ASRB NET — Farm Machinery & Power / Land & Water Management Engineering / Agricultural Structures & Process Engineering · India · Agricultural Scientists Recruitment Board (ICAR)
Original practice questions written to the published syllabus · not past papersPlanning a whole watershed: delineating it, classifying its land, budgeting its water and choosing harvesting structures with the people who live there.
In the exams: GATE AG Section 4 Watershed Management; ICAR AIEEA-PG Unit VII; ICAR AICE subject 40 Unit 6; TNPSC Unit III; RPSC AAE Unit 2
ASRB NET — Land & Water Management Engineering
Watershed management concepts and standard formulas, programme guidelines and evaluation, at the depth of an M.Tech course.
How our questions for ASRB NET spread across the units of Watershed Planning & Management. Difficulty: 1 easy, 19 medium, 18 hard.
| Cost-benefit analysis of watershed projects | 7 | |
| Watershed characterisation and morphometry | 6 | |
| Land capability classification | 5 | |
| Participatory watershed planning | 4 | |
| National watershed programmes | 4 | |
| Land irrigability classification | 3 | |
| Rainwater harvesting: check dams, percolation tanks and farm ponds | 3 | |
| Watershed delineation | 2 | |
| Water budgeting | 2 | |
| Roof-top rainwater harvesting | 2 |
Choose an answer, then open the working. Each explanation says why the right answer is right and why the others are not.
A watershed has minimum elevation 580 m, maximum elevation 1240 m and mean elevation 820 m. Using the elevation-relief ratio to approximate the hypsometric integral, which is correct?
D. HI ≈ 0.36, within Strahler's mature (equilibrium) range
E = (mean − min) / (max − min) = (820 − 580) / (1240 − 580) = 240/660 = 0.364. Strahler read values above about 0.6 as youthful (inequilibrium), about 0.35–0.6 as mature (equilibrium) and lower values as old (monadnock), so 0.36 is mature. 0.66 (mean ÷ max) is not the hypsometric integral; the interpretation is qualitative and also depends on lithology and tectonics.
Further reading: Strahler (1952, 1957); Pike and Wilson (1971) elevation-relief ratio
A 2,000 ha sub-watershed has three erosion intensity mapping units: 600 ha (weightage 17, delivery ratio 0.9), 900 ha (weightage 14, delivery ratio 0.8) and 500 ha (weightage 11, delivery ratio 0.7). Using SYI = [Σ(Ai × Wi × Di) / Aw] × 100 and the bands very high > 1300, high 1200–1300, medium 1100–1200, low 1000–1100, very low < 1000, the sediment yield index and priority are:
C. 1,156 — medium
Σ(Ai × Wi × Di) = 600×17×0.9 + 900×14×0.8 + 500×11×0.7 = 9,180 + 10,080 + 3,850 = 23,110. SYI = 23,110 / 2,000 × 100 = 1,155.5, which falls in the medium band (1100–1200). Leaving out the delivery ratio gives 1,415 and a false 'very high'; forgetting the factor 100 gives 11.6.
Further reading: AIS&LUS (Soil and Land Use Survey of India) priority delineation methodology
In land capability classification, the subclass symbols e, w, s and c stand for limitations due to:
A. erosion, excess water, soil root zone, and climate
The four subclasses are e (erosion hazard), w (wetness, drainage or overflow), s (soil root zone limitations such as shallowness, stones, low water capacity, salinity or sodicity) and c (climatic limitation). Salinity is included under s, and slope is expressed through erosion hazard.
Further reading: Klingebiel and Montgomery, USDA Agriculture Handbook 210 (1961)
A farmer's field is on a gentle slope with deep, slowly permeable clay soil in a region of fairly high rainfall. Which bund type suits it better, and why?
D. Graded bund, because it leads excess runoff safely to an outlet instead of ponding it on the clay
Contour bunds hold water behind them and suit low-rainfall areas with permeable soils, where the ponded water infiltrates. On slowly permeable clays with high rainfall, ponding causes waterlogging and bund overtopping, so graded bunds with a slight longitudinal grade lead excess water to a grassed waterway. Clay soils can erode, especially when wet.
The land capability classification of Klingebiel and Montgomery assumes which of the following?
B. Moderately high management
LCC interprets physical limitations under a moderately high level of management; it deliberately ignores location, markets, ownership and crop value. Reclamation (drainage, removal of stones) can change the effective class, so land is not assumed to be unchangeable.
Further reading: Klingebiel and Montgomery, USDA Agriculture Handbook 210 (1961)
In a nearly closed river basin, where downstream users already use most of the flow, an upstream programme builds many new check dams and farm ponds. From a basin water budget perspective, the most likely effect is:
C. a reallocation of water from downstream to upstream users rather than a net creation of new water
Harvesting structures capture runoff that would otherwise have flowed downstream; recharged water is then pumped and evapotranspired upstream. In a closed basin this shifts water between users. Storage created is not new supply, and increased irrigation upstream usually raises basin evapotranspiration.
Further reading: Brooks, Ffolliott and Magner, Hydrology and the Management of Watersheds
A percolation tank has an average water-spread area of 2.0 ha and an average stored depth of 1.5 m. It fills 3 times in the rainy season, and evaporation takes 20% of the water captured. Assuming all remaining water percolates, the seasonal recharge is:
C. 72,000 m³
One filling = 20,000 m² × 1.5 m = 30,000 m³. 3 fillings = 90,000 m³. Recharge = 90,000 × (1 − 0.2) = 72,000 m³. 90,000 m³ ignores evaporation; 24,000 m³ counts only one filling; 18,000 m³ is the evaporation loss.
In the mass-curve (supply-side) method of sizing a rainwater tank, the required storage is found from:
A. the maximum difference between the cumulative supply and demand curves during the period when demand exceeds supply
Plotting cumulative roof yield and cumulative demand month by month, the storage needed is the largest gap that must be carried over from surplus months to cover deficit months. Total annual yield sets the upper limit on supply but is not the tank size; the demand-side method uses dry days, not rainy days.
Further reading: Gould and Nissen-Petersen, Rainwater Catchment Systems for Domestic Supply
'Social fencing' in watershed management refers to:
C. protection of treated or closed areas through rules agreed and enforced by the community itself
Social fencing means the community agrees not to graze or cut in a regenerating area and enforces the rule itself, often with fines or watchers it appoints, instead of relying on physical fences or state orders that are hard to enforce.
China's Sloping Land Conversion Programme ('Grain for Green'), launched in 1999, aimed to:
D. pay farmers to convert steep sloping cropland to forest or grassland
Grain for Green compensated farmers with grain and cash for converting steep, erodible cropland to trees or grass, to reduce erosion and flooding. It is one of the largest land-use conversion programmes in the world.
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