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1.
In high-latitude catchments where permafrost is present, runoff dynamics are complicated by seasonal active-layer thaw, which may cause a change in the dominant flowpaths as water increasingly contacts mineral soils of low hydraulic conductivity. A 2-year study, conducted in an upland catchment in Alaska (USA) underlain by frozen, well-sorted eolian silt, examined changes in infiltration and runoff with thaw. It was hypothesized that rapid runoff would be maintained by flow through shallow soils during the early summer and deeper preferential flow later in the summer. Seasonal changes in soil moisture, infiltration, and runoff magnitude, location, and chemistry suggest that transport is rapid, even when soils are thawed to their maximum extent. Between June and September, a shift occurred in the location of runoff, consistent with subsurface preferential flow in steep and wet areas. Uranium isotopes suggest that late summer runoff erodes permafrost, indicating that substantial rapid flow may occur along the frozen boundary. Together, throughflow and deep preferential flow may limit upland boreal catchment water and solute storage, and subsequently biogeochemical cycling on seasonal to annual timescales. Deep preferential flow may be important for stream incision, network drainage development, and the release of ancient carbon to ecosystems.  相似文献   

2.
Change dynamics of permafrost thaw, and associated changes in subsurface flow and seepage into surface water, are analysed for different warming trends in soil temperature at the ground surface with a three-phase two-component flow system coupled to heat transport. Changes in annual, seasonal and extreme flows are analysed for three warming-temperature trends, representing simplified climate-change scenarios. The results support previous studies of reduced temporal variability of groundwater flow across all investigated trends. Decreased intra-annual flow variability may thus serve as an early indicator of permafrost degradation before longer-term changes in mean flows are notable. This is advantageous since hydrological data are considerably easier to obtain, may be available in longer time series, and generally reflect larger-scale conditions than direct permafrost observations. The results further show that permafrost degradation first leads to increasing water discharge, which then decreases as the permafrost degradation progresses further to total thaw. The most pronounced changes occur for minimum annual flows. The configuration considered represents subsurface discharge from a generic heterogeneous soil-type domain.  相似文献   

3.
为从整体上认识多年冻土活动层土壤水文过程季节变异特性,以黄河源区巴颜喀拉山北坡冻土剖面为例,结合大气降水、冻土土壤水分、冻土层上水的野外观测,采用HYDRUS-1D软件冻融模块进行模拟分析,分析冻融作用对活动层土壤水文过程的影响,研究结果表明:(1)冻土层上水位与土壤水热之间存在着相互影响、相互作用的关系,依据活动层土壤温度变化,基于冻融过程,多年冻土活动层土壤水分与冻土层上水位可划分为冻结稳定、快速融化、融化稳定和快速冻结4个阶段。(2)降雨入渗是坡面尺度下活动层土壤水文过程的主要驱动力,活动层冻融锋面是主要限制性因素,受冻融过程影响,冻结期降雨减少,土壤冻结,土壤储水能力下降,土壤水分下渗停止,坡面侧向流动减弱,土壤水分和冻土层上水位处于下降趋势;融化期降雨增多,土壤融化,土壤储水能力上升,土壤水分下渗强烈,坡面侧向流动增强,土壤水分和冻土层上水位处于上升趋势。(3)受坡面地形影响,上坡活动层厚度大于下坡,上坡冻融锋面变化较下坡平缓,上坡土壤水分和冻土层上水位的变化幅度相对下坡较为平缓,而上坡土壤水分相对下坡含量较低,下坡冻土层上水位相对稳定。  相似文献   

4.
Stable isotopes (180) are used to investigate hydrological processes in the small Pre-Alpine research catchment Rietholzbach in NE Switzerland. The catchment covers an area of 3.18 km2 and ranges from 680 to 960 m a.s.l. The180 concentration in rainfall and in runoff at various sites, including a lysimeter installed within the catchment, over a 2-a period are investigated. First, conceptual flow models are applied to determine the mean water residence times of different systems of the basin and their storage properties. As a second approach, the separation of runoff components using18O and Mg ions as tracer during some storm flow events was carried out. The following flow mechanisms can be identified from the modelling results: (i) lateral hillslope fluxes, which are faster in the part of the Tertiary Molasse sediments and slower in the part of the Quaternary deposits, and (ii) relatively slow vertical infiltration processes through the soil layer within the lysimeter. Mean residence times of 12.5 months result for the total catchment baseflow component and 24.5 months for the baseflow from the upper part of the catchment, respectively. For the lysimeter seepage water, a mean residence time of about 200 days was obtained. During the intensive storm events, a fast reaction of the stored subsurface water due to heavy precipitation and an expulsion of this storage water amounting to a considerable portion of the total basin runoff can be detected.  相似文献   

5.
作为滁州水文实验系统一部分的1号天然实验流域,面积7897m2,以安山岩为基底,上覆平均厚度2.46m的第四系沉积物。实测了包括地面径流和地面下径流的各种降雨径流响应,后者包括来自非饱和带的壤中流和饱和带的地下水径流。表明这些径流成分有着复杂的组合类型,主要是以地面径流为主的SR型和以地面下径流为主的SSR型,以及中间的和演化的类型。SR型实例中的地面径流量可占总径流的65%,而SSR实例中的地面下径流量可有90%。主要降水的7月,地面下贡献占54.5%,其中地下水径流即占33%。大部分地面径流与降水的18O组成有不小的差异,比较了同时进行测验的3个实验流域,在1400min的降水径流过程中,降水的平均δ18O为-1.210%,而同期地面径流的平均δ18O,2号水文山流域(512m2)为-1.132%,1号南大洼天然流域为-1.065%,3号只有薄层风化碎屑的牵牛花流域(4573m2)为-0.801%。这质疑了现行同位素流量过程线划分方法8个假定中的两个:地面径流的同位素组成不同于降水,天然流域尤其如此;各种水源在汇集过程中的同位素分馏影响并非都可忽略不计。实验流域因降水而产生径流,但所产生的径流却有着非本次降水的组分,这一降水径流悖论发生于各个实验流域。SR型和SSR型总的非本次降水组分分别达16%和64%。  相似文献   

6.
山坡表层关键带结构与水文连通性研究进展   总被引:2,自引:0,他引:2       下载免费PDF全文
山丘区是洪水的"策源地",山丘区坡地、沟谷及间歇性河道为洪水的形成提供了通道,同时也是水文连通时空变化最为强烈的地带。然而,对流域表层关键带结构特征及其水文连通机制等的认识尚存不足,限制了产汇流理论及模型方法的发展和应用。通过对比国内外山坡水文实验,发现山坡物理结构连通性控制并深刻影响着水流的连通过程,现有水文连通实验侧重孔隙等微观尺度的规律研究,与水文模型理论存在尺度上的巨大偏差。为此,提出水文连通性应侧重揭示水流在山坡地表、地下的宏观表象通道及分布特征,探索径流连通的动力学机制,即山坡水文连通性研究重在剖析其结构特征的水文累积效应,应保持关键带结构特征合理概化与产汇流理论适度复杂之间的平衡。  相似文献   

7.
红壤丘陵区地表水资源动态与合理调蓄利用研究   总被引:9,自引:0,他引:9       下载免费PDF全文
以红壤丘陵景观中相对独立且整体性强的集水区为基本单元,重点研究了集水区内降水、蒸散、水量蓄存等地表水资源的年变化。结果表明,降水资源在集水区内的陆面拦截蒸散、塘堰蓄存、排出集水区三者中的分布比例约为7:2:1,在水土保持型坡地的植被拦截、土壤渗流、地表径流三者中的分布比例约为3:5:2;每公顷1m土体中的土壤贮水量,在丰水季节,水土保持型坡地要比非水保坡地高出864.0~1067.0m3,少水季节则高出647.0~855.0m3。研究结果还表明,以集水区为单元的农业灌溉用水量,一般为年降水量的12%左右,蓄存此水量的塘堰面积应占集水区土地总面积的11%左右,对于塘堰面积已占土地总面积10%左右的红壤丘陵区而言,抗御季节性干旱依靠扩大塘堰蓄水已不现实,其主要途径应是充分发挥水库工程和"土壤水库"的巨大抗旱潜力。  相似文献   

8.
Flood generation in mountainous headwater catchments is governed by rainfall intensities, by the spatial distribution of rainfall and by the state of the catchment prior to the rainfall, e.g. by the spatial pattern of the soil moisture, groundwater conditions and possibly snow. The work presented here explores the limits and potentials of measuring soil moisture with different methods and in different scales and their potential use for flood simulation. These measurements were obtained in 2007 and 2008 within a comprehensive multi-scale experiment in the Weisseritz headwater catchment in the Ore-Mountains, Germany. The following technologies have been applied jointly thermogravimetric method, frequency domain reflectometry (FDR) sensors, spatial time domain reflectometry (STDR) cluster, ground-penetrating radar (GPR), airborne polarimetric synthetic aperture radar (polarimetric SAR) and advanced synthetic aperture radar (ASAR) based on the satellite Envisat. We present exemplary soil measurement results, with spatial scales ranging from point scale, via hillslope and field scale, to the catchment scale. Only the spatial TDR cluster was able to record continuous data. The other methods are limited to the date of over-flights (airplane and satellite) or measurement campaigns on the ground. For possible use in flood simulation, the observation of soil moisture at multiple scales has to be combined with suitable hydrological modelling, using the hydrological model WaSiM-ETH. Therefore, several simulation experiments have been conducted in order to test both the usability of the recorded soil moisture data and the suitability of a distributed hydrological model to make use of this information. The measurement results show that airborne-based and satellite-based systems in particular provide information on the near-surface spatial distribution. However, there are still a variety of limitations, such as the need for parallel ground measurements (Envisat ASAR), uncertainties in polarimetric decomposition techniques (polarimetric SAR), very limited information from remote sensing methods about vegetated surfaces and the non-availability of continuous measurements. The model experiments showed the importance of soil moisture as an initial condition for physically based flood modelling. However, the observed moisture data reflect the surface or near-surface soil moisture only. Hence, only saturated overland flow might be related to these data. Other flood generation processes influenced by catchment wetness in the subsurface such as subsurface storm flow or quick groundwater drainage cannot be assessed by these data. One has to acknowledge that, in spite of innovative measuring techniques on all spatial scales, soil moisture data for entire vegetated catchments are still today not operationally available. Therefore, observations of soil moisture should primarily be used to improve the quality of continuous, distributed hydrological catchment models that simulate the spatial distribution of moisture internally. Thus, when and where soil moisture data are available, they should be compared with their simulated equivalents in order to improve the parameter estimates and possibly the structure of the hydrological model.  相似文献   

9.
Polygonal ridge patterns with intervening hollows some 400 m across and with a relief of about 100 m are common as low hills on the northern dissected part of the Sepik piedmont. They are developed in Pliocene mudstone and sometimes in marl and greywacke. The crests of the highest flat‐topped hills have a veneer of Pleistocene fanglomerate on them.

The polygons were formed by water infiltrating through the fanglomerate on the former piedmont surface moistening and softening the sediments beneath. Swelling from centres of more intense weathering caused expansion. As the pressure centres impinged on each other a polygonal framework of rock under pressure took in less water and so remained least hydrated. On dissection the polygonal framework was exhumed and then differentially eroded to its present form.

Tensional stress fields or tectonic causes do not appear to help in explaining the origin of the polygons.  相似文献   

10.
The recently developed SWATDRAIN model was employed to assess the impact of controlled drainage on the water table dynamics, subsurface drainage, and surface runoff in an agricultural watershed in Ontario, Canada. Controlled drainage was defined with a depth of 1.0 m to restrict flow at the drain outlet to maintain the water table at 0.5 m below the surface level during the winter (November–April) and at 0.6 m during the summer (June–August) months. The effects of the absence, or implementation, of drainage water management were predicted for the 3-year period of 1991–1993. Implementing controlled drainage resulted in a 16 % reduction in the mean annual drain flow, while increasing surface runoff by as much as 71 %. This indicates that overall watershed hydrology could be significantly impacted by the implementation of controlled drainage. This research demonstrates the SWATDRAIN model’s ability to predict the controlled drainage in small agricultural watersheds.  相似文献   

11.
罗照华 《地质与勘探》2023,59(2):387-397
在南方丘陵区工程建设的场地整平时,常形成一些人工堆填岗地,受到下覆黏性土的阻隔,岗地上的填土会形成独立的上层滞水地下水系统,但目前对于这个地下水系统的特征及其工程危害却鲜有研究。本文利用某人工堆填岗地导致地下室破坏的上层滞水水位监测资料,研究了该地下水系统的水位动态和流场及其变化特征,分析了水位和流场及其变化的影响因素。研究结果表明:堆填岗地上的集、排水工程易遭受填土不均匀沉降的破坏而出现渗漏;堆填岗地上的上层滞水虽属于“路过”型地下水,但系统的抗干扰能力弱,在汇集的雨水集中灌入时,因排泄相对缓慢,水位上升迅速,滞留时间较长,由此对地下工程造成破坏,因此工程建设时需引起重视。考虑到集、排水工程渗漏对上层滞水水位的影响,地下工程的抗浮水位应在考虑岗地的地下水水位的动态变化特征的基础上,以集、排水工程的埋深及可排泄标高为依据。本地下工程事故可用调整场地规划、封堵或重建渗漏集排水结构、盲沟疏排与拉锚结构的防治结合方式处理。  相似文献   

12.
The recession hydrographs of karst springs provide important information about aquifer characteristics such as storage properties and drainage potential, karstification degree, and other hydrological features. The Faresban, Famaasb, Gonbad-e-Kabood, and Gian springs are the important karst springs which drain main karst aquifers in west of Iran. In this study, we evaluate hydrological characteristics of these four karst springs using different analytic equations. Almost, all the recession curves were well fitted by a function that consists of three main exponential terms. The initial portion of the recession curve represents the fast drainage of large fractures and conduits, ending with the slowly decreasing curve, where the drainage of rock matrix and small fissures or baseflow is dominant. The Gian spring has the largest storage volume but the lowest drained water (7%). Using Mangin’s equation, it is apparent that the baseflow supplies over 85% of the total drained water to the Gian spring, while a small quantity of total outflow is made up of quickflow periods. Of the water available to the Famaasb, Faresban, and Gonbad-e-Kabood springs, 85, 80, and 70% are drained during period of baseflow, respectively, whereas the quickflow periods have minor importance in some springs. Based on the Coutagne’s equation results, it can be concluded that the catchment of the Famaasb and Gonbad-e-Kabood springs have a karstified saturation zone with drainage channels that provide a rapid discharge with little storage capacity. At Gian catchment area, the initial discharge is not as rapid as karstification but is fairly homogeneous throughout the aquifer.  相似文献   

13.
青藏铁路冻土区路桥过渡段沉降原因分析   总被引:4,自引:4,他引:0  
青藏铁路开通近10 a以来,各类冻土工程稳定,保证了列车平稳安全的运行。然而,青藏铁路工程也不可避免出现了一些病害问题。现场调查资料表明,冻土区路桥过渡段下沉现象较为严重。通过冻土区路桥过渡段的沉降特点和工程地质条件综合分析,结果表明:地表水或冻结层上水水热侵蚀,引起人为多年冻土上限下降、高含冰量冻土层融化,致使路基发生强烈的融化下沉。建议这类工程病害应采取主动降温措施增强地基土的冻结能力,并加强防排水设施和改善地表水条件,消除水热侵蚀所产生的融化下沉。研究结果为青藏铁路路桥过渡段的稳定性和养护提供了科学依据。  相似文献   

14.
借助于15幅高分辨率的HiRISE影像与107幅MOC影像,对火星表面撞击坑壁与沙丘中出现的非常年轻冲沟形态特征进行了详细研究,并据此检验冲沟成因假说.影像特征分析结果首先支持沙丘中冲沟是由液态水携带泥沙冲刷而成的理论,而撞击坑壁出现的多边形土证实火星表面下冰的存在,且在适当的条件下可转变为液态水形成冲沟.   相似文献   

15.
The value of remote sensing and surface geophysical data for characterizing the spatial variability and relationships between land-surface and subsurface properties was explored in an Alaska (USA) coastal plain ecosystem. At this site, a nested suite of measurements was collected within a region where the land surface was dominated by polygons, including: LiDAR data; ground-penetrating radar, electromagnetic, and electrical-resistance tomography data; active-layer depth, soil temperature, soil-moisture content, soil texture, soil carbon and nitrogen content; and pore-fluid cations. LiDAR data were used to extract geomorphic metrics, which potentially indicate drainage potential. Geophysical data were used to characterize active-layer depth, soil-moisture content, and permafrost variability. Cluster analysis of the LiDAR and geophysical attributes revealed the presence of three spatial zones, which had unique distributions of geomorphic, hydrological, thermal, and geochemical properties. The correspondence between the LiDAR-based geomorphic zonation and the geophysics-based active-layer and permafrost zonation highlights the significant linkage between these ecosystem compartments. This study suggests the potential of combining LiDAR and surface geophysical measurements for providing high-resolution information about land-surface and subsurface properties as well as their spatial variations and linkages, all of which are important for quantifying terrestrial-ecosystem evolution and feedbacks to climate.  相似文献   

16.
The assessment of land use land cover (LULC) and climate change over the hydrology of a catchment has become inevitable and is an essential aspect to understand the water resources-related problems within the catchment. For large catchments, mesoscale models such as variable infiltration capacity (VIC) model are required for appropriate hydrological assessment. In this study, Ashti Catchment (sub-catchment of Godavari Basin in India) is considered as a case study to evaluate the impacts of LULC changes and rainfall trends on the hydrological variables using VIC model. The land cover data and rainfall trends for 40 years (1971–2010) were used as driving input parameters to simulate the hydrological changes over the Ashti Catchment and the results are compared with observed runoff. The good agreement between observed and simulated streamflows emphasises that the VIC model is able to evaluate the hydrological changes within the major catchment, satisfactorily. Further, the study shows that evapotranspiration is predominantly governed by the vegetation classes. Evapotranspiration is higher for the forest cover as compared to the evapotranspiration for shrubland/grassland, as the trees with deeper roots draws the soil moisture from the deeper soil layers. The results show that the spatial extent of change in rainfall trends is small as compared to the total catchment. The hydrological response of the catchment shows that small changes in monsoon rainfall predominantly contribute to runoff, which results in higher changes in runoff as the potential evapotranspiration within the catchments is achieved. The study also emphasises that the hydrological implications of climate change are not very significant on the Ashti Catchment, during the last 40 years (1971–2010).  相似文献   

17.
Modelling the effect of rainfall on instabilities of slopes along highways   总被引:1,自引:0,他引:1  
 During and after the very wet 1991/1992 winter experienced in Jordan, significant instabilities occurred in several sections of the new Irbid–Amman Highway in Jordan. A potential impact of surface and subsurface flow on the failed areas was noted. This paper is concerned with a hydrological study of the Irbid–Amman Highway, including watershed characteristics, hydrological data analysis, and hydraulic analysis of remedial works to failed areas and other parts of the highway drainage to minimize the impact of surface runoff and the effects of subsurface water with respect to the stability of the upslope and to limit the porewater pressure within the road formation. The study shows that the culvert capacity and the discharge velocity of the cross-highway drainage are deficient. Recommendations (e.g. gabion cascades) are therefore suggested to reduce drainage to the cross highway drainage structures. Grouting is suggested to stabilize the embankments above the inlets to culverts. Remedial drainage works are suggested for each major failed area. These include: culverts, table drain, drainage blanket beneath road formation, cut-off drains above cuttings, subsurface drains into the cut in the vicinity of springs, curtain drain beneath the lined table drain, and others. Received: 26 March 1997 · Accepted: 23 March 1998  相似文献   

18.
《Earth》2006,74(3-4):269-307
Wildfire can lead to considerable hydrological and geomorphological change, both directly by weathering bedrock surfaces and changing soil structure and properties, and indirectly through the effects of changes to the soil and vegetation on hydrological and geomorphological processes. This review summarizes current knowledge and identifies research gaps focusing particularly on the contribution of research from the Mediterranean Basin, Australia and South Africa over the last two decades or so to the state of knowledge mostly built on research carried out in the USA.Wildfire-induced weathering rates have been reported to be high relative to other weathering processes in fire-prone terrain, possibly as much as one or two magnitudes higher than frost action, with important implications for cosmogenic-isotope dating of the length of rock exposure. Wildfire impacts on soil properties have been a major focus of interest over the last two decades. Fire usually reduces soil aggregate stability and can induce, enhance or destroy soil water repellency depending on the temperature reached and its duration. These changes have implications for infiltration, overland flow and rainsplash detachment. A large proportion of publications concerned with fire impacts have focused on post-fire soil erosion by water, particularly at small scales. These have shown elevated, sometimes extremely large post-fire losses before geomorphological stability is re-established. Soil losses per unit area are generally negatively related to measurement scale reflecting increased opportunities for sediment storage at larger scales. Over the last 20 years, there has been much improvement in the understanding of the forms, causes and timing of debris flow and landslide activity on burnt terrain. Advances in previously largely unreported processes (e.g. bio-transfer of sediment and wind erosion) have also been made.Post-fire hydrological effects have generally also been studied at small rather than large scales, with soil water repellency effects on infiltration and overland flow being a particular focus. At catchment scales, post-fire accentuated peakflow has received more attention than changes in total flow, reflecting easier measurement and the greater hazard posed by the former. Post-fire changes to stream channels occur over both short and long terms with complex feedback mechanisms, though research to date has been limited.Research gaps identified include the need to: (1) develop a fire severity index relevant to soil changes rather than to degree of biomass destruction; (2) isolate the hydrological and geomorphological impacts of fire-induced soil water repellency changes from other important post-fire changes (e.g. litter and vegetation destruction); (3) improve knowledge of the hydrological and geomorphological impacts of wildfire in a wider range of fire-prone terrain types; (4) solve important problems in the determination and analysis of hillslope and catchment sediment yields including poor knowledge about soil losses other than at small spatial and short temporal scales, the lack of a clear measure of the degradational significance of post-fire soil losses, and confusion arising from errors in and lack of scale context for many quoted post-fire soil erosion rates; and (5) increase the research effort into past and potential future hydrological and geomorphological changes resulting from wildfire.  相似文献   

19.
Landslides are a main cause of human and economic losses worldwide. For this reason, landslide hazard assessment and the capacity to predict this phenomenon have been topics of great interest within the scientific community for the implementation of early warning systems. Although several models have been proposed to forecast shallow landslides triggered by rainfall, few models have incorporated geotechnical factors into a complete hydrological model of a basin that can simulate the storage and movement of rainwater through the soil profile. These basin and full hydrological models have adopted a physically based approach. This paper develops a conceptual and physically based model called open and distributed hydrological simulation and landslides—SHIA_Landslide (Simulación HIdrológica Abierta, or SHIA, in Spanish)—that is supported by geotechnical and hydrological features occurring on a basin-wide scale in tropical and mountainous terrains. SHIA_Landslide is an original and significant contribution that offers a new perspective with which to analyse shallow landslide processes by incorporating a comprehensive distributed hydrological tank model that includes water storage in the soil coupled with a classical analysis of infinite slope stability under saturated conditions. SHIA_Landslide can be distinguished by the following: (i) its capacity to capture surface topography and effects concerning the subsurface flow; (ii) its use of digital terrain model (DTM) to establish the relationships among cells, geomorphological parameters, slope angle, direction, etc.; (iii) its continuous simulation of rainfall data over long periods and event simulations of specific storms; (iv) its consideration of the effects of horizontal and vertical flow; and (vi) its inclusion of a hydrologically complete water process that allows for hydrological calibration. SHIA_Landslide can be combined with real-time rainfall data and implemented in early warning systems.  相似文献   

20.
Analysis of the maximum discharge of karst springs   总被引:2,自引:0,他引:2  
Analyses are presented of the conditions that limit the discharge of some karst springs. The large number of springs studied show that, under conditions of extremely intense precipitation, a maximum value exists for the discharge of the main springs in a catchment, independent of catchment size and the amount of precipitation. Outflow modelling of karst-spring discharge is not easily generalized and schematized due to numerous specific characteristics of karst-flow systems. A detailed examination of the published data on four karst springs identified the possible reasons for the limitation on the maximum flow rate: (1) limited size of the karst conduit; (2) pressure flow; (3) intercatchment overflow; (4) overflow from the main spring-flow system to intermittent springs within the same catchment; (5) water storage in the zone above the karst aquifer or epikarstic zone of the catchment; and (6) factors such as climate, soil and vegetation cover, and altitude and geology of the catchment area. The phenomenon of limited maximum-discharge capacity of karst springs is not included in rainfall-runoff process modelling, which is probably one of the main reasons for the present poor quality of karst hydrological modelling. Electronic Publication  相似文献   

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