feat(swf-gwf): generalize and improve SWF-GWF Exchange (#1910)

* feat(swf-gwf): add upstream weighting for swf-gwf exchange

* additional smoothing for the zdg package and upstream weighting to smoothing parameter for swf-gwf exchange

* minor change from dfn2f90

* fprettify

autotest/test_swf_dfw_gwf.py

@@ -59,9 +59,9 @@ def build_models(idx, test):
     add_gwf_model(sim)
 
     swfgwf_data = [
-        ((0,), (0, 0, 0), 1.0),
-        ((1,), (0, 0, 1), 1.0),
-        ((2,), (0, 0, 2), 1.0),
+        ((0,), (0, 0, 0), 1.0, 1.0),
+        ((1,), (0, 0, 1), 1.0, 1.0),
+        ((2,), (0, 0, 2), 1.0, 1.0),
     ]
     swfgwf = flopy.mf6.ModflowSwfgwf(
         sim,

doc/mf6io/mf6ivar/dfn/exg-swfgwf.dfn

@@ -19,6 +19,15 @@ longname keyword to print swfgwf flows to list file
 description keyword to indicate that the list of exchange flow rates will be printed to the listing file for every stress period in which ``SAVE BUDGET'' is specified in Output Control.
 mf6internal ipr_flow
 
+block options
+name fixed_conductance
+type keyword
+reader urword
+optional true
+longname keyword to indicate conductance is fixed
+description keyword to indicate that the product of the bedleak and cfact input variables in the exchangedata block represents conductance.  This conductance is fixed and does not change as a function of head in the surface water and groundwater models.
+mf6internal ifixedcond
+
 block options
 name obs_filerecord
 type record obs6 filein obs6_filename
@@ -77,7 +86,7 @@ description keyword and integer value specifying the number of SWF-GWF exchanges
 
 block exchangedata
 name exchangedata
-type recarray cellidm1 cellidm2 cond
+type recarray cellidm1 cellidm2 bedleak cfact
 shape (nexg)
 reader urword
 optional false
@@ -91,8 +100,8 @@ in_record true
 tagged false
 reader urword
 optional false
-longname cellid of first cell
-description is the cellid of the cell in model 1 as specified in the simulation name file. For a structured grid that uses the DIS input file, CELLIDM1 is the layer, row, and column numbers of the cell.   For a grid that uses the DISV input file, CELLIDM1 is the layer number and CELL2D number for the two cells.  If the model uses the unstructured discretization (DISU) input file, then CELLIDM1 is the node number for the cell.
+longname cellid of cell in surface water model
+description is the cellid of the cell in model 1, which must be the surface water model. For a structured grid that uses the DIS input file, CELLIDM1 is the layer, row, and column numbers of the cell.   For a grid that uses the DISV input file, CELLIDM1 is the layer number and CELL2D number for the two cells.  If the model uses the unstructured discretization (DISU) input file, then CELLIDM1 is the node number for the cell.
 numeric_index true
 
 block exchangedata
@@ -102,17 +111,26 @@ in_record true
 tagged false
 reader urword
 optional false
-longname cellid of second cell
-description is the cellid of the cell in model 2 as specified in the simulation name file. For a structured grid that uses the DIS input file, CELLIDM2 is the layer, row, and column numbers of the cell.   For a grid that uses the DISV input file, CELLIDM2 is the layer number and CELL2D number for the two cells.  If the model uses the unstructured discretization (DISU) input file, then CELLIDM2 is the node number for the cell.
+longname cellid of cell in groundwater model
+description is the cellid of the cell in model 2, which must be the groundwater model. For a structured grid that uses the DIS input file, CELLIDM2 is the layer, row, and column numbers of the cell.   For a grid that uses the DISV input file, CELLIDM2 is the layer number and CELL2D number for the two cells.  If the model uses the unstructured discretization (DISU) input file, then CELLIDM2 is the node number for the cell.
 numeric_index true
 
 block exchangedata
-name cond
+name bedleak
 type double precision
 in_record true
 tagged false
 reader urword
 optional false
-longname conductance
-description is the conductance between the surface water cell and the groundwater cell.
+longname bed leakance
+description is the leakance between the surface water and groundwater.  bedleak has dimensions of 1/T and is equal to the hydraulic conductivity of the bed sediments divided by the thickness of the bed sediments.
 
+block exchangedata
+name cfact
+type double precision
+in_record true
+tagged false
+reader urword
+optional false
+longname factor used for conductance calculation
+description is the factor used for the conductance calculation.  The definition for this parameter depends the type of surface water model and whether or not the fixed\_conductance option is specified.  If the fixed\_conductance option is specified, then the hydraulic conductance is calculated as the product of bedleak and cfact.  In this case, the conductance is fixed and does not change as a function of the calculated surface water and groundwater head.  If the fixed\_conductance option is not specified, then the definition of cfact depends on whether the surface water model represents one-dimensional channel flow or two-dimensional overland flow.  If the surface water model represents one-dimensional channel flow, then cfact is the length of the channel cell in the groundwater model cell.  If the surface water model represents two-dimensional overland flow, then cfact is the intersection area of the overland flow cell and the underlying groundwater model cell.