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Past Questions
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 m³/s
C)
5.6 m³/s
D)
5.1 m³/s
Option B is correct: 5.4 m³/s.
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
Option B is correct: The canal will experience silting.
What is the critical velocity ratio in irrigation canal design?
A)
Ratio of actual velocity to gravitational velocity
B)
Ratio of mean velocity to critical velocity
C)
Ratio of design velocity to maximum velocity
D)
Ratio of surface velocity to bottom velocity
Option B is correct: Ratio of mean velocity to critical velocity.
What does the term “Crop Water Requirement” refer to?
A)
The amount of water needed to cultivate a crop per year
B)
The total water required for a crop to grow and yield optimally
C)
The amount of water applied through irrigation alone
D)
The total groundwater required for irrigation
Option B is correct: The total water required for a crop to grow and yield optimally.
The main source of irrigation in India is-
A)
Wells
B)
Canals
C)
Rainwater
D)
Lakes
Option C is correct: Rainwater.
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
Option A is correct: 0.908 m/s.
Calculate the intensity of irrigation if the Gross Command Area (GCA) is 5000 hectares and the Culturable Command Area (CCA) is 4000 hectares.
A)
80%
B)
75%
C)
85%
D)
90%
Option A is correct: 80%.
What is the typical range of Manning’s roughness coefficient for concrete-lined canals?
A)
0.002 — 0.005
B)
0.006 — 0.009
C)
0.012 — 0.017
D)
0.02 — 0.03
Option C is correct: 0.012 — 0.017.
What is the major disadvantage of side slope canals?
A)
High construction cost
B)
Excessive water loss due to seepage
C)
Prone to landslides and slope instability
D)
Requires pumping stations
Option C is correct: Prone to landslides and slope instability.
Which factor has the most significant impact on the duty of water in an irrigation system?
A)
Type of irrigation method
B)
Rainfall in the region
C)
Soil fertility
D)
Crop maturity duration
Option A is correct: Type of irrigation method.
What is the primary purpose of irrigation in agriculture?
A)
Increase land value
B)
Prevent soil erosion
C)
Ensure adequate moisture for crops
D)
Reduce temperature
Option C is correct: Ensure adequate moisture for crops.
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)
Low initial investment cost
Option D is correct: Low initial investment cost.
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
Option B is correct: Reduced seepage losses and increased efficiency.
What is the critical velocity ratio in irrigation canal design?
A)
Ratio of actual velocity to gravitational velocity
B)
Ratio of mean velocity to critical velocity
C)
Ratio of design velocity to maximum velocity
D)
Ratio of surface velocity to bottom velocity
In open channel hydraulics and irrigation canal design, the 'Critical Velocity Ratio' (often associated with the Froude Number) is defined as the ratio of the actual mean velocity of flow to the critical velocity.
1. **Mean Velocity (v):** The average velocity of the water flowing through the cross-section of the canal.
2. **Critical Velocity (vc):** The velocity at which the specific energy is minimum for a given discharge. It is mathematically expressed as vc = √(g * d), where g is the acceleration due to gravity and d is the hydraulic depth.
When the ratio (v/vc) is less than 1, the flow is subcritical (tranquil); when it is equal to 1, the flow is critical; and when it is greater than 1, the flow is supercritical (rapid).
Comparing the options:
- Option (a) is incorrect as 'gravitational velocity' is not a standard term used in this ratio.
- Option (c) is incorrect as design velocity and maximum velocity are parameters for stability and erosion, not the critical ratio.
- Option (d) is incorrect as the ratio of surface to bottom velocity relates to the velocity distribution profile, not the critical state of flow.
The primary purpose of stream gauging station is-
A)
River velocity only
B)
Streamflow and discharge
C)
Rainfall intensity
D)
Groundwater table levels
A stream gauging station is a dedicated facility established on a river or stream to monitor and measure the volume of water flowing past a specific point per unit of time.
1. **Streamflow and Discharge**: The primary objective of these stations is to determine the 'discharge' (Q), which is the volume of water moving through a cross-section of the stream (typically measured in cubic meters per second, m³/s). This is achieved by measuring the water level (stage) using a gauge and correlating it with the flow velocity or using a rating curve.
2. **Why other options are incorrect**:
- **Option a (River velocity only)**: While velocity is measured to calculate discharge, it is a means to an end, not the primary purpose of the station. Discharge is the final required parameter.
- **Option c (Rainfall intensity)**: This is measured by rain gauges (pluviometers), not stream gauging stations.
- **Option d (Groundwater table levels)**: This is measured using observation wells or piezometers, which are distinct from surface water gauging stations.
Which of the following is NOT a component of the hydrological cycle?
A)
Evaporation
B)
Condensation
C)
Photosynthesis
D)
Precipitation
The hydrological cycle (water cycle) describes the continuous movement of water on, above, and below the surface of the Earth.
1. Evaporation (Option a): This is a primary component where liquid water from oceans, lakes, and rivers turns into water vapor due to heat from the sun.
2. Condensation (Option b): This occurs when water vapor in the atmosphere cools and changes back into liquid droplets, forming clouds.
3. Precipitation (Option d): This is the process where condensed water falls back to the Earth's surface as rain, snow, sleet, or hail.
Photosynthesis (Option c), however, is a biological process used by plants, algae, and some bacteria to convert light energy into chemical energy (glucose) using carbon dioxide and water. While water is a reactant in photosynthesis, the process itself is a part of the carbon cycle and biological energy production, not a fundamental driver or component of the global hydrological cycle.
How does drip irrigation help in reducing field irrigation requirement?
A)
By minimizing runoff
B)
By increasing infiltration
C)
By delivering water directly to the root zone
D)
All of the above
Drip irrigation (also known as trickle irrigation) is a highly efficient method of irrigation that reduces the overall field irrigation requirement through several mechanisms:
1. **Delivering water directly to the root zone (Option c):** This is the primary mechanism. By applying water slowly and precisely at the base of the plant, it eliminates water waste on non-cropped areas (inter-row spaces), significantly reducing the total volume of water needed compared to flood or sprinkler irrigation.
2. **Minimizing runoff (Option a):** Because water is applied at a very low rate (drop by drop), the application rate is typically lower than the soil's infiltration rate. This prevents surface ponding and subsequent runoff, ensuring almost all applied water enters the soil profile.
3. **Increasing infiltration/Efficiency (Option b):** While 'increasing infiltration' in a general sense might seem ambiguous, in the context of drip irrigation, it refers to the high efficiency of water penetration into the root zone without saturation of the entire field. It optimizes the soil-water-plant relationship by maintaining a moist 'wetting bulb' around the roots, reducing deep percolation losses.
Since all three factors contribute to the reduction of the total field irrigation requirement, the correct answer is 'All of the above'.
What happens if the base period of crop is increased while keeping Delta constant?
A)
The duty increases
B)
The duty decreases
C)
The duty remains unchanged
D)
The depth of irrigation increases
Option B is correct: The duty decreases.
Why does the duty of water increase as it moves downstream?
A)
Water loss due to infiltration
B)
Water use efficiency improves
C)
Reduction in seepage losses
D)
Increased evaporation
In irrigation engineering, 'Duty' is defined as the area of land that can be irrigated by a constant supply of 1 cumec of water throughout the base period. The relationship between Duty (D) and Delta (Δ) is given by the formula: D = 8.64 B / Δ.
When water is released from the head of a canal, a significant portion is lost due to seepage (infiltration into the ground) and evaporation as it travels downstream. Therefore, to deliver a specific amount of water (Delta) to a field at the downstream end, a larger volume of water must be released at the head.
However, the question asks why the 'Duty' increases as it moves downstream. This is a conceptual point regarding the 'Duty at the head' vs 'Duty at the field'. The Duty at the head is always lower than the Duty at the field because the head discharge must account for all transit losses. As water moves downstream, the 'losses' have already occurred; the water remaining is used more effectively for the remaining area. More accurately, the 'Duty' is higher at the field (downstream) than at the head because the water reaching the field does not need to cover the losses incurred during transit. Thus, the increase in duty downstream is a direct result of accounting for the water lost due to infiltration/seepage and evaporation upstream.
What does a hydrograph represent?
A)
Changes in groundwater table over time
B)
Flow variations in a stream over time
C)
Rainfall intensity variations
D)
Soil moisture variations
A hydrograph is a fundamental tool in hydrology defined as a graph showing the rate of flow (discharge) versus time past a specific point in a river or stream.
Step-by-step reasoning:
1. Definition: The term 'hydro' refers to water and 'graph' refers to a plot. In engineering hydrology, it specifically plots discharge (Q) on the y-axis and time (t) on the x-axis.
2. Purpose: It is used to analyze the response of a watershed to a specific rainfall event, helping engineers determine peak discharge and the time to peak, which are critical for designing culverts, bridges, and dams.
Analysis of other options:
- Option (a): Changes in the groundwater table over time are represented by a 'phreatic surface plot' or 'water table hydrograph' (a specific subset), but the general term 'hydrograph' refers to streamflow.
- Option (c): Rainfall intensity variations over time are represented by a 'Hyetograph'.
- Option (d): Soil moisture variations are typically monitored via sensors and plotted as moisture content curves, not hydrographs.
Why is it essential to conduct levelling before constructing a highway?
A)
To determine the exact quantity of cement required
B)
To establish the correct elevation and drainage slopes
C)
To identify underground water sources
D)
To check soil fertility
Levelling is a branch of surveying used to determine the relative heights (elevations) of points on the earth's surface. In highway construction, it is critical for two primary reasons: 1) Elevation: To design the vertical alignment of the road, ensuring that gradients are safe for vehicles and that the road follows the natural terrain efficiently to minimize earthwork (cutting and filling). 2) Drainage: Water is the primary enemy of pavement. Levelling allows engineers to establish precise slopes (camber and longitudinal gradients) so that rainwater drains away from the road surface into side drains, preventing hydroplaning and structural failure of the road.
Why other options are incorrect:
- Option (a): Cement quantity is determined by the structural design and volume of the pavement, not by levelling.
- Option (c): Identifying underground water sources requires geophysical surveys or bore-hole drilling, not surface levelling.
- Option (d): Soil fertility is a concern for agriculture, not for highway engineering; soil stability (CBR value) is checked via geotechnical testing, not levelling.
The key difference between plane and geodetic surveying is-
A)
The use of electronic instruments
B)
The type of data collected
C)
The consideration of earth’s curvature
D)
The number of surveyors required
In surveying, the fundamental distinction between plane and geodetic surveying is based on whether the curvature of the earth is taken into account.
1. Plane Surveying: In this method, the earth's surface is treated as a flat plane. The curvature of the earth is neglected, and all lines are considered straight and all angles are plane angles. This is acceptable for small areas (typically less than 250 square kilometers) where the error introduced by ignoring curvature is negligible.
2. Geodetic Surveying: This method accounts for the true spherical (or ellipsoidal) shape of the earth. It is used for large-scale surveys, high-precision work, and establishing national control networks. In geodetic surveying, lines are considered arcs and angles are spherical angles.
Analysis of other options:
- Option (a): Both plane and geodetic surveying can utilize electronic instruments (like Total Stations or GPS).
- Option (b): The type of data (distances, angles, coordinates) is essentially the same; only the mathematical treatment of that data differs.
- Option (d): The number of surveyors depends on the project scale and management, not the theoretical methodology of the survey.
Why do crops grown in dry climates typically develop deeper root systems compared to crops grown in humid climates?
A)
Dry climates have higher soil fertility
B)
Dry climates provide more groundwater recharge
C)
Roots grow deeper to access moisture stored at lower depths
D)
Higher temperature forces roots to extend horizontally
In dry (arid or semi-arid) climates, precipitation is low and evaporation rates are high, leading to a rapid depletion of moisture in the upper layers of the soil (the topsoil). To survive and maintain turgor pressure, plants evolve or adapt by extending their root systems deeper into the soil profile to reach the capillary fringe or deeper aquifers where moisture is stored and less susceptible to evaporation. In contrast, in humid climates, water is readily available in the upper soil layers, so plants do not need to invest significant metabolic energy into growing deep root systems.
Analysis of other options:
- Option (a) is incorrect because dry climates often have lower soil fertility due to lack of organic matter decomposition and leaching issues.
- Option (b) is incorrect because dry climates typically have lower groundwater recharge rates compared to humid climates due to low rainfall.
- Option (d) is incorrect because higher temperatures increase transpiration, which drives the need for vertical growth to find water, rather than horizontal extension.
Why is water requirement generally higher for crops grown in regions with high wind speeds?
A)
Wind reduces soil moisture content
B)
Wind increases evapotranspiration
C)
Wind increases the infiltration rate
D)
Wind prevents percolation losses
Step-by-step reasoning: 1. Water requirement for crops is primarily determined by the rate of water loss from the soil and the plant, a combined process known as evapotranspiration (ET). 2. Evapotranspiration consists of evaporation from the soil surface and transpiration from the plant leaves. 3. Wind affects this process by removing the saturated boundary layer of moist air immediately surrounding the leaf surface and the soil surface. 4. By replacing this moist air with drier air, wind maintains a steeper vapor pressure gradient between the plant/soil and the atmosphere, which significantly accelerates the rate of evaporation and transpiration. 5. Therefore, in regions with high wind speeds, the rate of evapotranspiration increases, leading to a higher water requirement for the crops to maintain turgidity and growth.
Analysis of other options:
- Option (a) is a result of the process, but 'increasing evapotranspiration' is the scientific mechanism that explains why the requirement is higher.
- Option (c) is incorrect because infiltration is the process of water entering the soil from the surface, which is primarily governed by soil texture and porosity, not wind speed.
- Option (d) is incorrect because percolation is the downward movement of water through the soil profile, which is not prevented by wind.
Effective rainfall is defined as:
A)
The total rainfall in a catchment
B)
The portion of rainfall that contributes to runoff and infiltration
C)
Rainfall that evaporates before reaching the ground
D)
The amount of rainfall stored in lakes
Effective rainfall (also known as excess rainfall) is the portion of the total precipitation that becomes direct runoff from a catchment area. In hydrology, when rain falls on a watershed, some of it is intercepted by vegetation, some evaporates, and a significant portion infiltrates into the soil. The water that remains after these losses (and after the soil reaches its saturation capacity) is what contributes to the streamflow or runoff. While the option text mentions 'runoff and infiltration', in the context of runoff hydrographs, effective rainfall specifically refers to the part of the rainfall that results in surface runoff. However, among the given choices, option (b) is the only one that correctly identifies effective rainfall as a 'portion' of the total rainfall contributing to the hydrological yield of the basin.
Why other options are incorrect:
- Option (a): This is 'Total Precipitation', not effective rainfall.
- Option (c): This describes 'Interception' or 'Evaporation', which are losses that reduce total rainfall to effective rainfall.
- Option (d): This describes 'Surface Storage', which is a destination for runoff, not the definition of the rainfall itself.