Irrigation Engineering Questions and Answers – Water Requirements – Duty and Delta of a Crop

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This set of Irrigation Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Water Requirements – Duty and Delta of a Crop”.

1. What is the time interval between two consecutive watering called?
a) Crop Period
b) Period
c) Base Period
d) Rotation Period

Explanation: Every type of crop requires different amount of water for its complete growth in certain fixed intervals of time. The time interval between two consecutive intervals is called a rotation period.

2. What is total depth of water, for complete growth of crop called?
a) Triangle
b) Delta
c) Duty of Water
d) Rotation Period

Explanation: The total quantity of water required by the crop for its complete growth can be expressed in terms of depth of water standing on the field. This total depth expressed in cm is called delta.

3. Duty of water helps in the work out of discharge required for designing the channel.
a) True
b) False

Explanation: Duty of water gives a relation volume of water required and the area of irrigated crop. So, in this way if we know the area of crop irrigated we can know discharge required for the channel.

4. What is the name of duty called as in direct irrigation?
a) Flow Duty
b) Quantity Duty
c) Duty
d) Delta

Explanation: When direct irrigation is used, then the units of duty, always expressed in hectares/cumec. Then duty is called flow duty.

5. Which type of period is slightly more than its counterpart period?
a) Crop Period
b) Period
c) Base Period
d) Rotation Period

Explanation: Crop period is time period between the instant of sowing to its harvesting. Base period is the time period between the first watering of crop to its final watering before harvesting.

6. Flow irrigation system has lower duty than lift irrigation system.
a) True
b) False

Explanation: In lift irrigation system due to the commanded area of each well near to it, gives a high value of duty when compared to flow irrigation system.

7. Which type of units is used to define high and low duty?
a) Hectare-meters
b) Hectares/cumec
c) Meters
d) Centimeters

Explanation: According to the number of hectares/cumec, if the irrigated area is large or small then it is called high or low duty respectively.

8. Which type of area is large in quantity compared to others?
a) Gross Commanded Area (G.C.A)
b) Culturable Commanded Area (C.C.A)
c) Culturable Cultivated Area
d) Culturable Uncultivated Area

Explanation: Gross Commanded Area (G.C.A) is the sum of Culturable Commanded Area (C.C.A) and unculturable area. Again Culturable Commanded Area (C.C.A) is divided into the sum of culturable cultivated and culturable uncultivated areas. Therefore, Gross Commanded Area (G.C.A) is a large quantity.

9. In what type of area crop is not sown for a particular season?
a) Gross Commanded Area (G.C.A)
b) Culturable Commanded Area (C.C.A)
c) Culturable Cultivated Area
d) Culturable Uncultivated Area

Explanation: This type of area is not kept under cultivation because, to restore the fertility of the soil, to provide pasture land for animals, to prevent water logging in the land.

10. Given that, a particular irrigation field has C.C.A as 200 hectares, out which 150 hectares of land is cultivated for rabi season and 100 hectares of land is cultivated for kharif season. What is the intensity of irrigation for each season?
a) 50%, 100%
b) 120%, 60%
c) 75%, 50%
d) 150%, 75%

Explanation: For rabi season:
Intensity of irrigation = (150/200) x 100
= 15 x 5
= 75%
For kharif season:
Intensity of irrigation = (100/200) x 100
= 0.5 x 100
= 50%.

11. Given that a particular crop requires about 20 cm depth of water at an interval of 40 days, and the base period is 400 days. Find the delta for the crop? Now using this delta find the duty of water for the crop?
a) 150 cm, 1150 hectares/cumec
b) 180 cm, 1825 hectares/cumec
c) 200 cm, 1728 hectares/cumec
d) 195 cm, 1920 hectares/cumec

Explanation: Given that base period is 400 days at an interval of 40 days. This number of waterings as = 400/40 = 10
Now delta = 10 x 20 = 200 cm.
Now we have relation between delta and duty as –
Delta = (864B)/D
B = base period, D = duty
200 = (864 x 400)/D
D = 864 x 2 = 1728 hectares/cumec.

12. It is said that a particular type of crop requires a depth of 6 cm of water every 24 days and the crop period is 168 days. Find the delta of the crop?
a) 50 cm
b) 42 cm
c) 20 cm
d) 95 cm

Explanation: Assume that crop period is equal to base period. So, given base period is 168 days, and it requires watering for every 24 days. Therefore number of waterings for entire cultivation = (168/24) = 7
Each watering needs 6 cm depth of water. So, therefore total depth of water required in 168 days = 7 x 6 = 42 cm.

13. How can we improve the duty of water?
a) Lining of Canals
b) Construction of Weir
c) Construction of Dam
d) Check Dams

Explanation: By lining of canals, carrying irrigation supplies we can reduce seepage and evaporation losses. Therefore reducing the field requirement of water increases the duty.

14. Which factor directly affects the duty of water?
a) Type of Crop
b) Useful Rainfall
c) Type of Soil
d) Canals

Explanation: If the rainfall useful is for the growth of crops, then more the rainfall less will be the requirement of water for the growth of crops and more will be the duty of irrigation water.

15. At which point in the entire canal system the duty of water will be more?

Explanation: As water flows from river to subsequent parts of the canal system some water losses takes place due to evaporation, and percolation. Due to this, the duty of water goes on increasing from starting point of canal system till its end point. Therefore, the duty of water is more at the last point of the system, i.e head of the water-course.

Sanfoundry Global Education & Learning Series – Irrigation Engineering.

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