Question

A 6 hr storm produced rainfall intensities of 7, 18, 25, 12, 10 and 3 mm/hr in successive one hour

2

intervals over a basin of 800 Km . The resulting runoff is observed to be 2640 hectare-meters.

Determine φ-index for the basin.

A 6 hr storm produced rainfall intensities of 7, 18, 25, 12, 10 and 3 mm/hr in successive one hour

2

intervals over a basin of 800 Km . The resulting runoff is observed to be 2640 hectare-meters.

Determine φ-index for the basin.

Answer 1

Firstly the value of w-index is determined then φ-index value will be evaluated.

SOL 6 hr Storm produced rainfall intensitles of 7,18,25, 12, 10 and 3 now. Sin Successive one hour interval. 25 So, Total Rainfall P=(7+18+25 + 12+10+3) 18 Р 75 mm "Cen/min) hozysugusto 12 10 Area of Basin = 800 km 7 Windex. 3 2 s time (hr) Again, the resulting rundt is obsersed =2640 ha-m : Depth of runoff a 2640 210 4 m3 800 x 106 mm 3.3 1000 m = 33 mm, Now, value of Windex la 75 -33 =7 mm/hr. let us, assume that Ohndex = wondes 7mm/r , with the assumed Value Pinckey = 7 mm/h. It can be seen that ffost and last duration are not the duration of rainfall excers and we will modity the value of $index as follows. & -Index 75 - (7xi) - (341) = 16.25 mm/m 6-1-1 :d-Index value for basin Ps 16:25 mm/m. (Ans). Index Wohndex. Z Notes