共查询到20条相似文献,搜索用时 0 毫秒
1.
The river Odra, which rises in the Czech Republic and disgorges into the Baltic, suffered an extreme flood in July 1997 which was responsible for the loss of 55 lives and over a billion dollars worth of damage in southern Poland. The return period of the flood is variously estimated between 250 and 1000 years. The paper describes the hydrological and hydraulic studies undertaken for a flood reservoir (storage capacity is approximately 180,000,000 m 3) to be constructed on the River Odra just upstream the ancient town of Raciborz, on the border between Poland and Czech Republic. These studies included the hydrodynamic modelling of a 220 km stretch of the river down to the city of Wroclaw where most of the damage occurred, flood damage analysis with and without the proposed reservoir, sensitivity analysis of operating rules for Nysa reservoirs and improvement of flood control capacity of existing channels and polders. Cost-benefits analysis, environmental impact assessments and resettlement plans, in addition to the engineering studies of the dam itself, were also carried out during the project stage but have not been included in the present paper. 相似文献
2.
A 210Pb chronology of sedimentation in a small floodplain lake in the Jamari river basin (Rondonia, Brazil) provided insight into the relationship between development and erosion in the Brazilian Amazon. Positive correlations between increased sedimentation in the lake and levels of deforestation and mining in the Jamari basin suggested a major increase in erosion associated with these activities. This increase in erosion could diminish agricultural yields in the basin and significantly reduce the useful life of a hydro-electric plant recently built on the river. 相似文献
3.
The Upper San Pedro River Basin in Mexico and the United States is an important riparian corridor that is coming under increasing
pressure from growing populations and the associated increase in groundwater withdrawal. Several studies have produced three-dimensional
maps of the basin fill sediments in the US portion of the basin but little work has been done in the Mexican portion of the
basin. Here, the results of a ground-based transient electromagnetic (TEM) survey in the Upper San Pedro Basin, Mexico are
presented. These basin fill sediments are characterized by a 10–40 m deep unsaturated surficial zone which is composed primarily
of sands and gravels. In the central portion of the basin this unsaturated zone is usually underlain by a shallow clay layer
20–50 m thick. Beneath this may be more clay, as is usually the case near the San Pedro River, or interbedded sand, silt,
and clay to a depth of 200–250 m. As you move away from the river, the upper clay layer disappears and the amount of sand
in the sediments increases. At 1–2 km away from the river, sands can occupy up to 50% of the upper 200–250 m of the sediment
fill. Below this, clays are always present except where bedrock highs are observed. This lower clay layer begins at a depth
of about 200 m in the central portion of the basin (250 m or more at distances greater than 1–2 km from the river) and extends
to the bottom of most profiles to depths of 400 m. While the depth of the top of this lower clay layer is probably accurate,
its thickness observed in the models may be overestimated due to the relatively low magnetic moment of the TEM system used
in this study. The inversion routine used for interpretation is based on a one-dimensional geologic model. This is a layer
based model that is isotropic in both the x and y directions. Several survey soundings did not meet this requirement which invalidates the inversion process and the resulting
interpretation at these locations. The results from these locations were rejected. 相似文献
4.
承德市滦河流域富锶矿泉水资源丰富,成因类型多样,具有典型研究意义。通过水化学图解与多元统计分析、离子比值分析、矿物平衡体系分析,分析富锶地下水形成的地球化学背景,分区阐述富锶地下水水化学特征,探讨富锶地下水的形成机制。结果表明,研究区水化学类型以HCO3-Ca·Mg、HCO3·SO4-Ca、HCO3-Ca、HCO3·SO4-Ca·Mg为主。富锶地下水的形成受地质构造格局和岩浆活动控制,地质建造锶元素丰度影响,水文地球化学条件制约。断裂构造和地层岩性控制着富锶地下水形成分布的总体特征,水文地质条件影响着地下水化学锶元素的地球化学响应机制。地下水锶富集来源为含水介质长石矿物、碳酸盐矿物的风化溶解和阳离子交换吸附作用,矿泉水出露机制分为构造断裂深循环淋溶型、裂隙浅循环淋溶型、补给富集埋藏型3种类型。坝上高原孔隙裂隙水系统富锶地下水形成作用主要受大气降水和溶滤作用控制,滦河中上游裂隙水系统地下水阳离子交换吸附作用强烈,滦河中游孔隙岩溶裂隙水系统地下水化学主要受溶滤作用控制,蒸发浓缩作用和人为活动影响。 相似文献
5.
This paper records the findings from c. 80 prehistoric sites that have been discovered in the alluvial deposits of the rivers Creuse, Cher, and Loir, tributaries of the middle Loire River, over the period since 1981. These deposits comprise river terrace aggradations formed during successive glacial–interglacial cycles which have recorded climate and environment during Quaternary time. The systematic dating of these river deposits by Electron Spin Resonance (ESR) applied to optically bleached sedimentary quartz has resulted in the establishment of a chronological framework for the evolution of these rivers during Lower and Middle Pleistocene (between 1.7 Ma and 130 ka). Evidence for Early Palaeolithic (Mode 1) industries with an in situ context (workshops, soils) in the highest aggradations indicates that Hominins were present in the study area, near the geographical centre of France (47°N), around 1.1 Ma. Examination of the sites indicates that Human occupations were located along valley bottom sites during temperate episodes. Subsequently, after a gap of several hundred thousand years industries with handaxes appear in the Middle Loire Basin in the interval between 700 and 600 ka, and then continuously from 400 ka. These two phases of settlement produced industrial assemblages with clear differences in their responses to the supplies of raw materials and in the modes of making flakes. 相似文献
6.
通过区域对比,根据岩石类型及其组合(岩性、颜色、层型、颗粒类型)、沉积旋同垂向序列、地质体几何形态、层内和层面的结构构造特征及其变化、生物类型及其组合、自生矿物和地球化学等相标志,将羌塘盆地中部甲丕拉组沉积相划分为大陆相区的洪积相、河流相,过渡相区的三角洲相和海洋相区的潮坪相、局限海台地相、沿岸沙坝相、火山喷发相和台地... 相似文献
7.
The continuously low efficiencies of flood relief service in responding to flooding disasters in Taiwan highlight a need for research. This service efficiency is negatively influenced by flood relief facility locations and their operational management structure. The Fazih River floodplain has been previously identified as a high-flood-risk area using an analytic hierarchy process. The purpose of this study is to use the location set covering problem and the maximal covering location problem to determine the number of relief facilities required and the maximum covering area of each facility for the case study area of the Fazih River floodplain. The findings showed that covering distances range from 3.0 to 6.6 km and the number of facilities required for improved service efficiency is between 1 and 4. 相似文献
8.
Geomorphological evidence and historical wind records indicate that eolian processes have heavily influenced San Miguel Island environments for much of the Late Quaternary. The island is almost constantly bombarded by prevailing northwesterly winds, with peak velocities exceeding 75 km/h and wind gusts reaching over 100 km/h. These strong winds played an important role in the location, formation, and preservation of the island's more than 600 archaeological sites. Excavation and surface collection at a stratified Middle and Late Holocene archaeological site on the island's north coast suggest that wind related disturbances result in significant displacement of light fish bones, produce concentrations of shellfish and heavy mammal bones, and cause significant abrasion, etching, and polishing of bones, shells, and artifacts. These data illustrate that wind not only alters surface materials but can significantly disturb subsurface deposits to a depth of at least 20 cm. Working in concert with a variety of taphonomic processes, wind can play a fundamental role in the preservation of archaeological sites and careful scrutiny during excavation and laboratory analysis is required to delineate its effects. © 2002 Wiley Periodicals, Inc. 相似文献
9.
利用黑河流域东部子水系中上游10个水文站60年径流、泥沙实测资料,应用数理统计方法分析了黑河流域东部子水系中上游各条河流控制水文站径流量和输沙量年际变化特征,应用径流量累积均值曲线法对黑河干流出山口莺落峡水文站2015、2020年径流量进行预测。结果表明:(1)黑河上游各站2001~2012年径流量比历年均值平均偏大10.5%。区间除马营河除外的4条较大支流历年径流量在锯齿型变化过程中呈现出逐步增大的趋势。中游莺落峡、高崖、正义峡3个水文站逐年径流量变化趋势相对应,高崖和正义峡径流过程线接近且有交叉现象,充分表明中游区域地表水和地下水转换频繁并十分复杂;(2)流域内札马什克、祁连、莺落峡、高崖、正义峡5个水文站2001~2012年各站时段平均输沙量均明显小于历年(1978~2012年)平均值,分别偏小-0.3%、-9.7%、-63.9%、-51.8%、-43.3%。分析得出了黑河流域东部子水系中上游水沙变化规律,对于保护和开发利用黑河流域水资源、改善黑河流域生态环境、促进黑河流域综合治理等具有重要作用。 相似文献
10.
Water temperature data from the Hudson River at Poughkeepsie from 1908 to the present were acquired. This long-term data set contains (with a few gaps) daily water temperatures at a constant location for the 82-yr period. We hypothesized that water temperatures, because of the dampened variability as compared to air temperatures, would provide a useful record of long-term temperature change. The data were analyzed for statistically significant trends, both annually and monthly for long-term and 10-yr blocks; both warming and cooling trends within all categories were found. The longest significant trend was a 0.12°C per decade increase from about 1920 to 1990. This increase, which was statistically significant for both simple regression and time-series analysis, is within the limits of the suggested rates of change on the global scale. On the other hand, there was no significant trend from the beginning of the record (1908) to the present, due to an apparent dramatic cooling from 1908 to about 1920. 相似文献
11.
Eco-environmental changes which generally manifest as the ecological landscape changes are mainly affected by natural and
human factors. Through complex interaction, natural factors and human activities alter the landscape structure and decide
the service function of regional ecosystem. With the development of geographical information system (GIS) and satellite remote
sensing (RS) techniques, the researches on quantitative analysis of landscape changes have made great strides forward. In
this paper, the landscape change dynamics in the Weigou River basin have been investigated by the combined use of high-resolution
RS images and GIS techniques. The objectives are to determine the landscape transition rates among landscape types and to
quantify changes of various landscape indexes using FRAGSTATS, one of the spatial pattern analysis programs for categorical
maps. Under man–machine interactive interpretation method, all of the 10-m resolution SPOT + TM images are classified into
six primary types (farmland, forest, grassland, water, construction area and desert) and 12 sub-types based on the interpretation
key which was established based on 1947 filed pictures in the Weigou River basin. A field check on the data accuracy shows
that the total interpretation accuracy approaches 97.53%. Significant land-use change has taken place in the Weigou River
basin over the six years from 1998 to 2004 due to rehabilitation measures. The results show that there has been a notable
decrease in farmland mainly due to conversion to forest and grassland, the landscape heterogeneity and evenness has increased,
and there is a greater connectivity. The dominance of farmland patch has decreased. And hence the ecological environment has
started to develop in a reversing direction. The study of the integration of high-resolution RS images and GIS technique is
an effective approach to analyze the landscape changes at river basin scale. 相似文献
12.
珠江口盆地陆丰A区中新统珠江组中-下段2370层是该地区主力油层之一, 但储层厚度差异大、分布不清, 严重制约了区域勘探部署.本文综合地震、测井和地质资料, 分析得出纵波阻抗和V P/V S为研究区识别岩性的敏感参数, 并通过叠前同步反演技术刻画出研究区2370层砂岩分布特征, 整体呈北厚南薄的展布.以地震振幅、分频属性及叠前反演属性为基础, 利用多属性反演技术分析统计了各属性与孔隙度之间的关系, 优选出密度、V P/V S、地震导数、LR、V P、25~30Hz地震分频6种属性为储层物性识别参数, 综合预测研究区2370层储层滨岸砂坝砂体孔隙度发育特征.多属性反演结果表明, 在研究区东北部、西部, 厚层的滩坝储集砂体的孔隙度发育, 普遍在18%以上; 而在中部和东部, 受滩间、坝间泥岩与滩坝砂的叠合区影响呈条带状分布, 孔隙度为10%~18%.预测结果与同期钻井的钻后结果基本一致, 预测成功率在75%以上.多属性反演技术在研究区的储层预测中表现出良好的有效性和实用性, 对类似地区的储层预测也具有借鉴意义. 相似文献
13.
In the upper Amazon Basin, aluminum previously accumulated in lateritic formations is massively remobilised in soils by podzolization and exported in waters. We have investigated the speciation of aluminum in the clay-size fractions of eight horizons of waterlogged podzols lying in a depression of a plateau. The horizons illustrate the main steps involved in the podzolization of laterites. They belong to eluviated topsoil A horizons and illuviated subsoil Bhs, Bh and 2BCs horizons of weakly and better-expressed podzols located at the margin and centre of the depression. For the first time, aluminum speciation is quantitatively assessed in soils by spectroscopic methods, namely FTIR, 27Al magic angle spinning (MAS) and multiple-quantum magic angle spinning (MQMAS), nuclear magnetic resonance (NMR). The results thus obtained are compared to chemical extraction data.Solid-state 27Al MAS NMR spectra enable to distinguish Al bound to organic compounds from that incorporated in secondary mineral phases detected by FTIR. MQMAS experiments additionally show that both chemical shifts and quadrupolar constants are distributed for Al nuclei linked with organic compounds. Similar amounts of chelated Al are obtained from NMR spectra and chemical extractions. The study enables to highlight three major steps in the fate of aluminum. (i) Aluminum is first released by mineral weathering, feeds complexing sites of organic matter and accumulates in subsurface Bhs horizons of weakly expressed podzols (acidocomplexolysis). (ii) Complexes of aluminum with organic matter (Al-OM) then migrate downwards in sandy horizons of better-expressed podzols and accumulate at depth in less permeable 2BCs horizons. (iii) The minor amounts of aluminum present in the 2BCs horizon of the downslope podzol show that aluminum is eventually exported towards the river network, either complexed with organic matter or as Al 3+ ions after desorption from organic compounds, due to decreasing pH or biodegradation of organic ligands. The direct spectroscopic determination of Al-speciation during the formation of podzolic soils opens new perspectives to trace metal loads in the rivers of the upper Amazon Basin. 相似文献
14.
通过河道断面法对黑河中上游河段河道渗漏量进行了比测试验,结果表明:河床岩性组成、河流平面几何形态变化以及人类活动对输水方式的改变等对河道渗漏量影响显著.黑河实施全流域调水前后河道渗漏量发生显著的跳跃性变化,莺落峡至312桥区间河道渗漏量调水前为1.2543×108 m3,调水后为4.3747×108 m3,调水后较调水前河道渗漏量增加3.1203×108 m3;河道流量越小其相应损失率愈大,河道流量越大,其相应损失率愈小,由此得出各河段不同流量单位河长的损失率服从倒数函数分布.研究结果是在黑河中上游实体河道上进行上下断面流量比测试验的基础上得出的,符合该河段的实际情况,可作为黑河中游地表水、地下水转化分析、地下水流系统模拟、流域水资源重复利用、水量调度计算各种模拟模型验证河道渗漏量的基础资料. 相似文献
15.
层序地层标准化是未来层序地层研究重要发展方向,层序成因模式、标准建立、工业化应用是核心;层序地层学分析的标准工作流程强调识别沉积物成因类型和层序地层界面的原因,向共同方法迈进。针对中国陆相沉积复杂多变的特点,可以利用野外露头伽马仪、元素捕获仪、探地雷达以及元素地球化学等多种手段进行高精度层序划分,识别三级层序界面与洪泛面,建立露头-钻井-地震层序地层格架。可以依据陆相湖盆沉积旋回在古水深、古气候、沉积地球化学特征等方面的定量表征,综合开展高精度层序地层研究。在四川盆地上三叠统须家河组层序岩相古地理研究中,将须家河组划分为5个三级层序,须家河组二段上、下亚段实际上是2个不同三级层序的基准面上升与下降体系域沉积,须二下段发育进积型三角洲,上段发育退积型三角洲;由于三角洲砂体发育机理明显不同,导致须二下段储层厚度和物性均好于上段,产层主要分布在下段。在层序岩相古地理研究基础上,进一步明确须二、四、六段是主要储层发育段,层间泥岩也可作为烃源岩。须一、三、五段是主要烃源岩发育段,盆缘规模较小的三角洲砂体也是重要的储层。 相似文献
16.
源—汇系统分析已成为沉积学领域的研究热点,其中关键参数定量恢复是源—汇系统分析的重要内容。以柴北缘鱼卡地区中侏罗世发育的陆相盆地源—汇系统为例,通过支点法进行源—汇系统收支定量分析。首先识别干流河道沉积,测量或计算河道尺寸,进行粒度分析;然后计算瞬时满岸水流量及沉积物流量,结合古气候与流域分析,对年均沉积物量进行计算,得出在给定地层持续时间内输送的沉积物量;再对沉积区的沉积物量进行测量统计,并与计算出的沉积物量进行对比,分析源—汇系统收支状况。对柴北缘鱼卡地区中侏罗统石门沟组下部沉积的源—汇系统收支定量分析显示,目标研究层段河流沉积的干流满岸深度在3.1~3.3 m,河道宽度为69~77 m,流经了较缓的坡度(0.000 204 6~0.000 217 8),流速一般为1.046~1.048 m/s,搬运了中—细砂为主的沉积物。该时期流域面积约为3 209.8~3 781.6 km2,流域长度介于177.8~196.2 km,满岸水流量为239.9~286.2 m3/s,满岸推移载荷流量为0.043~0.048 m3/s,满岸悬浮载荷流量范围为0.083~0.094 m3/s。基于现代类似河流的对比研究,计算出鱼卡地区干流年均沉积物搬运量介于158 862.4~179 242.3 m3,在层序S2所持续的2.2 Ma共向沉积区输入349.5~394.3 km3的沉积物,与沉积区所统计的沉积体积(322 km3)大致相符。河流沉积物输入体积的高值约为支点下游沉积区统计体积的1.22倍,如果这一分析结果准确,则表明存在一定程度的沉积物遗失现象,研究区局限发育的重力流沉积可能是沉积物遗失的主要方式。建立的收支模型可进一步推广应用于陆相河湖沉积组合的源—汇系统分析。 相似文献
17.
为推动黄河流域生态保护及高质量发展,解决地表水资源供需矛盾,亟需开展水平衡分析,建立水平衡模型,为水资源合理分配提供参考依据。作为黄河的重要支流,沁河流域位于黄河中游末端,由于近年来上游调水政策的施行以及流域内生活、生产用水的增加,用水矛盾突出,出现了河道断流、入黄水量偏枯等问题。为保障河流生态环境健康,优化引沁入汾跨流域提水工程实施后的流域水资源供需平衡,以2021年为现状年,在“自然-人工”二元水循环研究理论的指导下,运用水平衡分析理论与方法,以河道内生态需水为保障基础,对沁河流域水资源需求、供水能力与供需平衡进行了分析与讨论。结果表明:(1)沁河流域水资源供给和需求在空间分布上具有分异性,上游山西省境内各河段河道内均能够保障适宜的生态需水量,下游河南省境内,仅可满足最小生态需水量;(2)沁河流域可供给水资源总量为10.04×108 m3,河道外生产、生活及生态用水总量为8.89×108 m3,剩余河道内水量仅为1.15×108 m3,仅可满足河流最小生态需水;(3)推算至2030年,流域内工业生产及生活取用地表水量将达到6.98×108 m3,河道外用水总量将达到9.81×108 m3,剩余水量无法满足最小生态需水。建议采用降低工业用水量、提高农田灌溉用水利用率、推广使用高效节水技术,进一步增强水资源的有效利用,改善流域生态环境。研究结果可为合理规划沁河流域水资源调度提供参考,也可为黄河中游水平衡分析提供范例。 相似文献
18.
利用黑河流域东部子水系中上游10个水文站近60年气温、降水、蒸发观测资料,分析3个要素地域和年际变化特征。结果表明:(1)气温总体地域变化特征表现为从南向北随着海拔高程逐渐降低,多年平均气温呈现逐步升高的趋势。2000年以后气温平均升高0.9℃;(2)降水量总体地域变化特征表现为从南向北、从东向西随着海拔高程的逐渐降低,多年平均降水量呈现逐步减少的趋势。各站历年降水过程呈锯齿状高频振荡,深山区、走廊平原区(荒漠边缘区)降水量长期变化总体上是呈缓慢上升的趋势,浅山区降水量长期变化总体上是呈缓慢下降的趋势;(3)蒸发量地域分布规律跟降水量、气温地域分布规律密切相关,蒸发量总体地域变化特征表现为从南向北随着海拔高程逐渐降低,多年平均蒸发量呈现逐步增大的趋势。19802011年间深山区多年蒸发量变化趋势平稳,无明显增大或减小的变化趋势;浅山区和走廊平原区均呈现出蒸发量逐年减小的总体变化趋势。 相似文献
19.
巩乃斯河流域积雪阴、阳离子的空间变化以K++Na+、Ca2+与SO2-4和HCO-3等离子最明显;K++Na+与SO2-4、Ca2+与HCO-3变化基本同步.从新降雪阴、阳离子的时间变化上看,隆冬季节积雪深厚范围广,相应离子含量低.调查区积雪对局地人类活动所造成的污染有较明显的记录. 相似文献
20.
The Yakima River, a major tributary of the Columbia River, is currently overallocated in its surface water usage in part because of large agricultural water use. As a result, groundwater availability and surface water/groundwater interactions have become an important issue in this area. In several sub-basins, the Yakima River water is diverted and applied liberally to fields in the summer creating artificial recharge of shallow groundwater. Major ion, trace element, and stable isotope geochemistry of samples from 26 groundwater wells from a transect across the Yakima River and 24 surface waters in the Kittitas sub-basin were used to delineate waters with similar geochemical signatures and to identify surface water influence on groundwater. Major ion chemistry and stable isotope signatures combined with principal component analysis revealed four major hydrochemical groups. One of these groups, collected from shallow wells within the sedimentary basin fill, displays temporal variations in NO 3 and SO 4 along with high δ 18O and δD values, indicating significant contribution from Yakima River and/or irrigation water. Two other major hydrochemical groups reflect interaction with the main aquifer lithologies in the basin: the Columbia River basalts (high-Na groundwaters), and the volcaniclastic rocks of the Ellensburg Formation (Ca–Mg–HCO 3 type waters). The fourth major group has interacted with the volcaniclastic rocks and is influenced to a lesser degree by surface waters. The geochemical groupings constrain a conceptual model for groundwater flow that includes movement of water between underlying Columbia River basalt and deeper sedimentary basin fill and seasonal input of irrigation water. 相似文献
|