The Mekong from satellite imagery: A quick look at a large river   总被引：1，自引：1，他引：1  

Avijit Gupta  S.C. Liew 《Geomorphology》2007,85(3-4):259

Physical datasets on rivers, thousands of kilometres long, can be efficiently and rapidly acquired through satellite imagery. As large rivers commonly cross several tectonic and climatic zones, their channels are composed of a number of units, each with characteristic morphology and behaviour. Separating a large river into such units provides a framework for understanding the geomorphology of the river concerned, allowing acquisition of information for environmental impact analysis and river management.About 2500 km of the Mekong River, from the China border to the sea, has been examined with SPOT satellite images with a selection of MODIS and IKONOS scenes in support. Hydrological data of the Mekong River Commission, hydrographic maps of the Commission, and field observations have been used to verify and extend the findings from the satellite imagery. The technique provides a rapid and holistic conceptualisation of forms and functions along the derived eight-unit classification of the Mekong River. Such a framework is valuable for (1) determining selected aspects of the geomorphological behaviour of a large river system, (2) rapidly analysing project-related environmental impacts, and (3) examining the geological evolution of the river. Investigating large rivers is difficult and resource consuming, but satellite imagery provides an easy and rapid tool. The cost of the images, however, may be high as a number of them are required for this type of analysis.  相似文献   

Adequacy of satellite derived rainfall data for stream flow modeling   总被引：2，自引：0，他引：2  

Guleid Artan  Hussein Gadain  Jodie L. Smith  Kwabena Asante  Christina J. Bandaragoda  James P. Verdin 《Natural Hazards》2007,43(2):167-185

Floods are the most common and widespread climate-related hazard on Earth. Flood forecasting can reduce the death toll associated with floods. Satellites offer effective and economical means for calculating areal rainfall estimates in sparsely gauged regions. However, satellite-based rainfall estimates have had limited use in flood forecasting and hydrologic stream flow modeling because the rainfall estimates were considered to be unreliable. In this study we present the calibration and validation results from a spatially distributed hydrologic model driven by daily satellite-based estimates of rainfall for sub-basins of the Nile and Mekong Rivers. The results demonstrate the usefulness of remotely sensed precipitation data for hydrologic modeling when the hydrologic model is calibrated with such data. However, the remotely sensed rainfall estimates cannot be used confidently with hydrologic models that are calibrated with rain gauge measured rainfall, unless the model is recalibrated. G. Artan, J. L. Smith and K. Asante – work performed under USGS contract 03CRCN0001.  相似文献   

近20年粤港澳大湾区城市群时空演化格局分析     

邓昊键  李恒凯  熊永柱  郑春燕  李迎双 《世界地理研究》2020,29(6):1181-1189

粤港澳大湾区城市群作为世界四大湾区城市群之一，在国家发展格局中占有重要的地位。基于多源数据，利用重心迁移模型、扩张演化模型及改进的引力模型探究近20年粤港澳大湾区城市群的演化。结果表明：①在城市演化类型上，澳门、肇庆呈单向型演化，佛山、中山、珠海、惠州、香港呈双向型演化，广州、江门、东莞、深圳呈发散型演化；2008～2017年城市群整体的扩张速度与强度低于1998～2008年。②近20年粤港澳大湾区城市群的城市质量、关联度呈不断上升趋势，并表现出一定的区域性和不平衡性，城市质量与经济发展程度、城市空间呈正相关关系，城市质量高的城市与周边城市的关联度高；③粤港澳大湾区城市群的社会经济区位度存在明显“断层”，缺乏合理的梯度等级，并表现出一定的空间分异且部分城市的区位度演化显著。  相似文献   

粤港澳大湾区建设用地扩张与城市热岛扩张耦合态势研究   总被引：1，自引：0，他引：1  

杨智威  陈颖彪  吴志峰  郑子豪 《地球信息科学学报》2018,20(11):1592-1603

深入研究粤港澳大湾区建设用地扩张与城市热岛扩张的耦合态势,对改善大湾区生态环境、实现城市化的健康发展,具有重要的意义和科学价值。本文以粤港澳大湾区为研究区域,选取2000、2008和2016年的遥感影像数据和地表温度数据,提取大湾区的建设用地、划分城市热岛强度等级、识别城市热岛区域;在此基础上,使用总体耦合态势和空间耦合特征两种模型揭示大湾区在不同时期建设用地扩张和城市热岛扩张的耦合关系。结果表明：① 2000-2016年,粤港澳大湾区的建设用地扩张和城市热岛扩张趋势具有同步性;② 城市热岛区域面积不断增加,在珠江口两岸逐步形成了连接中山-佛山-广州-东莞-深圳-香港,大范围分布的倒“U”形城市热岛条带;③ 大湾区建设用地与城市热岛的总体耦合态势处于不断加强的过程,至2016年,两类指标的重心距离达到研究期内的最小距离,此时的总体耦合态势最强;④ 研究期内,大湾区未出现建设用地扩张和城市热岛扩张严重失调情况,建设用地扩张和城市热岛扩张耦合类型以耦合型、基本耦合型以及轻度不耦合型为主,空间耦合程度高。  相似文献   

Petrological constraints on the tectonic setting of the Kathmandu Nappe in the Langtang–Gosainkund–Helambu regions,Central Nepal Himalaya          下载免费PDF全文

G. Rapa  C. Groppo  P. Mosca  F. Rolfo 《Journal of Metamorphic Geology》2016,34(9):999-1023

The Gosainkund–Helambu region in central Nepal occupies a key area for the development of Himalayan kinematic models, connecting the well‐investigated Langtang area to the north with the Kathmandu Nappe (KN), whose interpretation is still debated, to the south. In order to understand the structural and metamorphic architecture of the Greater Himalayan Sequence (GHS) in this region, a detailed petrological study was performed, focusing on selected metapelite samples from both the Gosainkund–Helambu and Langtang transects. The structurally lowest sample investigated belongs to the Lesser Himalayan Sequence; its metamorphic evolution is characterized by a narrow hairpin P–T path with peak P–T conditions of 595 ± 25 °C, 7.5 ± 1 kbar. All of the other samples here investigated belong to the GHS. Along the Langtang section, two tectono‐metamorphic units have been distinguished within the GHS: the Lower Greater Himalayan Sequence (L‐GHS), characterized by peak P–T conditions at 728 ± 11 °C, 10 ± 0.5 kbar (corresponding to a T/depth ratio of 22 ± 1 °C km^?1), and the structurally higher Upper Greater Himalayan Sequence, with peak metamorphic conditions at 780 ± 20 °C, 7.8 ± 0.8 kbar (corresponding to a T/depth ratio of 31 ± 4 °C km^?1). This confirms the existence of a main tectono‐metamorphic discontinuity within the GHS, as previously suggested by other authors. The results of petrological modelling of the metapelites from the Gosainkund–Helambu section show that this region is entirely comprised within a sub‐horizontal and thin L‐GHS unit: the estimated peak metamorphic conditions of 734 ± 19 °C, 10 ± 0.8 kbar correspond to a uniform T/depth ratio of 23 ± 3 °C km^?1. The metamorphic discontinuity identified along the Langtang transect and dividing the GHS in two tectono‐metamorphic units is located at a structural level too high to be intersected along the Gosainkund–Helambu section. Our results have significant implications for the interpretation of the KN and provide a contribution to the more general discussion of the Himalayan kinematic models. We demonstrate that the structurally lower unit of the KN (known as Sheopuri Gneiss) can be correlated with the L‐GHS unit; this result strongly supports those models that correlate the KN to the Tethyan Sedimentary Sequence and that suggest the merging of the South Tibetan Detachment System and the Main Central Thrust on the northern side of the KN. Moreover we speculate that, in this sector of the Himalayan chain, the most appropriate kinematic model able to explain the observed tectono‐metamorphic architecture of the GHS is the duplexing model, or hybrid models which combine the duplexing model with another end‐member model.  相似文献   

1987—2017年粤港澳大湾区城市群的不透水地表扩张与梯度演化     

陈明发  刘帆  赵耀龙  杨光 《地球信息科学学报》2021,23(3):443-455

不透水地表是衡量城市化过程与空间扩张的重要特征。本文以我国最具经济活力的城市群-粤港澳大湾区城市（以下简称大湾区）为研究区,采用重心-标准差椭圆与梯度分析等方法,探讨其1987—2017年不透水地表的时空扩张分布特征与演化趋势。结果表明：① 30年来大湾区的不透水地表面积从1839.34 km²持续增长至12 385.93 km²。城市化进程进入21世纪后明显加快,整体形成了广、深、港、澳等中心城市带动,各次级城市组团,网络结构发展的空间扩张格局。② 大湾区不透水地表重心位于广州番禺与佛山顺德交界处附近,城市建设扩张靠近大陆海岸带区域,范围不断扩大。广、莞、佛等地的城市建设极大带动了不透水地表重心与方向的变化;③ 城市建设以珠江支流与大陆海岸线为轴心扩张的特征明显,各地核心城区与海湾区域的建设扩张共同构成了大湾区的发展核心,整体形成了中心城区为主、大陆海岸线为辅的协同发展趋势。粤港澳大湾区建设已上升为国家战略,未来需进一步强化内部各城市间的要素交互,在发挥核心城区辐射引领作用的同时,充分利用沿海产业优势,带动实现大湾区的城乡融合发展。  相似文献   

交通流空间视角下粤港澳大湾区网络结构多维测度     

廖创场  李晓明  洪武扬  郭仁忠 《地理研究》2023,42(2):550-562

交通流是表征区域联系的核心要素,也是区域空间结构新的测度手段。本文基于流空间理论与社会网络理论,使用高德导航数据,对粤港澳大湾区交通联系网络的空间组织结构、节点特征、联系机理进行识别与分析,以期对湾区未来发展规划提供决策支持。结果显示：(1)整合尺度后的大湾区呈现“四组团三圈层”的空间组织形态;(2)多中心化发展态势明显,依托广深莞核心交通资源出现高强集聚;(3)网络整体骨架尚未建立。本研究揭示区域城市间交互关系与结构特征,对推动大湾区构建多极化、组团化、协同化的发展格局具有重要意义。  相似文献   

Private equity,public affair: Hydropower financing in the Mekong Basin     

《Global Environmental Change》2014

Large-scale hydropower development is increasingly popular. Although international finance is a significant driver of hydropower market expansion, financial data is relatively obscure and literature remains scarce. This article tracks the financial process in hydropower development in the Mekong River Basin. It shows a shift in influence from traditional public international financial institutions to a diverse mix of private actors, who are enticed with attractive terms of trade and complete decision making power over water resource management. Traditional players have now taken on a more facilitating and regulatory role by providing guarantees and mitigating social and environmental impacts partly releasing the new global and regional private actors from these responsibilities. Because hydropower financing involves opaque processes and confidential documents public accountability is severely limited. While the private sector benefits from relatively short term returns, the public sector is left responsible for long term impacts.  相似文献   

Changes in hydrology and sediment delivery of the Mekong River in the last 50 years: connection to damming,monsoon, and ENSO   总被引：1，自引：0，他引：1  

Zuo Xue  J. Paul Liu  Qian Ge 《地球表面变化过程与地形》2011,36(3):296-308

As the population and economy boom, more and more dams are being built in the Mekong River basin. Previous studies have revealed that Manwan Dam had little influence on the runoff–SSC (suspended sediment concentration) relationship, and the sediment load was relatively stable over the past 40 years. However, little is known at present on the relationship among monsoons, El Niño Southern Oscillation (ENSO), precipitation, runoff, and the impact of dams on the delta dynamics. A comprehensive hydropower GIS database covering the entire Mekong basin is presented in this study. Mann–Kendall trend analysis showed no significant change in precipitation and runoff over the past 50 years. Spectral analysis showed that the runoffs of the middle to lower reach of Mekong River are correlated with the Indian Monsoon, where as the East Asian Monsoon's influence is mainly on the lower reach. With another 200 new dams to be added to the basin in the next couple of decades, changes are expected in both hydrological regime and delta dynamics. On one hand, the runoff showed a closer connection with the regional precipitation and ENSO in the post‐dam period (1993–2005) than in the pre‐dam period (1950–1993). Such a relationship is expected to be even closer when more dams are completed. On the other hand, both daily maximum and minimum water levels on the delta plain have shown an abrupt drop since the end of 1994. This reduced water‐level gradient between the river and sea inevitably weakens the sediment discharge to the coast, which might intensify the ongoing coastal erosion on the eastern part of the delta plain. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

澜沧江—湄公河流域跨界含水层研究          下载免费PDF全文

何静  韩再生  牛磊 《地学前缘》2011,18(6):358-366

跨界含水层由位于不同国家的含水层组成,是地下水资源系统的重要组成部分。妥善管理并公平合理地利用跨界含水层,对促进可持续发展及国家之间的睦邻友好关系有着重要意义。通过分析澜沧江—湄公河流域水文地质条件,划定流域的跨界含水层系统,并对地下水资源与环境问题进行探索,提出跨界含水层综合评价指标体系,结合澜沧江—湄公河流域4个跨界含水层相关的指标进行了综合评价。本次研究,对管理澜沧江—湄公河流域跨界含水层,建设和谐的东南亚国际环境有着重要意义。  相似文献