Recently, the PVI method has been extensively used on unsteady seepage problems in fracture networks and unsaturated flow problems in porous media  (Hu et al., 2016), where the boundary conditions on the seepage face and soil-atmosphere interfaces are described by a generalized complementary function.
Boundary conditions can be on the pressure head, flux, seepage face, and infiltration boundaries.
To calculate a volumetric flux of SGD ([m.sup.3] [d.sup.-1]), we must first estimate the area of the seepage face
at the head of Waquoit Bay, The length of the seepage face
(1760 m) was obtained from a false-color aerial infrared image (1-m resolution) taken at low tide in the fall of 2002 (Charette, unpubl, data).
The maximum flow from the alluvial seepage face
into the in-pit trenches and sumps was about 100 g/min (380 litres/min).
We also measured N concentrations at the seepage face of the Edgartown Great Pond estuary which lies roughly 500-1000 m downgradient in the groundwater flowpath from the forest.
We collected throughfall, and water from the vadose zone, aquifer, and seepage face from June 2000 to August 2001 and analyzed samples for [NH.sup.+.sub.4], [NO.sup.-.sub.3], and DON concentrations.
We examined small-scale heterogeneity of salinity, ammonium ([NH.sub.4]), nitrate ([NO.sub.3]), dissolved organic nitrogen (DON), and boron in both vertical and horizontal profiles near the sandy seepage face of Edgartown Great Pond (Martha's Vineyard, Massachusetts).
lD, E, F) along the top transect shown in Figure 1 (A, B, C) suggest how groundwater flow interacts with horizontal transportation to determine the small-scale patterns of concentration across the seepage face of this estuary (Fig.
To measure the nitrogen load moving in groundwater from land to estuary, we first determined nitrogen concentrations in samples of groundwater (salinity [less than] 0.5[per thousand]) at the seepage face
of the aquifer.
 analyzed the unsaturated flow and seepage faces by theory models.
Rudolph, "Significance of unsaturated flow and seepage faces in the simulation of steady-state subsurface flow, " Ground Water, vol.
In the areas where this occurs or where high-nitrate water moves out in seepage faces
, deeply rooted trees in Zone 1 or in seepage areas are essential.