ALTERNATIVE APPROACH TO THE FORMULATION OF BASIN HYDRAULIC GEOMETRY EQUATIONS1

ABSTRACT: Along a drainage network, there is a systematic variation of average flow parameters (width, depth, and velocity) at flows having the same flow duration. Hydraulic geometry equations mathematically express this interdependent relationship of stream-flow characteristics for a basin for annual flow durations varying from 10 to 90 percent. However, the equations proposed so far have had rather poor predictive performance for low flows. An independent investigation of the variation of discharge with drainage area and annual flow duration demonstrates a consistent relationship between these parameters. The relationship for the high to median-flow range differs, however, from that for the median— to low-flow range. The proposed equations provide a better predictive performance for low flows than previous formulations and a versatile means of estimating flow parameters for streams throughout a basin. The improved basin hydraulic geometry equations have a wide range of applications in areas such as stream habitat assessment, water quality modeling, channel design, and stream restoration projects.     

PARAMETER DETERMINATION FOR THE MUSKINGUM-CUNGE FLOOD ROUTING METHOD1

ABSTRACT: The proportionality coefficient, K, and the weighing parameter, X, required for the Muskingum-Cunge Flood Routing Method are dependent on the hydraulic characteristics of the channel and the dynamic characteristic of the flood wave. This work focuses on the determination of the Muskingum-Cunge Flood Routing Method parameters for streams where measured hydrographs are not available (i.e., ungaged streams) with floods that stay within the channel banks. In the present work, a gaged creek was used and a dynamic wave was routed to test the reliability of the parameters determined through the Schaefer and Stevens technique (Schaefer and Stevens, 1978). The predicted outflow hydrographs are compared to the hydrographs obtained for the same stream determined with the Muskingum Routing option of the HEC-1 program. Cypress Creek in Harris County, Texas, was the model for this work; and the corresponding data were extracted from the Grant Road and Westfield, Texas, USGS gaging stations.     

中国区域经济与资源丰度相关性研究

以省域面板数据为基础．选取水、耕地、森林、能源、矿产等五种资源．验证了1978—2004年中国不同种类资源丰度与区域经济发展之问的相关关系。研究表明：①资源诅咒原理在中国内部区域之间仍然成立，除水资源外．耕地、能源、矿产和森林等四种资源的丰度与区域经济发展水平都呈现负相关关系．其程度由裔到低依次是：耕地资源、矿产资源、能源资源、森林资源；②遭遇“资源诅咒”的省处于“资源丰度一经济发展”坐标系第Ⅳ象限。并绝大多数都位于西部地区和东北地区；③各省人均GDP与综合资源丰度的对数成反比．我国资源丰裕度与经济发展水平成相反的变化趋势；④自然资源对于经济增长的影响作用往往是通过多种机制共同作用的结果．中国资源诅咒的传导机制主要包括“荷兰病”效应、制度效应、“挤出”效应以及区位和交通因素等方面。     

高等植物细胞中的钙通道

钙通道在高等植物细胞中参与众多的信号转导过程,对钙通道的研究最近几年获得长足的进步：不仅在质膜中直接发现了电位依赖性的钙通道、牵张刺激激活的机械敏感性钙通道等,而且在液泡膜中发现了众多具有不同开放调控机制的钙通道：受化学信使控制的钙释放通道、电位依赖性钙通道、钙离子诱导的钙释放通道．本文对高等植物细胞中钙通道的研究进行了综述     

不同传输通道下珠江三角洲臭氧与前体物非线性响应关系

高度城市化的珠三角地区臭氧污染频发,臭氧污染的非线性、区域性以及气象过程影响使臭氧精确防控面临巨大挑战.本研究利用臭氧源解析技术OSAT,分析不同传输通道下珠三角臭氧敏感区分布差异,量化城市间的臭氧传输贡献,并通过敏感性试验,探讨珠三角及典型城市的臭氧污染控制策略.结果表明,静风条件下,VOCs敏感区集中在珠三角中部城...     

合肥市冬季颗粒物污染传输通道分析及通量研究

综合前后向轨迹聚类分析、激光雷达探测传输量及典型案例,系统分析2018—2020年冬季合肥市主要传输型重污染过程,揭示合肥大气污染输送通道的主要特征和污染期间PM_2.5的传输通量。结果表明：合肥市冬季污染主要输入通道分别为京津冀-山东西部-安徽北部-合肥(35%)、山东南部-安徽北部-南京-合肥(26%)、内蒙古-河北-山东-江苏中部-合肥(24%)、内蒙古-山西-河北南部-河南-安徽北部-合肥(15%);主要输出通道为合肥-六安或安庆-湖北-江西(54%)、合肥-安徽北部-江苏北部(18%)、合肥-河南南部-陕西(17%)、合肥-上海或浙江-海上(11%)。对激光雷达监测结果采用像素检测法分析,结果表明2018—2020年污染传输过程的平均传输通量分别可达20.3、33.7、19.5 t/h,年际差异较大。外源传输通量较高时的主导风向为偏北风,并且风速为3.1 m/s左右。合肥市处于安徽省自北向南污染传输通道的中游区域,受上游城市传输影响显著,典型污染传输型的平均传输通量可比上游城市(淮北市)低57.6%,比下游城市(池州市)高25.5%,且污染过程中常伴随PM...     

DETECTING CUMULATIVE EFFECTS ON HEADWATER STREAMS IN THE ROUTT NATIONAL FOREST,COLORADO1

ABSTRACT: This study evaluated the use of a modified pebble count procedure (Bevenger and King, 1995) to detect cumulative watershed effects on headwater streams in the Routt National Forest in northcentral Colorado. The 42 sample reaches were stratified by disturbance (reference or disturbed) and geologic terrene (granitic or mixed sedimentary-volcanic). Water surface slope was a significant control on the number of fine particles in the reference reaches in both terranes, and the data from the disturbed reaches were adjusted accordingly. The disturbed reaches in the granitic terrene generally had a higher percentage of fine particles, and the adjusted number of fine particles was significantly correlated with the number of road crossings. Disturbed reaches in the sedimentary-volcanic (s-v) terrane generally did not have significantly more fine particles, nor were the adjusted numbers of fine particles significantly correlated with any management index. The lack of significant trends in the s-v streams is probably due to differences in weathering between the two rock types, and the location of the sample reach relative to sedimentary outcrops. Two other procedures were also used to assess cumulative watershed effects, with the Pfankuch channel stability rating yielding stronger and more consistent differences between the reference and the disturbed streams than the Tarzwell substrate ratio. We conclude that it may be difficult to define a standard reference condition, and that the number of road crossings is more strongly correlated with the number of fine particles than equivalent clearcut area.     

Bioinspired and biomimetic membranes for water purification and chemical separation: A review

•The history of biological and artificial water channels is reviewed. •A comprehensive channel characterization platform is introduced. •Rationale designs and fabrications of biomimetic membranes are summarized. •The advantages, limitations, and challenges of biomimetic membranes are discussed. •The prospect and scalable solutions of biomimetic membranes are discussed. Bioinspired and biomimetic membranes that contain biological transport channels or attain their structural designs from biological systems have been through a remarkable development over the last two decades. They take advantage of the exceptional transport properties of those channels, thus possess both high permeability and selectivity, and have emerged as a promising solution to existing membranes. Since the discovery of biological water channel proteins aquaporins (AQPs), extensive efforts have been made to utilize them to make separation membranes–AQP-based membranes, which have been commercialized. The exploration of AQPs’ unique structures and transport properties has resulted in the evolution of biomimetic separation materials from protein-based to artificial channel-based membranes. However, large-scale, defect-free biomimetic membranes are not available yet. This paper reviews the state-of-the-art biomimetic membranes and summarizes the latest research progress, platform, and methodology. Then it critically discusses the potential routes of this emerging area toward scalable applications. We conclude that an appropriate combination of bioinspired concepts and molecular engineering with mature polymer industry may lead to scalable polymeric membranes with intrinsic selective channels, which will gain the merit of both desired selectivity and scalability.     

Expert views on sustainability and technology implementation

The role of non-timber forest products in sustaining rural economies of the southern African region has been underestimated because of inadequate policy recognition. As a result, factors affecting the sustainability of these important resources are being undermined. The aim of the paper is to examine trade in two selected NTFPs and implications for sustaining the resource base in Zimbabwe and South Africa. In eastern Zimbabwe, baobab (Adansonia digitata) bark is harvested for craft purposes, but in danger of destruction in the short term as a result of harvesting and trade arrangements. Unless appropriate harvesting and marketing mechanisms including harvesting cycles and adaptive management are adopted, the baobabs and livelihoods of humans will be threatened in the next decade. For wood products from communal woodlands in the South African study, uncontrolled trade poses danger to sustaining the natural woodlands. In both case studies, the role of non-resident NTFP dealers is a source of inevitable threat in promoting sustainable harvesting and trade. Market forces of demand and supply factors are identified as opportunities or threats and presented in a conceptualised framework. Additionally, the NTFP sector management will need to include opportunistic improvement of small-scale agropastoralism.