where Kb is the biological criticality index,Kb is typically within the range of 1-1.6; higher values are chosen for a river whose aquatic ecosystem is considered to be of a particular environmental value.
Kn is the naturalistic criticality index,
S is the catchment area, in km2,
Qspec is the specific flow-rate per unit area of the catchment, in l/(s.km2)
r.green.hydro.discharge q_spec=q_spec output_q_river=discharge k_b=k_b k_n=k_n output_mfd=mfd elevation=elevation output_streams=streams threshold=100000