# Energy Engineering Questions and Answers – Hydrographs – 1

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This set of Energy Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Hydrographs – 1”.

1. What do you call a graph which is plotted for discharge versus time?
a) Snow Graph
b) Hydrograph
c) Rain graph
d) Fluid graph

Explanation: The graph showing discharge of flowing water with respect to time for a specific time is known as hydrograph. The time period for discharge hydrograph may be hour, day, week or month. The discharge may m¬¬3/sec or day per second meter.

2. Choose the correct sentence about information available from hydrograph among the following options?
a) The mean annual runoff or mean runoff each week of the year
b) Total volume at that instant, as the area under hydrograph indicates the force of water during the duration
c) Rate of flow at any particular time during the duration period
d) Mean runoff for each month

Explanation: Mean runoff for each month is available. As compared to all other option, they would be- i) The mean annual runoff or mean runoff each month of the year. ii) Total volume at that instant, as the area under hydrograph indicates the volume of water during the duration. iii) Rate of flow at any instant during the duration period.

3. What does hydrograph based on day gives?
a) Idea about flood period during the month
b) Idea of rainfall
c) Idea of draught during the year
d) Idea of scarcity of water in the upcoming year

Explanation: The hydrograph can be drawn taking day, month or year. The hydrograph on the basis of day gives an idea of the flood period during the month. The hydrograph on basis of month gives an idea about the dry period of the year.
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4. What information does the year wise hydrograph gives?
a) Draught
b) Heavy rainfall
c) Rising cold
d) Water scarcity

Explanation: The hydrograph can be drawn taking Day, month or year as time axis. The hydrograph based on year wise data gives information concerning the lean or draught year. This is very essential for deciding the location and size of hydel power plant.

5. When is the Hydrograph called as a unit hydrograph?
a) When 1cm of runoff is resulted from a rain fall
b) When 3cm of runoff is resulted from rainfall
c) When 1mm of runoff is resulted from rainfall
d) When 3mm of runoff is resulted from rainfall

Explanation: If the rainfall distribution in the storms is similar with respect to time and area, the ordinate of each hydrograph will be proportional to volume of runoff. The unit hydrograph is a hydrograph with a volume of 1cm runoff resulting from a rainfall of specified duration and a real pattern.

6. Unit hydrograph was explained by Sherman in which year?
a) 1925
b) 1928
c) 1932
d) 1945

Explanation: This unit hydrograph principle was expressed by Sherman in 1932; he introduced the theory of unit hydrograph. He pointed out that all hydrographs have same time resulting from rainfalls of the given duration.

7. Hydrographs of similar rainfalls will be similar in shape.
a) True
b) False

Explanation: Hydrographs of various rainfalls will be similar in shape. The ordinates are proportional to the runoff volumes within a fixed duration and similar rate and a real distribution of rainfall. However, the occurrence of identical rainfall is very rare.

8. What is unit hydrograph helpful in?
a) Estimating runoff from a basin
b) Estimating no of days of rain fall
c) Knowing the draught months in a year
d) In deciding the land for hydel power plant

Explanation: Unit hydrograph is helpful in estimating runoff from a basin for a storm of given duration. It is also helpful in predicting the expected flood flow from a catchment if rainfall intensity in the catchment is known.

9. What is the theoretical number of unit hydrographs for given basin?
a) 500
b) 2900
c) 36000
d) infinite

Explanation: The number of unit hydrographs for a given basin is theoretically infinite. This is because there may be one unit hydrograph for possible duration of rainfall and every possible distribution pattern of rainfall in the basin.

10. Above which range should be the unit hydrographs be used?
a) Around 5000 sq km
b) Over 2500 sq km
c) Around 4000 sq km
d) Below 5000 sq km

Explanation: In practice, only a limited number of unit hydrographs are used for a given basin. It is also common practice to neglect the variations in rainfall distribution within the basin area. Hence it is not advisable to use unit hydrograph method for basins over 5000 sq km.

11. The unit hydrographs can be successfully applied to basin areas of what sq km?
a) 15000 sq km
b) 10000 sq km
c) 3000 sq km
d) 25000 sq km

Explanation: The unit hydrographs can be applied successfully to basin areas as large as 25000 sq km. provided distribution patterns are classified into different types and unit hydrographs are developed for each type it is always preferable to divide the large basin into sub-areas, utilize hydrographs for each sub area independently and combine the resulting hydrographs together.

12. The magnitude of runoff as ordinates against the corresponding percentage of time as abscissa gives ________
a) Mass duration curve
c) Power duration curve
d) Flow duration curve

Explanation: The magnitude of runoff as ordinates against the corresponding percentage of time as abscissa gives Flow duration curve. If the magnitude on the ordinate is the potential power contained in the stream flow, then the curve is known as power duration curve.

13. What is DWF?
a) Deep water flow
b) Dry weather flow
c) Drawing web format
d) Dam water flood

Explanation: Dry weather flow is a waste water flow in a sewer system during dry weathers with minimum filtration process while entering the ground. Insufficient flow velocities during DWF can increase retention.

14. What does CN stands for in hydrology?
a) Cyanide
b) Channel number
c) Cumulonimbus
d) Carbon nano-tube

Explanation: Cumulonimbus, from the Latin cumulus and nimbus, is a dense, towering vertical cloud associated with thunderstorms and atmospheric instability, forming from water vapor carried by powerful upward air currents.

15. What does ADF stand for in hydrology?
a) Automatic direction finder
b) Average daily flow
c) Average duration flow
d) Annual dry flow

Explanation: The daily effluent flow is required to calculate the area of septic field or the length of trench requires. It is also referred as the amount of water let out of a reservoir on the daily basis as per the requirement and demand.

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