Section 4: Soil and Water Conservation Engineering
Hydrology
Subtopic: Runoff estimation
Question Statement:
Match the following items between Column-I and Column-II with the most appropriate combinations:
| Column-I | Column-II |
|---|---|
| i) Direct runoff | 1) T-year rainfall depth |
| ii) Peak runoff | 2) Curve Number |
| iii) Tensiometer | 3) Aquifer |
| iv) Isoerodent map | 4) Rational formula |
| v) Isopluvial map | 5) 30-minute rainfall intensity |
| vi) Zone of saturation | 6) Field capacity |
Options:
(A) i-4, ii-2, iii-6, iv-5, v-1, vi-3
(B) i-2, ii-4, iii-6, iv-5, v-1, vi-3
(C) i-4, ii-2, iii-6, iv-1, v-5, vi-3
(D) i-2, ii-4, iii-6, iv-1, v-5, vi-3
Official Answer Key:
B
Step-by-Step Solution & Explanation
Direct runoff is estimated from the Curve Number (SCS-CN) method → (i–2). Peak runoff for small catchments is computed using the Rational formula → (ii–4). A tensiometer measures soil-water tension/matric potential, used to schedule irrigation up to field capacity → (iii–6). An isoerodent map shows contours of equal rainfall erosivity, which is indexed by the 30-minute rainfall intensity (used in the EI₃₀ erosivity term) → (iv–5). An isopluvial map shows contours of equal rainfall depth for a given return period (T-year rainfall depth) → (v–1). The zone of saturation in the subsurface is the region occupied by a saturated aquifer → (vi–3). This combination – i-2, ii-4, iii-6, iv-5, v-1, vi-3 – matches option (B) exactly.
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