# Engineering Hydrology Questions and Answers – Runoff and Surface Runoff and Yield of a Drainage Basin

This set of Engineering Hydrology Multiple Choice Questions & Answers (MCQs) focuses on “Runoff and Surface Runoff and Yield of a Drainage Basin”.

1. What is streamflow?
a) Runoff
b) Surface runoff
c) Direct runoff
d) Drainage

Explanation: Streamflow is actually known as runoff. It is the total amount of water flowing into the stream channel. It is also known as discharge.

2. Runoff and surface runoff are always the same estimates and defines the total amount of water that flows into the stream channel.
a) True
b) False

Explanation: Runoff and surface runoff are not always the same estimates. Runoff defines the total amount of water that flows into the stream channel. Surface runoff is that amount of water that flows into the stream channel without first percolating into the water table.

3. Yield of a drainage basin considers the amount of water flowing into the stream channel for long periods.
a) False
b) True

Explanation: Yield of a drainage basin is the amount of water flowing into the stream channel for long periods. It is similar to runoff but the only difference is that runoff is measured for small periods like the amount of water flowing into the stream channel per second.

4. What is the unit of yield of drainage basin?
a) m3/s
b) m3
c) m/s
d) M m3/hr

Explanation: Yield of a drainage basin gives the volume of water which flows into the stream channel. It is similar to runoff in this case but the difference is it takes account for long periods. So, it gives the volume of water flowing into the stream channel per year. So, its unit is M m3/hr.

5. The water that flows directly over ground surface is known as ________________
a) Direct surface runoff
b) True surface runoff
c) Surface runoff
d) Virtual surface runoff

Explanation: The surface runoff (SRO) is divided into two types in certain areas. One is true surface runoff and the other is sub-surface runoff. When water directly flows over ground surface then it is known as true surface runoff.

6. When surface runoff infiltrates through soil and before entering the water table flows into the stream channel then it is known as _____________
a) Direct runoff
b) True surface runoff
c) Sub surface runoff
d) Runoff

Explanation: The type of surface runoff in which the water infiltrates through soil, moves laterally and before entering the water table it flows into the stream channel. This type of surface runoff is known as sub surface runoff. It flows so quickly into the stream channel that it is difficult to distinguish between true surface runoff and sub surface runoff.

7. Ground water flow is often times long delayed before it reaches the stream channel.
a) True
b) False

Explanation: Sub surface runoff is that type of surface runoff which quickly reaches the stream before it enters the ground water table. Ground water runoff takes more time or is often delayed before it reaches the stream. So, sub surface runoff is treated as a part of surface runoff.

8. Which one of the following is not a constituent of runoff of river stream?
a) Base flow
b) Surface runoff
c) Direct precipitation
d) Infiltration

Explanation: The runoff of river stream consists of three parts which are as follows:
1. Direct precipitation on the surface
2. Surface runoff
3. Base flow
Direct precipitation on the surface is often ignored as the amount of it is very small as compared to the other constituents.

9. Direct precipitation is of huge amount so it is considered to be the largest constituent of runoff of river stream.
a) True
b) False

Explanation: The constituents of runoff are direct precipitation on the surface, Base flow and surface runoff. Among the constituents, direct precipitation is of very small quantity depending on the lake areas. The lake area of the rivers is large enough so more evaporation takes place in balance to precipitation. So, while calculating runoff of river stream, direct precipitation on the surface is avoided.

10. What is the formula of river stream runoff?
a) Surface runoff + base flow
b) Surface runoff + base flow + direct precipitation on the surface
c) Base flow + direct precipitation on the surface
d) Surface runoff + infiltration

Explanation: As direct precipitation on the surface is a small quantity so it is ignored in the calculation of river stream runoff. Therefore, river stream runoff is given by:
River stream runoff = Surface runoff + base flow

Sanfoundry Global Education & Learning Series – Engineering Hydrology.

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