Problem 12-1

A 85-km² catchment has a 4-h concentration time, with isochrones at 1-h intervals resulting in the following time-area histogram:

Time (h)			0-1			1-2			2-3			3-4
Area (km2)			17			21			31			16

Use the time-area method to calculate the outflow hydrograph from the following storm pattern:

Time (h)			0-1			1-2			2-3			3-4			4-5			5-6
Total rainfall (cm/h)			1			2			5			4			3			1

The runoff curve number is CN = 81.

Problem 12-2

Use the Clark method to derive a 2-h unit hydrograph for a catchment with the following time-area diagram:

Time (h)			0-1			1-2			2-3			3-4			4-5			5-6
Area (km2)			20			40			60			40			24			16

Use Δt = 1 h and K = 3 h.

Problem 12-3

Use Example 10-3 in the text (cascade of linear reservoir) to test program EH1000A. Then route the effective rainfall hyetograph of Example 10-3 (with time interval Δt = 6 h) using: (a) K = 12 h and N = 4 and (b) K = 18 h and N = 5.

Problem 12-4

Use program EH1000A to route the following storm hyetograph through a 485-km²catchment.

Time (h)			0-6			6-12			12-18			18-24
Effective rainfall depth (cm)			0.75			1.0			2.0			1.0

Set K = 10 h and N = 4. Report peak outflow and time-to-peak.