Rajasthan PSC — Assistant Agriculture Engineer (Agriculture Engineering syllabus) · India · Rajasthan Public Service Commission
Original practice questions written to the published syllabus · not past papersEstimating erosion and designing the bunds, terraces, waterways, spillways, ponds and dams that control it.
In the exams: GATE AG Section 4 Soil & Water Erosion; ICAR AIEEA-PG Unit VII; ICAR AICE subject 40 Unit 5; NCEES PE erosion; PRC ABE land and water (32%); state PSCs
How our questions for Rajasthan PSC spread across the units of Soil & Water Conservation Engineering. Difficulty: 14 easy, 11 medium, 5 hard.
| Contour and graded bunds | 6 | |
| Farm ponds | 6 | |
| Gully control | 5 | |
| Wind erosion control and shelterbelts | 4 | |
| Bench and broad-base terraces | 3 | |
| Drop, drop-inlet and chute spillways | 2 | |
| Mechanics of water erosion | 1 | |
| Soil loss estimation: USLE, RUSLE and MUSLE | 1 | |
| Agronomic and biological conservation measures | 1 | |
| Earthen dams: seepage and stability | 1 |
Choose an answer, then open the working. Each explanation says why the right answer is right and why the others are not.
Using VI = 0.3(S/3 + 2), with S in percent, the vertical interval between contour bunds on a 6% slope is:
D. 1.2 m
VI = 0.3 × (6/3 + 2) = 0.3 × 4 = 1.2 m. Forgetting to divide S by 3 gives 2.4; forgetting the 0.3 gives 4.0. Dropping the S/3 term gives 0.3 × 2 = 0.6 m.
Further reading: Suresh, R., Soil and Water Conservation Engineering
Surplus arrangements such as waste weirs are provided in contour bunds to:
B. let runoff in excess of the design storage pass safely without breaching the bund
A bund stores only the design runoff. Waste weirs at low points or ends pass the excess in a controlled way; without them water overtops at the weakest point and breaches the bund.
Further reading: Suresh, R., Soil and Water Conservation Engineering
On a 20% slope the soil is deep enough to allow at most 0.5 m of cut at the inner edge of a level bench (vertical risers, balanced cut and fill). The widest bench that can be built without cutting below this depth is:
A. 5.0 m
For a balanced level bench, the cut at the inner edge is VI/2. Cut ≤ 0.5 m gives VI ≤ 1.0 m. W = 100 VI/S = 100 × 1.0/20 = 5.0 m. Treating 0.5 m as the VI gives 2.5 m, an unnecessarily narrow bench. 0.2 m multiplies VI by S/100 instead of dividing.
Further reading: Suresh, R., Soil and Water Conservation Engineering
The usual order of the four stages of gully development is:
C. formation, development, healing, stabilisation
A gully first forms by scour of the topsoil, then enlarges and advances its head (most active stage), then vegetation begins to establish (healing), and finally the gully stabilises with a stable gradient and cover.
Further reading: Suresh, R., Soil and Water Conservation Engineering
Check dams with an effective height of 0.9 m are placed in a gully with a bed slope of 6%, using the head-to-toe rule. The spacing between dams is:
B. 15 m
Head-to-toe: L = H / S = 0.9/0.06 = 15 m, so the crest of each dam is level with the toe of the next one upstream. Using S = 6 gives 0.15 m. H × S (0.9 × 6) gives 5.4 m, and reading 6% as 0.6 gives 1.5 m.
Further reading: Suresh, R., Soil and Water Conservation Engineering
For an actively advancing gully with a large runoff-producing catchment above it, the first engineering step is to:
A. divert or control runoff above the gully head and stabilise the head
Gullies advance by head-cutting, so stopping runoff over the head and stabilising it comes first, alongside catchment treatment. Check dams and planting follow once the flow is controlled.
Further reading: Schwab et al. / Fangmeier et al., Soil and Water Conservation Engineering
A pond must collect 4,000 m³ of runoff in a season with 500 mm of rain. If the seasonal runoff coefficient of the catchment is 0.2, the catchment area required is:
A. 4 ha
Runoff depth = 0.2 × 0.5 m = 0.1 m. Area = 4,000/0.1 = 40,000 m² = 4 ha. Forgetting the runoff coefficient gives 0.8 ha; using rainfall in mm without converting gives a tiny area. Working in mm without converting gives 40 m² = 0.004 ha, and multiplying by the coefficient gives 0.16 ha.
Further reading: Schwab et al. / Fangmeier et al., Soil and Water Conservation Engineering
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