diff --git a/Overlap/CMakeLists.txt b/Overlap/CMakeLists.txt
index aec41a35f447756d01b7d2745db9e1fab3bc4d99..25225fc6e585ac88336da95fb95975e58b8b0d8b 100644
--- a/Overlap/CMakeLists.txt
+++ b/Overlap/CMakeLists.txt
@@ -10,8 +10,7 @@ add_executable(eddy_graph eddy_graph.f90
   weight.f90 send_snapshot.f90
   ${CMAKE_SOURCE_DIR}/Common/read_eddy.f90
   ${CMAKE_SOURCE_DIR}/Common/write_eddy.f90
-  ${CMAKE_SOURCE_DIR}/Common/derived_types.f90 unit_edge_m.f90
-  write_edge.f90)
+  ${CMAKE_SOURCE_DIR}/Common/derived_types.f90 unit_edge_m.f90)
 
 target_include_directories(eddy_graph PRIVATE ${fortrangis_INCLUDE_DIR})
 
diff --git a/Overlap/Tests/CMakeLists.txt b/Overlap/Tests/CMakeLists.txt
index b78bd969ba615c48972db45af0444adcc9921bf0..91afd320c0e119e393472f1385c4524db0d27b30 100644
--- a/Overlap/Tests/CMakeLists.txt
+++ b/Overlap/Tests/CMakeLists.txt
@@ -10,8 +10,7 @@ add_executable(test_overlap
   ${CMAKE_SOURCE_DIR}/Common/shp_tr_create.f90 write_overlap.f90
   ${CMAKE_CURRENT_LIST_DIR}/test_overlap.f90
   ${CMAKE_SOURCE_DIR}/Common/shp_tr_open.f90
-  ${CMAKE_SOURCE_DIR}/Common/shp_tr_close.f90 unit_edge_m.f90
-  write_edge.f90)
+  ${CMAKE_SOURCE_DIR}/Common/shp_tr_close.f90 unit_edge_m.f90)
 
 target_link_libraries(test_overlap shapelib_03 geometry contour_531
   gpc_f ezmpi nr_util jumble MPI::MPI_Fortran)
@@ -85,7 +84,7 @@ add_executable(test_write_overlap
   ${CMAKE_SOURCE_DIR}/Common/shp_tr_create.f90
   ${CMAKE_SOURCE_DIR}/Common/write_eddy.f90 write_overlap.f90
   ${CMAKE_CURRENT_LIST_DIR}/test_write_overlap.f90
-  ${CMAKE_SOURCE_DIR}/Common/shp_tr_close.f90 unit_edge_m.f90 write_edge.f90)
+  ${CMAKE_SOURCE_DIR}/Common/shp_tr_close.f90 unit_edge_m.f90)
 
 target_link_libraries(test_write_overlap shapelib_03 contour_531 nr_util jumble)
 target_include_directories(test_write_overlap PRIVATE ${fortrangis_INCLUDE_DIR})
diff --git a/Overlap/Tests/test_overlap.f90 b/Overlap/Tests/test_overlap.f90
index 257c0d25ff6244f46267cc28724ab6193a6d4da7..9ee409088f8d10f37cab55ee20f145c0730d2c19 100644
--- a/Overlap/Tests/test_overlap.f90
+++ b/Overlap/Tests/test_overlap.f90
@@ -15,7 +15,7 @@ program test_overlap
   use shp_tr_close_m, only: shp_tr_close
   use shp_tr_create_m, only: shp_tr_create
   use shp_tr_open_m, only: shp_tr_open
-  use unit_edge_m, only: open_edge_file, unit_edge_cyclo, unit_edge_anti
+  use unit_edge_m, only: open_edge_file, unit_edge
   use write_overlap_m, only: init_interpolated_eddy
 
   implicit none
@@ -98,22 +98,17 @@ program test_overlap
   call open_edge_file(rank = 0)
 
   ! Title lines:
-  write(unit_edge_cyclo, fmt = "(1x, a)") '"predecessor date subscript" ' &
+  write(unit_edge, fmt = "(1x, a)") '"predecessor date subscript" ' &
        // '"predecessor eddy subscript" "successor date subscript" ' &
        // '"successor eddy subscript"'
-  write(unit_edge_cyclo, fmt = *) "k1 i1 k2 i2 weight"
-  write(unit_edge_anti, fmt = "(1x, a)") '"predecessor date subscript" ' &
-       // '"predecessor eddy subscript" "successor date subscript" ' &
-       // '"successor eddy subscript"'
-  write(unit_edge_anti, fmt = *) "k1 i1 k2 i2 weight"
+  write(unit_edge, fmt = *) "k1 i1 k2 i2 weight"
 
   call shp_tr_create(hshp, shp_tr_dir = "SHPC")
   call init_interpolated_eddy
   call overlap(flow, nlon, nlat, periodic, dist_lim, hshp, k = k_test_2, &
        delta = max_delta, j = max_delta + 1)
-  close(unit_edge_cyclo)
-  close(unit_edge_anti)
-  print *, 'Created files "edgelist_cyclo.csv" and "edgelist_anti.csv".'
+  close(unit_edge)
+  print *, 'Created file "edgelist.csv".'
   CALL shp_tr_close(hshp)
   print *, 'Created shapefiles for interpolated eddies in SHPC.'
 
diff --git a/Overlap/Tests/test_write_overlap.f90 b/Overlap/Tests/test_write_overlap.f90
index 8bbaba2bdc03b605c814bfed85a1e9cdc2ff3c25..86b9bf0f7b09bf1fc16dfb45f3b4330aef7cb326 100644
--- a/Overlap/Tests/test_write_overlap.f90
+++ b/Overlap/Tests/test_write_overlap.f90
@@ -5,7 +5,7 @@ program test_write_overlap
   use derived_types, only: shp_tr
   use shp_tr_close_m, only: shp_tr_close
   use shp_tr_create_m, only: shp_tr_create
-  use unit_edge_m, only: open_edge_file, unit_edge_cyclo, unit_edge_anti
+  use unit_edge_m, only: open_edge_file, unit_edge
   use write_overlap_m, only: write_overlap, init_interpolated_eddy
 
   implicit none
@@ -28,14 +28,10 @@ program test_write_overlap
   call open_edge_file(rank = 0)
 
   ! Title lines:
-  write(unit_edge_cyclo, fmt = "(1x, a)") '"predecessor date subscript" ' &
+  write(unit_edge, fmt = "(1x, a)") '"predecessor date subscript" ' &
        // '"predecessor eddy subscript" "successor date subscript" ' &
        // '"successor eddy subscript"'
-  write(unit_edge_cyclo, fmt = *) "k1 i1 k2 i2 weight"
-  write(unit_edge_anti, fmt = "(1x, a)") '"predecessor date subscript" ' &
-       // '"predecessor eddy subscript" "successor date subscript" ' &
-       // '"successor eddy subscript"'
-  write(unit_edge_anti, fmt = *) "k1 i1 k2 i2 weight"
+  write(unit_edge, fmt = *) "k1 i1 k2 i2 weight"
   
   call shp_tr_create(hshp, shp_tr_dir = "SHPC")
   call init_interpolated_eddy
@@ -43,9 +39,8 @@ program test_write_overlap
        i_interp = 10 + [(j_interp, j_interp = 1, delta - 1)], &
        cyclone = .true., coord_extr_1 = coord_extr_1, ssh_extr_1 = ssh_extr_1, &
        coord_extr_2 = coord_extr_2, ssh_extr_2 = ssh_extr_2, w = 0.)
-  close(unit_edge_cyclo)
-  close(unit_edge_anti)
-  print *, 'Created files "edgelist_cyclo.csv" and "edgelist_anti.csv".'
+  close(unit_edge)
+  print *, 'Created file "edgelist.csv".'
   CALL shp_tr_close(hshp)
   print *, 'Created shapefiles in SHPC.'
 
diff --git a/Overlap/eddy_graph.f90 b/Overlap/eddy_graph.f90
index 1d5ae88e264b18e22f459e1d8a4dd40e83337c71..855b0403ea632d285d7ae1defb7dfe5a491c17ba 100644
--- a/Overlap/eddy_graph.f90
+++ b/Overlap/eddy_graph.f90
@@ -14,7 +14,7 @@ program eddy_graph
   use dispatch_snapshot_m, only: dispatch_snapshot
   use get_snapshot_m, only: get_snapshot
   use overlap_m, only: overlap
-  use unit_edge_m, only: open_edge_file, unit_edge_cyclo, unit_edge_anti
+  use unit_edge_m, only: open_edge_file, unit_edge
   use shp_tr_open_m, only: shp_tr_open
   use shp_tr_close_m, only: shp_tr_close
   use shp_tr_create_m, only: shp_tr_create
@@ -206,8 +206,7 @@ program eddy_graph
   CALL shp_tr_close(hshp)
   close(unit_isolated)
   close(unit_number_eddies)
-  close(unit_edge_cyclo)
-  close(unit_edge_anti)
+  close(unit_edge)
   call mpi_finalize 
 
 end program eddy_graph
diff --git a/Overlap/eddy_graph_in.sh b/Overlap/eddy_graph_in.sh
index c7c180c08fa7293cbfeecd0bf470589041b4f4f4..1dd8cf427b61f20f9cef53f35aef788ec0073bdf 100755
--- a/Overlap/eddy_graph_in.sh
+++ b/Overlap/eddy_graph_in.sh
@@ -1,7 +1,7 @@
 #!/bin/bash
 
-# This program creates edgelists and interpolated eddies. You run it
-# only once and it processes both anticyclones and cyclones.
+# This program creates the edge list and interpolated eddies, for a
+# given orientation of eddies.
 
 # Note: no need to sort number_eddies.csv, already sorted by construction.
 
@@ -36,11 +36,9 @@ rank=0
 while ((rank < $1))
 do
     cat number_eddies_$rank.csv >>number_eddies.csv
-    cat edgelist_cyclo_$rank.csv >>edgelist_cyclo_no_header.csv
-    cat edgelist_anti_$rank.csv >>edgelist_anti_no_header.csv
+    cat edgelist_$rank.csv >>edgelist_no_header.csv
     cat isolated_nodes_$rank.txt >>isolated_nodes.txt
-    rm number_eddies_$rank.csv edgelist_@(cyclo|anti)_$rank.csv \
-       isolated_nodes_$rank.txt
+    rm number_eddies_$rank.csv edgelist_$rank.csv isolated_nodes_$rank.txt
     ((rank += 1))
 done
 
@@ -48,18 +46,15 @@ done
 
 export LC_NUMERIC=C # for the sort command
 
-for orientation in cyclo anti
-do
-    cat >edgelist_$orientation.csv <<EOF
+cat >edgelist.csv <<EOF
  "predecessor date" "predecessor eddy subscript" "successor date" "successor eddy subscript"
  d1 i1 d2 i2 weight
-$(sort --key=1 --key=2 --numeric-sort edgelist_${orientation}_no_header.csv)
+$(sort --key=1 --key=2 --numeric-sort edgelist_no_header.csv)
 EOF
-    rm edgelist_${orientation}_no_header.csv 
-done
+rm edgelist_no_header.csv 
 
-echo "Created files \"number_eddies.csv\", \"edgelist_cyclo.csv\", " \
-     "\"edgelist_anti.csv\" and \"isolated_nodes.txt\"."
+echo "Created files \"number_eddies.csv\", \"edgelist.csv\", " \
+     "and \"isolated_nodes.txt\"."
 rm -rf SHPC
 mv SHPC_0 SHPC
 rank=1
diff --git a/Overlap/unit_edge_m.f90 b/Overlap/unit_edge_m.f90
index 3517b6c9b5cdb91133d9d5af50919dc2ed2eca2d..7506d5e58c067c260334b04f8d5a7d64590acb88 100644
--- a/Overlap/unit_edge_m.f90
+++ b/Overlap/unit_edge_m.f90
@@ -2,8 +2,8 @@ module unit_edge_m
 
   implicit none
 
-  integer, protected:: unit_edge_cyclo = - huge(0), unit_edge_anti = - huge(0)
-  ! logical unit numbers for files containing edge lists
+  integer, protected:: unit_edge = - huge(0)
+  ! logical unit numbers for file containing edge list
 
 contains
 
@@ -18,15 +18,9 @@ contains
 
     !--------------------------------------------------------------
 
-    call new_unit(unit_edge_cyclo)
-    write(unit = file, fmt = '("edgelist_cyclo_", i0, ".csv")') rank
-    open(unit_edge_cyclo, file = trim(file), status = "replace", &
-         action  = "write")
-
-    call new_unit(unit_edge_anti)
-    write(unit = file, fmt = '("edgelist_anti_", i0, ".csv")') rank
-    open(unit_edge_anti, file = trim(file), status = "replace", &
-         action  = "write")
+    call new_unit(unit_edge)
+    write(unit = file, fmt = '("edgelist_", i0, ".csv")') rank
+    open(unit_edge, file = trim(file), status = "replace", action  = "write")
 
   end subroutine open_edge_file
   
diff --git a/Overlap/write_edge.f90 b/Overlap/write_edge.f90
deleted file mode 100644
index 69538262fec14b92220859229bc24056453a71ea..0000000000000000000000000000000000000000
--- a/Overlap/write_edge.f90
+++ /dev/null
@@ -1,25 +0,0 @@
-module write_edge_m
-
-  implicit none
-
-contains
-
-  subroutine write_edge(cyclone, k1, i1, k2, i2, w)
-
-    use unit_edge_m, only: unit_edge_cyclo, unit_edge_anti
-
-    logical, intent(in):: cyclone
-    integer, intent(in):: k1, i1, k2, i2
-    real, intent(in):: w
-
-    ! Local:
-    integer unit_edge
-
-    !--------------------------------------------------------------------
-
-    unit_edge = merge(unit_edge_cyclo, unit_edge_anti, cyclone)
-    write(unit_edge, fmt = *) k1, i1, k2, i2, w
-    
-  end subroutine write_edge
-
-end module write_edge_m
diff --git a/Overlap/write_overlap.f90 b/Overlap/write_overlap.f90
index beb30bdc6d8f8b90ff5c7bcead5f338e4a72ddb6..6df325e809041ed1eb5b3a0b69ec1119179d853b 100644
--- a/Overlap/write_overlap.f90
+++ b/Overlap/write_overlap.f90
@@ -19,8 +19,8 @@ contains
     use nr_util, only: twopi
 
     use derived_types, only: shp_tr
+    use unit_edge_m, only: unit_edge
     use write_eddy_m, only: write_eddy
-    use write_edge_m, only: write_edge
 
     TYPE(shp_tr), intent(in):: hshp_interp
     integer, intent(in):: k ! date index
@@ -65,12 +65,12 @@ contains
 
        k_interp = k - delta + j_interp
        call write_eddy(e, hshp_interp, k_interp, i_interp(j_interp))
-       call write_edge(cyclone, k_interp - 1, i_pred, k_interp, &
-            i_interp(j_interp), w)
+       write(unit_edge, fmt = *) k_interp - 1, i_pred, k_interp, &
+            i_interp(j_interp), w
        i_pred = i_interp(j_interp)
     end do
 
-    call write_edge(cyclone, k - 1, i_pred, k, i2, w)
+    write(unit_edge, fmt = *) k - 1, i_pred, k, i2, w
 
   end subroutine write_overlap