New observations on the geomorphology and origins of Mountain Lake,Virginia     

Jon C. Cawley  Bruce C. Parker  Lee J. Perren 《地球表面变化过程与地形》2001,26(4):429-440

Mountain Lake is the only natural lake of significance in the unglaciated southern Appalachian Highlands. It is located near the summit of Salt Pond Mountain, Giles County Virginia, at an elevation of 1177 m. It is underlain by Ordovician and Silurian non‐calcareous shale and sandstone of the Martinsburg, Juniata and Clinch formations. Historical (250 years) and sediment (6000 years) records suggest that the size of the lake has varied periodically. In the 1930s lake origin was proposed as due to valley damming by a lateral landslide (Hutchinson and Pickford, 1932) or damming by scree (Sharp, 1933). A later theory modified the landslide hypothesis to the primarily vertical collapse of a canyon feature in the Clinch (Parker et al., 1975). Fracture trace analysis now reveals a regional lineation feature associated with the lake. This feature is present surficially both downgradient from the lake to the northwest, and upgradient to the southeast. Sonar bathymetry and diver reconnaissance show it expressed as a (relatively sediment‐free) narrow open crevice in the deepest (33 m) portion of the lake, probably a fault. Hydrologic observation and resistivity suggest preferential water movement along this fracture, as well as leakage directly from the lake. The present study suggests conduit erosion within this feature and periodic vertical downsettling of overlying Clinch material as the primary mechanism of lake origin and water‐level fluctuations through time. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

试论生态水文学主要问题及研究方法   总被引：13，自引：1，他引：13  

武强  董东林 《水文地质工程地质》2001,28(2):69-72

本文给出了生态水文学的初定义和基本概念，认为生态水文学是一个集地表水文学，地下水文学，植物生理学，生态学，土壤学，气象学和自然学地理学等于一体，彼此间相互影响渗透而形成的一门新型边缘交叉学科，在此基础上，论述了生态环境水文学研究的基本内容，并提出了这个学科所要解决的目前威胁人类生存的主要生态水文问题，文章最后探讨了生态水文学的一般研究方法和手段。  相似文献   

最大熵原理在水文水资源科学中的应用   总被引：21，自引：3，他引：21       下载免费PDF全文

王栋  朱元 《水科学进展》2001,12(3):424-430

简介最大熵原理的基本概念、理论和该原理在水文水资源科学领域中应用研究的进展,综述水文频串分析中推导概率分布和参数估计,时间序列最大熵谱分析等方面的研究成果,展望今后的研究趋向和应用前景。  相似文献   

中国陆地水元素组成的中子活化分析试验          下载免费PDF全文

顾慰祖  陆家驹  陈廷扬  徐其高  Norman E.Peters 《水科学进展》2003,14(5):535-541

对同期降水、江河水和地下水的元素组成,使用中子活化分析方法作了对比试验。降水取自分布于8个气候带的11个站,其海拔高程为5～3659m,年平均降水量为50～1571mm。河水取自各主要江河包括内陆河和海岛的12个测站以及3个实验流域,并在其附近采集地下水。降水中共检出35种元素,各站有19～31种元素,同期均有空间分布。河水中共检出39种元素,各河分别有21～31种元素。地下水中共检出35种元素,各站有30～32种元素。对其浓度组成作了由大于1000μg/L至小于0.01μg/L的分级综合。有些元素含量超出所报道的世界淡水浓度范围,小于其最低值,甚或远大于其最高值。  相似文献   

The Disastrous Flood of 1998 and Long Term Mitigation Strategies for Dhaka City     

Faisal  I. M.  Kabir  M. R.  Nishat  A. 《Natural Hazards》2003,28(1):85-99

The disastrous flood of 1998 was a result of excessiverainfall all over the catchment areas of the major rivers of Bangladesh. Dhaka City, which is surroundedby rivers on all sides, was seriously affected despite the completion of Phase I of the Dhaka IntegratedFlood Protection Project (DIFPP). Water entered into the protected part of the city throughhydraulic leakage such as buried sewerage pipes, breached and incomplete floodwalls, ungated culverts andinoperative regulators. The drainage network and retention ponds of the city were found to be in poorconditions and capacities of the pumping stations were found inadequate. There was a serious lack of coordinationbetween the agencies responsible for flood protection and drainage of the city. These issues must beaddressed to achieve long-term flood mitigation. In addition, feedback from both the experts andgeneral public indicated that completion of Phase II of DIFPP was essential to bring the eastern part ofthe city under flood protection. Other structural measures suggested in this paper include installing andmaintaining adequate drainage and pumping capacity and timely operation of regulators. This studyalso suggests a set of non-structural measures for flood mitigation that include protectingthe retention ponds, raising public awareness on maintaining the city drains, introducing landzoning and flood proofing in the eastern part of Dhaka, and stream lining institutional bottlenecks.  相似文献   

GIS技术及其在水文学和水资源管理方面的应用   总被引：4，自引：0，他引：4  

王疆霞  李云峰  徐中华 《西北地质》2003,36(1):109-113

介绍了地理信息系统(GIS)技术及其发展现状。通过实例介绍了GIS在水文学和水资源管理方面的典型应用，并提出了今后地理信息系统在水文学和水资源管理领域应用发展的建议。  相似文献   

The influence of autocorrelation on the ability to detect trend in hydrological series   总被引：3，自引：0，他引：3  

Sheng Yue  Paul Pilon  Bob Phinney  George Cavadias 《水文研究》2002,16(9):1807-1829

This study investigated using Monte Carlo simulation the interaction between a linear trend and a lag‐one autoregressive (AR(1)) process when both exist in a time series. Simulation experiments demonstrated that the existence of serial correlation alters the variance of the estimate of the Mann–Kendall (MK) statistic; and the presence of a trend alters the estimate of the magnitude of serial correlation. Furthermore, it was shown that removal of a positive serial correlation component from time series by pre‐whitening resulted in a reduction in the magnitude of the existing trend; and the removal of a trend component from a time series as a first step prior to pre‐whitening eliminates the influence of the trend on the serial correlation and does not seriously affect the estimate of the true AR(1). These results indicate that the commonly used pre‐whitening procedure for eliminating the effect of serial correlation on the MK test leads to potentially inaccurate assessments of the significance of a trend; and certain procedures will be more appropriate for eliminating the impact of serial correlation on the MK test. In essence, it was advocated that a trend first be removed in a series prior to ascertaining the magnitude of serial correlation. This alternative approach and the previously existing approaches were employed to assess the significance of a trend in serially correlated annual mean and annual minimum streamflow data of some pristine river basins in Ontario, Canada. Results indicate that, with the previously existing procedures, researchers and practitioners may have incorrectly identified the possibility of significant trends. Copyright © Environment Canada. Published by John Wiley & Sons, Ltd.  相似文献   

Recharge and aquifer response: Northern Guam Lens Aquifer, Guam, Mariana Islands   总被引：1，自引：0，他引：1  

J. M. U. Jocson  J. W. Jenson  D. N. Contractor   《Journal of Hydrology》2002,260(1-4):231-254

The Northern Guam Lens Aquifer is an island karst aquifer in uplifted young, highly conductive limestone. Calculations of recharge based on differences between daily rainfall and daily pan evaporation suggest that the maximum annual mass of water delivered to the freshwater lens is about 67% of mean annual rainfall. Hydrographs of daily well-level responses plotted against daily rainfall indicate that the rate at which water is delivered to the lens is a function of rainfall intensity and the relative saturation of the vadose zone. Together, these variables determine the degree to which stormwater is shunted into fast flow through preferred pathways that bypass the bedrock matrix, rather than percolating slowly through the bedrock matrix.

Data from the 40-year interval from 1956 to 1995 show that some 17% of rainfall on northern Guam arrives in small amounts (<0.6 cm/day). Most of this light rainfall is probably lost to evapotranspiration. At least another 20% of total rainfall on Guam arrives at very high intensities (>5.0 cm/day), which tend to promote fast flow at the expense of percolation. Rapid recovery of the water table from rapid recharge suggests that the lens either takes such recharge into storage very rapidly, discharges it rapidly without taking it into storage, or some combination of both. Significant vadose buffering of recharge to the lens is indicated by the fact that simulations assuming that the recharge from precipitation received in any given month is transmitted to the lens during the same month consistently over-predict observed peak mean monthly water levels and under-predict the minima.  相似文献   

Sedimentological and palaeohydrological responses to tectonics and climate in a small, closed, lacustrine system: Oligocene As Pontes Basin (Spain)   总被引：1，自引：0，他引：1  

A. Sáez  L. Cabrera 《Sedimentology》2002,49(5):1073-1094

ABSTRACT A small, closed, lacustrine system developed during the restraining overstep stages of the Oligocene As Pontes strike‐slip basin (Spain). The increase in basin accommodation and the headward spread of the drainage, which increased the water input, triggered a change from shallow, holomictic to deeper, meromictic conditions. The lower, shallow, lacustrine assemblage consists of mudstone–carbonate cycles recording lacustrine–palustrine ramp deposition in a saline lake. High Sr content in some early diagenetic calcites suggests that aragonite and calcite made up the primary carbonate muds. Early dolomitization took place together with widespread pedogenic activity. The upper, deep, freshwater, lacustrine assemblage includes bundles of carbonate–clay rhythmites and fine‐grained turbidite beds. Primary calcite and diagenetic siderite make up the carbonate laminae. The Mg content of the primary carbonates records variations in Mg/Ca ratios in lacustrine waters. δ¹⁸O and δ¹³C covariance trends in calcite reinforce closed drainage conditions. δ¹⁸O data indicate that the lake system changed rapidly from short‐lived isotopically light periods (i.e. from seasonal to pluriannual) to longer steady‐state periods of heavier δ¹⁸O (i.e. from pluriannual to millennial). The small δ¹³C changes in the covariant trends were caused by dilute inflow, changing the contributions of dissolved organic carbon in the system and/or internal variations in lacustrine organic productivity and recycling. In both shallow and deep carbonate facies, sulphate reduction and methanogenesis may account, respectively, for the larger negative and positive δ¹³C shifts recorded in the early diagenetic carbonates (calcite, dolomite and siderite). The lacustrine system was very susceptible to high‐frequency, climatically forced water balance variations. These climatic oscillations interfered with the low‐frequency tectonic and morphological changes in the basin catchment. This resulted in the superposition of high‐order depositional, mineralogical and geochemical cycles and rhythms on the lower order lacustrine infill sequence.  相似文献   

流域水文模型研究中的若干问题   总被引：50，自引：3，他引：50       下载免费PDF全文

芮孝芳 《水科学进展》1997,8(1):94-98

论述了流域水文模型出现的必然性,剖析了现有流域水文模型的局限性和用于水文预报需要解决的问题,并提出了若干建议,以期能推进流域水文模型的研究  相似文献