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1.
The groundwater divide is a key feature of river basins and significantly influenced by subsurface hydrological processes. For an unconfined aquifer between two parallel rivers or ditches, it has long been defined as the top of the water table based on the Dupuit–Forchheimer approximation. However, the exact groundwater divide is subject to the interface between two local flow systems transporting groundwater to rivers from the infiltration recharge. This study contributes a new analytical model for two-dimensional groundwater flow between rivers of different water levels. The flownet is delineated in the model to identify groundwater flow systems and the exact groundwater divide. Formulas with two dimensionless parameters are derived to determine the distributed hydraulic head, the top of the water table and the groundwater divide. The locations of the groundwater divide and the top of the water table are not the same. The distance between them in horizontal can reach up to 8.9% of the distance between rivers. Numerical verifications indicate that simplifications in the analytical model do not significantly cause misestimates in the location of the groundwater divide. In contrast, the Dupuit–Forchheimer approximation yields an incorrect water table shape. The new analytical model is applied to investigate groundwater divides in the Loess Plateau, China, with a Monte Carlo simulation process taking into account the uncertainties in the parameters. 相似文献
2.
Glaciers and snow cover are important constituents of the surface of the Tibetan Plateau. The responses of these phenomena to global environmental changes are sensitive, rapid and intensive due to the high altitudes and arid cold climate of the Tibetan Plateau. Based on multisource remote sensing data, including Landsat images, MOD10A2 snow product, ICESat, Cryosat-2 altimetry data and long-term ground climate observations, we analysed the dynamic changes of glaciers, snow melting and lake in the Paiku Co basin using extraction methods for glaciers and lake, the degree-day model and the ice and lake volume method. The interaction among the climate, ice-snow and the hydrological elements in Paiku Co is revealed. From 2000 to 2018, the basin tended to be drier, and rainfall decreased at a rate of −3.07 mm/a. The seasonal temperature difference in the basin increased, the maximum temperature increased at a rate of 0.02°C/a and the minimum temperature decreased at a rate of −0.06°C/a, which accelerated the melting from glaciers and snow at rates of 0.55 × 107 m3/a and 0.29 × 107 m3/a, respectively. The rate of contribution to the lake from rainfall, snow and glacier melted water was 55.6, 27.7 and 16.7%, respectively. In the past 18 years, the warmer and drier climate has caused the lake to shrink. The water level of the lake continued to decline at a rate of −0.02 m/a, and the lake water volume decreased by 4.85 × 108 m3 at a rate of −0.27 × 108 m3/a from 2000 to 2018. This evaluation is important for understanding how the snow and ice melting in the central Himalayas affect the regional water cycle. 相似文献
3.
利用钻孔测井资料并运用地层倾角测量信息分析法,给出了江汉盆地地应力最大水平主压应力方向为NE60~65° 相似文献
4.
张德厚 《大地测量与地球动力学》1994,(1)
本文从地貌、水系形式论述江汉盆地新构造的特点。指出江汉盆地为一继承性沉降盆地,同时新构造又具新生性。新构造运动的类型有差异升降运动、掀斜和拗折运动。江汉平原第四纪植物孢粉组合反映气候冷暧交替。鄂西山地发育了山谷冰川,平原区为湖河交错,受新构造运动影响,云梦泽逐渐解体。 相似文献
5.
The purpose of this work was to reinvestigate the existing hydrogeological conceptual model of the basin of Madrid, Spain. A cumulative chemical isotopic diagram which enabled the distinction between different groups of water as well as calculation of the mode of their blending was used for this investigation. It was found that the groups of discharge were lighter in their isotopic composition than that of recharge. The previous explanation of this fact, backed by carbon-14 dating, was the long residence time due to flow lines going down to depths of more than 1000 m. This flow model assumes homogenous conditions to these depths. This assumption can not be supported by evidence from deep wells. Thus a modified model is suggested which maintains homogenous conditions only to about 300 m and a deep confined aquifer below containing paleowater. The higher degree of depletion of this water has been explained by a colder climate on top of an altitude effect. Another interesting observation was the correlation between the isotopic composition of the rains, the month of the rain event and the composition of the recharge group groundwater. It could be seen that the winter rains resemble the groundwater composition, which shows that practically all the spring and summer rains were evapotranspirated. 相似文献
6.
Antony J. Long Sarah A. Woodroffe Sue Dawson David H. Roberts Charlotte L. Bryant 《第四纪科学杂志》2009,24(4):345-359
In West Greenland, early and mid Holocene relative sea level (RSL) fall was replaced by late Holocene RSL rise during the Neoglacial, after 4–3 cal. ka BP (thousand calibrated years before present). Here we present the results of an isolation basin RSL study completed near to the coastal town of Sisimiut, in central West Greenland. RSL fell from 14 m above sea level at 5.7 cal. ka BP to reach a lowstand of ?4.0 m at 2.3–1.2 cal. ka BP, before rising by an equivalent amount to present. Differences in the timing and magnitude of the RSL lowstand between this and other sites in West and South Greenland record the varied interplay of local and non‐Greenland RSL processes, notably the reloading of the Earth's crust caused by a Neoglacial expansion of the Greenland Ice Sheet (GIS) and the subsidence associated with the collapse of the Laurentide Ice Sheet forebulge. This means that the timing of the sea level lowstand cannot be used to infer directly when the GIS advanced during the Neoglacial. The rise in Late Holocene RSL is contrary to recently reported bedrock uplift in the Sisimiut area, based on repeat GPS surveys. This indicates that a belt of peripheral subsidence around the current ice sheet margin was more extensive in the late Holocene, and that there has been a switch from subsidence to uplift at some point in the last thousand years or so. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
7.
8.
Based on our detailed structural characterization, we examine possible relationships between thrust faults and strike-slip faults and thrust-cored folds and depositional units in the Silla Syncline, a 4 km wide fold composed of fine-grained mudstone, coarse sandstone and conglomerate deposits of the Cerro Toro Formation in the Magallanes foreland basin, Chilean Patagonia. The syncline is bounded on its western flank by an asymmetric anticline and on its eastern flank by a broad zone of thrust faults and associated folds, which are oriented sub-parallel to the syncline axis. Deposition of the coarse-grained units of the Silla Syncline appears to have taken place in this structurally defined trough controlled primarily by thrust fault related growth structures flanking the syncline.The syncline and surrounding area have also been deformed by two sets of strike-slip faults, one right-lateral and one left-lateral. The strike-slip and thrust faulting operated contemporaneously for much of their active periods, although it appears that thrust faulting, confined within the fine-grained units, initiated slightly earlier than strike-slip faulting. In addition, younger igneous intrusions at high angle to bedding generally localize along the strike-slip faults. The cross-cutting relationships among the intrusions, strike-slip faults, and flexural slip faults show that all these structures were active during the same period, which extends beyond mid-Miocene.These conclusions support the premise that structures in deep-water sediments are important for understanding not only the deformation of a foreland basin, but also its depositional architecture. 相似文献
9.
J. L. Simón M. A. Soriano L. E. Arlegui J. Gracia C. L. Liesa A. Pocoví 《Environmental Geology》2008,53(5):1057-1065
Space and time variations of alluvial karst subsidence in the central Ebro Basin are analysed in trenches (paleodolines),
aerial photographs (historical dolines) and field surveys (present-day active dolines). The measured subsidence rates, as
well as a comparison between densities of paleodolines computed in randomly selected scan-lines and density of active dolines
computed in maps, suggest that present-day subsidence in favourable areas is more intense than that of Pleistocene times.
According to diachronic maps drawn from (a) different aerial photographs taken after 1946 and (b) field surveys on deformations
in urbanized areas, subsidence behaved as a nearly steady process while the whole area was used for agriculture. In contrast,
rapid changes (through periods of several tens of years) have occurred in urbanized areas, in which dolines expand their boundaries
through small marginal collapses, shifting sharply their sinking centres to neighbouring sites. These rapid changes do not
have an equivalent in observed paleodolines. 相似文献
10.
印支运动的沉积学响应——以湖北秭归盆地中、上三叠统为例 总被引:2,自引:0,他引:2
通过对秭归盆地南缘中、上三叠统巴东组和沙镇溪组地层剖面的实测及1∶10万秭归幅地质填图发现,中三叠统巴东组在秭归盆地东南缘存在不同程度的缺失,秭归郭家坝一带,只沉积巴东组一段、二段地层。秭归楠家湾一带,整个巴东组全部缺失,上三叠统沙镇溪组直接覆盖于早三叠世嘉陵江组之上。而秭归盆地西缘沙镇溪、巴东麂子岩一带,巴东组发育齐全。上述现象表明,在早三叠世末期,由于印支运动的影响,巴东组地层出现了较大差异。沙镇溪组在沉积上继承了巴东组高低不平的古地貌特征,沉积厚度变化较大。上三叠统沙镇溪组与中统巴东组之间,在盆地不同的部位可呈现出整合或平行不整合的接触关系,而不存在断层接触关系。 相似文献