# Engineering Hydrology Questions and Answers – Base Flow

This set of Engineering Hydrology Multiple Choice Questions & Answers (MCQs) focuses on “Base Flow”.

1. What is the formula of runoff hydrograph of river?
a) River discharge / Time
b) Surface discharge / Time
c) Direct discharge / Time
d) Drainage discharge / Time

Explanation: The runoff hydrograph of river is given by:
Runoff hydrograph of river = River discharge / Time
River discharge constitutes surface runoff and ground water inflow (base flow).

2. Base flow must be subtracted from runoff graph to obtain ___________
a) Hydrograph
b) Hyetograph
c) Surface runoff graph
d) Drainage graph

Explanation: When base flow is subtracted from runoff graph then surface runoff graph is obtained. So, it is important to note the movement of ground water into the river.

3. Ground water always enters a river and never flows out of it.
a) False
b) True

Explanation: Ground water may enter the river or it may flow out of the river. So, it is very important to note the movement of ground water. This movement depends upon the flow of water into the channel or out of the channel.

4. A channel may behave like two types of stream. What are they?
a) Inflow stream and outflow stream
b) Effluent stream and influent stream
c) Open stream and closed stream
d) Flow stream and stagnant stream

Explanation: Water may flow out of the channel or flow into the channel. Depending on the movement of water in a channel, it is divided into two types of stream. One is effluent stream and the other is influent stream. A single channel may act as both effluent and influent streams.

5. The water table is at a higher level then the river water level in which season?
a) Summer season
b) Autumn season
c) Winter season
d) Spring season

Explanation: A condition is seen when water table reaches a higher level then the river water level. This condition occurs during summer season after the rains have passed away. So, the water flows from ground water inflow into the river.

6. Water level of the water table may be higher or lower than the water level in the river.
a) True
b) False

Explanation: The water level of the ground water table may be at a higher or lower position than the water level in the river. After rainfall, the ground water table reaches to a higher level than the river water level. Similarly, the ground water table is at a lower position than the river water level at our time of a year. Depending upon this level difference water either flows into the river or out of the river.

7. During summer season, river gets more supply of water from ____________
a) Rainfall
b) Ground water inflow
c) Surface runoff
d) Drainage

Explanation: During summer season, the ground water table is at a higher position than the water level of the river. So, due to difference in hydrostatic pressure water flows from ground water table to the river till both the levels equalize. Therefore, during summer season river gets more supply of water from ground water inflow.

8. During which season the ground water table is at a lower position than the river water level?
a) Summer season
b) Winter season
c) Rainy season
d) Autumn season

Explanation: During rainy season, due to heavy rainfall both the levels of river water and ground water table rises but the water in the river exceeds more than the ground water table. So, water moves from the river to the ground water table.

9. What is bank storage?
a) Movement of water to river from ground water inflow
b) Movement of water from river to ground water table
c) Movement of water from ground water table to river
d) Supply of water to the river by rainfall

Explanation: When the river water level is higher than the ground water table then water flows from river to the ground water table. This is called bank storage. At this point of time, water flowing from ground water inflow stops.

10. The outflow from river into the ground water table takes place for ___________
a) Long periods
b) Short periods
c) No periods
d) Yearly

Explanation: When river water flows to the ground water table, it is called bank storage. So, when river water reaches a peak value then only it starts flowing to the ground water table and stops when the bank storage is filled and both the levels equalize that is when the peak value of river water gets lowered. It is similar to infiltration and takes very short time and this amount of water transferred from river is also small so it is ignored. Therefore, only the inflow to the river from the ground water table is considered as baseflow.

Sanfoundry Global Education & Learning Series – Engineering Hydrology.

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