋势通过了显著性检验(p<0.05),但升温幅度存在明显差异。②汉江流域全年和夏季P_(re)均未发生突变,春、秋季P_(re)在1970年代中后期发生突变下降,冬季P_(re)在1984年突变增加;除夏季T_(max)和T_(ave)外,其余时序气温集中在1990年代中后期至2000年代前期发生了突变上升。③汉江流域全年P_(re)自东南向北递减,四季P_(re)空间分布规律各异,全年和四季T_(max)、T_(min)和T_(ave)皆自南向北递减;全年及四季P_(re)、T_(max)、T_(min)和T_(ave)变化趋势具有较强的空间异质性。④1998~2012年汉江流域出现Hiatus现象,尤其以冬季最为明显;停滞后春夏季快速增温,秋冬季依旧呈降温趋势。研究成果对于制定汉江流域防灾减灾、供水保障应对策略具有重要的科学意义。

生态调度控制汉江中游入侵沉水植物过度生长效果研究

针对汉江中游江段入侵沉水植物伊乐藻(Elodea nuttallii)过度生长的问题,以2019年调查监测为基础,采用生物量、分布面积、流速、流量等指标,于2020-2021年在汉江丹江口水库联合王甫洲水利枢纽开展了控制伊乐藻过度生长的生态调度试验并评估其生态效果。结果表明:(1)丹江口−王甫洲区间适宜入侵沉水植物伊乐藻生长的水域面积达16.8 km^(2),主要分布在坝前两岸浅水区、泄水闸上游洲滩、水岸新城、中洲岛、木排港、羊皮滩等区域;(2)生态调度的控制效果显著,伊乐藻生物量和分布面积呈逐年减少趋势,其年度峰值生物量变化与春季萌发期1-3月流量极值比(r=-0.997)和生长旺盛期4−8月平均流量(r=-0.963)的相关系数均大于0.9,与全年平均流量(r=-0.748)和4−8月平均水温(r=0.732)的相关系数大于0.7,流量(流速)和水温是影响伊乐藻生物量的关键因子;(3)根据王甫洲坝前漂浮伊乐藻日打捞量与入库流量统计,可以对伊乐藻成熟团聚体产生明显冲刷影响的王甫洲入库流量(即丹江口水库下泄流量)条件为不小于1500m^(3)/s;丹江口水库峰值流量为3500m^(3)/s的单次汛期调度过程,可减少研究区间内约40%的伊乐藻生物量。