SSC JE Irrigation Questions with Detailed Solutions

​$$\textbf{Given Data:} \\[6pt]\text{Side slope: } 2H:1V \Rightarrow m = 2 \\\text{Depth: } y_0 = 5 \,\text{m} \\[12pt]\textbf{Step 1: Calculate Top Width (T)} \\[6pt]\text{The formula for top width of a triangular channel is:} \\T = 2 \times m \times y_0 \\[6pt]T = 2 \times 2 \times 5 = 20 \,\text{m} \\[12pt]\textbf{Step 2: Calculate Cross-Sectional Area (A)} \\[6pt]\text{The formula for area of a triangle is:} \\A = \tfrac{1}{2} \times T \times y_0 \\[6pt]A = \tfrac{1}{2} \times 20 \times 5 = 50 \,\text{m}^2$$​​

Gross Command Area (GCA):
Total area that can be physically irrigated by an irrigation project.
 Unculturable Area:
Part of GCA that cannot be cultivated (e.g., due to rocky land, roads, buildings, etc.)
 Culturable Command Area (CCA):
It is the portion of GCA that is suitable for cultivation.
So,
CCA = GCA−Unculturable Area

Assertion – True
 In lined canals, the velocity is generally higher than in unlined canals.
 Higher velocity helps prevent silting, as the sediment doesn't settle.
Reason – True
 Lining (e.g., concrete or masonry) reduces resistance (friction) → leads to higher flow velocity.
The Reason directly explains why silting is reduced — because the lining leads to higher velocity, which in turn prevents deposition.

The Assertion is true:
Intercepting drains are indeed provided near irrigation canals to collect seepage or percolated water and prevent waterlogging of adjacent land.
The Reason is also true:
These drains do intercept percolated water and carry it away, often connecting it to natural drainage systems like streams or rivers.
Also, the Reason correctly explains the Assertion.

Drip irrigation systems require pipes, emitters, filters, pressure regulators, and controllers, which make the initial setup cost high — a well-known disadvantage.
Drip systems can get clogged due to fine particles or algae, hence they require regular flushing, maintenance, and supervision to ensure uniform operation.

The method of applying excess water to dissolve and flush out soluble salts from the root zone of the soil is known as leaching.
It is commonly used for the reclamation of saline soils.
Water percolates down, carrying salts away from the plant root zone.

Deep ploughing improves the soil's structure and porosity, which helps roots access water more efficiently, ultimately reducing water requirement and increasing duty (Duty = Area irrigated / Quantity of water).
Proper and deep ploughing enhances the moisture-retention capacity by loosening compact soil layers.

Crop Period: Total number of days from sowing to harvesting.
 Base Period: Duration between the first and last irrigation (i.e., period of actual water application).
Since irrigation may not be needed on the first and last few days of the crop's life cycle, the base period is generally slightly less than the crop period.

A cross regulator is a canal regulation structure built across the parent canal to control and regulate the flow of water. It is mainly used to:
 Raise the water level upstream to divert it into off-taking canals.
 Stop or reduce water flow downstream of the canal during repairs or maintenance.

The cost of lining a canal includes expenses related to materials and their transportation. Hence, if materials are far from the site, transportation increases the cost.
Using locally available materials minimizes transportation charges, thus reducing overall expenditure.

An ogee fall is a type of canal fall that is designed with a combination of a convex and a concave curve in its profile. It allows water to drop smoothly from a higher level to a lower level, reducing the impact and preventing scouring of the bed.
Key Features of Ogee Fall:
Smooth transition for water flow
Reduces hydraulic jump impact
Suitable for moderate discharges and heights
Other Types of Falls (for Comparison):

Given:
Crop water requirement = 60 cm
Effective rainfall = 15 cm
Effective (Δ) = 60 - 15 = 45 cm
Time period (R) = 15 days
Formula Used:
Duty (D) =  $$\frac{864\times B}{Δ}$$​​
Calculation:
D = (864 × 15) / 45
D = 288 ha/cumec

Drip irrigation delivers water directly to the root zone of plants in a controlled and precise manner using emitters or micro-tubes. This method has:
 Minimum water loss due to evaporation or runoff
 Localized application – ideal for water-scarce areas
 Efficiency as high as 90–95%

Tube well is a sub-surface source of water, as it draws water from underground aquifers.
 Other options like reservoirs, streams, and dams are surface water sources.
Sub-surface sources are typically:
 Tube wells
 Dug wells
 Springs (some types)