If the READ HYD object is used to read an external hydrograph file into the model, then the file must be coded in the correct format. This format is in the same format as the hydrograph files used in OTTHYMO-89/INTERHYMO. Therefore, previously made hydrograph files (from SAVE HYD command) may be used. The file format is described below.

1st line: 2 (1 indicates in/hr, 2 indicates mm/hr)
2nd line: comment line (up to 60 characters in length)
3rd line: 5 (storm time step, min)
4th line: 50 (the catchment area from which the hydrograph was obtained, ha or acre)
5th line: 0.000 (1st hydrograph ordinate, m³/s or cfs)
6th line: 0.100 (2nd hydrograph ordinate, m³/s or cfs)
7th line: 0.200 (3rd hydrograph ordinate, m³/s or cfs)
…th line: …
xth line: 0.100 (xth and last hydrograph ordinate)
last line: -1 (indicates the end of the file).

An example of a Hydrograph data file (test.hyd) is as follows:
2
HYDROGRAPH FROM OUR TEST CATCHMENT
5
50
0
0.000
0.100
0.200
0.300
1.000
1.200
4.500
8.150
10.000
9.500
5.450
2.000
1.000
0.500
0.300
0.100
-1