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1.
The sand dredging and its impacts on riverbed evolution and tidal dynamic change in the lower reaches and delta of the Dongjiang River are examined in this paper. The large amount of sand, totally 3.32 billion m^3 from 1980 to 2002, was mined from the riverbeds of the lower reaches and delta of the Dongjiang River. Increasing of the channel capacity, lowering of the average riverbed elevation, deepening of the water depth and decreasing of the longitudinal riverbed gradient are the main effects on the riverbed evolution brought by the large amount of sand dredging. Under the strong sand dredging and associated significant riverbed deformation, the notable changes of the tidal dynamic in the lower reaches and delta of the Dongjiang River occurred, including： （1）in the upper reaches of the Dongjiang River delta and lower reaches of the Dongjiang River, tidal level dropped apparently, tidal range widened, flood tidal duration became longer, amplitudes for major tidal components became bigger and tidal dynamics intensified; （2） tidal wave spread faster; and （3） the limits of the tidal level, tidal current and salt water moved upstream. 相似文献
2.
长江大通-河口段枯季的径流量变化 总被引：1，自引：1，他引：0
Based on hydrometric data and extensive investigations on water-extracting projects, this paper presents a preliminary study on water discharge changes between Datong and Xuliujing during dry season. The natural hydrological processes and human factors that influence the water discharge are analyzed with the help of GIS method. The investigations indicate that the water-extracting projects downstream from Datong to Xuliujing had amounted to 64 in number by the end of 2000,with a water-extracting capacity up to 4,626 m3/s averaged in a tidal cycle. The water extraction from the Changjiang River has become the most important factor influencing the water discharge downstream Datong during dry season. The potential magnitude in water discharge changes are estimated based on historical records of water extraction and a water balance model. The computational results were calibrated with the actual data. The future trend in changes of water discharge into the sea during dry season was discussed by taking into consideration of newly built hydro-engineering projects. The water extraction downstream Datong in dry season before 2000 had a great influence on discharges into the sea in the extremely dry year like 1978-1979. It produced a net decrease of more than 490 m^3/s in monthly mean discharges from the Changjiang into the sea. It is expected that the water extraction will continually increase in the coming decades, especially in dry years, when the net decrease in monthly mean water discharge will increase to more than 1000 m^3/s and will give a far-reaching effect on the changes of water discharge from the Changjiang into the sea. 相似文献
3.
Study on hydroclimatological changes in the mountainous river basins has attracted great interest in recent years. Changes in temperature, precipitation and river discharge pattern could be considered as indicators of hydroclimatological changes of the river basins. In this study, the temperatures （maximum and minimum）, precipitation, and discharge data from 1980 to 2009 were used to detect the hydroclimatological changes in the Bagmati River Basin, Nepal. Simple linear regression and Mann-Kendall test statistic were used to examine the significant trend of temperature, precipitation, and discharge. Increasing trend of temperature was found in all seasons, although the change rate was different in different seasons for both minimum and maximum temperatures. However, stronger warming trend was found in maximum temperature in comparison to the minimum in the whole basin. Both precipitation and discharge trend were increasing in the pre-monsoon season, but decreasing in the post-monsoon season. The significant trend of precipitation could not be observed in winter, although discharge trend was decreasing. Furthermore, the intensity of peak discharge was increasing, though there was not an obvious change in the intensity of maximum precipitation events. It is expected that all these changes have effects on agriculture, hydropower plant, and natural biodiversity in the mountainous river basin of Nepal. 相似文献
4.
Hydrological processes were compared,with and without the influence of precipitation on discharge,to identify the differences between glacierized and non-glacierized catchments in the Urumqi River source region,on the northern slope of the eastern Tianshan Mountains,during the melting season(May-September) in 2011.The study was based on hydrological data observed at 10-min intervals,meteorological data observed at 15-min intervals,and glacier melting and snow observations from the Empty Cirque,Zongkong,and Urumqi Glacier No.1 gauging stations.The results indicated that the discharge differed markedly among the three gauging stations.The daily discharge was more than the nightly discharge at the Glacier No.1 gauging station,which contrasted with the patterns observed at the Zongkong and Empty Cirque gauging stations.There was a clear daily variation in the discharge at the three gauging stations,with differences in the magnitude and duration of the peak discharge.When precipitation was not considered,the time-lags between the maximum discharge and the highest temperature were 1-3 h,10-16 h,and 5-11 h at the Glacier No.1,Empty Cirque,and Zongkong gauging stations,respectively.When precipitation was taken into consideration,the corresponding time-lags were 0-1 h,13 h,and 6-7 h,respectively.Therefore,the duration from the generation of discharge to confluence was the shortest in the glacierized catchment and the longest in the catchment where was mainly covered by snow.It was also shown that the hydrological process from the generation of discharge to confluence shortened when precipitation was considered.The factors influencing changes in the discharge among the three gauging stations were different.For Glacier No.1 station,the discharge was mainly controlled by heat conditions in the glacierized region,and the discharge displayed an accelerated growth when the temperature exceeded 5℃ in the melt season.It was found that the englacial and subglacial drainage channel of Glacier No.1 had become simpler during the past 20 years.Its weaker retardance and storage of glacier melting water resulted in rapid discharge confluence.It was also shown that the discharge curve and the time-lag between the maximum discharge and the highest temperature could be used to reveal the evolution of the drainage system and the process of glacier and snow melting at different levels of glacier coverage. 相似文献
5.
近60年黄河水沙变化及其对三角洲沉积的影响 总被引：1，自引：1，他引：0
In order to find out the variation process of water-sediment and its effect on the Yellow River Delta, the water discharge and sediment load at Lijin from 1950 to 2007 and the decrease of water discharge and sediment load in the Yellow River Basin caused by human disturbances were analyzed by means of statistics. It was shown that the water discharge and sediment load into the sea were decreasing from 1950 to 2007 with serious fluctuation. The human activities were the main cause for decrease of water discharge and sediment load into the sea. From 1950 to 2005, the average annual reduction of water discharge and sediment load by means of water-soil conservation practices were 2.02×109 m3 and 3.41×108 t respectively, and the average annual volume by water abstraction for industry and agriculture were 2.52×1010 m3 and 2.42×108 t respectively. The average sediment trapped by Sanmenxia Reservoir was 1.45×108 t from 1960 to 2007, and the average sediment retention of Xiaolangdi Reservoir was 2.398×108 t from 1997 to 2007. Compared to the data records at Huanyuankou, the water discharge and sediment load into the sea decreased with siltation in the lower reaches and increased with scouring in the lower reaches. The coastline near river mouth extended and the delta area increased when the ratio of accumulative sediment load and accumulative water discharge into the sea (SSCT) is 25.4–26.0 kg/m3 in different time periods. However, the sharp decrease of water discharge and sediment load into the sea in recent years, especially the Yellow River into the sea at Qing 8, the entire Yellow River Delta has turned into erosion from siltation, and the time for a reversal of the state was about 1997. 相似文献
6.
The stratigraphical cross-sections of the Yangtze River incised-valley near the No.1,No.3 and No.4 Nanjing Yangtze River bridges were established with respective bore date and documents.By 14C age analysis of the samples of four drilling cores near the No.4 Bridge(to be built),we can find that the time range of paleo-valley is dated in the LGM at a depth of-60 m to-90 m near Nanjing.It is also indicated that the deep incised-valley channel was narrow and the river flowed swiftly.The ancient Yangtze River deep channel presented partially and deeply incised features near the No.1 Bridge.According to previous publications,much research has been done on the main paleo-channel of the Yangtze River,but few results have been achieved on discharge estimation.In this paper,the incipient velocity and average velocity of the LGM was calculated with Vc = 4.60 d 1/3 h1/6,95 Vc 1.28lg 13.15.h.gd,d = 6 * 90 V 6.5u h≈ d,etc.,in terms of the river shape,sedimentary grain size and sequences near the No.3 and No.1 bridges.Moreover,the discharge in Nanjing reach of the Yangtze River during the LGM has been estimated to be around 12,000-16,000 m3/s according to the relationship of discharge,velocity of flow and cross-section. 相似文献
7.
Evolution of sedimentary environments of the middle Jiangsu coast, South Yellow Sea since late MIS 3 总被引：3，自引：0，他引：3
Fei Xia Yongzhan Zhang Qiang Wang Yong Yin Karl W. Wegmann J. Paul Liu 《地理学报(英文版)》2013,23(5):883-914
An evolutionary model of sedimentary environments since late Marine Isotope Stage 3 （late MIS 3, i.e., ca. 39 cal ka BP） along the middle Jiangsu coast is presented based upon a reinterpretation of core 07SR01, new correlations between adjacent published cores, and shallow seismic profiles recovered in the Xiyang tidal channel and adjacent northern sea areas. Geomorphology, sedimentology, radiocarbon dating and seismic and sequence stratigraphy are combined to confirm that environmental changes since late MIS 3 in the study area were controlled primarily by sea-level fluctuations, sediment discharge of paleo-rivers into the South Yellow Sea （SYS）, and minor tectonic subsidence, all of which impacted the progression of regional geomorphic and sedimentary environments （Le., coastal barrier island freshwater lacustrine swamp, river floodplain, coastal marsh, tidal sand ridge, and tidal channel）. This resulted in the formation of a fifth-order sequence stratigraphy, comprised of the parasequence of the late stage of the last interstadial （Para-Sq2）, including the highstand and forced regressive wedge system tracts （HST and FRWST）, and the parasequence of the postglacial period （Para-Sql）, including the transgressive and highstand system tracts （TST and HST）. The tidal sand ridges likely began to develop during the postglacial transgression as sea-level rise covered the middle Jiangsu coast at ca. 9.0 cal ka BP. These initially submerged tidal sand ridges were constantly migrating until the southward migration of the Yellow River mouth to the northern Jiangsu coast during AD 1128 to 1855. The paleo-Xiyang tidal channel that was determined by the paleo-tidal current field and significantly different from the modern one, was in existence during the Holocene transgressive maxima and lasted until AD 1128. Following the capture of the Huaihe River in AD 1128 by the Yellow River, the paleo-Xiyang tidal channel was infilled with a large amount of river-derived sediments from AD 1128 to 1855, causing the emergence of some of the previously submerged tidal sand ridges. From AD 1855 to the present, the infilled paleo-Xiyang tidal channel has undergone scouring, resulting in its modern form. The modern Xiyang tidal channel continues to widen and deepen, due both to strong tidal current scouring and anthropogenic activities. 相似文献
8.
黑河流域土地利用变化对地下水资源的影响 总被引：1，自引：0，他引：1
Land use and land cover changes have a great impact on the regional hydrological process. Based on three periods of remote sensing data from the 1960s and the long-term observed data of groundwater from the 1980s, the impacts of land use changes on the groundwater system in the middle reach of Heihe River Basin in recent three decades are analyzed by the perspective of groundwater recharge and discharge system. The results indicate that with the different intensities of land use changes, the impacts on the groundwater recharge were 2.602 × 10^8 m^3/a in the former 15 years （1969-1985） and 0.218 × 10^8 m^3/a in the latter 15 years （1986-2000）, and the impacts on the groundwater discharge were 2.035 × 10^8 m^3/a and 4.91 × 10^8 m^3/a respectively. When the groundwater exploitation was in a reasonable range less than 3.0 × 10^8 m^3/a, the land use changes could control the changes of regional groundwater resources. Influenced by the land use changes and the large-scale exploitation in the recent decade, the groundwater resources present apparently regional differences in Zhangye region. Realizing the impact of land use changes on groundwater system and the characteristics of spatial-temporal variations of regional groundwater resources would be very important for reasonably utilizing and managing water and soil resources. 相似文献
9.
60年来黄河流域径流量时空变化(英文) 总被引：4，自引：1，他引：3
Water discharge data of the Yellow River over the past 60 years was analyzed using the continuous wavelet transform (CWT) and Mann-Kendall (MK) test methods to identify spatial and temporal variation patterns. Potential connections between water discharge in the Yellow River Basin and El Ni o/Southern Oscillation (ENSO) were also examined by the cross wavelet and wavelet coherence methods. CWT results show that the periodic oscillations in water discharges had occurred at the temporal scales of 1-, 2to 4-, 6to 8and 10to 22-year. It was also found that at the annual timescale (1-year) the phase relations between water discharge and ENSO were indistinct probably due to the strong influence by human disturbances. However, over the longer time scales, the phase relation becomes much clearer with an anti-phase relation being found mainly at inter-annual scale (2to 8-year) and in-phase relation at decadal scale (16to 22-year). According to the MK test results water discharge at most stations except Tangnaihai have decreased significantly and the abrupt change occurred in the mid-1980s or the early 1990s. The changes in water discharge were found to be influenced by both climate changes and human activities. Before 1970 the change in water discharge was positively related to precipitation variations in the river basin, but after 1970 the decrease in water discharge has been largely caused by various human activities including constructions of reservoirs, water abstraction and water-soil conservation with water abstraction being the main cause. 相似文献
10.
长江口水域悬沙浓度时空变化与泥沙再悬浮 总被引：4，自引：0，他引：4
A detailed analysis of suspended sediment concentration (SSC) variations over a year period is presented using the data from 8 stations in the Yangtze River estuary and its adjacent waters, together with a discussion of the hydrodynamic regimes of the estuary. Spatially, the SSC from Xuliujing downwards to Hangzhou Bay increases almost constantly, and the suspended sediment in the inner estuary shows higher concentration in summer than in winter, while in the outer estuary it shows higher concentration in winter than in summer, and the magnitude is greater in the outer estuary than in the inner estuary, greater in the Hangzhou Bay than in the Yangtze River estuary. The sediments discharged by the Yangtze River into the sea are resuspended by marine dynamics included tidal currents and wind waves. Temporally, the SSC shows a pronounced neap-spring tidal cycle and seasonal variations. Furthermore, through the analysis of dynamic mechanism, it is concluded that wave and tidal current are two predominant factors of sediment resuspension and control the distribution and changes of SSC, in which tidal currents control neap-spring tidal cycles, and wind waves control seasonal variations. The ratio between river discharge and marine dynamics controls soatial distribution of SSC. 相似文献
11.
基于经验模型的长江口南支上段压咸临界流量 总被引：1，自引：0，他引：1
河口区域盐水入侵,威胁三角洲地区城市淡水资源取用及生态环境安全,合理确定压咸临界径流流量,有助于进一步改进流域水库群的调度模式。以长江口南支为例,利用2009-2014年期间60余个潮周期氯度资料,综合分析多种盐度预测经验模型的有效性,确定了抑制咸潮入侵的临界径流流量。结果表明：① 咸潮入侵强度随径流与潮差组合而不同,长江口径流流量小于30000 m 3/s时可发生盐度超标现象,69%的盐度超标天数发生在流量小于15000 m 3/s时期,当径流量小于12000 m 3/s时盐度超标几率达65%;② 盐度与潮差之间为指数型曲线关系,潮差总体呈半月周期变化,根据潮差累积频率分布得到平均意义上“连续10 d盐度超标”临界条件对应的青龙港潮差约为2.7 m,由此推算得到临界大通流量略大于11000 m 3/s;③ 采用多种盐度预测经验模型进行计算,避免连续10 d盐度超标对应的临界径流流量区间为11000~12000 m 3/s,平均阈值取为11500 m 3/s;④ 在三峡及上游梯级水库联合运行后,2008-2015年长江入海最低径流流量有所增加,但仍低于压咸潮临界阈值,建议优化水库调度模式,控制长江入海径流最低流量在11500 m 3/s以上。 相似文献
12.
在候选预报因子的基础上,通过Pearson相关系数和重要度指数分别确定了主要预报因子及其滞后期,进而利用确定滞后期的预报因子建立基于随机森林的咸潮预报模型,并应用于磨刀门水道大涌口站的枯水期咸潮预报。结果发现：通过相关系数确定的主要预报因子与含氯度之间存在1~3 d不等的滞后期;考虑预报因子滞后作用的随机森林模型,其预报结果不仅能很好地满足咸潮预报的精度要求,而且明显优于未考虑预报因子滞后作用的随机森林模型,即考虑预报因子的滞后作用能显著提高模型的拟合效果。此外,与传统的马尔科夫链相比,随机森林模型的预报结果不仅精度更高,而且在中长期预报上更有优势。 相似文献
13.
本文通过长江口实测氯度与流量和潮位资料的相关分析,预估了未来河口水质的变化。计算表明,当大通站下泄流量不足13×103m3/s时,未来东线调水及海平面上升,将使长江口南支河段水质严重恶化;三峡水库建成后,枯季1-3月增加下泄水量虽可抵消东线调水的影响,但在水库蓄水的10月遇枯水年分,水质将大幅度下降。 相似文献
14.
基于1960－2016年东平水道三水、紫洞、澜石、浮标厂月均潮差、余水位数据及三水、马口站月均流量数据,以1993年三水－马口分流比突变为切入口,探讨余水位坡度及潮波衰减率等径－潮动力改变下,东平水道水面线与余水位曲率的时空演变特征及其影响因素。结果表明：东平水道在1993年三水分流比剧增之后,1）余水位坡度或潮波衰减率与流量的双累积曲线斜率下降,即余水位坡度或潮波衰减率对流量的依赖性减弱;2）东平水道水面坡度整体下降且上游（紫洞－三水河段）降幅最大,不同季节坡度的变化率介于-67%~-4%,水面线由下凹转为上凸,即曲率由正转负。同时,曲率波动幅度明显减弱,1993年前曲率波动介于2×10-10~5.48×10-10,而1993年后波动介于-0.9×10-10~-0.07×10-10。上述曲率变化在冬季较夏季显著;3）上述水面线异变的主要原因为,东平水道中上游河道挖沙导致河床地形大幅下切、水位下降、来水量增大,且同时期的航道疏浚加剧这一变化;下游主要受滩涂围垦影响,河道淤浅。以上地形变化导致河道中游径、潮流量增大,径－潮双向顶托使水面线转变为上凸型。受北江上游飞来峡水库调蓄影响以及过水断面宽深比、海平面变化等季节性调节作用,东平水道冬季水面线及曲率变化较夏季显著。 相似文献
15.
采用数学模型手段对珠江河口的盐通量进行了计算和分析.该平面二维水流盐度模型范围包括珠江三角洲河网与八大口门在内,计算结果与实测值符合良好,较好地反映了模拟区域盐度场的时空分布特点.结果显示:珠江河口枯季大潮时的总盐通量为1 954×104t,小潮时总盐通量为512×104t,仅为大潮时的26.2％;无论是在大潮还是小潮期间,大虎和官冲的盐通量所占比例最大,说明盐水入侵主要是通过虎门与崖门这两个通道进入;盐通量沿程明显减少,这是盐度、水通量等沿程变化的综合作用.不同类型水体的盐度等值线在枯季大小潮期间的分布 相似文献
16.
The sand dredging and its impacts on riverbed evolution and tidal dynamic change in the lower reaches and delta of the Dongjiang River are examined in this paper. The large amount of sand, totally 3.32 billion m3 from 1980 to 2002, was mined from the riverbeds of the lower reaches and delta of the Dongjiang River. Increasing of the channel capacity, lowering of the average riverbed elevation, deepening of the water depth and decreasing of the longi-tudinal riverbed gradient are the main effects on the riverbed evolution brought by the large amount of sand dredging. Under the strong sand dredging and associated significant riverbed deformation, the notable changes of the tidal dynamic in the lower reaches and delta of the Dongjiang River occurred, including: (1) in the upper reaches of the Dongjiang River delta and lower reaches of the Dongjiang River, tidal level dropped apparently, tidal range widened, flood tidal duration became longer, amplitudes for major tidal components became bigger and tidal dynamics intensified; (2) tidal wave spread faster; and (3) the limits of the tidal level, tidal current and salt water moved upstream. 相似文献
17.
海平面上升对珠江三角洲咸潮入侵的影响 总被引：16，自引：0，他引：16
海平面上升,潮汐作用加强,在无其它因素影响下,通常认为必然导致包括盐水入侵灾害加剧。根据河口盐淡水混合扩散原理,结合珠江三角洲河口整治延伸规划及河口淤积发展趋势,动态分析了海平面上升对珠江三角洲咸潮入侵的影响,认为海平面上升后,盐水入侵对珠江三角洲的影响总的来说不会加剧,而且还会逐步减弱。 相似文献
18.
Kayla Deasley Jennifer B. Korosi Joshua R. Thienpont Steven V. Kokelj Michael F. J. Pisaric John P. Smol 《Journal of Paleolimnology》2012,48(2):287-296
An increase in the frequency and intensity of marine storm surges is a predicted consequence of climate warming, and therefore it is important to better understand the biological responses to such events in coastal regions. In late September 1999, a major storm surge resulted in a saltwater intrusion event over a large area of the Mackenzie Delta (NT, Canada) front, causing rapid salinization of lakes on the alluvial plain. Due to a lack of long-term ecological monitoring data in the region, the impacts that the saltwater intrusion event had on the biota of affected lakes were unknown. We used high-resolution paleolimnological approaches to reconstruct past assemblage changes in Cladocera from impacted Lake DZO-29 (unofficial name) in order to determine how different cladoceran species responded to a major increase in lake salinity following the 1999 storm surge. Camptocercus were extirpated from the lake following the saltwater intrusion and have not recovered. We also observed an initial decrease in Alona relative abundance following the marine flooding, likely reflecting a loss of A. quadrangularis, A. barbulata, and A. costata from the lake. A. circumfimbriata, Chydorus biovatus, C. brevilabris, and Bosmina spp. were abundant both before and after the saltwater intrusion, and Paralona pigra was present following the storm surge, but not prior to it. The most notable shift in Cladocera in the recent sedimentary record, however, occurred much earlier, with an increase in pelagic Bosmina taxa and a subsequent decrease in the benthic/littoral taxa Chydorus and Camptocercus, an assemblage shift that is consistent with a response to climate warming in this region, and strongly correlated to other changes in the lake inferred to be as a result of regional warming. 相似文献
19.
钱春林 《云南地理环境研究》1993,5(2):41-45
引滦工程后滦河三角洲水文过程发生很大变化,滦河入海水量骤减河海动力平衡破坏,海洋作用相对增强,滦河口盐度增加,盐水入侵长度增大,三角洲地下水含盐量增高,土壤盐渍化的面积扩大。 相似文献
20.
Shanghai is a megacity that increasingly relies on water drawn from the Yangtze River estuary. During periods of low flow, water in the estuary can become too saline for use in city water supplies. River flow is measured at the Datong gauging station 680 km upstream from the river mouth. Several existing and planned river water extractions are located below Datong, including the Eastern Route of the South-North Water Diversion Project (ERP). The effect of these extractions on discharge into the estuary and the associated salinity levels may be significant, even though the extractions are not reflected in the discharge at Datong. We estimate the effects of these downstream extractions on water discharge into the estuary (rather than at Datong), particularly the critical discharge level below which salinity compromises water security in Shanghai. Our results show that the ERP will cause the discharge into the estuary to fall below critical levels between December and February in dry years and January to February in normal years. Future water transfer projects along the lower Yangtze River will further compound the problem. Maintaining Shanghai's water security is therefore a significant challenge for China's water resource management institutions. 相似文献