# obsname        type  lay  row  col
  rv1-3-1        RIV    1    3    1
  rv1-4-2        RIV    1    4    2
  rv1-5-3        RIV    1    5    3
  rv1-5-4        RIV    1    5    4
  rv1-6-5        RIV    1    6    5
  rv1-c6         RIV    riv1_c6     # river flow at river boundary "riv1_c6"
  rv1-c7         RIV    riv1_c7     # river flow at river boundary "riv1_c7"
  rv2-upper      RIV    riv2_upper  # sum of river flows at boundaries named "riv2_upper"
  rv2-7-4        RIV    1    7    4
  rv2-8-5        RIV    1    7    5
  rv2-9-6        RIV    1    6    6
