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.

Downscaling GCMs Using the Smooth Support Vector Machine Method to Predict Daily Precipitation in the Hanjiang Basin

General circulation models （GCMs） are often used in assessing the impact of climate change at global and continental scales. However, the climatic factors simulated by GCMs are inconsistent at comparatively smaller scales, such as individual river basins. In this study, a statistical downscaling approach based on the Smooth Support Vector Machine （SSVM） method was constructed to predict daily precipitation of the changed climate in the Hanjiang Basin. NCEP/NCAR reanalysis data were used to establish the statistical relationship between the larger scale climate predictors and observed precipitation. The relationship obtained was used to project future precipitation from two GCMs （CGCM2 and HadCM3） for the A2 emission scenario. The results obtained using SSVM were compared with those from an artificial neural network （ANN）. The comparisons showed that SSVM is suitable for conducting climate impact studies as a statistical downscaling tool in this region. The temporal trends projected by SSVM based on the A2 emission scenario for CGCM2 and HadCM3 were for rainfall to decrease during the period 2011–2040 in the upper basin and to increase after 2071 in the whole of Hanjiang Basin.

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.

Current Situation and Development of Technology Extension System for Suburban Agriculture:A Case Study of Hanjiang District of Yangzhou City

Through the survey on agricultural technology extension system in Hanjiang District of Yangzhou City,this paper analyzed possible problems in the agricultural technology extension system.Combining with newly revised Agricultural Technology Extension Law and modern agricultural extension theory,it discussed the new development direction.Finally,it came up with approaches and measures for establishing the agricultural technology extension system in Hanjiang District.

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.

Hanjiang Machine Tool Plant

The Hanjiang Machine Tool Plant is located in Hanzhong City,Shaanxi Province.It is a state-owned large key enterprise producing precision thread grinders,and was esablished in 1969.At present it occupies a site of 919,000 sqm and its floor space of industrial building is 149,000 sqm,with a constanttemperature floor sqace of 10,000 sqm,It has 1,800 items of production equipment,including imported RG2000 digital controlled thread grinders,HP5528A laser measuring instuments and other equipment and instruments of the

Preliminary study on the depositional model in the wavedominated delta evolution during the Anthropocene:a case study of the Hanjiang River Delta in China

The deltas serve as the primary interactive zone where terrestrial and marine environments converge,playing a pivotal role in the coastal deposition.In the Holocene,climate changes and sea level fluctuation are the principal driving factors in the evolution of deltas.However,human activities such as the construction of dams and reservoirs in the Anthropocene have significantly altered sediment transport in rivers,leading to depositional pattern variation during deltaic evolution.In this study,we have conducted a comparative analysis of the morphological variations(1986-2021)in the barrier system of the Hanjiang River Delta(HRD)using satellite remote sensing(SRS)method.Additionally,we have examined the lithological changes and facies alterations observed in eight boreholes on the present barrier spit.Our findings indicate that the intensification of anthropogenic activities led to a significant reduction in the sediment flux of the Hanjiang River(HR),resulting in depocenter landward migration at the estuary.SRS analysis reveals their periodical morphological characteristics and spatial variations of estuarine sandbars(1986-1992),barrier islands-lagoons(1993-2009),and barrier spits(2010-2021)during 1986 to 2021.The stratigraphy of boreholes demonstrates a south-to-north facies transition from lagoon to lagoon-barrier spit and barrier spit in vertical lithology.Therefore,the depositional evolution of the HRD barrier system is categorized into three phases:estuarine sandbar-barrier island phase(1986-1998);barrier island-lagoon phase(1999-2009);and barrier spit phase(2010-2021).During the estuarine sandbar-barrier island phase,fluvial processes played a predominate role in the deposition.Consequently,with a significant decrease in river sediment load,the dominant factors driving depositional processes shifted towards wave action and alongshore current.Based on the conceptual model in the Holocene,we propose a modified depositional model of wave-dominated deltas during Anthropocene that encompasses three evolutionary phases:estuarine sandbars and delta front platforms,barrier island-lagoon formation and landward migration of barrier spits.This pattern highlights that human-induced reduction in river sediment flux has led to a seaward deltaic progradation driven by barrier landward migration.

Predicted Climate Change will Increase Landslide Risk in Hanjiang River Basin,China

Landslides are widespread geomorphological phenomena with complex mechanisms that have caused extensive causalities and property damage worldwide.The scale and frequency of landslides are presently increasing owing to the warming effects of climate change,which further increases the associated safety risks.In this study,the relationship between historical landslides and environmental variables in the Hanjiang River Basin was determined and an optimized model was used to constrain the relative contribution of variables and best spatial response curve.The optimal MaxEnt model was used to predict the current distribution of landslides and influence of future rainfall changes on the landslide susceptibility.The results indicate that environmental variables in the study area statistically correlate with landslide events over the past 20 years.The MaxEnt model evaluation was applied to landslide hazards in the Hanjiang River Basin based on current climate change scenarios.The results indicate that 25.9%of the study area is classified as a high-risk area.The main environmental variables that affect the distribution of landslides include altitude,slope,normalized difference vegetation index,annual precipitation,distance from rivers,and distance from roads,with a cumulative contribution rate of approximately 90%.The annual rainfall in the Hanjiang River Basin will continue to increase under future climate warming scenarios.Increased rainfall will further increase the extent of high-and medium-risk areas in the basin,especially when following the RCP8.5 climate prediction,which is expected to increase the high-risk area by 10.7%by 2070.Furthermore,high landslide risk areas in the basin will migrate to high-altitude areas in the future,which poses new challenges for the prevention and control of landslide risks.This study demonstrates the usefulness of the MaxEnt model as a tool for landslide susceptibility prediction in the Hanjiang River Basin caused by global warming and yields robust prediction results.This approach therefore provides an important reference for river basin management and disaster reduction and prevention.The study on landslide risks also supports the hypothesis that global climate change will further enhance the frequency and intensity of landslide activity throughout the course of the 21st Century.

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.

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.

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.

韩江流域生态文明建设的实践探索

2020年,习近平总书记到潮州市视察时作出“让韩江秀水长清”的重要指示。近年来,粤东地区通过抓好顶层设计、强化组织引领,坚持精准施策、提高治理能力,基本实现建设与宣传并重、生态与经济共赢,韩江流域生态文明建设呈现持续向好的发展态势。为进一步贯彻落实习近平总书记的重要指示,积极践行习近平生态文明思想的粤东实践,必须高度重视并严格遵循人与自然是生命共同体原则、经济发展与生态保护协同共进原则、生态文明建设系统推进原则,在“六个必须坚持”科学方法的指导下探索韩江流域生态文明建设的实践路径。

中国式现代化视域下韩江流域生态文明建设:理念、方法与路径

人与自然和谐共生是中国式现代化的中国特色和本质要求。推进韩江流域生态文明建设,必须坚持以习近平生态文明思想为根本遵循、以绿美广东建设提升行动为抓手、以韩江流域生态资源禀赋为出发点,坚持习近平生态文明思想的世界观、方法论,通过持续植绿扩绿护绿做大“绿蛋糕”,减污节约降碳做优“绿蛋糕”,畅通“生态美、产业兴、百姓富”的转化通道,把“绿蛋糕”转化为“金蛋糕”,在书写中国式现代化建设中绘出韩江流域美丽画卷。

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。

引江补汉工程千米级深孔地应力测试及近场断裂稳定性分析

引江补汉工程是南水北调后续工程的首个开工建设项目,其引水隧洞穿越了蠕滑型活动断裂-通城河断裂,研究活动断裂近场地应力特征对工程稳定性具有重要意义。选择较为复杂的通城河活动断裂近场区内开展了原位地应力测试及断裂构造稳定性分析,揭示断裂构造内现今地应力状态及断裂构造滑动失稳临界条件。通过在通城河活动断裂近场2个千米级深孔进行原位水压致裂法地应力测试。最后,基于实测地应力资料,结合库伦摩擦滑动准则及Byerlee定律对活动断裂稳定性进行了分析。结果表明:测试范围内存在应力分区,并推测以潜在转换深度900±20 m为界,空间主应力状态呈现由复合型(逆断型与走滑型)或逆断型向正断型的转换,表明近场地应力受交汇构造影响;实测最大水平主应力方向随孔深增加由NW向转为NWW向,与活动断裂运动力学特性、交汇断裂的左旋运动机制以及震源机制解基本一致;通城河活动断裂近场应力积累水平较低,尚未到失稳滑动水平,地壳是相对稳定的。研究结果为引江补汉工程穿通城河活动断裂工程区稳定性评价提供基础地质力学资料,为跨活动断裂的工程设计提供参考依据。

减压井在汉江遥堤管涌险情整治中的应用效果

汉江遥堤属国家Ⅰ级堤防,是汉北平原和武汉市的重要防洪安全屏障,天门李家洲段为历史险段;2021年汉江秋汛该段发生管涌群险情,汛后除险加固采用了新型减压井技术。根据地质和设计资料建立了三维精细有限元渗流模型,开展了减压井效果论证,为减压井设计提供参数依据。模拟表明,洪水工况下减压井具有显著的排水减压效果,堤内满足渗透稳定要求。2023年汉江洪水期该堤段水位超2021年出险时外江水位约1.3 m,堤内再无管涌险情发生,减压井发挥了显著的防洪减灾效益。实际应用表明,针对典型的二元结构堤基管涌险情隐患,减压井是最有效措施之一。研究成果可为类似堤防管涌隐患处理提供借鉴。

引江补汉工程丹江口下游近坝段枯水期通航水位恢复试验研究

引江补汉工程补水口位于丹江口大坝下游安乐河出口约5 km处,且补水量与调水量基本一致,工程对航道的影响主要体现在减水段,为恢复枯水期通航水位需要开展航道综合治理。利用河工模型试验论证了综合治理方案的效果,并对方案进行了优化及进一步论证。结果表明,减水-补水212 m 3/s方案尾门水位分别为86.47、85.90 m条件下,引航道口—黄家港段水位下降,黄家港以下水位保持不变,其中引航道口水位下降幅度最大,分别下降0.08、0.19 m;综合治理方案1实施后引航道口水位下降均为0.02 m,减水段的水位仍未恢复至调水前的水平,主因是从安乐河口补水的水流并未能进入到左侧主航道内;基于试验研究结果,建议对综合治理方案进行优化,在沧浪洲出水口下沿布置2道护底带;通过试验论证了护底带的4个高程,建议护底带高程为85.5 m,并对护底带高程进一步细化论证;优化后的方案可使引航道口至黄家港段的水位略超过调水前的水平,其中引航道口处最大水位抬高0.06 m。