LESSON 3.5

Question 1

It is the rainfall at a single station. For small areas less than 50 km2, point rainfall may be taken as
the average depth over the area.

Answer 1

Point rainfall

Question 2

As the rainfall over a
large area is not uniform, the average depth of rainfall over the area is determined by one of the following three
methods:

Answer 2

Arithmetic average method
Thiessen polygon method
The isohyetal method

Question 3

It is obtained by simply averaging arithmetically the amounts of rainfall at
the individual rain-gauge stations in the area

Answer 3

Arithmetic Average Method

Question 4

method attempts to allow for non-uniform distribution of gauges by
providing a weighting factor for each gauge.

Answer 4

Thiessen Polygon Method

Question 5

the point rainfalls are plotted on a suitable base map and the
lines of equal rainfall (isohyets) are drawn giving consideration to orographic effects and storm
morphology

Answer 5

Isohyetal Method