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1.
喀斯特流域径流量时序演变特征分析——以贵州省为例 总被引：2，自引：0，他引：2
以贵阳水文站近45年年径流量序列为例,利用Morlet小波变换对喀斯特流域径流量时序演变特性进行了分析预测。结果表明:(1)贵阳水文站年径流主要存在4a和25a两个时间尺度的周期变化,在这两种时间尺度下,径流演变呈现出较明显的丰、枯交替振荡。(2)2000年以后的10a左右,年径流量有由丰转为枯、逐步下降的趋势。(3)年平均径流量的丰、枯周期变化主要受年平均降水量的影响;人类活动对喀斯特流域年径流量有增加和减小两方面的影响,总体上会使径流量略有增加。 相似文献
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水质预测是水环境规划、评价和管理的重要依据,对促进水资源可持续利用及生态发展具有重要意义。针对水质预测中各项因子的不确定性,基于未确知测度理论(unascertained measure,UM),采用改变网络初值的方法,对BP神经网络加以改进,并利用黑河流域莺落峡水文站1998~2011年的水质监测资料进行分析和预测。以挥发酚为参考序列,用灰色关联方法分析参考序列与其他因子的关联度,并最终确定BP网络的输入节点为CODmn、DO、SO42-、Cr6+以及挥发酚,输出节点为挥发酚,从而建立UMBP模型。分析结果表明,UM-BP预测模型比标准的BP神经网络模型具有更高的预测精度。因此,该模型应用于黑河流域水质预测是可行的。 相似文献
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《地下水》2021,(2)
乌拉斯台沟是新疆博尔塔拉河左岸的一条较小支流,为解决流域灌区工程性缺水,在出山口处拟建设拦河渠首工程。本文以该渠首工程区域为研究对象,以博尔塔拉河上的温泉水文站和阿合奇水文站作为参证站,对两大水文站多年泥沙资料进行分析,研究该区域泥沙变化特征。结果可知:河流含沙量的多少,受当时流域气候干旱程度、暴雨强度及下垫面条件影响较大,河流泥沙分布基本集中在山区暴雨洪水期和平水期,枯水期泥沙很少。研究区地层属于第四系砂砾石覆盖层厚,透水性强,在洪水期泥沙易形成淤积;通过对采用的两个参证站输沙量估算结果进行分析比较,推荐采用以温泉水文站为参证站的估算成果,即乌拉斯台沟拟建渠首多年平均年输沙总量为0.535×10~4t。研究结果以期为相关设计及施工等部门提供基础参考。 相似文献
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黄河的输沙量：过去、现在和将来——距今15万年以来的黄河泥沙收支表 总被引：4，自引：0，他引：4
黄河于150 ka BP切穿三门峡，东流入海。黄河泥沙90%来自黄土高原。黄土高原土地利用和植被的变化对黄河输沙有决定性的影响。15万年以来，黄河进入华北平原的泥沙约70 000×108 t，其中10 ka BP以前占80%。10 ka BP以后的输沙量中，最后1040年黄土高原滥垦时期占60%。黄河泥沙的归宿，建造华北大平原占73%，流入海洋占26%。现在，黄河每年流入北黄海的泥沙不足0.2×108 t，其输运主要受海洋环流系统的影响。现在黄海每年向东海输运悬浮沉积物0.2×108~0.3×108 t，主要为废黄河三角洲及水下三角洲受侵蚀再悬浮的黄河泥沙。1996—2000年黄河下游连年断流，利津站的年径流量和输沙量只有1950—1979年30年平均的19%左右。今后20~30年内，由于气候变暖、工业、城市等引黄水量增加，黄河的入海泥沙量仍将偏少。 相似文献
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为研究植被环境中床面泥沙起动特性，以天然河道中的植被及沙床为原型，对刚性植被环境中床面形态变化及泥沙起动规律进行了试验研究，并采用单位床面空间平均流速表述植被环境中泥沙的起动流速。研究结果表明，淹没植被条件下动床床面泥沙运动可分为3个阶段，即静止、部分起动及全部起动阶段，定义第3个阶段为刚性植被环境中泥沙起动的标准；推导的淹没刚性植被环境中的泥沙起动流速半经验函数关系式可以表述植被环境中泥沙起动特性，其中植被因子Fv对泥沙起动的影响最明显；植被密度一定时，植株周围冲坑深与空间平均流速成线性关系。研究认为采用植被环境中单位床面空间平均流速表述泥沙起动特性的方法是可行的。 相似文献
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变化环境下流域水文物理特性常呈现"非稳态"特征,代表流域特性的模型参数也会随之发生变化,因此,开展水文模型参数时变研究有助于提高水文模拟精度。考虑植被条件和人类活动对水文过程的影响,基于植被归一化指数、人口、地区生产总值、粮食产量和有效灌溉面积5个指标建立两参数月水量平衡模型参数的时变函数表达式,并考虑4种参数时变情形。选取直门达、张家山、咸阳、横江、丹江口和峡江站6个水文站分析对比4种情形下模型的径流模拟结果及其不确定性。结果表明:所有站点在1982—2006年内水文物理特性呈现"非稳态"特征;且较常参数而言,时变参数模型模拟效果更好,并获得更优的确定性预报结果,其中直门达站径流模拟精度提高最为显著,率定期和检验期内的纳西效率系数（NS）分别提高了10.3%和8.8%。该研究可以为变化环境下流域水库调度、水资源规划与管理等提供理论依据和技术支撑。 相似文献
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为研究洮河流域径流预报,根据河流集合预报方法,利用红旗水文站实时监测资料,基于中国洪水预报系统开发的三水源蓄满产流、滞后演算和马斯京根模块构建全流域洪水预报模型,并应用该模型分析预测红旗水文站径流及其概率分布统计。结果表明:径流拟合过程拟合较好,取得了较好的预报效果,模型满足河流集合预报应用的条件,结论可为洮河流域水资源开发利用、防汛保安提供参考依据。 相似文献
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根据郁江南宁站1954～2001年的流量和输沙率资料，对流量和输沙率之间进行了回归分析，得出了多年平均月均流量～输沙率的相关性、各年月均流量～输沙率的相关性、各月月均流量～输沙率年际变化的相关性和年均流量～输沙率的相关性，分析了南宁站的水沙变化趋势，得出了两者变化趋势的规律。 相似文献
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针对沈阳地铁一号线重工街站至启工街站区间隧道开挖引发地面沉降变形的问题,利用现场实测的地表沉降变形数据建立BP神经网络模型,并进行网络训练与预测。预测结果表明,时间序列神经网络模型能够很好地表达地面沉降监测数据序列间的非线性关系。利用BP神经网络建立的预测模型,所得预测值与实测值拟合很好,是预测地铁施工引发地面沉降变形的一种有效方法,能为沈阳地铁隧道的设计及施工提供科学合理的依据。 相似文献
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流域输沙的估算是水资源管理中广泛面临的问题。基于时间序列自回归滑动平均(ARIMA)预测模型,分别对补远江曼安水文站1993～2008年雨季、旱季月平均含沙量资料进行建模拟合。综合AIC值、相对误差,确定模型的阶数,运用Marquardt非线性最小二乘法估计模型参数,建立ARIMA预测模型。经检验,雨季AIC=-61.046,旱季AIC=-131.785,相对误差低于20%的合格率分别为92.1%、76.9%,残差序列均为白噪声序列,表明旱季ARIMA(1,1,1)、雨季ARIMA(1,1,2)模型较为合理。应用模型对2009～2011年曼安水文站的雨季、旱季平均含沙量进行了预测,实现了河流输沙状况的短期预报。 相似文献
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Holocene chemical weathering and climatic oscillations in north China: evidence from lacustrine sediments 总被引：1，自引：0，他引：1
ZHANGDONG JIN JINGLU WU JUNJI CAO SUMIN WANG JI SHEN NANHUA GAO CHENJUAN ZOU 《Boreas: An International Journal of Quaternary Research》2004,33(3):260-266
Holocene lacustrine sediments from two isolated lakes in north China are investigated. Based on palaeoclimatic significance of independent proxies in lake sediments, Holocene chemical weathering, and hence climate change, has been reconstructed for dated sediment cores from Daihai Lake and Aibi Lake. During early to mid-Holocene, higher weathering intensity occurred in the Daihai catchment under warm and humid climate conditions, and this reached a maximum at ∼5 kyr BP. However, synchronous proxy shifts from the two widely separated, isolated lake sediments indicate that there was a cool climate event during the early to mid-Holocene transition. This is characterized by reduced weathering in each catchment, low δ 13 C and δ 18 O of authigenic carbonate, and by lake level fluctuations. These might correspond to a global cooling signal identified in lakes, oceans, mollusc sequences, and polar ice cores, typically centred between ∼8.0 and 8.5 kyr BP. Dry conditions were experienced in Greenland, the North Atlantic and surrounding regions, and in broad monsoonal regions including Daihai at this time. However, recent extensive evidences as well as our data from the Aibi Lake sediments show that cool but wet conditions occurred in the central Eurasian continent at this time. After ∼2.5 kyr BP, a significant shift of independent sediment proxies indicates the beginning of the Neoglaciation with a higher frequency of fluctuations, including both the Medieval Warm Period (MWP) and the Little Ice Age (LIA). Our continental records provide new evidence of the Holocene climate variability with global significance and highlight the different spatial nature of the response to oscillations associated with different climate patterns. 相似文献
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Sediment cores from Lake Pupuke in Auckland City, New Zealand, contain a high‐resolution millennial to centennial‐scale record of changing climate and catchment hydrology spanning the past ca. 10 000 years. Here, we focus on the period between 9500 ± 25 and 7000 ± 155 cal. yr BP during which grain size, diatom palaeoecology, biogenic silica concentrations, sediment elemental and carbon isotope geochemistry reflect changes in sediment sources and lake conditions, with a significant event commencing at ca. 8240 cal. yr BP, commensurate with a lowering of lake level, faster erosion rates and increased sediment influx with a duration of ca. 360 yrs. However, the changes in the lake are not reflected in the terrestrial vegetation, where the pollen record indicates that podocarp forest dominated the Auckland region, with apparent environmental stability during this part of the early Holocene. The synchronous change in most of the proxies between ca. 8240 and 7880 cal. yr BP at Lake Pupuke indicates the presence of a sustained episode of relatively low lake level and concomitant increased rate of erosion in the early Holocene that appears to be at least partly coeval with the 8200 cal. yr BP meltwater event proposed for the North Atlantic region. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
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地质历史时期长江入海沉积物的来源和组成特征是探讨东亚边缘海地区沉积物“从源到汇”过程的核心问题之一。崇明岛H12钻孔沉积物元素与同位素地球化学分析揭示，Nd同位素、Eu异常、Cr/Th、Sc/Th等指标在1858—1906年间明显波动，波动的年份与文献记载的洪水事件发生时间基本一致；而在1906年之后沉积物中以上各地球化学指标趋于稳定。结合长江不同支流的沉积地球化学组成特征，运用物源混合模型进行判别，结果显示过去150年来长江入海沉积物主要来自上游支流及汉江，不同支流的洪水信号可以通过入海沉积物通量和化学组成来提取。20世纪以来H12钻孔沉积的各物源指标波动明显减小，推测与崇明岛当地的人类活动逐渐增强有关，防护堤、海塘等工程修建改变了长江入海沉积物在崇明岛的沉积方式，使得洪水时期沉积物无法在岛上淤积，因而钻孔记录中很难再发现洪水事件信号，沉积地球化学物源指标趋于稳定。 相似文献
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Carl Regnll Haflidi Haflidason Jan Mangerud John Inge Svendsen 《Boreas: An International Journal of Quaternary Research》2019,48(2):432-443
We present a well‐dated, high‐resolution and continuous sediment record spanning the last c. 24 000 years from lake Bolshoye Shchuchye located in the Polar Ural Mountains, Arctic Russia. This is the first continuous sediment succession reaching back into the Last Glacial Maximum (LGM) ever retrieved from this region. We reconstruct the glacial and climate history in the area since the LGM based on sedimentological and geochemical analysis of a 24‐m‐long sediment core. A robust chronology was established using a combination of AMS 14C‐dating, the position of the Vedde Ash and varve counting. The varved part of the sediment core spans across the LGM from 24 to 18.7 cal. ka BP. We conclude that the lake basin remained ice‐free throughout the LGM, but that mountain glaciers were present in the lake catchment. A decrease in both glacial varve preservation and sedimentation rate suggests that these glaciers started to retreat c. 18.7 cal. ka BP and had disappeared from the catchment by 14.35 cal. ka BP. There are no indications of glacier regrowth during the Younger Dryas. We infer a distinct climatic amelioration following the onset of the Holocene and an Early to Middle Holocene thermal optimum between 10–5 cal. ka BP. Our results provide a long‐awaited continuous and high‐resolution record of past climate that supplements the existing, more fragmentary data from moraines and exposed strata along river banks and coastal cliffs around the Russian Arctic. 相似文献
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Antony G. Brown 《第四纪科学杂志》1990,5(1):39-51
This paper attempts to explain downstream variations in the rates and processes of Holocene floodplain formation in a small to medium-sized, lowland catchment in Central England. Four macro-reaches were identified and horizons from at least one stratigraphic cross-section from each were radiocarbon dated. Considerable diachronism was revealed with the basal age and hence minimum residence time of the top two metres varying from 1000-9000yrs. The trend, a decrease in minimum residence time downstream, is explained by the basin-and-gorge bedrock long-profile inherited from the Devensian glaciation of the area. This is illustrated by a positive relationship between the mean floodplain accumulation rate and the SL index (slope-stream length product). Pollen analysis of the organic sediments shows that floodplain clearance took place around 1 300 BP, but probably locally, pre-dated and post-dated accelerated alluviation associated with agricultural expansion in the catchment. This study concludes that (a) different macro-reaches in this small to medium-sized catchment have adjusted in different ways to long-term catchment changes as part of autogenic floodplain evolution, (b) this has involved a change in the catchment's sediment conveyance characteristics during the Holocene, and (c) an important control on channel behaviour and floodplain sedimentation throughout the Holocene (as well as at present) has been the valley slopes inherited from the Quaternary glaciation of the area. 相似文献
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LOVISA ZILLÉN IAN SNOWBALL 《Boreas: An International Journal of Quaternary Research》2009,38(3):493-503
Mineral magnetic and carbon analyses of a continuous varved lake sediment sequence in west-central Sweden (Lake Mötterudstjärnet) complement similar palaeoclimate proxies obtained from two varved lake sediment sequences in northern Sweden and one in central Finland. The varve chronology is supported by tephrochronology, palaeomagnetic secular variations and 14 C AMS dating of terrestrial macrofossils. We apply a simple model in which the transport and deposition of catchment mineral matter reflect the amount of winter snow accumulation, spring snow-melt and stream discharge. Our data show that winter snow accumulation was generally enhanced in Sweden between 8100 and 7750 cal. yr BP. If dating errors are taken into account, the 350-year period of increased erosion is the geomorphic response to a multi-centennial scale climatic cooling that occurred some time between 8500 and 7500 cal. yr BP. The most significant erosion event in central Sweden was centred at 8050 cal. yr BP. It lasted 150 years (between 8100 and 7950 cal. yr BP) and is equivalent to the most extreme Holocene climate anomaly in the northern hemisphere, known as the 8 ka or 8200 cal. yr BP climate event. Our high-resolution paramagnetic susceptibility and ferrimagnetic grain-size parameters suggest that snowpack accumulation increased most significantly in northern Sweden between 7900 and 7750 cal. yr BP. We suggest that this north–south difference was a response to the re-establishment of moisture-laden westerly air masses, as meridional Atlantic overturning circulation was re-established at the beginning of the Holocene thermal maximum. 相似文献
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M.R. Box M.D. Krom R.A. Cliff M. Bar-Matthews A. Almogi-Labin A. Ayalon M. Paterne 《Quaternary Science Reviews》2011,30(3-4):431-442
Changes in 87Sr/86Sr and major element geochemistry, from two sediment cores (9509 and 9501) in the Eastern Mediterranean (EM), were used to resolve changes in sediment provenance and, hence, determine climate changes in the Nile catchment and Eastern Sahara desert over the past 25 ka. The sediment was described by a three end-member system comprising Blue Nile (BN; 87Sr/86Sr = 0.7506; Sr = 210 ppm), White Nile (WN; 87Sr/86Sr = 0.7094; Sr = 72.5 ppm) and Saharan dust (SD; 87Sr/86Sr = 0.7183; Sr = 99 ppm). The sedimentary record of these cores represents the suspended load carried down the Nile river and discharged into the S.E. Levantine basin and thus records palaeoclimatically controlled changes in erosion and transport in the catchment. During arid periods (0–5 ka BP) and prior to 11 ka BP, fluxes of BN sediment at 9509 (～6 g/cm2/yr & 10–12 g/cm2/yr, respectively) were greater than during the peak of the African Humid Period (AHP) from 5 to 11 ka BP (<2 g/cm2/yr); this latter period witnessed the deposition of the youngest organic-rich sediment, termed sapropel (S-1), in the EM basin. By contrast the flux of WN increased during the AHP from ～5 g/cm2/yr at ～13 ka BP to >15 g/cm2/yr. In the Ethiopian Highlands (BN catchment) increases in the amount and duration of the monsoon during the AHP caused more vegetation to grow resulting in less soil erosion. In the WN catchment increased rainfall caused more catchment erosion and higher sediment flux through the Sudd marshes. The sedimentation rate in core 9509 increased during the AHP because of the greater importance of the WN sediment flux relative to the BN sediment flux. Saharan dust flux also decreased during the AHP reaching a minimum at ～6 ka BP (core 9509) due to ‘greening’ of the Sahara desert. At the onset of S-1, the changes in Nile flow as determined by 87Sr/86Sr and climatic changes in the EM basin determined by δ18O of planktonic foraminifera were simultaneous, confirming that such isotopic tracers cannot be used directly to determine the cause of the circulation changes in the EM at this time. The increase in the proportion of BN sediment at 9509 with a somewhat higher grain size during the H-1 period (15–17 ka BP) was caused by erosion and redistribution of sediment from the Nile delta and/or the Israeli coast as sea-level rose. 相似文献