Efficient Delineation of Nested Depression Hierarchy in Digital Elevation Models for Hydrological Analysis Using Level‐Set Method

In terrain analysis and hydrological modeling, surface depressions (or sinks) in a digital elevation model (DEM) are commonly treated as artifacts and thus filled and removed to create a depressionless DEM. Various algorithms have been developed to identify and fill depressions in DEMs during the past decades. However, few studies have attempted to delineate and quantify the nested hierarchy of actual depressions, which can provide crucial information for characterizing surface hydrologic connectivity and simulating the fill‐merge‐spill hydrological process. In this paper, we present an innovative and efficient algorithm for delineating and quantifying nested depressions in DEMs using the level‐set method based on graph theory. The proposed level‐set method emulates water level decreasing from the spill point along the depression boundary to the lowest point at the bottom of a depression. By tracing the dynamic topological changes (i.e., depression splitting/merging) within a compound depression, the level‐set method can construct topological graphs and derive geometric properties of the nested depressions. The experimental results of two fine‐resolution Light Detection and Ranging‐derived DEMs show that the raster‐based level‐set algorithm is much more efficient (~150 times faster) than the vector‐based contour tree method. The proposed level‐set algorithm has great potential for being applied to large‐scale ecohydrological analysis and watershed modeling.     

Modeling Hydrological and Environmental Consequences of Climate Change and Urbanization in the Boise River Watershed,Idaho

The potential impacts driven by climate variability and urbanization in the Boise River Watershed (BRW), located in southwestern Idaho, are evaluated. The outcomes from Global Circulation Models (GCMs) and land use and land cover (LULC) analysis have been incorporated into a hydrological and environmental modeling framework to characterize how climate variability and urbanization can affect the local hydrology and environment at the BRW. The combined impacts of future climate and LULC change are also evaluated relative to the historical baseline conditions. For modeling exercises, Hydrological Simulation Program‐Fortran (HSPF) is used in parallel computing and statistical techniques, including spatial downscaling and bias correlation, are employed to evaluate climate consequences derived from GCMs as well. The implications of climate variability and land use change driven by urbanization are then observed to evaluate how these overall global challenges can affect water quantity and quality conditions at the BRW. The results show the combined impacts of both climate change and urbanization can lead to more seasonal variability of streamflow (from ?27.5% to 12.5%) and water quality, including sediment (from ?36.5% to 49.3%), nitrogen (from ?24% to 124.2%), and phosphorus (from ?13.3% to 21.2%) during summer and early fall over the next several decades.     

闽江水利工程引起的水文环境灾(危)害浅析

闽江干一支流众多水利工程的建成和运营,显著地影响和改变了闽江干一支流河流的水动力场和水化学场的时空状态,导致其纳污量(强度)、稀释扩散净化能力、水化学成分和水体质量等水文环境参数发生变化,引起水文环境灾(危)害问题日益突出.本文概述了闽江干一支流点源污染及面源污染程度和时空状态及其与水利工程建设运营的关系,同时以水口水...     

基于DEM地表水文特征和汇水子流域的提取研究

文章以天津于桥水库上游流域为研究对象,以DEM(数字高程模型)为基础数据,对DEM生成方法、DEM精度、流域地形地貌特征及阈值的选取三个方面分别作了详细研究。试验结果表明,从于桥水库上游流域的水文特征所提取的河网分布与河流与实际分布情况基本吻合,淋河、沙河、黎河三大流域的面积误差范围分别为-3.44%、2.28%和7.63%。     

煤矿安全管理的系统动力学仿真分析

从安全投入和安全产出的角度分析煤矿安全管理系统各要素之间错综复杂和相互依存的关系;运用系统动力学的相关理论和方法研究煤矿安全管理与控制问题;利用VENSIM建模软件做出各要素之间的因果关系图,建立煤矿安全管理的系统动力学流图模型。采用宁煤集团灵新煤矿的实际安全生产数据进行模拟分析,确立最优安全管理与控制方案,提升煤矿安全生产水平。     

不同水文情景下白洋淀水体好氧反硝化菌群对水质因子的动态响应

为探究不同水文情景下白洋淀水体好氧反硝化菌群的演变规律和驱动机制,基于水质调查和高通量测序技术,进行了水体水质因子分析、好氧反硝化菌群α多样性分析、物种组成和网络分析.结果表明,白洋淀水体呈弱碱性,丰水期水体T最高,DO最低,冰封期T最低,DO最高.白洋淀水体在枯水期、丰水期、平水期和冰封期下NH₄⁺-N、NO₂^--N、NO₃ ^--N、TN、高锰酸盐指数、Fe和Mn之间均存在显著差异（P < 0.01）,其中TP在不同水文情景下不存在显著差异（P > 0.05）.不同水文情景下水体中最大的细菌门类为Proteobacteria,相对丰度较高的属为Magnetospirillum、Aeromonas、Pseudomonas、Azospirillum和Bradyrhizobium.此外,好氧反硝化菌群的α多样性均存在显著差异（P < 0.001）,冰封期菌群丰富度最高,枯水期和冰封期菌群的多样性和均匀度最高.经RDA、Mantel分析,菌群的水质驱动因子在不同水文情景下有所差异,枯水期菌群的水质驱动因子为pH、NO₃^--N、NO₂^--N和高锰酸盐指数,丰水期菌群的驱动因子为pH、T、DO、NO₂^--N和TP,平水期的驱动因子为NO₂^--N、Fe和高锰酸盐指数,冰封期菌群的驱动因子为NO₃^--N和NO₂^--N.网络分析表明与水质驱动因子相关的物种存在时间差异,枯水期与水质驱动因子相关的属为Magnetospirillum、Aeromonas和Azoarcus,与丰水期相关的属为Magnetospirillum、Pseudomonas和Aeromonas,与平水期相关的属为Magnetospirillum、Pseudomonas和Limnohabitans,与冰封期相关的属为Magnetospirillum、Azoarcus和Pseudomonas.不同水文情景关键水质因子（主要是T、DO、NO₃^--N和高锰酸盐指数）与好氧反硝化菌群之间的关联关系,随着时间演变也在逐渐发生变化.综上,通过对不同水文情景下白洋淀水体好氧反硝化菌群演变特征及环境因子驱动机制进行研究,可为认识天然环境中好氧反硝化菌群演变机制提供依据.     

基于GIS的城市工程地质环境质量变权评价

城市工程地质环境质量传统评价方法中,指标权重确定后,无论各指标值如何变化,指标权重值总是固定不变,无法反映各项指标内部差异性对城市工程地质环境质量的影响,进而影响评价结果的客观公正性。为此,将变权原理引入城市工程地质环境质量评价。根据城市工程地质环境特点及评价精度要求,构建城市工程地质环境质量评价指标体系,采用分段强惩罚-激励型变权模型,并结合GIS空间分析功能对其进行评价。以郑州市为例,采用常权和变权两种方法对其工程地质环境质量进行评价。结果表明,变权评价结果与常权评价结果趋势性较为一致,且变权评价结果比常权评价结果更易区分评价等级,在一定程度上避免了常权法在权重分配中的缺陷,充分体现了各项评价指标内部差异性对城市工程地质环境质量整体性的影响,提高了城市工程地质环境质量评价等级的可信度。     

Wetland Flowpaths Mediate Nitrogen and Phosphorus Concentrations across the Upper Mississippi River Basin

Eutrophication, harmful algal blooms, and human health impacts are critical environmental challenges resulting from excess nitrogen and phosphorus in surface waters. Yet we have limited information regarding how wetland characteristics mediate water quality across watershed scales. We developed a large, novel set of spatial variables characterizing hydrological flowpaths from wetlands to streams, that is, “wetland hydrological transport variables,” to explore how wetlands statistically explain the variability in total nitrogen (TN) and total phosphorus (TP) concentrations across the Upper Mississippi River Basin (UMRB) in the United States. We found that wetland flowpath variables improved landscape-to-aquatic nutrient multilinear regression models (from R² = 0.89 to 0.91 for TN; R² = 0.53 to 0.84 for TP) and provided insights into potential processes governing how wetlands influence watershed-scale TN and TP concentrations. Specifically, flowpath variables describing flow-attenuating environments, for example, subsurface transport compared to overland flowpaths, were related to lower TN and TP concentrations. Frequent hydrological connections from wetlands to streams were also linked to low TP concentrations, which likely suggests a nutrient source limitation in some areas of the UMRB. Consideration of wetland flowpaths could inform management and conservation activities designed to reduce nutrient export to downstream waters.     

基于力学机制的钢筋混凝土柱抗剪承载力模型∗

为了兼顾钢筋混凝土(RC)柱抗剪承载力分析的计算精度和简便性,研究建立了一种基于力学机制的RC柱抗剪承载力简化模型。首先基于变角桁架-拱模型理论,结合变角桁架模型的力平衡条件以及变角桁架模型和拱模型之间的变形协调条件,建立了RC柱抗剪承载力分析的理论模型;然后利用38组试验数据进行统计分析,分别确定了混凝土、箍筋和拱模型的抗剪承载力贡献系数近似取值,在此基础上建立了R C柱抗剪承载力分析的简化模型;最后通过与试验数据进行对比分析,验证了该模型的计算精度和适用性。分析结果表明,该模型不仅可以合理分析混凝土、箍筋和拱作用的抗剪承载力贡献,具有较高的计算精度,而且计算公式较为简洁。     

基于水资源耦合价值的绿色水价模型及其应用——以下辽河平原为例

为了准确体现水资源价值的差异性、动态性及其整体性,提出基于绿色核算的水资源耦合价值评价指标体系及绿色水价模型。以下辽河平原为例,引入可变模糊综合评价法,结合熵值法和层次分析法对水资源耦合价值进行评价,计算该区水资源天然价值系数、附加价值系数、经济价值系数、社会（公益）价值系数、生态价值系数及环境价值系数,据此得出绿色水价标准：城乡居民生活用水为3.54 元/m³,农村居民生活用水（暂行）为132 元/（a·人）,农工商服务业用水为6.14 元/m³,农田灌溉用水（暂行）为0.79 元/m³,行政事业用水为4.72 元/m³,园林绿化用水为7.34 元/m³,特种行业用水为12.33 元/m³。各行政分区水资源耦合价值及各单项价值的评价结果基本符合该区客观实际,绿色水价模型体现了区域水资源禀赋,反映了经济社会发展及生态环境等对水资源的需求。