(a) The Horton's initial infiltration capacity for a catchment is 204 mm/h and the constant infiltration value at saturation is 60 mm/h. For a rainfall in excess of 204 mm/h maintained at this rate for 50 minutes, the infiltrated volume was observed to be 50.6 mm. Determine the value of k in Horton's equation.
(b) Soil infiltration characteristics (based on Horton's equation) and an observed 4-hr duration rainfall values for a 100 ha parkland catchment are given below:
f_{o} = 15 mm/hr, f_{c} = 5.0 mm/hr, k=0.6 hr^{-1}
Duration
0 - 1 hr
1 - 2 hr
2 - 3 hr
3 - 4 hr
Rainfall
in mm
17.5
12.5
15
7.5
i. Calculate the total depth of infiltration
ii. What is the total volume of runoff in m^{3} for the observed rainfall
iii. Estimate f index of the catchment