Why this topic is important for ECET?
In ECET Civil, irrigation engineering concepts like Duty, Delta, and Base Period are repeatedly asked in exams because they connect water requirements of crops with hydrology and irrigation design.
If you master these, you can solve numerical problems quickly and secure guaranteed marks in Irrigation & Hydrology section.
📘 Concept Notes
1. Base Period (B)
- The time between first watering (sowing) and last watering (before harvesting) of a crop.
- It is usually expressed in days.
Example: If paddy requires water from June to October, the base period is about 120 days.
2. Delta (Δ)
- The total depth of water required by a crop during its base period.
- Expressed in cm or meters.
Example: Paddy requires about 120 cm (1.2 m) water → Delta = 1.2 m.
3. Duty (D)
- The area of land that can be irrigated with 1 cumec (1 m³/s) of water flow during the base period.
- Expressed in hectares/cumec.
Example: If 1 cumec water irrigates 2000 hectares → Duty = 2000 hectares/cumec.
4. Relationship between Duty, Delta & Base Period
These three are related by the important formula:
where
= Delta (m),
= Base Period (days),
= Duty (hectare/cumec).
👉 Remember: Higher duty = More area irrigated = Less delta.
⚙️ Formulas
🔟 10 MCQs
Q1. Base period is measured in:
a) Litres
b) cm
c) Days
d) Cumecs
Q2. If a crop requires 120 days from sowing to last watering, its base period is:
a) 4 months
b) 120 days
c) 1 year
d) 60 days
Q3. Duty is expressed as:
a) Hectares/cumec
b) Cumec/hectares
c) cm/s
d) Days
Q4. A crop requires a Delta of 1.2 m and base period 120 days. Find Duty.
a) 864 ha/cumec
b) 8640 ha/cumec
c) 720 ha/cumec
d) 1000 ha/cumec
Q5. If Duty = 1728 ha/cumec and base period = 120 days, find Delta.
a) 0.6 m
b) 0.4 m
c) 0.2 m
d) 0.9 m
Q6. High duty means:
a) More area irrigated
b) Less area irrigated
c) High delta
d) Less efficiency
Q7. If Delta = 0.8 m and Duty = 1200 ha/cumec, find Base period.
a) 120 days
b) 110 days
c) 100 days
d) 90 days
Q8. Which factor affects Duty most?
a) Soil type
b) Crop type
c) Climate
d) All of these
Q9. For paddy crop, approximate Delta is:
a) 50 cm
b) 120 cm
c) 200 cm
d) 20 cm
Q10. The equation connecting Duty, Delta and Base Period is:
a) 
b) 
c) 
d) None
✅ Answer Key
| Q | Answer |
|---|---|
| 1 | c |
| 2 | b |
| 3 | a |
| 4 | a |
| 5 | b |
| 6 | a |
| 7 | c |
| 8 | d |
| 9 | b |
| 10 | b |
🧠 Explanations
- Q1: Base period = time → measured in days → (c).
- Q2: By definition → 120 days → (b).
- Q3: Duty is land irrigated per cumec → hectares/cumec → (a).
- Q4:
→ 
→ D = 864 ha/cumec → (a). - Q5:
→ (b). - Q6: High duty = more area with same water → (a).
- Q7: →
→ B = 111.1 ≈ 100 days → (c). - Q8: All listed factors influence duty → (d).
- Q9: Paddy needs about 120 cm water → (b).
- Q10: Standard relation → → (b).
🎯 Motivation / Why Practice Matters
In ECET 2026, irrigation problems are direct formula-based.
- If you remember Duty–Delta–Base Period relation, you can solve numerical problems in 30 seconds.
- Many students confuse the units – practicing these ensures speed + accuracy.
👉 By practicing daily, you convert these into guaranteed scoring questions in the exam.
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