31.3.2. W-index

Try these first

1. 1.

   What does the W-index account for that the φ-index does not?

   Hint

   Consider what happens to rainfall before it infiltrates.

2. 2.

   State the formula for calculating the W-index.

   Hint

   What factors influence runoff and infiltration?

3. 3.

   What is the main purpose of the W-index in hydrology?

   • To simplify runoff calculations
   • To account for initial losses
   • To represent rainfall intensity

   Hint

   Think about what happens before water infiltrates.

4. 4.

   True or False: The W-index only works for rural areas.

   • True
   • False

   Hint

   Consider the implications of urbanization.

5. 5.

   In a storm event, total rainfall is found to be 120 mm, with an observed direct runoff of 50 mm, and initial losses estimated at 20 mm over a storm duration of 3 hours. Calculate the W-index and discuss the implications of initial losses on overall runoff estimation.

   Hint

   Plug in the values into the W-index formula.

6. 6.

   Imagine a catchment area that experiences varying absorption rates due to different land uses. Discuss how this variation would affect the application of the W-index.

   Hint

   Consider how land use influences infiltration characteristics.