Over-exploited groundwater is expected to remain the predominant source of domestic water in suburban areas of Hanoi, Vietnam. In order to evaluate the effect on groundwater recharge, of decreasing surface-water bodies and land-use change caused by urbanization, the relevant groundwater systems and recharge pathways must be characterized in detail. To this end, water levels and water quality were monitored for 3 years regarding groundwater and adjacent surface-water bodies, at two typical suburban sites in Hanoi. Stable isotope (δ18O, δD of water) analysis and hydrochemical analysis showed that the water from both aquifers and aquitards, including the groundwater obtained from both the monitoring wells and the neighboring household tubewells, was largely derived from evaporation-affected surface-water bodies (e.g., ponds, irrigated farmlands) rather than from rivers. The water-level monitoring results suggested distinct local-scale flow systems for both a Holocene unconfined aquifer (HUA) and Pleistocene confined aquifer (PCA). That is, in the case of the HUA, lateral recharge through the aquifer from neighboring ponds and/or irrigated farmlands appeared to be dominant, rather than recharge by vertical rainwater infiltration. In the case of the PCA, recharge by the above-lying HUA, through areas where the aquitard separating the two aquifers was relatively thin or nonexistent, was suggested. As the decrease in the local surface-water bodies will likely reduce the groundwater recharge, maintaining and enhancing this recharge (through preservation of the surface-water bodies) is considered as essential for the sustainable use of groundwater in the area.
A numerical technique is presented to estimate ultimate skin friction of a driven pile using instrumentation installed at the top and bottom of a pile. The scheme is based on an analytical solution of the 1D wave equation with static skin friction and damping along with a genetic algorithm for solution. Specifically, acceleration and strains measured at both the top and bottom of the pile are used to develop an observed Green's function, which is matched to an analytical Green's function, which is a function of secant stiffness and viscous damping. Requiring 1–3 s of analysis time per blow, the algorithm provides a real time assessment of average skin friction along the pile. The technique was applied to four driven piles having ultimate skin frictions varying from 700 to 2000 kN, with the predicted skin frictions generally consistent with measured static load test results. 相似文献
A first account of paleontological data from three Cenozoic on-shore basins in Northern Vietnam, i.e. the Na Duong, Cao Bang, and Hang Mon basins, reveals a rich fossil fauna and flora of supposed Oligocene age, offering a great potential for taxonomic, paleoenvironmental, and paleobiogeographic studies. Two excavation campaigns unearthed well-preserved fossil remains of mammals, crocodiles, at least six turtle species, some 20 fish taxa, some other 20 mollusc species, and different plant remains. The majority of these taxa are regarded as new to science. However, close affinities to modern faunas of northern Southeast Asia demonstrate the importance of these fossils for an evaluation of the biological history of this modern biodiversity hot spot. Moreover, the fossil assemblages may help to disentangle the intricate Cenozoic tectonic evolution of Southeast Asia by application of paleobiogeographic modelling. Finally, the discovery of complex paleo-food-webs and the presence of several taxa indicative of certain ecological conditions provide a solid base for autecologic, synecologic and paleoclimatic studies. The potential biostratigraphic value of the macrofauna has to be demonstrated yet, as evolutionary concepts for most of the respective groups have not been proposed to date. 相似文献
Natural Resources Research - River water quality modeling using crucial artificial intelligent (AI) models has become an essential tool for river assessment and management. The simplified approach... 相似文献
The groundwater in the karst region of northeastern Vietnam is found in various structural zones such as the Ha Lang, Song Hien, Hon Gai, Song Lo, Song Gam, and Hoang Lien Son Zones, etc. Results from this study show that groundwater in this region is at different depths: ~120 m deep at Quang Ninh, ~100 m at Lang Son, ~80 m at Cao Bang (The most water-abundant depth observed at Cao Bang varies from 40 to 45 m) while it varies from 18–25 to 80 m deep at Quan Ba (Ha Giang), especially at Meo Vac (Ha Giang), where groundwater is observed at 700–800 m deep (equivalent to local base level of the Nho Que River). Overall, groundwater in the region is fresh with total minerals varying from 250 to 400 mg/l; except for the coastal area of Quang Ninh, where groundwater is characterized by much higher total minerals (M = 3–18 g/l) due to the mixing with the saline sea water. The chemistry of water in the region demonstrates that the water is mainly bicarbonate with a [HCO3?] concentration varying from 150 to 265 mg/l, pH is of 6.5–8.1, and its hardness is of 3.7–6.0 meq/l. 相似文献
Computational Geosciences - We propose several numerical approaches building on upstream mobility two-point flux approximation finite volumes to solve Richards’ equation in domains made of... 相似文献
The iGeoTrans is an iOS application designed for navigation purposes for iPhone, iPad and iPod Touch. This application uses Global Positioning System (GPS), Assisted GPS system, GLONASS, Wi-Fi and Cellular Network for positioning. The iGeoTrans has included datum transformations and map projections that enable users to convert the collected data between different coordinate systems for almost all areas in the world. In addition, other features are also included such as distance, area measurements, and GPS results could be exported to the AutoCad dxf format for GIS softwares. The average horizontal and vertical root mean square errors (RMSEs) for the static test are around 4.11 and 3.51?m, respectively. The horizontal RMSE for the dynamic outdoor test is around 2.72?m. The iGeoTrans application can be used to support surveying, mapping and geosciences fieldworks for any area in the world. 相似文献