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Pieter S. Pauw Sjoerd E.A.T.M. van der Zee Anton Leijnse Gualbert H.P. Oude Essink 《Ground water》2016,54(4):521-531
This article deals with the quantification of saltwater upconing below horizontal wells in freshwater lenses using analytical solutions as a computationally fast alternative to numerical simulations. Comparisons between analytical calculations and numerical simulations are presented regarding three aspects: (1) cyclic pumping; (2) dispersion; and (3) finite horizontal wells in a finite domain (a freshwater lens). Various hydrogeological conditions and pumping regimes within a dry half year are considered. The results show that the influence of elastic and phreatic storage (which are not taken into account in the analytical solutions) on the upconing of the interface is minimal. Furthermore, the analytical calculations based on the interface approach compare well with numerical simulations as long as the dimensionless interface upconing is below 1/3, which is in line with previous studies on steady pumping. Superimposing an analytical solution for mixing by dispersion below the well over an analytical solution based on the interface approach is appropriate in case the vertical flow velocity around the interface is nearly constant but should not be used for estimating the salinity of the pumped groundwater. The analytical calculations of interface upconing below a finite horizontal well compare well with the numerical simulations in case the distance between the horizontal well and the initial interface does not vary significantly along the well and in case the natural fluctuation of the freshwater lens is small. In order to maintain a low level of salinity in the well during a dry half year, the dimensionless analytically calculated interface upconing should stay below 0.25. 相似文献
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P.S. Pauw S.E.A.T.M. Van der Zee A. Leijnse J.R. Delsman P.G.B. De Louw W.J. De Lange G.H.P. Oude Essink 《Ground water》2015,53(5):771-781
Groundwater‐surface water (GW‐SW) interaction in numerical groundwater flow models is generally simulated using a Cauchy boundary condition, which relates the flow between the surface water and the groundwater to the product of the head difference between the node and the surface water level, and a coefficient, often referred to as the “conductance.” Previous studies have shown that in models with a low grid resolution, the resistance to GW‐SW interaction below the surface water bed should often be accounted for in the parameterization of the conductance, in addition to the resistance across the surface water bed. Three conductance expressions that take this resistance into account were investigated: two that were presented by Mehl and Hill (2010) and the one that was presented by De Lange (1999). Their accuracy in low‐resolution models regarding salt and water fluxes to a dense drainage network in a confined aquifer system was determined. For a wide range of hydrogeological conditions, the influence of (1) variable groundwater density; (2) vertical grid discretization; and (3) simulation of both ditches and tile drains in a single model cell was investigated. The results indicate that the conductance expression of De Lange (1999) should be used in similar hydrogeological conditions as considered in this paper, as it is better taking into account the resistance to flow below the surface water bed. For the cases that were considered, the influence of variable groundwater density and vertical grid discretization on the accuracy of the conductance expression of De Lange (1999) is small. 相似文献
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Vincent E. A. Post Gualbert Oude Essink Adam Szymkiewicz Mark Bakker Georg Houben Emilio Custodio Clifford Voss 《Hydrogeology Journal》2018,26(6):1767-1770
The Salt Water Intrusion Meetings, or SWIMs, are a series of meetings that focus on seawater intrusion in coastal aquifers and other salinisation processes. 2018 marks the 50th year of the SWIM and the 25th biennial meeting. The SWIM proceedings record half a century of research progress on site characterisation, geophysical and geochemical techniques, variable-density flow, modelling, and water management. The SWIM is positioning itself to remain a viable platform for discussing the coastal aquifer management challenges of the next 50 years. 相似文献
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The aim of this paper is to improve understanding of the adaptive capacity of European agriculture to climate change. Extensive
data on farm characteristics of individual farms from the Farm Accountancy Data Network (FADN) have been combined with climatic
and socio-economic data to analyze the influence of climate and management on crop yields and income and to identify factors
that determine adaptive capacity. A multilevel analysis was performed to account for regional differences in the studied relationships.
Our results suggest that socio-economic conditions and farm characteristics should be considered when analyzing effects of
climate conditions on farm yields and income. Next to climate, input intensity, economic size and the type of land use were
identified as important factors influencing spatial variability in crop yields and income. Generally, crop yields and income
are increasing with farm size and farm intensity. However, effects differed among crops and high crop yields were not always
related to high incomes, suggesting that impacts of climate and management differ by impact variable. As farm characteristics
influence climate impacts on crop yields and income, they are good indicators of adaptive capacity at farm level and should
be considered in impact assessment models. Different farm types with different management strategies will adapt differently. 相似文献
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An automated method for 3D modelling of complex highway interchanges is presented. Laser data and 2D topographic map data have been combined in an innovative 3D reconstruction procedure. Complex situations as shown in this paper demand knowledge to guide the automatic reconstruction. This knowledge has been used in the fusion procedure to constrain the topological and geometrical properties of the reconstructed 3D model. These additions are needed to take care of the lack of data in occluded areas. Laser data has been segmented and filtered before it is fused with map data. In the surface-growing algorithm combining map and laser points, the laser data is assigned to the corresponding road element. Although results are shown using two specific data sources, the algorithm is designed to be capable of dealing with any polygon-based topographic map and any aerial laser scanner data-set. 相似文献
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