Extracting drainage networks and their connectivity using LiDAR data          下载免费PDF全文

Jennifer Roelens  Ine Rosier  Stefaan Dondeyne  Jos Van Orshoven  Jan Diels 《水文研究》2018,32(8):1026-1037

Policies, measures, and models geared towards flood prevention and managing surface waters benefit from high quality data on the presence and characteristics of drainage ditches. As a cost and labour effective alternative for acquiring such data through field surveys, we propose a method (a) to extract vector data representing ditch drainage networks based on local morphologic features derived from high resolution digital elevation models (DEM) and (b) to identify possible connections in the ditch network by calculating a probability of the connectivity using a logistic regression where the predictor variables are characteristics of the ditch centre lines or derived from the DEM. Using Light Detection and Ranging (LiDAR) derived DEMs with a 1 m resolution, the method was developed and tested for a mixed agricultural residential area in north‐eastern Belgium. The derived ditch segments had an error of omission of 8% and an error of commission of 5%. The original positional accuracy of the centre lines of the extracted ditches was 0.6 m and could be improved to 0.4 m by shifting each vertex to the position of the lowest LiDAR point located within a radius equal to the spatial resolution of the used DEM. About 69% of the false disconnections in the network were identified and corrected leading to a reduction of the unconnected parts of the ditch network by 71%. The extracted and connected network approximated the reference ditch network fairly well.  相似文献   

Modelling the effect of changing precipitation inputs on deep soil water utilization          下载免费PDF全文

Ji Qi  Daniel Markewitz  David Radcliffe 《水文研究》2018,32(5):672-686

Forests in the Southeastern United States are predicted to experience future changes in seasonal patterns of precipitation inputs as well as more variable precipitation events. These climate change‐induced alterations could increase drought and lower soil water availability. Drought could alter rooting patterns and increase the importance of deep roots that access subsurface water resources. To address plant response to drought in both deep rooting and soil water utilization as well as soil drainage, we utilize a throughfall reduction experiment in a loblolly pine plantation of the Southeastern United States to calibrate and validate a hydrological model. The model was accurately calibrated against field measured soil moisture data under ambient rainfall and validated using 30% throughfall reduction data. Using this model, we then tested these scenarios: (a) evenly reduced precipitation; (b) less precipitation in summer, more in winter; (c) same total amount of precipitation with less frequent but heavier storms; and (d) shallower rooting depth under the above 3 scenarios. When less precipitation was received, drainage decreased proportionally much faster than evapotranspiration implying plants will acquire water first to the detriment of drainage. When precipitation was reduced by more than 30%, plants relied on stored soil water to satisfy evapotranspiration suggesting 30% may be a threshold that if sustained over the long term would deplete plant available soil water. Under the third scenario, evapotranspiration and drainage decreased, whereas surface run‐off increased. Changes in root biomass measured before and 4 years after the throughfall reduction experiment were not detected among treatments. Model simulations, however, indicated gains in evapotranspiration with deeper roots under evenly reduced precipitation and seasonal precipitation redistribution scenarios but not when precipitation frequency was adjusted. Deep soil and deep rooting can provide an important buffer capacity when precipitation alone cannot satisfy the evapotranspirational demand of forests. How this buffering capacity will persist in the face of changing precipitation inputs, however, will depend less on seasonal redistribution than on the magnitude of reductions and changes in rainfall frequency.  相似文献   

Compression reference of soil structure evaluation with reconstituted clays at different initial water contents     

Ling-Ling Zeng  Zhen-Shun Hong  Yu-Jun Cui  Martin D. Liu 《Marine Georesources & Geotechnology》2018,36(7):759-767

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深水铺管船托管架疲劳分析及动态监测点选取研究     

闫宏生  王哲  王晓波  陈永訢  孟祥伟 《海洋工程》2018,36(1):107-113

作为S型铺管作业的关键性装备,托管架长期承受着交变载荷的作用,随着海洋开发向超深水发展,结构疲劳破坏问题不容忽视。采用疲劳谱分析的方法并结合线性累积损伤理论,对托管架结构频域下的变形进行了分析,计算了正常海况下和极端海况下托管架疲劳损伤度并对疲劳寿命进行了评估。研究发现托管架在正常海况下作业符合安全要求,在极端海况下局部结构会受到破坏。并从托管架结构安全监测角度,筛选了结构疲劳分析关键点位,为监测点位的选取提供了依据。  相似文献   

中国区域水资源系统韧性与效率的发展协调关系评价   总被引：1，自引：0，他引：1  

孙才志  孟程程 《地理科学》2020,40(12):2094-2104

在界定水资源系统韧性概念的基础上，综合应用赋权法、SBM-DEA模型及发展协调度模型对2000—2016年全国31个省区的区域水资源系统的效率、韧性以及两者之间的发展协调关系进行评价。结果如下：① 中国区域水资源系统效率整体上处于非有效区，在研究期间呈现出在波动中上升的趋势。② 中国区域水资源系统韧性的平均值为0.39，总体水平较低，研究期间整体上呈波动上升趋势。③ 中国区域水资源系统效率与韧性的发展度总体呈现平稳上升—较快上升—急剧下降—上升的趋势，呈倒“U”型发展；协调度在研究期间呈现波动中上升趋势，大部分省区的发展度较好，而协调度较弱。④ 2000—2016年，水资源效率与韧性的发展协调度一直维持着“东?中?西”阶梯式递减格局，失调省区的数量降低，初级协调、中级协调、良好协调省区的数量逐渐提升，整体向协调趋势发展；空间格局上呈现由2000年倒“E”型对称式分布格局向如今北部围绕天津、中部围绕上海、南部围绕广东的三级格局演变，格局分布与中国三大经济区基本吻合，可知中国水资源系统效率与韧性的发展协调水平与经济发展水平之间有明显的关系。  相似文献   

极地冰钻关键技术研究进展          下载免费PDF全文

张楠  王亮  Pavel Talalay  范晓鹏  王如生  杨阳  洪嘉琳  宫达  孙友宏  李院生  李冰 《探矿工程》2020,47(2):1-16

极地冰钻技术是获取冰芯，研究冰盖-冰架-海洋相互作用，以及获取极地冰下基岩与冰下水环境样品，开展冰下环境探测的重要手段。目前极地冰钻技术的难点与前沿主要包括深冰芯钻探、冰架热水钻、冰下基岩钻和冰下水环境采样与观测技术。本文针对以上4个极地冰钻关键技术，对国内外相关技术的研究进展与项目开展情况进行了总结与梳理。综合来看，虽然我国开展极地钻探技术研究起步较晚，但随着我国极地战略不断推进，我国的极地冰钻关键技术与装备的研究正持续向着赶超极地钻探强国方向迈进，这必将为我国的极地科学研究提供强有力的技术支撑。  相似文献   

全球尺度水文模型： 机遇、 挑战与展望   总被引：4，自引：2，他引：2  

高红凯  赵舫 《冰川冻土》2020,42(1):224-233

水循环发生在全球尺度， 局地和流域水问题的解决也往往需要全球视角， 因此全球尺度水文模型应运而生。从科学意义和国家需求等多个视角， 论述了全球水文学研究的意义和巨大的发展潜力， 系统总结了现有全球尺度水文模型发展现状， 剖析了十余个主流全球尺度水文模型的结构和功能， 以及全球水文-气象-地理信息等全球模型所需数据集。进而分析了现有全球尺度水文模型存在的主要问题和挑战， 为进一步完善模型提供参考。最终分别从模型机理、 大数据、 新技术、 多部门模型耦合等几个方面， 探讨了全球尺度水文模型未来发展的重要方向。  相似文献   

青岛台体应变短周期气压系数变化原因探讨     

岳龙  徐清风  臧艺博  李志强  刘云  李炜  孙忠礼 《大地测量与地球动力学》2020,40(7):765-770

青岛台体应变短周期(小于128 min)气压系数2018-01出现阶变，通过对观测系统、台站周边施工情况、监测环境等逐项现场核实，排除观测系统、周边施工的影响。利用离散小波变换和回归分析发现，钻孔水位的气压系数与体应变气压系数同步阶变，结合台站钻孔施工当天体应变钻孔水位变化、体应变趋势变化、其他相邻台站水位气压系数变化等数据认为，台站钻孔施工是导致体应变气压系数变化的原因，并定性分析其变化机理。  相似文献   

连续台风时期香港区域的水汽变化分析     

周苏娅  闻德保  梅登奎 《大地测量与地球动力学》2020,40(1):82-86

利用香港卫星定位参考站网GNSS观测数据,提取强热带风暴"塔拉斯"与热带风暴"洛克"影响期间各测站天顶方向对流层延迟,反演香港区域大气可降水量;根据香港区域49个天文台气象站提供的实测降雨量数据,分析大气可降水量与实际降雨量的相关性,以及两次台风对香港区域水汽时空分布的不同影响。结果表明,大气可降水量在台风影响前期均上升,在大量降雨后回落,但在连续台风的间歇期间,仍高于台风来临前的水平;水汽累积是大量降雨的前提条件,当水汽累积量相近时,水汽累积时长与累积降雨量呈正相关;台风期间大气可降水量值超过65 mm的区域面积与台风等级相关,台风路径对局部水汽分布有一定的影响。  相似文献   

围海造陆条件下排海高温浓盐水对渤海湾温盐场分布影响模拟及预测     

白玉川  温志超  徐海珏 《海洋学报》2019,41(3):62-75

自2000年以来围绕渤海湾的围海工程剧增，致使工程区附近潮流场发生变化，进而影响排海高温浓盐水的时空分布特征。本文通过建立2000年和2015年两种不同岸线、地形条件下的三维数学模型对渤海湾沿岸3个电厂高温浓盐水表层排海问题进行模拟，研究结果表明，渤海湾的潮流场和高温浓盐水输移扩散特征在近十几年发生了较大变化:工程后，渤海湾平均盐度增大0.203，平均温度升高了0.105℃，同时曹妃甸附近海域浓盐水输移扩散速度明显增加。增大排放口流量至12.7 m3/s，湾内最高温度为26.46℃，较2015年最高温度增加了2.72℃。本文模型可准确模拟及预测排海废水盐度、温度分布特征，为合理布置水电联产设备排放口的位置提供理论基础。  相似文献