Description: We now consider a catchment with a total area of 9.0 km , where the

Question

Description:

We now consider a catchment with a total area of 9.0 km , where the runtime principle applies. The area is subdivided in 5 regions (A1 to A5) in such a way that every individual area has a runtime of 30 minutes. The areas drain sequentially. A5 is at the top of the catchment and A1 at the bottom of the catchment near the outlet.

We assume that the rain falls uniformly over the catchment, and that the discharge starts immediately after the start of the rain. The discharge only occurs as a result of the net (i.e. eective) rain.

Question 8

Assume rain with a net intensity of 4.5 mm/hr, that lasts (in theory) innitely long. What will eventually be the discharge in [m³/s] at the outlet of the catchment? If applicable, round your answer to two decimals. (Enter the the discharge in [m³/s])

Question 9

Now assume that the rain of 4.5 mm/hr lasts exactly 30 minutes. How large is the discharge in [m³/s] after 30 minutes? If applicable, round your answer to two decimals. (Enter the discharge in [m³/s])

Question 10

Again assume that the rain of 4.5 mm/hr lasts exactly 30 minutes. How large is the discharge in [m³/s] after 60 minutes? If applicable, round your answer to two decimals. (Enter the discharge in [m³/s]).

Explanation / Answer

Answer: 8, 9, 10

Discharge can be calculated by following formula;

Discharge = CiA

where, C= runoff coefficient, i= rainfall intensity, A= area of catchment.

Since, the net intensity of rainfall is 4.5mm/hr for infinite time therefore, discharge are about 40.5m3/s.

And, according to above equation, the discharge would not depend upon time of rainfall, therefore it would be same as 40.5 m3/s.

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