Question

What is a falling limb of a synthetic unit hydrograph?

• A. A part of hydrograph where discharge decreases
• B. Peak discharge of hydrograph
• C. A part of hydrograph where discharge increases
• D. The total volume of water in the hydrograph

Hint:

• A hydrograph plots discharge (flow rate) against time.
• Key parts of a hydrograph:
  • Rising limb: Discharge increases.
  • Peak (crest): Maximum discharge.
  • Falling limb (recession limb): Discharge decreases.
• This terminology applies to all types of hydrographs, including storm hydrographs and unit hydrographs (derived or synthetic).

Answer 1

The Correct Option is A

To understand what a falling limb of a synthetic unit hydrograph is, we need to define the components of a hydrograph and how they relate to streamflow.

1. Understanding the Concepts:

- Hydrograph: A graph showing the rate of flow (discharge) versus time past a specific point in a river, stream, or channel.
- Unit Hydrograph: A hydrograph representing the direct runoff from a watershed due to one unit (e.g., 1 inch or 1 cm) of excess rainfall occurring uniformly over the watershed at a uniform rate during a specified period of time.
- Synthetic Unit Hydrograph: A unit hydrograph derived from empirical equations rather than observed data. This is used when observed data is not available.
- Rising Limb (Ascending Limb): The part of the hydrograph where the discharge is increasing.
- Peak Discharge: The maximum discharge on the hydrograph.
- Falling Limb (Recession Limb or Descending Limb): The part of the hydrograph where the discharge is decreasing after the peak.

2. Defining the Falling Limb:

The falling limb represents the period after the peak discharge when the streamflow is receding as the contribution from direct runoff diminishes.

3. Evaluating the Options:

- The falling limb is the part where discharge decreases.
- The peak discharge is a single point, not the falling limb.
- The rising limb is where discharge increases.
- The total volume of water is represented by the area under the entire hydrograph, not just the falling limb.

Final Answer:

A falling limb of a synthetic unit hydrograph is A part of hydrograph where discharge decreases.