The stream order of main river depends upon the threshold value taken for upstream drainage area to generate the 1st order stream in any basin. If the threshold value is taken as high as more than the half of the total area of basin, the main river will become 1st order. On the other side, if threshold value of upstream drainage area is reduced, the stream order of main river goes on increasing.
so the selection of threshold value, there may be two criteria-
1) based on percentage area of total basin
2) constant value irrespective of basin area
please suggest me if there is any universal criteria.