(a) Compare the advantages and disadvantages of Thiessen Polygon Method and Isohyetal Method for estimating areal average rainfall of a catchment. (b) For the catchment, with highly uneven topography, shown in Worksheet Q1, estimate the areal (average) rainfall due to a storm event occurred over that catchment. The rainfall measurements at gauges A, B, C, D and E are 15 mm, 50 mm, 70 mm, 80 mm and 25 mm, respectively.
(i) Use Thiessen Polygon method
(ii) Use Arithmetic average method
(iii) Comment on the suitability of the above two methods to the given catchment.