Question

If the base period of a 6-hour hydrograph of a basin is 84 hours, then a 12 hours unit hydrograph derived from this 6 hour unit hydrograph will have a base period of

• A. 72 hours
• B. 78 hours
• C. 84 hours
• D. 90 hours

Answer 1

The correct option is D 90 hours

The 12 hr Unit Hydrograph will be obtained by adding the ordinates of 6-hr and ordinates of 6-hr UH lagged by 6-hr and then dividing the ordinates by 2. So the base period for 12 hr UH will be, $84+6=90hr$.