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2017


               streambeds to recharge groundwater systems is essential to sustainable management of scarce

               water resources in arid and semi-arid areas. An inverted water table (IWT) can develop under a
               stream in response to the desaturation between the stream and underlying aquifer as the system

               changes from a connected to disconnected status. However, previous studies have suggested that
               the IWT can only occur at the bottom of a low permeability streambed in which only the vertical

               flow between the stream and groundwater during disconnection was assumed. In the present
               study, numerical simulations revealed that the lateral flow induced by capillarity or heterogeneity

               also plays an essential role on interactions between streams and aquifers. Three pathways were
               identified for the transition from connection to disconnection in homogenous systems; notably,

               the lowest point of an IWT can develop not only at the bottom of the streambed but also within
               the streambed or the aquifer in response to the initial desaturation at, above, or below the

               interface between the streambed and aquifer (IBSA), respectively. A sensitivity analysis indicated
               that in wide streams, the lowest point of an IWT only occurs at the bottom of the streambed;

               however, for a stream half width of 1 m above a 6 m thick sandy loam streambed, the lowest
               point occurs in the streambed as stream depth is less than 0.5 m. This critical stream depth

               increases with streambed thickness and decreases with stream width. Thus, in narrow streams the
               lowest point can also develop in a thick streambed under a shallow stream. In narrow streams, the

               lowest point also forms in the aquifer if the ratio of the hydraulic conductivity of the streambed
               to that of the aquifer is greater than the ratio of the streambed thickness to the sum of the

               stream depth and the streambed thickness; correspondingly, the streambed is thin but relatively
               permeable and the stream is deep. Furthermore, in heterogeneous streambed systems, two or

               three pathways can simultaneously occur
               and various parts of the IWT occur at

               distinct positions relative to the IBSA. This
               challenges the commonly held assumption

               that streambed under a disconnected
               stream is always fully saturated, and limits

               the methods which introduce a negative or
               atmospheric pressure value at the IBSA to

               calculate seepage rate or assess stream-aquifer connectivity.
                    论文链接:https://doi.org/10.1016/j.jhydrol.2017.03.011

                    10.High  salinity  facilitates  dolomite  precipitation  mediated  by  Haloferax volcanii


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