The observed runoff due to a 12h storm of uniform intensity of 0.5 cm/h was a triangular direct runoff hydrograph of base 64 h and maximum ordinate 30 m3/s. if the catchment area is 120 km2 , the ϕ index for the basin, cm/h is
1
1.20
2
0.26
3
0.52
4
0.88
5
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