Movement Properties of Pipe Flow Along Granite Slope of Three Gorges Area of Yangtze River in China

It is well known that, in most cases, soil water doesn't move in the form of laminar flow as described by Darcy law. Only when Reynolds number ( Re ) is no more than 10, does water movement follow Darcy law. A soil profile with 2 9 m long and 2 13 2 60 m deep was excavated on a lower slope located at Zigui County, Hubei Province, China. Field observation found that soil pipes were mainly distributed in the transient layer between horizon B with higher degree of granite weathering and horizon C with lower degree of granite weathering. At the foot of the slope, about 5 7 soil pipes per meter were observed along the vertical direction of the slope. The observed results, obtained by continuous observation of soil pipes and pipe flow processes at granite slope for many rainfall events, indicate that the relationship between velocity of pipe flow and hydraulic gradient along the pipe is parabolic rather than linear. Based on the investigated data of soil, landform, and land use etc., combined with observed data of pipe flow derived from many rainfall events, a pipe flow model was developed. For velocity V p, discharge Q p of pipe flow and radius r of soil pipe, great similarity was found between simulated and observed values. Particularly, the simulated length of soil pipes reflects the great difference among soil pipes as a result of its different position in the soil profile. The length values of 4 soil pipes were estimated to be 98 1%, 27 6%, 11 0% and 3 0% of the longest distance of the catchment, respectively. As a special case of water movement, soil pipe flow follows Darcy Weisbach law. Discharge of pipe flow is much greater than infiltration discharge in common. Only when the depth of groundwater is more than the diameter of soil pipe and water layer submerges soil pipes during rainfall, may pipe flow occur. Under these circumstances, discharge of pipe flow is directly proportional to the depth of groundwater.

Characteristics and influencing mechanisms of production-living-ecological space dynamics in the Three Gorges Reservoir Area(TGRA),Chongqing,China

The Three Gorges Reservoir Area(TGRA)is an important ecological barrier in the Yangtze River Basin,China.Therefore,it is of great importance to understand the spatio-temporal variation and the driving factors of production-living-ecological spaces for sustainable and high-quality development in the TGRA.This study investigated the dynamic variation of production-living-ecological spaces in the TGRA by employing land use data in 2000,2005,2010,2015,and 2018,and detected the influencing factors by using the Geographic detector(GeoDetector).Results implied that the structure and dynamic trajectories of production-living-ecological spaces in the TGRA varied in both horizontal and vertical directions,and the study area was dominated by ecological space.A spatial orientation towards the northeast was detected in the evolution of production-living-ecological spaces during 2000-2018.In terms of quantity,the transition from ecological space(grassland and woodland)to agriculture land accounted for the largest proportion from 2000 to 2018.However,the reverse transition from agriculture land to ecological space has increased since 2000 with the efforts of“Grain for Green”.In terms of temporal scale,there was a fluctuating trend in production space with the continuous expansion of living space,while ecological space showed an inverted U-shaped trend during 2000-2018.The dynamic pattern of production-living-ecological spaces in the TGRA was influenced by both physical and socio-economic variables as basic determinants and dominant driving factors,respectively.Finally,the harmonization and protection of production-living-ecological spaces still require policy-makers’efforts.This work may have potential in advancing our understanding about land use conflicts,and provide a reference for rational layout of spatial functions and the realization of sustainable development in the TGRA.

Intensive Observation of Reservoirinduced Seismicity and Preliminary Analysis on the Causes of Earthquakes in the Three Gorges Reservoir Area,Yangtze River

In accordance with the requirements of the National Key Technology R＆D Program of the 11th ＂Five-year Plan＂, a densified seismic network consisting of 26 seismic stations was established at the Three Gorges Reservoir area in the section of Hubei Province in March 2009 （21 short-period seismographs, 5 broadband digital seismographs）. From March to December, 2009, a total of 2,995 ML -0. 8 - 2. 9 earthquakes were detected during the trial impounding of the Three Gorges Reservoir （ water level rose from 145 m to 172.8m）. Using the double difference earthquake location algorithm, 2,837 earthquakes were precisely re-located. The results show that the pattern of small local earthquake swarms in the Three Gorges Reservoir area took on a linear distribution or mass-like cluster distribution, the mass-like clusters of events were generally within a distance of 5 km from waterfront, and the linear distribution of the earthquakes could be extended to a distance of 16 km away from the waterfront. In the Hubei section of the Three Gorges Reservoir, earthquakes were mainly concentrated in the northern end of the Xiannvshan and Jiuwanxi faults near the Xiangxihe River, and along the banks of the Yangtze River at the west of Xietan township and the Shenlongxi area on the northern bank in the Badong region, with focal depths less than 10km, and 4km in average. Earthquake frequency in the reservoir region had a positive correlation with reservoir water level fluctuations, indicating that the seismicity belongs to reservoir induced earthquakes. Along the Shenlong River in the reservoir area, earthquakes showed three linear distributions in the northern Badong county, and distributed according to Karst distribution. There are underground rivers in the carbonate strata. When the reservoir was impounded, water permeated into the underground rivers, thus inducing earthquakes. Earthquakes in the areas on the crossriver segment of Xiannvshan fault, the Jiuwanxi fault and at the areas west of Xietan, Shazhen and Xizhen, may be related to the softening of discontinuities, such as the Nukou fault, the Xiannvshan fault, or the bedding joints, which would lead to failure of rock masses, thus, inducing earthquakes. However, convincing conclusions about the triggering mechanism still need further study. Additionally, near the areas south of Wenhua and Yanglin of Zigui county and at Rangkou town east of Badong county, mininginduced earthquakes occurred at the mines nearby, and on the shores of the reservoir are some collapse earthquakes.

Three-Gorges Reservoir Area on the Yangtze River Faced with Risk of Induced Destructive Earthquakes

The Three-Gorge Water Conservancy Project on the Yangtze River started to impound water by locking gates on June 1, 2003. A swarm of more than 2000 small earthquakes suddenly occurred densely along the river section in Xinling Town north of Badong, Hubei Province, on June 7. This caused grave concern in the following years, but, with the completion of the second- and third-phase engineering construction, the water level in the reservoir will rise up to 156 m and 175 m respectively, no matter whether it can induce larger and stronger earthquakes. After an analysis of the distribution of active faults in the eastern part of the reservoir area, their intersections and capability to generate earthquakes from a seismo-tectonic viewpoint, we consider that after the reservoir impounding, two potential focal zones existing in Badong and Zigui counties may generate M 5.5 earthquake, the seismic intensity of which may reach Ⅷ. It will induce landslide bodies in the reservoir area to be reactivated and slide. The evidence is the large-scale landslide occurring on the Shazhenxi Creek river in Zigui County on June 12, 2003.

Malaria Transmission Potential in the Three Gorges Reservoir of the Yangtze River, China

Objective To define and evaluate the malaria transmission potential in the Yangtze River, following construction of the Three Gorges Reservoir. Methods Six villages, namely, Kaixian, Fengjie, Wanzhou, Fuling, Yubei, and Zigui were selected for investigating the malaria transmission potential in the reservoir. Transmission potential was estimated by mathematical modeling and evaluation of the local malaria situation. Factors that influenced the transmission potential were analyzed using Poisson regression analysis in combination with Grey Systematic Theory （based on evaluation by the Delphi method）. Results Indirect fluorescent antibody data and the incidence of malaria in the local population were consistent with the malaria transmission potential calculated for the area. Multivariate Poisson regression analysis showed a statistically significant association between the riparian zone and the man‐biting rate. Conclusion The risk of a malaria epidemic can be forecasted using the malaria transmission potential parameters investigated here which was closely correlated with the riparian zone.

Provenance of Detrital Magnetites from Quaternary Sediments in the Yichang Area and its Significance to the Birth of the Three Gorges, Yangtze River

Objective In recent years, the birth time and evolution of the Three Gorges, Yangtze River has become a focused topic. Different from previous studies, this study used provenance analysis of Quaternary sediments to discuss this question. Among those minerals in Quaternary sediments, magnetite was rarely studied. This paper presents element geochemistry and backscatter images of detrital magnetites from the Quaternary sediments in the Yichang area of Hubei Province. By discussing the provenance changes of detratic magnetites, we suggested the birth time of the Three Gorges of the Yangtze River.

Impact of soil texture and sweetpotato cropping system on soil erosion and nutrient loss in the Three Gorges Reservoir Area of the Changjiang River

This study investigated the impact of soil texture and sweetpotato cropping system on soil erosion and nutrient loss in the drought infield of the Three Gorges Reservoir Area of Changjiang River under field conditions. A factorial experiment was conducted in the study using five soil textures and two cropping systems. The lost soil during the crop season was recovered by a soil-blocking device and the dry weights for the total lost soil and its nutrient components, such as ammonium nitrogen, effective phosphorus, K^＋ and organic matter were analyzed. We found that soil texture significantly affected the dry weights of the total lost soil, effective phosphorus, K^＋, and organic matter, while sweetpotato cropping systems and interaction between soil texture and sweetpotato cropping system affected the dry weights of the total lost soil, the effective phosphorus and organic matter. Among the five soil textures tested, Da and Huang caused significantly less soil erosion and nutrient loss compared with the other three soil textures; intercropping sweetpotato with corn significantly reduced soil erosion and nutrient loss.

Grey Prediction of Seismic Activity in the Three Gorges Area of the Yangtze River

On the basis of historical earthquake data and recent observations, two grey models prediction of the next seismic active period and the maximal magnitude of earthquakes which might occur during that period are constructed on the basis of the grey theory. As predicted by the two models, the next seismic active period would last 79 years, and that the maximal magnitude of earthquakes occurring within the period would not exceed 5.2. These results provide an important basis for the assessment of earthquake risks and reduction of disasters in the Three Gorges area.

Filling of the Three Gorges Reservoir to the 135-m Level: Instant Effects on the Yangtze Discharge and Suspended Sediment Concentration Entering the Estuary

Via the valuable opportunity of the Three Gorges Reservoir (TGR) 135-m filling in June 2003, the Yangtze discharge and suspended sediment concentration (SSC) entering the estuary during the period from 15 May to 15 July 2003 were analyzed to examine the instant effects of the filling on them. The Yangtze discharge and SSC entering the estuary in the periods before, during and after the filling clearly indicated three phases: 1) the pre-storage phase characterized by natural conditions, in which the SSC increased with increasing water discharge; 2) the storage phase, during which the SSC decreased dramatically with decreasing water discharge; and 3) the post-storage phase, during which both the SSC and water discharge remained at relatively low levels first until the end of June, then the SSC increased gradually with increasing water discharge. It seems that the times for the instant effects of the decreasing discharge downstream from the upper Yangtze on the Yangtze discharge and SSC entering the estuary due to the TGR 135-m filling to take place were about 5 d and 1 d respectively, while both were about 18 d for those of the increasing discharge. This probably reflects the buffering and resultantly hysteresis of the 1800-km stretch from the upper Yangtze to the estuary. The results are helpful for scientific and hydrological investigation of the Yangtze mainstream downstream from the TGR Dam and of the estuarine and adjacent coastal waters.

Eutrophication investigation and assessment of the Daning River after water storage of the Three Gorges Reservoir

The Daning River is a very important tributary in the Three Gorges Reservoir area. It is also a famous scenic spot. Anomalies appeared after water storage of the reservoir in June, 2003. In September, 2003, eutrophication monitoring in the 135-m backwater reach of the Daning River was conducted and the data were simply analyzed. The assessment result is that water body in the segment from Shuanglong to Longmen was mesotrophic or eutrophic. At the same time, the causes of its nutritional change were discussed, and counter-measures have been proposed.

AN ANALYSIS ON THE STRUCTURE TYPES AND BENEFITS OFSLOPELAND AGROFORESTRY SYSTEMS-Taking the Three Gorge Reservoir Area As An Example

The modem term 'agroforestry system' is derived from agricultural practices. It is an organic combination of agriculture and forestry, ecology and economy, product variation and scientific management. On the basis of analyzing the types and structure of agroforestry system in the Three Gorges Reservoir area,the paper poins out that agroforestry system can be divided into diffend structutal levds. Taking some typical cases as examples, it compares the benefits of four kinds of structures. The result illustrates that the hedge row agroforestry system on slopeland is an effective way to realize coordinate development of ecology and economy.

Seasonal variation and longitudinal distribution of copepods in the main river area of the Three Gorges Reservoir

The ecosystem of the Three Gorges in the Yangtze River was changed into an artificial lake(reservoir)ecosystem after impoundment in June 2003.We surveyed the seasonal variation and spatial distribution of copepods from April 2004 to January 2005 in order to provide data for clarifying the successional pattern of the ecosystem.From Jiangjin to Maoping,eight copepod species were collected and classified into Calanoida(2),Harpacticoida(1),and Cyclopoida(5).Among them,Mesocyclops pehpeiensis,M.leuckarti and Sinocalanus dorrii had a relatively wide distribution.No distinct difference in species number was found among the sampling sites,but the species composition was different.Species composition,distribution and density of copepods showed significant seasonal variations.In addition,copepod density showed an obvious gradient with the distance from the reservoir dam:the nearer to the dam,the denser the copepods.

三峡水库库容智慧化管理的水文实践与思考

推动水库库容管理智慧化是提升水库运行管理精准化、信息化、现代化水平的重要环节。分析了水库库容智慧化管理中的关键问题,即运行数据感知、运行管理信息化、多目标调度、库容维持,提出了三峡水库库容智慧化管理关键感知技术,并从防洪预报调度、泥沙减淤调度、库容计算与管理等方面总结了长江水文技术实践在三峡水库库容智慧化管理中取得的应用成果与效益,如“长江流域控制性水利工程综合调度系统”“长江水文库容计算管理系统”等,覆盖洪水预报调度、泥沙减淤调度、库容计算等方面,并对下一步工作重点进行了展望。

长江中游宜昌—监利河段洪峰沙峰异步传播特性及成因分析

洪峰沙峰异步传播会对河床演变产生重要影响,三峡水库蓄水以来,长江中游沙量更加集中于场次洪水,明确场次洪水过程的洪峰沙峰异步运动变化对深入认识水库下游河道冲淤调整尤为重要,但目前对于三峡水库蓄水前后长江中游洪峰沙峰异步特性变化及成因的认识还存在局限。本文基于长江中游宜昌—监利河段1993—2020年的实测水文资料,分析三峡水库蓄水运行前后坝下游的洪峰沙峰异步特性产生和变化的原因。结果表明:三峡水库蓄水前,宜昌—监利的场次洪水沙峰通常滞后于洪峰;三峡水库蓄水后,尤其是实施中小洪水调度期间,宜昌站沙峰滞后现象更加显著,坝下泥沙的补给效应减弱了沿程传播过程中沙峰的滞后特性。本文可为长江中下游防洪安全和优化水库运行管理等研究提供科学支撑。

加快三峡水库管理保护立法 为长江经济带高质量发展提供良好法治保障

三峡工程是“国之重器”,是保护和治理长江的关键性骨干工程。三峡水库功能效益显著,地理位置重要,管理保护涉及事项复杂。在长江流域生态环境保护和高质量发展由量变到质变的关键时期,加快推进立法工作,依法依规加强三峡水库管理保护,对工程安全运行和综合效益发挥,以及库区和流域高质量发展十分必要和迫切。建议从国家层面制定出台专门行政法规,协调和规范三峡水库的开发、利用、管理、保护行为,统筹库区和上下游生态环境保护和经济社会发展事项,为长江经济带高质量发展提供良好法治保障。

长江流域以三峡水库为核心的水库群统一联合调度思路、举措和成效

三峡水库因其所处地理位置、巨大调节能力居于长江流域控制性水库群的核心地位。为发挥好三峡水库巨大的防洪减灾作用和综合利用效益,水利部长江水利委员会持续推进以三峡水库为核心的长江流域控制性水库群统一联合调度研究和实践。从防洪、供水、发电、航运、生态方面阐述了长江流域水库群联合调度需求,从防洪调度、水资源调度、生态调度、泥沙调度、应急调度视角阐述了长江流域水库群联合调度原则与目标,明确了长江流域水库群统一联合调度思路。实施长江流域水库群统一联合调度以来,防洪调度方式不断深化优化,水资源利用策略不断丰富,生态保障措施不断完善,预报能力不断提升,决策支持体系不断完备;在防洪、供水、生态、发电、航运方面取得显著成效。总结了坚持流域统筹、坚持创新驱动、坚持制度保障、坚持共建共享的长江流域水库群统一联合调度实践经验。

三峡库区澎溪河上游段沉积物重金属分布特征及风险评价

为研究三峡库区右岸最大支流澎溪河上游段表层重金属本底情况,选择澎溪河上游开州区域采集了66个表层沉积物样品,并对表层沉积物中的重金属锌(Zn)、铬(Cr)、镍(Ni)、铜(Cu)、铅(Pb)、砷(As)和镉(Cd)进行了测定,分析了重金属元素的分布特征,根据区域实地情况分析污染来源,选用地累积指数法评估区域污染程度,采用潜在生态风险指数法评估潜在生态风险。结果表明:澎溪河流域上游段表层沉积物中,重金属As、Cd的含量(质量比)范围分别为2.70~22.07、0.05~0.60 mg·kg^(-1),平均含量(质量比)为10.62、0.21 mg·kg^(-1),分别是三峡库区背景值的1.82、1.62倍。Cr、Ni、Cu、Zn和Pb均低于背景值,含量(质量比)范围分别为18.20~165.63、7.13~69.21、8.13~52.08、0.76~256.30、5.99~33.22 mg·kg^(-1),平均含量(质量比)为42.53、18.83、16.77、51.54、16.58 mg·kg^(-1)。Pb分布较均匀,其他指标空间分布差异较大。Cd和As的高值区为东河的东华社区、大堰场镇和汉丰湖坝下。相关性分析表明,Cr、Ni、Cu三者之间,Pb和Cu,Pb和Zn均呈极显著强相关,Pb和Cd呈显著强相关,即Cr、Ni、Cu、Zn、Cd、Pb来源相似或相同,而As与其他元素来源有一定区别。结合主成分分析,Cu、Cr、Ni主要来自岩石风化、土壤侵蚀等自然源,Cd、Zn、Pb来自工业和农业生产活动等混合来源,As来自农业源。地累积指数评价结果显示,研究区Pb处于清洁水平,As、Zn、Ni、Cu为清洁至轻微污染水平,Cr和Cd为清洁至偏中度污染水平。潜在生态风险评价表明,区域整体面临中等生态风险,7个指标中Cd为主要风险源,其贡献率为66.95%。

极端天气下三峡库区土地利用对河流水质的多时空尺度影响

为探究极端天气下流域内水质对土地利用的响应关系,本研究基于不同空间尺度(1000 m河段缓冲区、500 m河岸带缓冲区及子流域)的土地利用指数以及旱季(2019年11月)、雨季-洪水期(2020年7月)和雨季-干旱期(2022年8月)的水质数据,探究流域内土地利用对水质的多时空尺度影响,从而得到保护流域水质和规划流域内土地利用格局的最佳时空尺度和对水质影响最显著的预测因子。研究表明:(1)流域水质受极端天气影响,降雨会增强水体的稀释能力,高温会加快水中微生物反应速率,具体表现为雨季-洪水期的水质较好,雨季-干旱期次之,旱季较差。(2)土地利用对水质指标的影响存在时空尺度效应,土地利用在子流域和旱季尺度下对河流水质影响最显著。(3)不同土地利用指数对流域水质影响存在差异,耕地、林地、斑块密度、最大斑块指数和边缘密度是影响水质指标最显著的解释变量。其中林地与多数水质指标具有负相关关系,建设用地、耕地、斑块密度与较多水质指标存在正相关关系。本研究结果为合理规划土地利用格局以及保护河流水质提供科学依据,对三峡库区环境可持续发展及生态保护具有一定意义。

基于栖息地法的水库变动回水区鱼类产卵场生态流量及调控策略研究

揭示水库变动回水区鱼类产卵场栖息地适宜性变化的规律,确定水库变动回水区鱼类产卵场栖息地生态流量阈值及保护调控的方法,为鱼类产卵场栖息地保护提供参考与借鉴。以三峡变动回水区的广阳-石沱江段为研究区域,选取四大家鱼、铜鱼、长鳍吻鮈、圆筒吻鮈和中华金沙鳅等8种产漂流性卵鱼类为研究对象,通过鱼类产卵场栖息地模拟,在耦合8种鱼类生态需求的基础上计算生态流量阈值,并制定相应的调控策略。结果表明,三峡水库在145、150、155、160、165 m和天然情形下变动回水区最小生态流量分别为:6543、7130、9943、13713、17603、6106 m^(3)/s;最大生态流量分别为:17028、17526、23110、28291、29858、15753 m^(3)/s;最适生态流量分别为10002、10916、14479、18810、23226、9365 m^(3)/s,上、下阈值分别为13515、14221、18794、23550、26542、12559 m^(3)/s;8272、9023、12211、16262、20414、7736 m^(3)/s。流量较小时,一定流量范围内,降低水位有利于增加加权可利用面积(AWU);流量较大时,流量增加到一定值后,增加水位有利于增加AWU;而流量在两者之间时,可参考研究结果中的水位及生态流量阈值进行调控决策。

三峡库区源头溪流湾滩河浮游植物群落特征

为探讨山地河流源头溪流浮游植物群落的空间格局和生物多样性维持机制,对湾滩河流域浮游植物群落空间结构变化特征及其与环境因子的关系进行研究;在三峡库区汤溪河上游的湾滩河干支流设置9个样地,调查浮游植物物种组成和环境变量,进行Spearman相关性分析。结果表明:丰水期和枯水期的浮游植物物种组成均主要以硅藻-绿藻型为主;均匀度指数和Simpson生物多样性指数变化不大,水质较为清洁;丰水期和枯水期浮游植物密度分别为1.9856×10^(4)~5.7263×10^(4),2.0332×10^(4)~6.0060×10^(4)cells·L^(-1);pH值、溶解氧(DO)、总磷(TP)、海拔是影响湾滩河浮游植物特征指数变化的关键因子。