# Irrigation Engineering Questions and Answers – Reservoir Capacity Determination Using Hydrograph and Mass-curve – 1

This set of Irrigation Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Reservoir Capacity Determination Using Hydrograph and Mass-curve – 1”.

1. Average yield of a storage reservoir is the arithmetic average of its ________________
a) firm yields over a long period
b) secondary yields over a long period
c) firm and secondary yields over a long period
d) reservoir yield over a long period

Explanation: Firm yield is the yield corresponding to the most critical year on record. Secondary yield is the water available in excess of the firm yield during years of higher inflows. Average yield is the average of both firm yield and secondary yield.

2. While planning a water supply reservoir as compared to an irrigation reservoir the design yield may be kept __________________
a) higher
b) lower
c) equal
d) lower or higher as per designers discretion

Explanation: The dependability percentage value will depend upon the risk which can be absorbed for the proposed use of water. The city water supply projects can absorb lesser risk as compared to the irrigation projects. Hence, higher percentage values are considered.

3. Yield of a reservoir represents ___________________
a) the inflow into the reservoir
b) the capacity of the reservoir
c) the outflow demand on the reservoir
d) the optimum value of catchment yield

Explanation: The yield of the catchment is the long-range runoff from a catchment. It helps in designing the capacity of the reservoir. The outflow from the reservoir (reservoir yield) is represented by the mass demand line.

4. Design yield of a storage reservoir is kept _______________
a) higher than its firm or safe yield
b) lower than its firm or safe yield
c) equal to its firm or safe yield
d) higher or lower than the firm yield depending upon the designer’s intuition

Explanation: An intermediate dependability percentage such as 50% to 75% is used to compute the design yield or dependable yield. This value will depend upon the risk which can be absorbed for the proposed use of water.

5. Who did the first effort to give empirical relations for converting the yearly rainfall value into the yearly runoff for the given catchment?
a) Mr. W L Strange
b) Alexander Binnie
c) Mr. T.G Barlow
d) Sir Inglis

Explanation: The first effort made in India was from Sir Alexander Binnie to connect the long-range rainfall and the yield. The observations were made on two rivers in the central provinces for the entire monsoon period. He worked out certain percentages to connect the monthly rainfall with the monthly yield which was further adjusted by Mr. Garret.
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6. In which of the following method, the catchments were categorized as good, bad and average catchments to account for the general characteristics of the catchment?
a) Binnie’s percentages
b) Strange’s tables
c) Barlow’s tables
d) Inglis formula

Explanation: Strange’s tables was an improvement over Binnie’s tables. The catchments prone to producing higher yield were good catchments and that of low yields were bad catchments. Average catchments were the intermediate types.

7. What is the value of Barlow’s runoff percentage (K) for hills and plains with little cultivation?
a) 10
b) 15
c) 20
d) 25

Explanation: For Flat, cultivated, and adsorbent soils, the runoff percentage is taken as 10 and for flat, partly cultivated stiff soils, it is taken as 15. For average catchment, the value is taken as 20 and for hills and plains with little cultivation, the value of the runoff percentage is 25.

8. What is the value of Lacey’s monsoon duration factor for a good year?
a) 0.5
b) 1.2
c) 1.5
d) 1.8

Explanation: The monsoon duration factor (m) for a bad year is 0.5 and that of the normal year the value is 1.2. For a good year, the monsoon duration factor is 1.5.

9. Which of the following yield formula is used for the catchments of West Maharashtra state of India?
a) Inglis formula
b) Khosla’s formula
c) Lacey’s formula
d) Barlow’s table

Explanation: Inglis formula was given by Sir Inglis derived his formula for catchments of Maharashtra state of India. He divided the areas into ghat areas (Sahyadri ranges) and non-ghat areas depending upon the rainfall intensity and gave the formula to determine the yield.

10. Which of the following formula for calculating yield can be applied to all catchments?
a) Inglis formula
b) Khosla’s formula
c) Lacey’s formula
d) Barlow’s table

Explanation: Khosla formula is based upon the recent research work conducted in the field. It is a simple and useful formula and can be applied to the entire country. The formula is given as-
Yield (Q) = P – 0.48 Tm where Q = the yield in cm, P = rainfall in cm, and Tm = mean annual temperature of the area.

11. According to the Inglis formula, the non-ghat areas are the one where rainfall is _____________
a) 200 cm or more
b) 200 cm or less
c) 100 cm or more
d) 100 cm or less

Explanation: The ghat area is the one where rainfall is 200 cm or more and in non-ghat areas the rainfall is less than 200 cm. The formulas are-
For ghat areas, Yield = (0.85P – 30.48)
For non-ghat areas, Yield = [P (P – 17.78)] / 254 where P is the rainfall in cm.

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