Question

Based on the hydrograph above, what is the lag time between the start of the rain and the peak river stage?

a) 1 hour
b) 2 hours
c) 3 hours
d) 4 hours

Answer 1

The lag time between the start of the rain and the peak river stage is 1 hour. Option a is correct.

Step-by-step explanation:

A hydrograph is a graph that shows the flow rate of water (discharge) over time at a specific point. It's like a snapshot of the river's health and activity. Think of it like a heart rate monitor for the river. The hydrograph shows that the rain began at 8am on June 27th, and the river stage peaked at 9am. Therefore, the lag time is 1 hour.

The other options are incorrect:

• Option (b) is incorrect because the river stage does not peak until 9am, which is more than 2 hours after the rain begins.
• Option (c) is incorrect because the river stage does not peak until 9am, which is more than 3 hours after the rain begins.
• Option (d) is incorrect because the river stage does not peak until 9am, which is less than 4 hours after the rain begins.

Therefore, the correct answer is (a).