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1.
基于稳定同位素的海河源区地下水与地表水相互关系分析 总被引：4，自引：0，他引：4
对海河流域源区的丰、枯水期降水、地下水、河水进行取样测试,分析了海河源区不同水体氢氧稳定同位素组成及水化学的时空分布特征,同时运用同位素二元混合模型对典型采样点地表水地下水间的相互作用进行了定量分析。结果表明：① 丰水期地下水及地表水δD和δ18O及总溶解性固体(TDS）表现出显著的空间差异性,而枯水期只有地下水的同位素组成及水化学特性表现出空间差异。②研究区的地下水水化学类型以Ca-HCO3·SO4、Ca-HCO3型为主,丰水期河水与地下水化学类型较为相似,枯水期地下水化学类型与同时期的河水及大气降水的水化学类型存在显著的差异,说明枯水期地表水与地下水之间的转化关系不明显。Gibbs分析结果表明,控制海河源区水体化学性质的主要影响为岩石风化作用。③枯水期地下水受其他水体影响较弱,而丰水期河水及大气降水对地下水具有显著的补给作用,3个源流区中西源的地表河水对地下水影响最显著。 相似文献
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长江三峡阶地的成因机制 总被引：15，自引：0，他引：15
根据对长江三峡阶地堆积物进行的野外调查与室内分析发现三峡阶地的成因具有以下特点:构成阶地上部的河漫滩相堆积、中部的冲积砾石层与作为阶地基座的基岩平台是在不同时期形成的;阶地上部河漫滩相堆积是在中全新世气候温暖、长江三峡高水位条件下形成的.因此,长江三峡阶地是在构造上升的基础上由于气候及长江三峡流量及水位变化而形成的,并非一定是间歇性构造上升的标志. 相似文献
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Richard A. Marston Jacky Girel Guy Pautou Herve Piegay Jean-Paul Bravard Chris Arneson 《Geomorphology》1995,13(1-4)
The purpose of this paper is to describe and explain channel metamorphosis of the Ain River in east-central France and the effects of this metamorphosis on floodplain disturbance and vegetation development. The Ain River is a 195 km long stream originating in the Jura Mountains which flows into the Rhône River between Lyon, France, and Geneva, Switzerland. The lower 40 km of the Ain River, beyond the mountain front, are situated in a valley of outwash deposits where the floodplain is 0.2 to 1.2 km wide. A complex mosaic of floodplain landscape units has developed. Maps dating back to 1766 and six sets of aerial photographs dated between 1945 and 1991 were used to document changes in channel pattern. Aerial photos and field surveys were used to compile maps of landscape units based on dominant vegetation life-forms, species, and substrate. Six maps dated between 1945 and 1991 were digitized in ARC/INFO and an overlay was generated to determine the changes in landscape units as related to channel disturbance. Change from a braided to a single-thread meandering channel probably took place in the period 1930–1950. The process of river entrenchment has occurred throughout the Holocene but has accelerated in the present century due to shortening of the river course, construction of lateral embankments, and vegetation encroachment following reservoir construction and cessation of wood-cutting and grazing. The increase in horizontal channel stability coupled with channel entrenchment have decreased floodplain disturbance and lowered the water table by approximately one meter. Pioneer and disturbance-dependent landscape units have experienced a more terrestrial-like succession to an alluvial forest. Abandoned channels have also been replaced by alluvial forests. On poorly drained soils, shrub-swamp communities of willow and hydrophytic herbaceous plants have been replaced by mixed forests of ash, alder, black poplar, and oak. On well drained alluvial soils, ash and oak dominated hardwood forests have declined in favor of mesophytic stands of black poplar. All types of vegetation, but particularly dry grasslands-shrublands, have been cleared for mines, campgrounds, agriculture, and other types of development. Using several measures, landscape diversity decreased between 1945 and 1991. 相似文献
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The geomorphology and dynamics of the Mfolozi River floodplain and estuary, located in the subtropical region of northern KwaZulu-Natal, South Africa, were considered with respect to existing models of avulsion and alluvial stratigraphy. The Mfolozi River floodplain may be divided into regions based on longitudinal slope and dominant geomorphic processes. Confinement of the Mfolozi River above the floodplain has led to the development of an alluvial fan at the floodplain head, characterized by a relatively high sedimentation rate and avulsion frequency, at a gradient of 0.10%. The lower floodplain is controlled by sea level, with an average gradient of 0.05%. Between the two lies an extremely flat region with an average gradient of 0.02%, which may be controlled by faulting of the underlying bedrock.Avulsion occurrences on the Mfolozi floodplain are linked to the two main zones of aggradation, the alluvial fan at the floodplain head, and toward the river mouth in the lower floodplain. On the alluvial fan, normal flow conditions result in scour from local steepening. During infrequent, large flood events, the channel becomes overwhelmed with sediment and stream flow, and avulses. The resulting avulsion is regional, and affects the location of the channel from the floodplain head to the river mouth. Deposits resulting from such avulsions contribute significantly to the total volume of sediment stored in the floodplain, and tend to persist for long periods after the avulsion. Contrastingly, on the lower floodplain, reaching of the avulsion threshold is not necessarily linked to large flood events, but rather to long-term aggradation on the channel that decreases the existing channels gradient while increasing its elevation above the surrounding floodplain. Resultant avulsions tend to be local and do not contribute significantly to the overall volume of floodplain alluvium. 相似文献
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《Polar Science》2014,8(3):232-241
This study analyzes long-term (40–60 years) discharge and water temperature records collected near the basin outlets of the Yukon and Mackenzie Rivers. It defines seasonal cycles of discharge, water temperature (WT), and heat flux (HF) for the basins, and compares their main features to understand their similarity and difference. Both rivers have similar hydrographs, i.e. low flows in winter and high discharge in summer, with the peak flood in June due to snowmelt runoff. Mackenzie River has many large lakes and they sustain the higher base flows over the fall/winter season. Mackenzie basin is large with high precipitation, thus producing 50% more discharge than the Yukon River to the Arctic Ocean. The WT regimes are also similar between the two rivers. Yukon River WT is about 2–3 °C warmer than the Mackenzie over the open water months. Both rivers have the highest WT in the mid summer and they transport large amount of heat to the polar ocean system. Yukon River monthly HF is lower by 10–60% than the Mackenzie mainly due to smaller discharge. Mackenzie River heat transport peaks in July, while the Yukon HF reaches the maximum in June and July. These results provide critical knowledge of river thermal condition and energy transport to the northern seas. They are useful for large-scale climate and ocean model development and validation, and climate/hydrology change research in the northern regions. 相似文献
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基于印度河流域及周围54个地面气象站气温、降水资料,结合CRU气温和GPCC降水全球格点化陆面再分析资料,通过插值构建了一套0.5°×0.5°分辨率1980—2016年逐月格点数据集。采用Thornthwaite方法计算了潜在蒸散发,基于标准化降水蒸散指数（SPEI）,探讨了印度河流域气候变化及干旱演变特征。结果表明：（1）1980—2016年,印度河流域年平均气温以0.30℃·（10 a）-1的速率呈显著上升趋势,21世纪初增温幅度最大;干季（11月~次年4月）升温速率较快,达0.36℃·（10 a）-1,湿季（5~10月）增速0.25℃·（10 a）-1。年降水量呈现少雨—多雨—少雨—多雨年代际振荡。伴随着持续升温,年和各季的潜在蒸发量增加显著。干季干旱频率较多,但湿季干旱强度高,各季干旱频率与降水呈现较一致的年代际波动;干旱的影响面积在干季呈现微弱地增加趋势,湿季却略有减少趋势。（2）空间上,除西北局部,流域其他区域的年和季平均气温、潜在蒸发量增加趋势显著,均达到95%置信水平。其中南部平原和东北山区升温幅度较高,南部平原区潜在蒸发量增加也较大。新德里到喀布尔的东南至西北带状区域的年和湿季降水量,以及喀布尔周围地区的干季降水量呈显著增加趋势。东南平原区和东北局部山区的干季,以及东北和西南局部山区的湿季呈现显著的干旱化态势,需要加强防灾减灾的意识并采取相应措施,以规避干旱增多带来的不利影响。 相似文献
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地下水氢氧稳定同位素的组成与空间分布规律可为研究地下水补给及深入认识水循环过程提供重要理论依据。基于青海湖沙柳河流域浅层地下水样品的氢氧稳定同位素数据,通过空间插值法和δD-δ18O线性关系法,分析了氢氧稳定同位素组成、空间分布特征及地下水补给关系。结果表明：沙柳河流域中下游地区浅层地下水δ18O与δD值分别为-8.54‰~-6.02‰和-58.6‰~-34.6‰,平均值分别为-6.79‰和-41.8‰;δ18O值在流域空间上表现为西北、中部高,南北低的特征;流域西北和中部地区地下水主要受降水补给,补给来源单一、蒸发作用强是该区域地下水同位素值较高的原因,降水→地下水→泉水是其主要补给、排泄关系;流域北部、南部地区地下水与降水、河水、泉水等水体水力联系密切,不同补给来源的平滑作用是该区域地下水同位素值较低的原因,其补给、排泄关系主要为降雨→河水→地下水→泉水（或降雨→地下水→泉水→河水）。 相似文献
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以分析青海巴音河流域地表水与地下水转化关系为目标,2016年8月,沿巴音河采集了23组地表水样、13组地下水样和9组泉水样,室内分析得到了其对应的主要水化学离子和氘氧稳定同位素数据,运用统计分析、Piper三线图、Gibbs图分析了流域水化学特征;以溶解性总固体（TDS）、氯离子（Cl-）和氧同位素（δ18O）作为示踪剂,定性分析了巴音河沿程地表水与地下水的转化关系;基于质量平衡法,运用δ18O定量计算了巴音河沿程地表水和地下水之间的转化量。研究结果表明：TDS、Cl-、δ18O可用于定性分析巴音河流域不同河段地表水与地下水之间的转化关系,定量评估其转换强度;巴音河流域地表水和地下水的水化学类型主要为HCO3·Cl-Ca·Mg,地下水水化学类型更为多样,地表水受控于岩石风化作用,地下水与泉水受到岩石风化与蒸发作用的影响;地表水与地下水水力联系密切,沿巴音河流向,二者相互转化频繁,上游河段,地下水主要接受地表水渗漏和沿途侧向径流补给,补给比例分别为65.33%、34.67%,至黑石山水库上游,地表水接受上游地下水和溢出泉水的补给,补给比例分别为49.54%、50.46%;中游河段,地下水接受地表水和北部山区侧向径流补给,补给比例分别为65%、35%;下游河段,地表水接受地下水和泉水补给,补给比例分别为53.12%、46.88%。研究结果有助于建立流域水循环模式、揭示水资源形成机制,可以为巴音河流域水资源可持续开发利用和生态环境保护提供理论和技术支持。 相似文献
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We conducted a paleolimnological investigation of late Holocene deposits on a distal, constrained floodplain of the Cauca River, northern Colombia, i.e. the La Caimana sedimentary succession. The record starts sometime between 4,500 and 4,000 cal yr BP, when the first high-energy fluvial events inundated an ancient soil surface. From that time until about 3,260 cal yr BP, a stable and probably seasonal flooding regime was established on the floodplain. From ~3,260 to ~2,800 cal yr BP, ephemeral and shallow swamps developed on the floodplain. Their formation and duration depended on their connection with the Cauca River. From ~2,800 to ~2,400 cal yr BP, fluvial influence became more dominant, establishing a semi-permanent connection between the river and the floodplain. From ~2,400 to 1,400 cal yr BP, episodic formation of ephemeral swamps occurred. During this stage, floodplain lakes displayed high salinity and nutrient concentrations, and possibly alkaline conditions as a consequence of reduced water volume when the connection with the river was reduced or lost completely. A change in the hydrological regime occurred from ~1,400 to ~850 cal yr BP, when high-energy fluvial events were punctuated by periods of reduced flooding that enabled soil formation. Generally, connection with the Cauca River resulted in lake waters with low salinity and nutrient concentration, whereas loss of connection with the river led to lakes with greater salinity and nutrient content. Paleocurrent analyses indicate that flows came predominantly from the Cauca River, suggesting the lakes were formed by the impoundment of La Caimana Creek. The sedimentary succession of La Caimana offers a unique, high-resolution record of the evolution and dynamics of an ancient floodplain of the Cauca River and its aquatic ecosystems. 相似文献
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地下水稳定同位素组成的时空变化特征可以反映不同时期、不同区域地下水补给来源的差异。通过青海湖沙柳河流域浅层地下水氢氧稳定同位素组成的时空变化特征以及地下水、河水与降雨之间的补给关系的分析,结果显示：季风时期,地下水主要受降雨入渗和河流侧向补给为主,在补给过程中蒸发作用是影响地下水稳定同位素值的主要因素;非季风期,冰雪融水对低值区的地下水影响显著,同时降水的快速入渗则是该时期高值区地下水的主要补给方式之一。地下水同位素高值区,地下水与河水间补给作用较弱,补给时间超过5个月;地下水同位素低值区,地下水与河水补给关系较为密切,补给时间在1~4个月间。本文所得结论可初步反映干旱半干旱内陆流域地下水稳定同位素特征以及补给方式的基本规律,在一定程度上可为流域地下水及其他水体间的转换研究提供科学依据,并为地下水资源管理和水环境治理提供一定理论指导。 相似文献
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The fluvial geomorphological development of the Tagliamento River and its flooding history is analysed using historical documents and maps, remote-sensed data and hydrological information. The river has been building a complex alluvial fan starting from the middle part of its alluvial course in the Venetia–Friuli alluvial plain. The riverbed is aggrading over its entire braided length. The transition from braiding to meandering near Madrisio has shifted downstream where the river width determined by the dikes becomes narrower, causing major problems. The flood hazard concentrates at those places and zones where flooding occurred during historical times. Prior to the agrarian and industrial revolution, land use was adjusted to the flooding regime of the river. Subsequent land-use pressure led to a confinement of the river by dikes to such an extent that the flood risk in the floodplain downstream of Madrisio has increased consistently, and represents nowadays a major territorial planning issue. The planned retention basins upstream of the middle Tagliamento will alleviate the problem, but not solve it in the medium and long term. Therefore, fluvial corridors in the lower-middle parts (from Pinzano to the sea) have been identified on the basis of the flooding history in relation to fluvial development during historical times. The result should be used for hydraulic simulation studies and land-use planning. 相似文献
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Leal A. K. Mertes Darin L. Daniel John M. Melack Bruce Nelson Luiz A. Martinelli Bruce R. Forsberg 《Geomorphology》1995,13(1-4)
The spatial heterogeneity of hydrology and vegetation during high-water periods in geomorphically distinct reaches of the Amazon River in Brazil was determined based on semivariance statistics. The spatial statistics were derived from three classified Landsat Thematic Mapper images representing upstream to downstream geomorphic characteristics. In the upstream river reach, scroll-bar topography on the floodplain tends to channelize floodwater into floodplain drainage channels, thus reducing the diversity of water types by reducing opportunities for mixing of flooding river water with locally derived floodplain water. The highest diversity of vegetation types is along floodplain drainage channels, while the rest of the floodplain has a more homogeneous cover. In the middle reach of the river the diversity of wetland classes as measured by semivariance is higher than both upstream and downstream, perhaps because of exposure to more water types and landforms. The diversity of water types is high, because flooding river water flows onto the floodplain as diffuse, non-channelized overbank flow, as well as through drainage channels. The non-channelized overbank flow readily mixes with locally derived floodplain water. Floodplain landforms available for colonization by vegetation include scroll bars, swales, lake shores, lake deltas, and floodplain drainage channels. In the downstream reach where the floodplain is wide, relatively flat, and covered with huge lakes, the floodplain supports a moderately heterogeneous mix of vegetation communities. Where landforms are similar, the spatial distribution of the vegetation is similar to that of the middle reach of the river. In the downstream reach flooded forest comprised only 37% of the wetland vegetation. In contrast, in both the upstream and middle reaches, over 70% of the wetland vegetation was flooded forest. Agricultural clearing of the floodplain is more. common in downstream reaches and may account for the smaller percent of floodplain forest cover. 相似文献
14.
Hyporheic zone(HZ) influences hydraulic and biogeochemical processes in and alongside streams, therefore, investigating the controlling geographic factors is beneficial for understanding the hydrological processes in HZ. Slack water pool (SWP) is an essential micro-topographic structure that has an impact on surface water and groundwater interactions in the HZ during and after high flows. However, only a few studies investigate HZ surface water and groundwater exchange in the SWP. This study used the thermal method to estimate the HZ water exchange in the SWP in a segment of the Weihe River in China during the winter season. The findings show that on the flow-direction parallel to the stream, river recharge dominates the HZ water exchange, while on the opposing flow-direction bank groundwater discharge dominates the water exchange. The water exchange in the opposing flow-direction bank is about 1.6 times of that in the flow-direction bank. The HZ water exchange is not only controlled by flow velocity but also the location and shape of the SWP. Great water exchange amount corresponds to the shape with more deformation. The maximum water exchange within the SWP is close to the river bank where the edge is relatively high. This study provides some guidelines for water resources management during flooding events. 相似文献
15.
天山山区典型内陆河流域径流组分特征分析 总被引：1，自引：0，他引：1
通过对天山南北坡的两个典型流域降水、地下水、河流、融冰雪水δD和δ18O及水化学检测,基于同位素径流分割模型定量分析了年内径流组分特征。结果表明：（1）两条河流的径流组成中地下水为构成径流的主要成分,其次是冰川融水,融雪水及降水,但南北坡径流组分表现出较明显的差异,乌鲁木齐河流域中冰川融水的比重要大于黄水沟流域,对气候变化响应明显。（2）两条河流在不同季节径流组分也表现出较大差异,春季径流组分差异最为明显。 相似文献
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雅鲁藏布江河谷加查-米林段沙丘成因 总被引：2，自引：2，他引：0
加查-米林段位于雅鲁藏布江河谷中游下段,分布沙丘89片。通过实地考察、遥感卫星影像解译、DEM分析、粒度分析等方法对加查-米林段沙丘成因进行分析。结果表明：依据沙丘沙物质来源可将加查-米林段沙丘划分为河漫滩型沙丘、阶地型沙丘和谷坡型沙丘。河漫滩型沙丘形成与雅鲁藏布江水位关系密切。丰水期洪水淹没河漫滩,泥沙沉积;枯水期水位降低,泥沙出露,经风的吹蚀、搬运、堆积形成河漫滩型沙丘。阶地型沙丘和谷坡型沙丘形成与表层覆盖的黄土层（粉质砂土）破坏有关。雅鲁藏布江不断下切,在阶地及谷坡不同高度残留古河流冲积沙,遭受风蚀后风蚀堆积物形成古沙丘。因环境演变,古沙丘表面沉积黄土,形成致密坚硬的黄土层,不易被风吹蚀,成为古沙丘的保护层。黄土层受风蚀、水蚀及人类活动破坏,导致下伏古沙丘裸露,形成现代流动沙丘。 相似文献
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The Mkuze Wetland System, forming part of the iSimangaliso World Heritage Site, is South Africa’s largest freshwater wetland area and is known to act as a sink for naturally occurring solutes within the landscape. The chemistry of groundwater and porewater samples, collected from two transects on the Mkuze River floodplain, was investigated to identify processes involved in the control of solute concentrations. Results show that solutes in the groundwater become increasingly concentrated under the influence of evapotranspiration, resulting in the saturation, precipitation, and accumulation of less soluble compounds. Trends in porewater chemistry and calculated saturation indices support previously documented mineralogical and sediment geochemical investigations, with CaCO3 and silica precipitation, and Fe-rich smectite neoformation identified as the major controls on solute concentration. The association of these mineral phases with zones of high salinity suggests that mineral precipitation is an active process on the floodplain which results in the progressive development of salinity, particularly in areas dominated by deep-rooted trees. Similarities between geochemical processes documented in the Okavango Delta (Botswana) and those identified in this study suggest that evapotranspiration-induced chemical sedimentation is an important process in southern African wetlands, which has the potential to influence vegetation distribution, hydrological flows, and local topography. 相似文献
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