Tamil Nadu PSC Water Resources Management, Floods & Canal Systems: practice questions

1 · Reservoirs · medium

Contours 5 m apart enclose 2.0 km² and 3.2 km² of a reservoir basin. Using the cone (prismoidal) formula, what is the storage between them?

1. 12.88 Mm³
2. 13.00 Mm³
3. 26.00 Mm³
4. 6.44 Mm³

2 · Reservoirs · hard

What is valley storage, and why does it matter in assessing a flood-control dam?

1. The volume the natural channel and flood plain held before the dam; the net gain is reservoir volume minus it
2. The storage above the maximum water level up to the dam top; it is kept empty as extra flood space at all times
3. The storage below the outlet sill reserved for sediment; it is excluded from all yield and flood studies alike
4. The water that seeps into the banks as the reservoir rises; it is added to the flood-control benefit in full

3 · Canal operation · hard

Why do designers prefer proportional or slightly sub-proportional outlets near the tail of a distributary?

1. So that the water level in each watercourse downstream controls the discharge entering every field channel
2. So that farmers can adjust their own outlets freely without causing any change in the distributary flow
3. So that when the distributary runs low, head outlets do not take more than their share and starve the tail
4. So that tail outlets receive their full discharge even while the distributary is closed for maintenance work

4 · Canal operation · easy

Under warabandi, how is each farmer's turn on a watercourse fixed?

1. Equal hours for every farmer on the watercourse, whatever the size of each holding
2. Whenever the farmer applies, in the order in which applications are received at the canal office
3. A fixed time on a fixed day of a weekly cycle, in proportion to the farmer's landholding
4. A fixed volume per hectare measured at the field inlet, however long the delivery takes

5 · Flood estimation · medium

Using Ryves' formula Q = C·A^(2/3) with C = 6.8 (Q in m³/s, A in km²), what is the peak flood from a 500 km² catchment?

1. About 152 m³/s
2. About 719 m³/s
3. About 3,400 m³/s
4. About 428 m³/s

6 · Flood control measures · easy

Which measure reduces flood damage to a house without changing the flood itself?

1. Raising the plinth above the expected flood level
2. Widening and deepening the river channel nearby
3. Raising the crest of the levee along the river
4. Building a detention basin on a tributary upstream

7 · Minor irrigation · easy

Under India's classification by culturable command area, a scheme with a CCA of 1,500 ha is

1. a medium irrigation project
2. a major irrigation project
3. a minor irrigation project
4. a command area development project

8 · Minor irrigation · hard

A tank's 15 km² catchment receives 900 mm of rain, with a runoff coefficient of 0.25. After 30% losses to evaporation and seepage, the crops need a delta of 0.5 m. About how much area can be irrigated?

1. About 330 ha
2. About 1,890 ha
3. About 675 ha
4. About 470 ha

9 · Minor irrigation · easy

What is the function of the sluice in an irrigation tank?

1. To bring water into the tank from the catchment or upper tank
2. To release controlled amounts of stored water to the command
3. To drain the foreshore so that it can be cultivated after the rains
4. To pass flood water safely when the tank is full to its crest

10 · Water users' associations and participatory irrigation management · medium

Which Indian state passed the Farmers' Management of Irrigation Systems Act in 1997, an early state law creating water users' associations?

1. Himachal Pradesh
2. Andhra Pradesh
3. Punjab
4. Rajasthan