Analytical investigation of the exact groundwater divide between rivers beyond the Dupuit–Forchheimer approximation     

Ruoyi Li  Xu-Sheng Wang 《水文研究》2021,35(2):e14036

The groundwater divide is a key feature of river basins and significantly influenced by subsurface hydrological processes. For an unconfined aquifer between two parallel rivers or ditches, it has long been defined as the top of the water table based on the Dupuit–Forchheimer approximation. However, the exact groundwater divide is subject to the interface between two local flow systems transporting groundwater to rivers from the infiltration recharge. This study contributes a new analytical model for two-dimensional groundwater flow between rivers of different water levels. The flownet is delineated in the model to identify groundwater flow systems and the exact groundwater divide. Formulas with two dimensionless parameters are derived to determine the distributed hydraulic head, the top of the water table and the groundwater divide. The locations of the groundwater divide and the top of the water table are not the same. The distance between them in horizontal can reach up to 8.9% of the distance between rivers. Numerical verifications indicate that simplifications in the analytical model do not significantly cause misestimates in the location of the groundwater divide. In contrast, the Dupuit–Forchheimer approximation yields an incorrect water table shape. The new analytical model is applied to investigate groundwater divides in the Loess Plateau, China, with a Monte Carlo simulation process taking into account the uncertainties in the parameters.  相似文献   

The Natural Resource Management Planning Portal: Perspectives for NRM Planning and Reporting     

Birgita D. Hansen  Peter G. Dahlhaus  Robert G. Milne  Andrew D. MacLeod  Chris Pitfield 《社会与自然资源》2019,32(6):709-719

Natural Resource Management (NRM) is often conducted as a partnership between government and citizens. In Australia, government agencies formulate policy and fund implementation that may be delivered on-ground by community groups (such as Landcare). Since the late 1980s, over AUS$8b of Commonwealth investment has been made in NRM. However, quantitative evidence of environmental improvements is lacking. The NRM Planning Portal has been developed to (1) provide an online spatial information system for sharing Landcare and agency data; and (2) to facilitate NRM priority setting at local and regional planning scales. While the project successfully federates Landcare NRM activity data, challenges included (1) unstructured, non-standardized data, meaning that quantitative reporting against strategic objectives is not currently possible, and (2) a lack of common understanding about the value proposition for adopting the portal approach. Demonstrating the benefit of technology adoption is a key lesson for digital NRM planning.  相似文献   

Forest operations,tree species composition and decline in rainfall explain runoff changes in the Nacimiento experimental catchments,south central Chile     

Andrés Iroumé  Julia Jones  James C. Bathurst 《水文研究》2021,35(6):e14257

Few long-term studies have explored how intensively managed short rotation forest plantations interact with climate variability. We examine how prolonged severe drought and forest operations affect runoff in 11 experimental catchments on private corporate forest land near Nacimiento in south central Chile over the period 2008–2019. The catchments (7.7–414 ha) contain forest plantations of exotic fast-growing species (Pinus radiata, Eucalyptus spp.) at various stages of growth in a Mediterranean climate (mean long-term annual rainfall = 1381 mm). Since 2010, a drought, unprecedented in recent history, has reduced rainfall at Nacimiento by 20%, relative to the long-term mean. Pre-drought runoff ratios were <0.2 under 8-year-old Eucalyptus; >0.4 under 21-year-old Radiata pine and >0.8 where herbicide treatments had controlled vegetation for 2 years in 38% of the catchment area. Early in the study period, clearcutting of Radiata pine (85%–95% of catchment area) increased streamflow by 150 mm as compared with the year before harvest, while clearcutting and partial cuts of Eucalyptus did not increase streamflow. During 2008–2019, the combination of emerging drought and forestry treatments (replanting with Eucalyptus after clearcutting of Radiata pine and Eucalyptus) reduced streamflow by 400–500 mm, and regeneration of previously herbicide-treated vegetation combined with growth of Eucalyptus plantations reduced streamflow by 1125 mm (87% of mean annual precipitation 2010–2019). These results from one of the most comprehensive forest catchment studies in the world on private industrial forest land indicate that multiple decades of forest management have reduced deep soil moisture reservoirs. This effect has been exacerbated by drought and conversion from Radiata pine to Eucalyptus, apparently largely eliminating subsurface supply to streamflow. The findings reveal tradeoffs between wood production and water supply, provide lessons for adapting forest management to the projected future drier climate in Chile, and underscore the need for continued experimental work in managed forest plantations.  相似文献   

基于ArcGIS Engine与ArcGIS Server的海域定级信息管理系统设计与开发   总被引：1，自引：0，他引：1  

卞盼盼  白珏莹  付丹丹  王英刚  周立 《海洋科学》2018,42(6):12-17

以Visual Studio 2012为平台,利用ArcGIS Engine强大的空间分析功能,以C#为开发语言结合第三方插件设计开发海域定级决策子系统,实现了不同用海方式海域的自动化定级,对海域定级基础数据、过程数据和结果数据进行综合管理,构建了一个具有一定实用价值的海域定级信息管理系统原型;此外,利用WebGIS将海域定级决策子系统分析生成的结果数据发布成服务,实现海域定级信息共享子系统。本研究为海域定级提供智能化平台,提高对海域定级及评估效率,有利于海洋可持续发展。  相似文献   

Terrestrial discharge influences microbioerosion and microbioeroder community structure in coral reefs     

SA Mwachireya  M Carreiro-Silva  BE Hartwick  TR McClanahan 《African Journal of Marine Science》2018,40(1):25-42

Microbioerosion rates and microbioeroder community structure were studied in four Kenyan protected coral-reef lagoons using shell fragments of Tridacna giant clams to determine their response to the influence of terrestrial run-off. Fourteen different microbioeroder traces from seven cyanobacteria, three green algae and four fungi species were identified. The river discharge-impacted reef and ‘pristine’ reef showed similar composition but higher microbioeroder abundance and total cyanobacteria- and chlorophyte-bioeroded areas when compared with the other study reefs. Cyanobacteria dominated during the north-east monsoon (NEM) relative to the south-east monsoon (SEM) season, with algae and cyanobacteria being major microbioeroders in the river-impacted and pristine reefs. The rate of microbioerosion varied between 4.3 g CaCO3 m^?2 y^?1 (SEM) and 134.7 g CaCO₃ m^?2 y^?1 (NEM), and was highest in the river-impacted reef (127.6 g CaCO₃ m^?2 y^?1), which was almost double that in the pristine reef (69.5 g CaCO₃ m^?2 y^?1) and the mangrove-fringed reef (56.2 g CaCO₃ m^?2 y^?1). The microbioerosion rates measured in this study may not be high enough to cause concern with regard to the health and net carbonate production of Kenya’s coral reefs. Nevertheless, predicted increases in the frequency and severity of stresses related to global climate change (e.g. increased sea surface temperature, acidification), as well as interactions with local disturbances and their influence on bioerosion, may be increasingly important in the future.  相似文献   

长江经济带城市土地利用效率的影响因素及其空间溢出效应研究     

周晓艳  章芳  张苗苗 《测绘与空间地理信息》2020,(4):1-6

在人多地少的基本国情下,提高城市土地利用效率是促进区域可持续发展和建设生态文明的内在要求。本文在对2009-2016年长江经济带108个地级及以上城市土地利用效率的研究基础上,采用空间相关性研究方法分析了时空分布格局,通过构建空间杜宾模型(SDM)对其空间溢出效应进行分析。研究结果表明:1)2009-2016年长江经济带城市土地利用效率整体呈现稳定上升趋势;基本呈现以上海、南京、武汉等不同城市群中心城市向外逐步降低的“中心-外围”的分布格局。2)通过构建空间杜宾模型分析发现,经济发展水平、产业结构有显著为正的直接效应和溢出效应;土地市场化水平有显著为正的溢出效应;城市固定资产投资对城市土地利用效率具有正的直接效应和负的溢出效应;政府财政支出水平则对城市土地利用效率的直接效应和溢出效应均不明显。3)不同影响因素对经济带上中下游城市土地利用效率的空间效应存在一定差异性。  相似文献   

风和径流量对长江口缺氧影响的数值模拟   总被引：1，自引：1，他引：0  

郑静静  刘桂梅  高姗  李云  李志杰 《海洋学报》2018,40(9):1-17

受自然和人类活动的影响，海洋缺氧现象日益严重，威胁着海洋生态环境，海洋缺氧问题已经引起了人们的广泛关注。本文应用区域海洋模式并耦合生态模式，对东海的生态系统进行了数值模拟和分析研究。与观测数据比较显示，该模型能较好地模拟长江口外生态变量的分布趋势。另外本文通过设置不同敏感性实验，探讨风和径流量对长江口底层缺氧现象的影响，结果分析表明，风和径流量对长江口外缺氧区的形成有显著的影响。径流量变化虽然对长江口外缺氧区的季节变化影响并不显著，但是对缺氧区域面积却存在显著的影响。径流量增加，水体层化增强，表层叶绿素浓度增加，最终导致缺氧区域范围扩展；径流量减小，水体层化减弱，表层叶绿素浓度减小，缺氧区域范围缩小。风向和风速的改变不仅影响长江口外缺氧区的季节变化，还影响缺氧区域面积。  相似文献   

Flexural deformation controls on Late Quaternary sediment dispersal in the Garo-Rajmahal Gap,NW Bengal Basin     

Jean-Louis Grimaud  Celine Grall  Steven Goodbred  Michael S. Steckler  Ryan Sincavage  Jennifer L. Pickering  Chris Paola  Leonardo Seeber  Md. Saddam Hossain 《Basin Research》2020,32(5):1242-1260

Subsurface deformation is a driver for river path selection when deformation rates become comparable to the autogenic mobility rate of rivers. Here we combine geomorphology, soil and sediment facies analyses, and geophysical data of the Late Quaternary sediments of the central Garo-Rajmahal Gap in Northwest Bengal to link subsurface deformation with surface processes. We show variable sedimentation characteristics, from slow rates (<0.8 mm/year) in the Tista megafan at the foot of the Himalaya to nondeposition at the exposed surface of the Barind Tract to the south, enabling the development of mature soils. Combined subsidence in the Tista fan and uplift of the Barind Tract are consistent with a N-S flexural response of the Indian plate to loading of the Himalaya Mountains given a low value of elastic thickness (15–25 km). Provenance analysis based on bulk strontium concentration suggests a dispersal of sediment consistent with this flexural deformation—in particular the abandonment of the Barind Tract by a Pleistocene Brahmaputra River and the current extents of the Tista megafan lobes. Overall, these results highlight the control by deeply rooted deformation patterns on the routing of sediment by large rivers in foreland settings.  相似文献   

Census survey approach to quantifying īnanga spawning habitat for conservation and management     

Shane Orchard  Michael J. Hickford 《新西兰海洋与淡水研究杂志》2018,52(2):284-294

Here, we describe a methodology for quantifying the spawning habitat of īnanga (Galaxias maculatus), a protected native fish species. Our approach is demonstrated with a survey of the Heathcote/ōpāwaho following the Canterbury earthquakes that produced unexpected findings. Spawning habitat was detected over a 2.5?km reach and the area occupied by spawning sites (75m²) was much larger than in previous records (ca.?21m²). Sites dominated by the invasive Phalaris arundinaceae were found to support high egg numbers. Spawning has not previously been recorded on this species and it is identified in the literature as a threat to spawning habitat. Considerable spatio-temporal variation was also detected in the location of spawning sites and pattern of egg production. Together, these aspects illustrate the need for a comprehensive survey methodology to reliably quantify spawning habitat. The Heathcote/ōpāwaho example shows the utility of our census approach for achieving this, and supporting habitat conservation objectives.  相似文献   

基于云存储技术的海岛信息管理和 展示平台设计与实现     

孙超  汪愿愿  潘增弟  孙亚伟 《海洋通报》2019,38(2):233-240

随着海岛遥感影像数据的不断积累,传统数据存储管理方法越来越难以满足需求。针对上述问题,利用云存储技术对海岛影像数据进行分块组织,建立分布式海岛影像数据集,并在优化数据存储的同时,设计了一套海岛信息多形式展示平台。实现了信息检索、数据传输与审核、分析评价、成果展示和共享等功能。  相似文献