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.

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.

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.

Numerical simulation of pollutant diffusion and decay process after a water pollution incident in the Three Gorges Reservoir

We established a hydrodynamic model to simulate the pollutant transport and decay process in the case of a pollution incident in the sections of the Yangtze and the Jialing passing through the city area of Chongqing. The Boussinesq assumptions and the Navier-Stokes equations of incompressible fluid were applied to setting up the pollutant diffusion equations and the equations for the decay process. E. colt was taken as the example pollutant, and chloride dosage, light, temperature and ultraviolet intensity were considered in the equations for bacterial decay process. The calculated values of the fluid velocities in the two rivers agree well with corresponding measured results, indicating an ideal accuracy of the model. In simulation, the concentration of E. colt in water was assumed to be zero before the accident. The and 1.75 m/s for the Yangtze flow, and the downriver boundary was upriver boundary velocity was -1.35 m/s for the Jialing flow water depth set at 0. Simulation results show that the bacteria are transported downstream along the riverbank. A long and narrow pollutant belt develops at 12 h after the start of the accident ascribed to the quick longitudinal transfer. After the pollution sources are cut off, the pollutant concentration decreases slowly, mostly by advection and diffusion, suggesting inadequate self-purification ability of the rivers and the necessity of effective decontaminating measures in the case of a pollution incident, The model can be a useful tool for understanding the polluting situations of an improper discharge incident and evaluating the effects of decontaminating measures for the water body of the Three Gorges Reservoir.

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.

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.

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.

Carbon dioxide emissions from the Three Gorges Reservoir,China

Carbon dioxide(CO_2) emission from the rivertype reservoir is an hotspot of carbon cycle within inland waters. However, related studies on the different types of reservoirs are still inadequate. Therefore, we sampled the Three Gorges Reservoir(TGR), a typical river-type reservoir having both river and lake characteristics, using an online system(HydroCTM/CO_2) and YSI-6600v2 meter to determine the partial pressure of carbon dioxide(pCO_2)and physical chemical parameters in 2013. The results showed that the CO_2 flux from the mainstream ranged from 26.1 to 92.2 mg CO_2/m^2h with average CO_2 fluxes of 50.0 mg/m^2h. The CO_2 fluxes from the tributary ranged from-10.91 to 53.95 mg CO_22/mh with area-weighted average CO_2 fluxes of 11.4 mg/m^2h. The main stream emits CO_2 to the atmosphere the whole year; however, the surface water of the tributary can sometimes act as a sink of CO_2 for the atmosphere. As the operation of the TGR, the tributary became more favorable to photosynthetic uptake of CO_2 especially in summer. The total CO_2 flux was estimated to be 0.34 and 0.03 Tg CO_2/year from the mainstream and the tributaries, respectively. Our emission rates are lower than previous estimates, but they are in agreement with the average CO_2 flux from temperate reservoirs estimated by Barros et al.(Nat Geosci 4(9):593–596, 2011).

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.

The analysis on reservoir sediment deposition and downstream river channel scouring after impoundment and operation of TGP

According to the measured data after impoundment and operation of the Three Gorges Reservoir,the reservoir sediment deposition and downstream river channel scouring are described briefly and compared with the research results achieved in the demonstration stage.It is indicated through analysis that the reservoir sediment deposition and downstream river channel scouring during 8-year impoundment and operation are still within the original forecast,so the original forecasting results are feasible.The further observation and comparison should be conducted because the comparison between the observed data and the original forecast is not so sufficient in time and the prototype observation and related research work should be strengthened in the future.

Algal community composition and abundance near the confluence of the Jialing and Yangtze Rivers and in Shuanglong Lake in Chongqing,P.R.China

To understand the potential impact of the Three Gorges Reservoir on the aquatic ecosystem after the damming of the Yangtze River,we studied the community composition and temporal abundance distribution of algae in two types of water bodies:a segment of the Jialing River near its confluence with the Yangtze River as an example of the river-lake type,and Shuanglong Lake in Chongqing as an example of the lake type.In total,107 species belonging to 58 genera of 7 phyla were identified in the study area of the Jialing River,dominated by three groups with 49.5% diatoms,29.0% chlorophytes,and 11.4% cyanobacteria in the community composition.There were 122 species belonging to 66 genera of 8 phyla in Shuanglong Lake,dominated by the same three groups with 19.7% diatoms,48.4% chlorophytes,and 22.2% cyanobacteria.The densities of total algae and individual dominant groups were all much higher in the lake.More species of diatoms were found in the river-lake segment;whereas more chlorophyte species and cyanobacteriaum species were in the lake.There were 17 dominant species including 8 diatoms,4 chlorophytes,3 cyanobacteria and 2 cryptophytes in the river-lake segment,and 21 species in the lake,including 2 diatoms,9 chlorophytes,6 cyanobacteria,3 cryptophytes and a dinoflagellate.In eutrophic conditions,chlorophytes and cyanobacteria may proliferate in a lake-type area and diatoms may cause algal bloom in a relatively faster-flow lake-river type area.

三峡水库小江回水区水华暴发期浮游植物群落结构及其与环境因子的关系

三峡水库蓄水以来,支流水华频发,尤以小江情况最为严重,给三峡库区的生态安全带来较大隐患。为探究支流水华暴发特征和主控因素,于20142021年小江水华暴发期间在小江高阳江段进行浮游植物及环境因子调查,并使用单因素方差分析、聚类分析、百分比相似性分析以及基于距离的线性模型等方法,对小江水华暴发期间浮游植物和环境因子在不同年份不同水层间的差异以及二者的关系进行研究。结果表明:小江水华暴发期内,浮游植物的种类数在43~70种之间,其中2015年蓝藻种类数明显减少,2018年以后硅藻种类数明显减少;采样期间浮游植物平均细胞密度在0.66×10^(6)~61.28×10^(6)cells/L之间,同期表层细胞密度明显高于中层和底层;各层水体间水华微囊藻、铜绿微囊藻、不定微囊藻等10种藻的密度存在明显差异,是主要差异种;显著影响表层、中层和底层浮游植物群落结构变动的环境因子是水位的日平均变幅;水位的日平均变幅与藻类优势种拟合关系显示,当日水位下降幅度在0.5 m以上时,浮游植物平均密度会呈指数级减少。研究结果可为三峡库区支流水华的防控提供数据支持。

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。

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。

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。

太湖新银鱼种群摄食对小江浮游动物群落结构的影响

明晰太湖新银鱼(Neosalanx taihuensis)种群生长与浮游动物群落结构的动态变化关系,可为小江水华暴发的控制与水生态健康管理提供理论依据。2019年逐月对小江太湖新银鱼与浮游动物样品进行采集,并分析太湖新银鱼胃含物组成与浮游动物群落结构特征。结果表明:(1)太湖新银鱼的饵料生物主要为桡足类,其次为枝角类,轮虫占比较少;(2)3月至6月(太湖新银鱼春群繁殖期)太湖新银鱼生物量迅速上升,而浮游动物群落结构在此期间呈小型化趋势,生物量由28.93 mg/L下降至1.13 mg/L,密度由21173.39个/L增加至26808.23个/L;7月小江禁捕结束,太湖新银鱼生物量开始急剧下降,小江浮游动物中桡足类和枝角类的密度与生物量迅速升高,于8月达到全年最高;(3)由于太湖新银鱼对枝角类和桡足类具有较强的选择性,故在其生物量较高的时期(5、6月),水体中枝角类和桡足类生物量占比显著低于其他时期(P<0.05)。由此认为,太湖新银鱼生物量与浮游动物群落结构变化存在较强的关联性,太湖新银鱼种群摄食的下行效应可能是小江浮游动物生物量下降及群落结构小型化的关键原因。

小江不同食性鱼类氮磷排泄及其对养分循环的影响

探究小江流域不同食性鱼类排泄对初级生产养分循环的作用,为三峡库区支流鱼类群落调控及养分再循环提供理论参考。2019年在小江设置5个断面对水质、浮游物、鱼类进行监测和采样,并选取小江4种典型食性鱼类,即滤食性鱼类鳙、草食性鱼类草鱼、杂食性鱼类鲫和肉食性鱼类黄颡鱼,分析其氮磷排泄率的差异及其与温度的关系,通过模型反演估算不同食性鱼类排泄对小江藻类初级生产的贡献。结果表明:(1)滤食性鱼类氮排泄率最高,滤食性鱼类和肉食性鱼类磷排泄率相对较高;(2)不同食性鱼类氮磷排泄率随水温升高均有所增大,且杂食性鱼类氮排泄率受水温变化影响最大,而草食性鱼类磷排泄率受水温变化影响最小;(3)小江鱼类总生物量约11.08t,氮、磷排泄率分别为16.92、2.11ng/(L·d);(4)小江鱼类氮磷排泄对藻类养分循环贡献均较小,分别占初级生产力所需氮、磷含量的0.015%和0.022%;(5)在4种食性鱼类中,肉食性鱼类对初级生产力的贡献率最高。

长江-鄱阳湖顶托作用评价指标研究

长江与鄱阳湖形成的江湖交汇系统存在复杂的河床演变与物质能量交换,江湖顶托关系是影响江湖水量交换的重要因素,同时对整个区域的水资源、防洪、灌溉、航运、生态有着重要影响。以长江与鄱阳湖的交汇区为研究对象,从动量基本方程出发,建立了一套评估长江与鄱阳湖顶托强度的指标体系,提出了顶托强度指标——顶托角。研究结果表明:自20世纪80年代以来,顶托角整体上没有发生趋势性变化,说明长江对鄱阳湖的顶托作用在三峡水库蓄水后变化不明显。但从年内变化来看,在枯水期,由于三峡水库的补水作用,长江对鄱阳湖的顶托作用明显增强;在汛期,由于三峡水库的削减洪峰以及汛末蓄水,长江对鄱阳湖的顶托作用减弱。长江对鄱阳湖的顶托作用变化会在4~6月使湖水滞留湖区,易发生流域性洪水;在7~10月加速湖水的入江,使鄱阳湖的低水位形势持续恶化。研究成果可为长江和鄱阳湖的治理与保护提供参考。