Tamil Nadu PSC Watershed Planning & Management: practice questions

C. 1.40 per km²

Stream frequency Fs = ΣN / A = 63 / 45 = 1.40 segments per km². 0.71 inverts the ratio; stream frequency counts segments, not length, so it is not the same as drainage density. 0.14 is a decimal slip in the area (63/450); 2,835 multiplies instead of dividing (63 × 45).

Further reading: Horton (1945); Strahler (1957); Schumm (1956); Miller (1953) — as summarised in Suresh, Soil and Water Conservation Engineering

D. recreation, wildlife or water supply

Class VIII has limitations that preclude commercial plant production, including grazing and woodland production. Occasional cultivation fits class IV; controlled grazing and woodland fit classes VI and VII.

Further reading: Klingebiel and Montgomery, USDA Agriculture Handbook 210 (1961)

A. cultivable land with severe limitations, erosion hazard being the dominant one

Class III is arable but has severe limitations that reduce the choice of crops or need special conservation practices; the subclass e shows that erosion hazard is the dominant limitation. Moderate limitations define class II, and w would denote wetness.

Further reading: Klingebiel and Montgomery, USDA Agriculture Handbook 210 (1961)

B. 13,000 m³

Runoff = C × P × A = 0.25 × 0.65 m × 80,000 m² = 13,000 m³. 52,000 m³ is total rainfall on the catchment (runoff coefficient omitted). The other two are factor-of-ten slips in converting hectares to m².

Further reading: Critchley and Siegert, FAO Water Harvesting manual (1991)

D. A narrow, well-defined channel with stable high banks and a gentle bed slope upstream

A narrow section keeps the structure short and cheap; stable banks prevent outflanking; a gentle bed slope makes the stored pool extend far upstream; and nearby users make use of the stored water and recharge. Steep beds give short pools and wide channels need long, costly structures.

B. pass the water through a filter and keep the structure away from septic tanks, soak pits and polluted runoff

Recharge structures deliver water directly to the aquifer, so silt and contaminants must be kept out: filter media (boulders, gravel, sand) and distance from pollution sources are essential. Very shallow water tables leave no room for recharge and increase waterlogging risk.

Further reading: IS 15797 Roof Top Rainwater Harvesting — Guidelines

B. Tamil Nadu

Tamil Nadu made rainwater harvesting structures compulsory for all buildings across the state in the early 2000s, after severe urban water shortages in Chennai. Many cities in other states have since made harvesting compulsory for new buildings above a set plot size, with rules that differ by city.

A. small works of immediate, visible benefit to the whole community, done early to build trust

Entry point activities in the preparatory phase, such as repairing a drinking-water source, show that the project responds to villagers' priorities and build trust before bigger decisions about land and grazing are made. Hand-over happens in the consolidation and withdrawal phase.

Further reading: Government of India, Common Guidelines for Watershed Development Projects (2008, revised 2011)

C. It tests genuine demand and builds a fund and a sense of ownership for maintenance after the project

Contribution in cash or labour signals that farmers want the work, and the collected money commonly goes into a watershed development fund for later maintenance. Programmes set lower rates for small and marginal and disadvantaged farmers precisely so the poor are not excluded.

Further reading: Government of India, Common Guidelines for Watershed Development Projects (2008, revised 2011)

B. the rural employment guarantee scheme (MGNREGS)

Water conservation and harvesting are among the permissible works under the Mahatma Gandhi National Rural Employment Guarantee Scheme, which combines wage employment with asset creation. The other programmes deal with roads, urban areas and railways.