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Past Questions — 2025
Which is the most water-efficient irrigation method?
A)
Furrow irrigation
B)
Sprinkler irrigation
C)
Drip irrigation
D)
Flood irrigation
Water efficiency in irrigation is measured by the percentage of water that actually reaches the root zone of the plant versus the amount applied.
1. **Drip Irrigation (c):** This is the most efficient method because it delivers water slowly and precisely to the root zone through a network of valves, pipes, and emitters. It minimizes evaporation and eliminates surface runoff, often achieving efficiency rates of 90% or higher.
2. **Sprinkler Irrigation (b):** While more efficient than surface methods, it loses significant water to evaporation (especially in windy or hot conditions) and wind drift. Its efficiency is generally lower than drip irrigation.
3. **Furrow Irrigation (a):** A type of surface irrigation where water flows in small parallel channels. It is prone to deep percolation and runoff, making it less efficient than pressurized systems.
4. **Flood Irrigation (d):** The least efficient method. Water is applied over the entire field surface, leading to massive losses through evaporation, deep percolation, and runoff.
Contour lines that are very close together indicate:
A)
Flat terrain
B)
A steep slope
C)
A river valley
D)
A depression in the land
In surveying, contour lines are imaginary lines connecting points of equal elevation. The horizontal distance between these lines indicates the gradient of the terrain.
1. **Steep Slope**: When contour lines are drawn very close together, it means the elevation changes rapidly over a short horizontal distance, which characterizes a steep slope.
2. **Flat Terrain**: Conversely, when contour lines are spaced far apart, it indicates a gentle slope or flat terrain, as the elevation changes slowly over a larger distance.
3. **River Valley**: A river valley is typically represented by V-shaped contours with the apex of the 'V' pointing upstream.
4. **Depression**: A depression is indicated by closed contour lines with hachure marks (small ticks) pointing inward toward the center of the depression.
Therefore, closely spaced contour lines are a definitive indicator of a steep slope.
A “benchmark” in surveying is used to measure-
A)
Horizontal distances
B)
Vertical elevations
C)
Magnetic north
D)
The width of a structure
In surveying, a Benchmark (BM) is a permanent point of known elevation (reduced level) relative to a fixed datum (such as Mean Sea Level). It serves as a reference point from which the elevations of other points in the survey area are determined through a process called leveling.
Analysis of options:
- Option (a) Horizontal distances are measured using tapes, chains, or EDM (Electronic Distance Measurement) instruments, not benchmarks.
- Option (b) Vertical elevations are the primary purpose of a benchmark; it provides the starting height for leveling operations.
- Option (c) Magnetic north is determined using a compass (Prismatic or Surveyor's compass).
- Option (d) The width of a structure is a linear horizontal measurement, typically done with a measuring tape or laser meter.
Which of the following is NOT a type of surface drainage system?
A)
Open ditches
B)
Graded border system
C)
Tile drainage
D)
Field drains
Agricultural drainage systems are broadly classified into two categories: Surface Drainage and Sub-surface Drainage.
1. Surface Drainage: This involves the removal of excess water from the soil surface. Examples include:
- Open ditches (Option a): Open channels dug to carry water away.
- Graded border system (Option b): A method where the land is graded to allow water to flow toward a collector drain.
- Field drains (Option d): Small channels within a field used to move surface water to larger ditches.
2. Sub-surface Drainage: This involves the removal of excess water from the root zone (below the soil surface).
- Tile drainage (Option c): This involves installing perforated pipes (originally clay tiles, now usually plastic) underground to lower the water table. Because these pipes are buried, it is a sub-surface drainage system, not a surface drainage system.
Therefore, Tile drainage is the only option that is NOT a type of surface drainage system.
What is the hydraulic radius of a trapezoidal channel with: Bottom width b=6m, Depth h=3m, Side slope m=1
A)
1.86m
B)
2.12m
C)
2.54m
D)
2.86m
To find the hydraulic radius (R) of a trapezoidal channel, we use the formula: R = Area (A) / Wetted Perimeter (P).
1. **Given Data:**
- Bottom width (b) = 6 m
- Depth (h) = 3 m
- Side slope (m) = 1 (Horizontal:Vertical = 1:1)
2. **Calculate the Cross-sectional Area (A):**
The area of a trapezoid is given by: A = (b + m*h) * h
A = (6 + 1 * 3) * 3
A = (6 + 3) * 3 = 9 * 3 = 27 m²
3. **Calculate the Wetted Perimeter (P):**
The wetted perimeter for a trapezoidal channel is: P = b + 2 * h * sqrt(1 + m²)
P = 6 + 2 * 3 * sqrt(1 + 1²)
P = 6 + 6 * sqrt(2)
P = 6 + 6 * 1.4142
P = 6 + 8.4852 = 14.4852 m
4. **Calculate the Hydraulic Radius (R):**
R = A / P
R = 27 / 14.4852
R ≈ 1.8639 m
Rounding to two decimal places, we get 1.86m. Therefore, option (a) is the correct answer.
Why is the selection of a particular type of irrigation system highly dependent on soil type?
A)
Some soils absorb water too quickly, making certain methods inefficient
B)
All irrigation methods work equally well, regardless of soil type
C)
Soil type only affects crop growth, not the irrigation method
D)
Irrigation system selection is only based on water availability
The selection of an irrigation system is fundamentally tied to the soil's physical properties, specifically its infiltration rate and water-holding capacity.
1. **Infiltration Rate:** Sandy soils have high infiltration rates (water drains quickly), making surface irrigation (like flood or furrow irrigation) inefficient because water seeps deep into the ground before it can reach the end of the field. In such cases, drip or sprinkler irrigation is preferred. Conversely, clayey soils have low infiltration rates, making them suitable for surface irrigation but prone to runoff if sprinkler rates are too high.
2. **Water Holding Capacity:** Different soils store water differently, which dictates the frequency and volume of water application required.
Evaluating the other options:
- **Option b** is incorrect because irrigation efficiency varies wildly across soil types (e.g., flood irrigation in sand is highly wasteful).
- **Option c** is incorrect because soil type directly influences the hydraulic conductivity, which is a primary factor in choosing the irrigation method.
- **Option d** is incorrect because while water availability is a constraint, it is not the *only* factor; soil, topography, crop type, and climate are all critical determinants.
In levelling, the term “backsight” refers to-
A)
The last reading taken before moving the instrument
B)
The first reading taken from a known elevation
C)
A reading taken at a change point
D)
A reading used for error correction
In leveling, a Backsight (BS) is defined as the first staff reading taken after the leveling instrument (level) is set up. This reading is always taken on a point of known elevation (either a Benchmark or a previously established point) to determine the Height of Instrument (HI).
Analysis of options:
- Option (a) describes a 'Foresight' (FS), which is the last reading taken before moving the instrument to a new position.
- Option (b) is correct as it describes the fundamental purpose of a backsight: establishing the instrument's elevation relative to a known point.
- Option (c) is partially true in practice (a reading at a change point is both a foresight for the old setup and a backsight for the new setup), but the primary definition of a backsight is the first reading taken from a known elevation.
- Option (d) is incorrect; while readings are used in calculations, a backsight is a specific type of measurement, not a general term for error correction.
If the velocity ratio V/Vc is less than 1 in a canal, what does it indicate?
A)
The canal will experience scouring
B)
The canal will experience silting
C)
The canal is in equilibrium
D)
The canal will have constant velocity
In canal engineering, the stability of the bed is determined by comparing the actual velocity (V) of the water with the critical velocity (Vc), also known as the non-silting or non-scouring velocity.
1. **Critical Velocity (Vc):** This is the velocity at which the sediment transported by the water is neither deposited nor eroded from the bed. This state is known as the 'regime' or 'equilibrium' condition.
2. **Velocity Ratio (V/Vc) < 1:** When the actual velocity (V) is less than the critical velocity (Vc), the water does not have enough kinetic energy to keep the sediment particles in suspension. Consequently, the particles settle down on the bed of the canal, leading to the accumulation of sediment. This process is called **silting**.
3. **Velocity Ratio (V/Vc) > 1:** When the actual velocity is greater than the critical velocity, the water has excess energy that removes particles from the bed, leading to erosion. This process is called **scouring**.
4. **Velocity Ratio (V/Vc) = 1:** This represents the equilibrium condition where no silting or scouring occurs.
Therefore, since the question specifies V/Vc < 1, the canal will experience silting.
The main source of irrigation in India is-
A)
Wells
B)
Canals
C)
Rainwater
D)
Lakes
In India, groundwater irrigation (which includes wells and tube wells) is the primary source of irrigation. According to data from the Ministry of Agriculture and Farmers Welfare and various government reports, more than 60% of the total irrigated area in India is covered by groundwater sources.
1. Wells/Tube wells (Option a): These are the most dominant source due to their accessibility and the ability of farmers to control the timing and quantity of water application.
2. Canals (Option b): While significant, especially in Northern India (Punjab, Haryana), canal irrigation covers a smaller percentage of the total irrigated area compared to wells.
3. Rainwater (Option c): Rainwater is the basis for 'rain-fed' agriculture, but by definition, 'irrigation' refers to the artificial application of water to land. Therefore, rainwater is not considered a source of irrigation, but rather a natural source of moisture.
4. Lakes (Option d): Lakes are not a primary or widespread source of systematic irrigation in India.
Using Manning’s formula, determine the velocity of flow in a canal with: Hydraulic radius (R) = 1.5 m, Slope (S) = 0.0003, Manning’s coefficient (n) = 0.025
A)
0.908 m/s
B)
0.851 m/s
C)
0.932 m/s
D)
0.899 m/s
To determine the velocity of flow in the canal, we use Manning's formula for open channel flow:
Formula: V = (1/n) * R^(2/3) * S^(1/2)
Given values:
- Manning's coefficient (n) = 0.025
- Hydraulic radius (R) = 1.5 m
- Slope (S) = 0.0003
Step-by-step Calculation:
1. Calculate R^(2/3):
R^(2/3) = (1.5)^(2/3) ≈ 1.31037
2. Calculate S^(1/2):
S^(1/2) = √(0.0003) ≈ 0.01732
3. Substitute the values into the formula:
V = (1 / 0.025) * 1.31037 * 0.01732
V = 40 * 1.31037 * 0.01732
V = 52.4148 * 0.01732
V ≈ 0.9078 m/s
Rounding to three decimal places, we get V = 0.908 m/s.
Comparing this result with the given options:
- Option (a) 0.908 m/s matches our calculation.
- Options (b), (c), and (d) are incorrect as they do not align with the mathematical result of the Manning's formula for the provided parameters.
The process of artificially supplying water to land for agricultural purposes is called-
A)
Drainage
B)
Irrigation
C)
Evaporation
D)
Infiltration
Step-by-step reasoning:
1. Analysis of the definition: The question asks for the term describing the artificial application of water to land for agriculture.
2. Evaluating Option (b) Irrigation: By definition, irrigation is the artificial process of applying controlled amounts of water to land to assist in the production of crops, especially in areas where rainfall is insufficient.
3. Evaluating Option (a) Drainage: Drainage is the opposite of irrigation; it is the natural or artificial removal of excess surface and sub-surface water from the land.
4. Evaluating Option (c) Evaporation: Evaporation is a physical process where liquid water changes into water vapor due to heat; it is a loss of water from the soil/plant system, not a supply method.
5. Evaluating Option (d) Infiltration: Infiltration is the process by which water on the ground surface enters the soil. While it happens during irrigation, it describes the movement of water into the soil, not the act of supplying it to the land.
Therefore, 'Irrigation' is the only correct term for the artificial supply of water for agricultural purposes.
Which of the following is NOT an advantage of sprinkler irrigation?
A)
Suitable for undulating terrain
B)
Efficient water distribution
C)
Reduces soil erosion
D)
Lowinitial investment cost
Sprinkler irrigation is a pressurized irrigation system. Let's evaluate the options based on engineering principles:
1. **Suitable for undulating terrain (Option a):** This is an ADVANTAGE. Unlike surface irrigation (which requires precise land leveling), sprinklers can be used on slopes and uneven ground because water is delivered under pressure.
2. **Efficient water distribution (Option b):** This is an ADVANTAGE. Sprinklers allow for precise control over the amount of water applied, reducing waste compared to flood irrigation.
3. **Reduces soil erosion (Option c):** This is generally an ADVANTAGE. Because water is applied in small droplets (simulating rain) rather than in heavy flows or floods, it prevents the surface runoff that typically causes soil erosion on slopes.
4. **Low initial investment cost (Option d):** This is NOT an advantage; it is a DISADVANTAGE. Sprinkler systems require a significant initial capital investment for pumps, piping, nozzles, and control valves, making them much more expensive to install than traditional surface irrigation methods.
Therefore, option (d) is the correct answer as it is a drawback, not an advantage.
A trapezoidal canal has a bottom width of 4 m, depth of 2 m, and side slope of 1:1. What is the top width?
A)
6m
B)
8m
C)
10m
D)
12m
To find the top width of a trapezoidal canal, we use the geometry of the cross-section.
1. **Given Data:**
- Bottom width (b) = 4 m
- Depth (d) = 2 m
- Side slope (z) = 1:1 (This means for every 1 unit of vertical rise, there is 1 unit of horizontal run. Therefore, z = 1).
2. **Formula for Top Width (T):**
The top width of a trapezoidal channel is calculated as:
T = b + 2 * (z * d)
3. **Calculation:**
T = 4 + 2 * (1 * 2)
T = 4 + 2 * (2)
T = 4 + 4
T = 8 m
4. **Analysis of Options:**
- Option (a) 6m: Incorrect. This would occur if the side slope was 0.5:1.
- Option (b) 8m: Correct. Matches the calculated value.
- Option (c) 10m: Incorrect. This would occur if the side slope was 1.5:1.
- Option (d) 12m: Incorrect. This would occur if the side slope was 2:1.
A canal has a bed slope of 1 in 5000, what is the value of S?
A)
0.0001
B)
0.0002
C)
0.0005
D)
0.0010
In hydraulics and civil engineering, the bed slope (S) of a canal is defined as the ratio of the vertical drop (fall) to the horizontal distance.
Given:
Bed slope = 1 in 5000
Calculation:
S = Vertical Drop / Horizontal Distance
S = 1 / 5000
S = 0.0002
Verification of options:
- Option a: 0.0001 corresponds to a slope of 1 in 10,000.
- Option b: 0.0002 corresponds to a slope of 1 in 5,000. (Correct)
- Option c: 0.0005 corresponds to a slope of 1 in 2,000.
- Option d: 0.0010 corresponds to a slope of 1 in 1,000.
A trapezoidal canal has a discharge of 10 m3/s. If the velocity is 2 m/s, what is the required cross-sectional area?
A)
2.5 m2
B)
5.0 m2
C)
10.0 m2
D)
15.0 m2
To find the cross-sectional area of the canal, we use the fundamental Continuity Equation for fluid flow:
Discharge (Q) = Area (A) × Velocity (V)
Given values:
- Discharge (Q) = 10 m³/s
- Velocity (V) = 2 m/s
Rearranging the formula to solve for Area (A):
A = Q / V
A = 10 m³/s / 2 m/s
A = 5.0 m²
Regardless of the shape of the canal (trapezoidal, rectangular, or circular), the relationship between discharge, area, and velocity remains the same.
Comparing this result to the options:
- Option (a) 2.5 m² is incorrect (result of 5/2).
- Option (b) 5.0 m² is correct.
- Option (c) 10.0 m² is incorrect (this is the value of the discharge).
- Option (d) 15.0 m² is incorrect.
Which of the following is NOT a type of canal alignment?
A)
Watershed canal
B)
Contour canal
C)
Side slope canal
D)
Lateral canal
In canal engineering, 'alignment' refers to the path or layout of the canal relative to the topography of the land.
1. **Watershed Canal (Option a):** This is a type of alignment where the canal is aligned along the ridge line (watershed) of the area. This allows irrigation to be provided to both sides of the canal by gravity.
2. **Contour Canal (Option b):** This is an alignment that follows a constant elevation (contour line) of the terrain. It is used when the land is hilly or sloping, ensuring the canal maintains a steady grade without excessive cutting or filling.
3. **Lateral Canal (Option d):** While often categorized by function, in terms of layout, a lateral is a branch canal that takes off from a main canal to distribute water to specific fields. It is a recognized part of the canal network alignment system.
4. **Side Slope Canal (Option c):** This is NOT a recognized type of canal alignment. 'Side slope' refers to the geometric slope of the canal banks (the ratio of horizontal to vertical distance) to ensure the stability of the embankment, but it does not describe the path or alignment of the canal across the landscape.
What is sub-surface drainage?
A)
A system that removes excess water from below the root zone
B)
A method to increase irrigation water
C)
A method to reduce fertilizer application
D)
A way to improve plant growth by adding chemicals
Sub-surface drainage refers to the removal of excess water from the soil profile (specifically from the root zone and below) to maintain an optimal balance of air and water for plant growth. This is typically achieved using perforated pipes, tiles, or gravel drains buried underground.
Analysis of options:
- Option (a) is correct because the primary purpose of sub-surface drainage is to lower the water table and remove saturated water from below the surface to prevent waterlogging.
- Option (b) is incorrect because drainage is the process of removing water, whereas irrigation is the process of adding water.
- Option (c) is incorrect because while drainage can improve nutrient uptake efficiency, its primary definition is not the reduction of fertilizer application.
- Option (d) is incorrect because drainage is a physical/hydraulic process of water removal, not a chemical additive process.
Using Chezy’s formula, V = C √(RS). If C=50, R=1.8 m, and S=0.0005, find velocity V.
A)
2.5m/s
B)
3.0m/s
C)
2.68 m/s
D)
1.5 m/s
Option C is correct: 2.68 m/s.
What is the primary advantage of using lined canals over unlined canals?
A)
Increased seepage losses
B)
Reduced seepage losses and increased efficiency
C)
Easier maintenance of canal embankments
D)
Reduced flow velocity
In canal engineering, lining refers to providing an impermeable layer (such as concrete, bricks, or plastic membranes) on the wetted perimeter of the canal.
1. **Seepage Control**: The primary purpose of lining is to prevent water from percolating into the ground (seepage), which is a major source of water loss in unlined canals. This ensures that more water reaches the intended command area.
2. **Increased Efficiency**: By reducing seepage and providing a smoother surface (lower Manning's roughness coefficient), the flow velocity increases. This allows for a smaller cross-sectional area to carry the same discharge, reducing land acquisition costs and increasing overall conveyance efficiency.
Analysis of other options:
- Option (a) is incorrect because lining *decreases* seepage losses, not increases them.
- Option (c) is incorrect because while lining helps prevent erosion, the primary 'advantage' is hydraulic efficiency and water conservation, not necessarily the ease of embankment maintenance.
- Option (d) is incorrect because lining reduces friction, which actually *increases* flow velocity compared to the rougher surface of an unlined canal.
Which of the following is NOT a preventive measure for waterlogging?
A)
Using well-planned irrigation techniques
B)
Installing drainage systems
C)
Growing water-demanding crops in all seasons
D)
Using raised beds for planting
Waterlogging occurs when the soil becomes saturated with water, displacing air from the soil pores and hindering root respiration. To prevent this, measures must focus on controlling the amount of water entering the soil or facilitating its removal.
- Option (a) 'Using well-planned irrigation techniques' (such as drip or sprinkler irrigation) prevents waterlogging by applying only the required amount of water, avoiding over-irrigation.
- Option (b) 'Installing drainage systems' (such as surface or subsurface drains) is a primary preventive and corrective measure to remove excess water from the root zone.
- Option (d) 'Using raised beds for planting' helps prevent waterlogging by elevating the root zone above the saturated soil level, allowing for better aeration.
- Option (c) 'Growing water-demanding crops in all seasons' is NOT a preventive measure. While water-demanding crops (like rice) can tolerate waterlogging, planting them in all seasons does not prevent the soil from becoming waterlogged; in fact, if the soil is naturally prone to waterlogging or if irrigation is excessive, it does not solve the underlying drainage problem and may lead to soil degradation or salinity issues in the long run.
Which factor is most important when designing a drainage system layout?
A)
Soil type and permeability
B)
Color of the soil
C)
Plant height in the previous season
D)
The amount of fertilizers used
In agricultural drainage design, the primary goal is to remove excess water from the root zone to prevent waterlogging and salinity. The efficiency of water movement toward the drainage pipes or ditches is governed by the hydraulic conductivity of the soil, which is directly determined by the soil type (e.g., sandy, loamy, or clayey) and its permeability. Engineers use these factors to determine the spacing between drains and the depth of the system.
Why other options are incorrect:
- b. Color of the soil: While soil color can indicate drainage conditions (e.g., grey colors indicating anaerobic conditions), it is a symptom/indicator, not a design parameter used to calculate layout specifications.
- c. Plant height in the previous season: This is a biological outcome and does not influence the physical engineering requirements of the drainage infrastructure.
- d. The amount of fertilizers used: Fertilizer application is a nutrient management practice; it does not dictate the physical layout or hydraulic capacity of a drainage system.
Which method is NOT a technique of contouring?
A)
Direct method
B)
Indirect method
C)
Compass method
D)
Grid method
Contouring is the process of determining the layout of a surface by joining points of equal elevation. There are two primary methods of contouring:
1. Direct Method: In this method, the points on the contour line are located directly in the field using a level and a staff. It is highly accurate but very time-consuming.
2. Indirect Method: In this method, a grid or a series of cross-sections are established, and elevations are taken at specific points. The contour lines are then interpolated between these points in the office. Common techniques under the indirect method include:
- Grid method (or Square method)
- Cross-section method (or Radial line method),
- Tacheometric method.
Option (c) 'Compass method' is used for measuring directions (bearings) and plotting the horizontal plan of an area (traversing), but it cannot measure vertical elevations or be used as a technique to generate contour lines. Therefore, it is NOT a technique of contouring.
Which of the following best describes the primary function of a theodolite in surveying?
A)
Measuring horizontal and vertical angles with high precision
B)
Determining elevations and contours of land
C)
Measuring distances directly between two points
D)
Capturing digital survey data with automated processing
A theodolite is a precision instrument used in surveying primarily for the measurement of angles in both the horizontal and vertical planes.
1. Why Option (a) is correct: The fundamental design of a theodolite consists of a telescope mounted on two axes (horizontal and vertical), allowing the surveyor to sight targets and read the precise angular difference between them using graduated circles. This makes it the primary tool for establishing directions, calculating bearings, and determining vertical angles for trigonometric leveling.
2. Why Option (b) is incorrect: Determining elevations and contours is the primary function of a Level (e.g., Dumpy level or Auto level). While a theodolite can be used for trigonometric leveling, it is not its primary function compared to a level.
3. Why Option (c) is incorrect: Measuring distances directly is the function of a tape, chain, or Electronic Distance Measurement (EDM) device. A standard theodolite measures angles, not linear distances (though a 'Total Station' combines a theodolite with an EDM).
4. Why Option (d) is incorrect: Capturing digital survey data with automated processing describes a Total Station or GPS/GNSS receiver. A traditional theodolite is an optical instrument; while digital theodolites exist, the 'primary function' remains angle measurement, not the overall data processing workflow.
The discharge (Q) in a rectangular channel is: Width of channel (b) = 3 m, Depth of flow (h) = 1.2 m, Velocity (V)=1.5 m/s
A)
4.9 m3/s
B)
5.4 m/s
C)
5.6m*/s
D)
5.1 m*/s
To find the discharge (Q) in a rectangular channel, we use the continuity equation: Q = A × V, where 'A' is the cross-sectional area of the flow and 'V' is the average velocity.
Step 1: Calculate the cross-sectional area (A) of the rectangular channel.
Area (A) = Width (b) × Depth of flow (h)
A = 3 m × 1.2 m = 3.6 m²
Step 2: Calculate the discharge (Q).
Q = A × V
Q = 3.6 m² × 1.5 m/s = 5.4 m³/s
Note on Options: While the correct numerical value is 5.4, the unit provided in option (b) is written as 'm/s' (velocity unit) instead of 'm³/s' (discharge unit). However, based on the calculation, 5.4 is the only mathematically correct value. Options a, c, and d are numerically incorrect. Therefore, option (b) is the intended correct answer despite the typographical error in the unit.
In which situation is a contour canal preferred over a watershed canal?
A)
When the region has a flat terrain
B)
When the land has undulating topography with steep slopes
C)
When there are many natural streams in the area
D)
When the canal needs to avoid excessive excavation
In canal engineering, the choice between a watershed canal and a contour canal depends primarily on the topography of the land:
1. **Watershed (Ridge) Canal**: This canal is aligned along the ridge line of the watershed. Its primary advantage is that it can irrigate land on both sides of the canal by gravity. However, it is only feasible when the ridge line is relatively straight and the terrain allows for such alignment.
2. **Contour Canal**: A contour canal is aligned approximately parallel to the contours of the land. It is specifically preferred in undulating topography or hilly regions where the land has steep slopes. Because it follows a constant elevation (or a very slight gradient), it avoids the massive excavation and embankment work that would be required if one tried to force a ridge alignment in rugged terrain.
Analysis of options:
- Option (a) is incorrect because in flat terrain, simple aligned canals are used; contouring is not a necessity.
- Option (b) is correct because contour canals are the standard solution for undulating and steep terrains to maintain a steady bed slope while minimizing earthwork.
- Option (c) is incorrect as the presence of natural streams affects the number of aqueducts or siphons needed, but not the fundamental choice between ridge and contour alignment.
- Option (d) is a general goal of all canal engineering, but the specific 'situation' that triggers the preference for a contour canal over a watershed canal is the topography (undulating/steep slopes).