a) Explain Thiessen's method for calculating average depth of precipi…

Previous year question for Hydrology and Irrigation Engineering.

Question

a) Explain Thiessen's method for calculating average depth of precipitation over an area with a neat sketch. (10)

b) A storm with a $15\text{cm}$ precipitation produced a direct runoff of $8.7\text{cm}$. The time distribution of the storm is as follows:

| Time from start (in hr) | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 |

|---|---|---|---|---|---|---|---|---|

| Incremental rain fall in each hr. (in cm) | 0.6 | 1.35 | 2.25 | 3.45 | 2.7 | 2.4 | 1.5 | 0.75 |

Estimate the $\phi_{\text{index}}$ of the storm (10)