A comparison of methods to estimate groundwater recharge from bare soil based on data observed by a large-scale lysimeter     

Zaiyong Zhang  Wenke Wang  Chengcheng Gong  Ming Zhang 《水文研究》2020,34(13):2987-2999

Effectively estimating groundwater recharge is critical to manage water resources, especially in arid and semi-arid regions as impacted by intensive human activities and climate changes. Rare insights have been gained into groundwater recharge since direct observation is hard to carry out. Although several methods are currently available to estimate groundwater recharge, the estimated results may cover noticeable bias. The behaviours of different methods based on different conceptual frameworks and exhibiting different levels of complexity should be examined to estimate actual groundwater recharge. This study aims to assess the performance of four common methods to estimate groundwater recharge. For this end, large-scale lysimeters equipped with soil water content sensors and water table sensors were set up at a research site established in Guanzhong Basin of China. The data achieved by 1-year observation were employed to compare four estimation methods. As revealed from the results, the following findings are drawn. (a) Groundwater level fluctuation (GLF) method is simple, whereas its accuracy is determined by specific yield, and adopting a water balance method to estimate specific yield can considerably enhance the accuracy of GLF. (b) The calibrated numerical model can obtain the optimal result compared with the other methods, whereas long-term observation data are required for parameter calibration. (c) In the water balance method, the maximum entropy production (MEP) model and a practical method (estimating evaporation between two rainfall events) were used to calculate evaporation. As indicated by the results, water balance method combined with MEP is capable of obtaining more reliable results of groundwater recharge compared with the practical method. (d) With an analytical model based on linearized Richards' equation, accurate results can be achieved. What is more, the analytical model only needs the measurement of soil moisture near the surface. The limitation of this method is that it is difficult to determine the maximal water flux. The mentioned findings are of critical implications to the management and sustainable development of groundwater.  相似文献   

Landsat时序数据支持下的藏东南植被时空变化监测     

王华  杨乾鹏  郭山川  旦增  次仁多吉 《测绘通报》2020,(11):7

本文利用GEE平台和1990—2019年巴宜区Landsat遥感影像，采用像元二分模型、相关性分析等方法分析了巴宜区植被覆盖度的时空变化特征与驱动力。研究结果表明：①1990—2019年巴宜区植被覆盖度总体呈稳中有增的趋势，其中，河谷区域增加明显，而高海拔区域相对稳定；②1990—2019年巴宜区气温呈显著升高，降水略有下降，总体呈“暖干化”，气温较降水量对植被覆盖变化更明显，但气候变化对植被覆盖变化影响总体不明显；③1990—2019年巴宜区植被覆盖变化与人类活动有很好的相关性，其中，低、中低、中、中高植被覆盖区域，呈显著的负相关，而高植被覆盖区域呈正相关。本文基于遥感大数据和地理云计算的植被覆盖监测动态监测和定量分析方法，能对高山峡谷区生态评估和演替分析提供一定的技术支撑和科学数据。  相似文献   

基于深度残差网络的机载LiDAR点云分类     

赵传  郭海涛  卢俊  余东行  张保明 《测绘学报》2020,49(2):202-213

机载LiDAR点云的分类是利用其进行城市场景三维重建的关键步骤之一。为充分利用现有的图像领域性能较好的深度学习网络模型,提高点云分类精度,并降低训练时间和对训练样本数量的要求,本文提出一种基于深度残差网络的机载LiDAR点云分类方法。首先提取归一化高程、表面变化率、强度和归一化植被指数4种具有较高区分度的点云低层次特征;然后通过设置不同的邻域大小和视角,利用所提出的点云特征图生成策略,得到多尺度和多视角点云特征图;再将点云特征图输入到预训练的深度残差网络,提取多尺度和多视角深层次特征;最后构建并训练神经网络分类器,利用训练的模型对待分类点云进行预测,经后处理得到分类结果。利用ISPRS三维语义标记竞赛的公开标准数据集进行试验,结果表明,本文方法可有效区分建筑物、地面、车辆等8类地物,分类结果的总体精度为87.1%,可为城市场景三维重建提供可靠的信息。  相似文献   

复杂地形景区三维导览图的设计与实现     

吴思锴  李百寿  郭家豪  李雪  张卫平 《北京测绘》2020,(1):38-43

为满足复杂地形景区对三维地图导览的需求,构建更为清晰的三维地图模型,提供良好的三维导览地图设计方案显得尤为重要。为了更好地与卫星影像进行贴合,DEM数据的采样密度要与卫星影像的分辨率一致。本文通过对比当下常用的四种空间插值方法的适用范围与运用特点,设置相关阈值及权重,直观比较了四种插值方法产生的插值结果,选择更适合复杂景区DEM插值的插值方法并对其进行精度提升,以此得到符合精度要求的DEM数据。最后利用相应地区的卫星影像进行地图投影及影像贴图,两种数据结合构建复杂景区的三维地图模型,给游客带来更为精确直观的定位信息和空间要素信息。  相似文献   

Quantifying suitable dynamic water levels in marsh wetlands based on hydrodynamic modelling     

Peng Hu  Zefan Yang  Qiande Zhu  Weize Wang  Qin Yang 《水文研究》2021,35(2):e14054

The water level of marsh wetlands is a dominant force controlling the wetland ecosystem function, especially for aquatic habitat. For different species, water level requirements vary in time and space, and therefore ensuring suitable water levels in different periods is crucial for the maintenance of biodiversity in marsh wetlands. Based on hydrodynamic modelling and habitat suitability assessment, we determined suitable dynamic water levels considering aquatic habitat service at different periods in marsh wetlands. The two-dimensional hydrodynamic model was used to simulate the temporal and spatial variation of water level. The habitat suitability for target species at various water levels was evaluated to obtain the fitting curves between Weighted Usable Area (WUA) and water levels. And then suitable water levels throughout the year were proposed according to the fitting curves. Using the Zhalong Wetland (located in northeastern China) as a case study, we confirmed that the proposed MIKE 21 model can successfully be used to simulate the water level process in the wetland. Suitable water levels were identified as being from 143.9–144.2 m for April to May, 144.1–144.3 m for June to September, and 144.3–144.4 m for October to November (before the freezing season). Furthermore, proposed water diversion schemes have been identified which can effectively sustain the proposed dynamic water levels. This study is expected to provide appropriate guidance for the determination of environmental flows and water management strategies in marsh wetlands.  相似文献   

A high-precision time–frequency analysis for thin hydrocarbon reservoir identification based on synchroextracting generalized S-transform     

Ying Hu  Hui Chen  Hongyan Qian  Xinyue Zhou  Yuanjun Wang  Bin Lyu 《Geophysical Prospecting》2020,68(3):941-954

Improving the seismic time–frequency resolution is a crucial step for identifying thin reservoirs. In this paper, we propose a new high-precision time–frequency analysis algorithm, synchroextracting generalized S-transform, which exhibits superior performance at characterizing reservoirs and detecting hydrocarbons. This method first calculates time–frequency spectra using generalized S-transform; then, it squeezes all but the most smeared time–frequency coefficients into the instantaneous frequency trajectory and finally obtains highly accurate and energy-concentrated time–frequency spectra. We precisely deduce the mathematical formula of the synchroextracting generalized S-transform. Synthetic signal examples testify that this method can correctly decompose a signal and provide a better time–frequency representation. The results of a synthetic seismic signal and real seismic data demonstrate that this method can identify some reservoirs with thincknesses smaller than a quarter wavelength and can be successfully applied for hydrocarbon detection. In addition, examples of synthetic signals with different levels of Gaussian white noise show that this method can achieve better results under noisy conditions. Hence, the synchroextracting generalized S-transform has great application prospects and merits in seismic signal processing and interpretation.  相似文献   

The tunnel seismic advance prediction method with wide illumination and a high signal-to-noise ratio     

Xinglin Lu  Xian Liao  Yao Wang  Guimei Wang  Zhihong Fu  HengMing Tai 《Geophysical Prospecting》2020,68(8):2444-2458

Tunnel seismic prediction is widely used in the field of tunnel seismic advance detection. The illumination of the target and the signal-to-noise ratio of the data are two key factors affecting the precision of data interpretation. Current seismic prospecting has shortcomings on sites: (1) The lighting shots are solely towards one side of the tunnel wall, (2) the geophones are placed far away from the tunnel face and (3) the surface waves from the tunnel wall dominate over the reflection waves, lowering the signal-to-noise ratio of the data at the tunnel wall. This paper proposes a tunnel symmetrical geometry to tackle the above challenges. The arrangement is to place 12 sources uniformly on each side of the tunnel wall and six geophones on the tunnel wall and face. Results of simulated data and measured data show that the proposed method enables (1) broad illumination of the target body, (2) the enhancement of illumination energy of the target body, and (3) higher data signal-to-noise ratio. The proposed symmetrical geometry method provides better interpretation in terms of broader coverage, higher quality and greater distance of investigation.  相似文献   

Effects of rainfall intensity and compaction on water transport from opencast coal mine soils: An experimental study     

Fengjiao Wang  Jinman Wang 《水文研究》2020,34(2):258-269

The use of heavy machinery during opencast coal mining can result in soil compaction. Severe soil compaction has a negative impact on the transport of water and gas in the soil. In addition, rainfall intensity has traditionally been related to soil surface sealing affecting water transport. To assess the effects of rainfall intensity and compaction on water infiltration and surface runoff in an opencast coal mining area, the disturbed soils from the Antaibao opencast mine in Shanxi Province, China, were collected. Four soil columns with different bulk densities (i.e., 1.4 g cm^-3, 1.5 g cm^-3, 1.6 g cm^-3, and 1.7 g cm^-3) were designed, and each column received water five times at rainfall intensities of 23.12, 28.91, 38.54, 57.81, and 115.62 mm hr^-1. The total volume of runoff, the time to start runoff, and the volumetric water contents at the depths of 5 cm, 15 cm, 25 cm, 35 cm, 45 cm, 55 cm, and 65 cm were measured. Under the same soil bulk density, high rainfall intensity reduced infiltration, increased surface runoff, and decreased the magnitude of change in the volumetric water contents at different depths. Under the same rainfall intensity, the soil column with a high bulk density showed relatively low water infiltration. Treatments 3 (1.6 g cm^-3) and 4 (1.7 g cm^-3) had very small changes in volumetric water contents of the profiles even under a lower rainfall intensity. Severe soil compaction was highly prone to surface runoff after rainfall. Engineering and revegetation measures are available to improve compacted soil quality in dumps. Our results provide a theoretical basis for the management of land reclamation in opencast coal mine areas.  相似文献   

基于AUKF的框架结构离线模型更新混合试验方法     

陈凡  郭玉荣 《地震工程与工程振动》2020,(1):162-170

模型更新混合试验在传统混合试验方法的基础上更新与试验构件具有相同恢复力特性的构件,扩展了混合试验方法的应用范围。本文旨在提高模型更新混合试验的精度,降低试验的成本并简化模型更新混合试验方法的流程。自适应UKF(AUKF)算法在传统UKF的基础上加入方差自适应模块,能够减轻初始参数设定对参数识别结果的影响,本文基于AUKF提出一种模型更新混合试验方法。对以Bouc-Wen为恢复力模型的防屈曲约束支撑(BRB)进行低周反复加载虚拟试验,通过Matlab编制AUKF算法程序进行参数识别,验证了AUKF算法的高效准确性。对一榀8层4跨带BRB的钢框架进行混合试验数值仿真,结果表明离线模型更新试验结果较在线模型更新更接近真实结果,且简化了试验流程。  相似文献   

无人机在重大地质灾害应急调查中的应用   总被引：4，自引：0，他引：4  

郭晨  许强  董秀军  巨袁臻  宁浩 《测绘通报》2020,(10):6

传统的地质灾害应急调查受限于地形、天气等外界条件，不能快速全面地获取灾害的详细信息，而无人机具有灵活性强、时效性高和不受复杂地形影响等特点，在地质灾害应急调查中有独特的优势。本文以“6·24”新磨村滑坡和“10·11”白格滑坡为例，阐述了无人机数据获取及处理流程，重点介绍了无人机获取的数字地形产品在地质灾害精确描述、定性及定量分析中的应用。结果表明：无人机摄影测量技术为重大地质灾害应急调查提供了更加科学高效的现场影像采集和遥感成果处理及应用方案，为应急救灾工作的顺利实施及分析研判提供了重要数据支撑，科学有效地保证了现场施工救援人员的安全。  相似文献