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Past Questions
Irrigation canals are generally aligned along-
A)
Ridgeline
B)
Valley line
C)
Contour line
D)
Both (a) & (b) as per the design requirement
In irrigation engineering, the alignment of a canal is critical for efficient water distribution.
1. **Ridgeline Alignment (Watershed Alignment):** A canal aligned along the ridgeline (the highest point of the land) is known as a 'Watershed Canal'. The primary advantage of this alignment is that it allows the canal to irrigate land on both sides of the canal using gravity. This maximizes the command area and minimizes the need for expensive pumping or cross-drainage works.
2. **Contour Alignment:** While canals often follow a contour to maintain a steady slope (gradient), a pure contour alignment only allows irrigation on one side (the downhill side), which is less efficient than a ridgeline alignment.
3. **Valley Line Alignment:** Aligning a canal along a valley line is generally avoided because it would require the canal to be elevated on embankments or would lead to the canal acting as a drain for the surrounding area, necessitating numerous and costly cross-drainage structures (like aqueducts or siphons) to handle natural streams crossing the valley.
Therefore, for maximum command area and gravity-based distribution, the ridgeline is the preferred general alignment.
The duty of water is defined as:
A)
The depth of water required per hectare
B)
The amount of water required per unit crop area
C)
The number of hectares irrigated per unit discharge
D)
The loss of water due to evapotranspiration
In irrigation engineering, 'Duty' (D) is defined as the area of land that can be irrigated by a constant unit discharge of water flowing throughout the base period of the crop. It is typically expressed in hectares per cumec (ha/cumec).
Mathematically, Duty = Area / Discharge.
Analysis of options:
- Option (a) and (b) describe 'Delta' (Δ), which is the total depth of water required by a crop during its entire growth period.
- Option (c) correctly defines 'Duty' as the relationship between the area irrigated and the rate of flow (discharge).
- Option (d) describes 'Evapotranspiration', which is a component of water loss, not the definition of duty.
Which statement best describes the relationship between Delta, Duty, and Base Period?
A)
Higher Delta leads to lower Duty
B)
Lower Base Period increases Delta
C)
Duty is independent of Base Period
D)
Higher Duty reduces Base Period
The relationship between Duty (D), Delta (Δ), and Base Period (B) is defined by the fundamental irrigation formula:
Δ = (8.64 * B) / D
Or rearranged as:
D = (8.64 * B) / Δ
Where:
- Δ (Delta) is the total depth of water required by a crop during the entire base period (measured in meters or cm).
- D (Duty) is the area of land that can be irrigated by a unit discharge of water flowing continuously for the base period (measured in hectares/cumec).
- B (Base Period) is the time between the first watering and the last watering of a crop (measured in days).
Analysis of the options:
1. Option (a): According to the formula D = (8.64 * B) / Δ, Duty (D) is inversely proportional to Delta (Δ). Therefore, if the total depth of water required (Delta) increases, the area that a unit of water can cover (Duty) decreases. This is correct.
2. Option (b): Delta is a characteristic of the crop and the soil; it is not increased by lowering the Base Period. In fact, Delta is the total water depth over the entire Base Period.
3. Option (c): Duty is directly proportional to the Base Period (D ∝ B). If the base period increases, the same unit of water can serve a larger area over time. Thus, Duty is not independent of the Base Period.
4. Option (d): Higher Duty means the water is used more efficiently to cover more area; it does not inherently reduce the biological Base Period of the crop.
Plane table surveying is best suited for-
A)
Large-scale geodetic surveys
B)
Highly accurate and precise measurements
C)
Quick and small-scale mapping
D)
Hydrographic surveys
Plane table surveying is a graphical method of surveying where field observations and plotting are done simultaneously.
1. Why Option (c) is correct: Because the plotting is done in the field, there is no need for separate field notes or office-based plotting. This makes the process very fast (quick). It is typically used for filling in details between primary control points or for mapping small areas where extreme precision is not the primary requirement, making it ideal for quick, small-scale mapping.
2. Why Option (a) is incorrect: Geodetic surveys account for the curvature of the earth and require extremely high precision and complex calculations. Plane table surveying assumes the earth is a flat plane, making it unsuitable for geodetic surveys.
3. Why Option (b) is incorrect: Plane table surveying is generally less accurate than theodolite or total station surveying because it is subject to errors in plotting and sighting in the field.
4. Why Option (d) is incorrect: Hydrographic surveys involve mapping water bodies. Plane table surveying requires a stable, flat surface to set up the board and direct line-of-sight to land-based features, which is not applicable to underwater or deep-water mapping.
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 (Horizontal:Vertical). This means for every 1 unit of vertical depth, the width increases by 1 unit on each side.
2. **Formula for Top Width (T):**
The top width of a trapezoidal channel is calculated as:
T = b + 2 * (z * d)
3. **Calculation:**
- Horizontal projection of one side slope = z * d = 1 * 2 m = 2 m
- Since there are two side slopes (left and right), the total increase in width is 2 * 2 m = 4 m.
- Top Width (T) = 4 m (bottom width) + 4 m (side projections) = 8 m.
4. **Verification of Options:**
- Option (a) 6m: Incorrect. This would occur if the side slope was 0.5:1.
- Option (b) 8m: Correct.
- 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.
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.
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 levelling, a Backsight (BS) is defined as the first staff reading taken after the instrument is set up. This reading is 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.
- 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) describes a 'Change Point' reading, which serves as both a Foresight (for the old instrument position) and a Backsight (for the new instrument position), but the term 'backsight' specifically refers to the reading taken *back* to the known point.
- Option (d) is incorrect as backsights are primary measurements, not specific tools for error correction (though they are used in calculations to check for errors).
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 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 can be a BS), but the definition of a BS is specifically the reading taken *back* toward a known point, whereas the reading taken *away* from the instrument at a change point is the FS. Option (b) is the more precise general definition.
- Option (d) is incorrect; while BS is used in calculations, it is not a specific 'reading used for error correction' (that would be a check reading or a closing reading).
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 Canal (Ridge Canal):** This canal is aligned along the ridge line (watershed) of the area. It allows irrigation on both sides of the canal through gravity. However, it is only feasible in regions where the ridge is relatively straight and the terrain is not excessively steep or undulating.
2. **Contour Canal:** A contour canal is aligned approximately parallel to the contours of the land. It is specifically preferred in hilly or undulating terrain where the land has steep slopes. Because it follows the natural contour, it minimizes the need for massive earthworks (cutting and filling) that would be required to maintain a ridge alignment in rugged terrain.
**Analysis of Options:**
- **Option (a):** In flat terrain, a ridge canal or a simple aligned canal is preferred; contouring is unnecessary.
- **Option (b):** Correct. In undulating topography with steep slopes, following the contour is the most practical way to maintain a steady gradient for water flow while minimizing construction costs.
- **Option (c):** The presence of natural streams affects the number of aqueducts or siphons needed, but it is not the primary deciding factor between watershed and contour alignment.
- **Option (d):** While contour canals do reduce excavation compared to a forced ridge alignment in hills, the *primary situation* that necessitates their use is the topography itself (undulating/steep slopes).
If a rain gauge recorded 50 mm of rainfall in 10 hours, what is the average intensity of rainfall?
A)
2.5 mm/hr
B)
5 mm/hr
C)
7.5 mm/hr
D)
10 mm/hr
The average intensity of rainfall is defined as the total depth of precipitation recorded divided by the duration of the rainfall event.
Given data:
- Total rainfall depth (P) = 50 mm
- Duration of rainfall (t) = 10 hours
Formula:
Average Intensity (I) = Total Rainfall / Duration
I = 50 mm / 10 hours
I = 5 mm/hr
Evaluating the options:
- Option (a) 2.5 mm/hr is incorrect as it would result from 25 mm of rain in 10 hours.
- Option (b) 5 mm/hr is correct based on the calculation.
- Option (c) 7.5 mm/hr is incorrect as it would result from 75 mm of rain in 10 hours.
- Option (d) 10 mm/hr is incorrect as it would result from 100 mm of rain in 10 hours.
Why is geodetic surveying necessary for large infrastructure projects?
A)
It simplifies the survey process
B)
It considers the earth’s curvature
C)
It reduces project costs
D)
It eliminates the need for levelling
Surveying is broadly divided into two categories: Plane Surveying and Geodetic Surveying.
1. Plane Surveying: Assumes the earth's surface to be a flat plane. This is acceptable for small areas (typically less than 250 sq km) because the effect of the earth's curvature is negligible.
2. Geodetic Surveying: Accounts for the true ellipsoidal or spherical shape of the earth. For large-scale infrastructure projects (such as national highways, long-distance pipelines, or state-wide irrigation networks), the curvature of the earth becomes significant. If ignored, it leads to cumulative errors in distance and angle measurements, which can cause catastrophic misalignment in construction.
Analysis of options:
- Option (a) is incorrect because geodetic surveying is significantly more complex and mathematically intensive than plane surveying.
- Option (c) is incorrect because geodetic surveying usually increases costs due to the need for high-precision instruments (like GPS/GNSS) and complex calculations.
- Option (d) is incorrect because levelling is still required to determine elevations; geodetic surveying deals with the horizontal shape/curvature, not the elimination of vertical control.
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
Step-by-step reasoning:
1. **Definition**: Crop Water Requirement (CWR) is defined as the total quantity of water required by a crop for its normal growth and yield. This includes water used for transpiration by the plant and water evaporated from the soil surface and plant parts (collectively known as Evapotranspiration, ET).
2. **Components**: CWR accounts for the water needed to replace losses due to evapotranspiration and to satisfy the metabolic needs of the plant throughout its growth cycle.
3. **Analysis of Options**:
- **Option (a)** is incorrect because CWR is not just a yearly figure; it is specific to the growth cycle of the crop and varies by crop type and climate.
- **Option (b)** is correct as it encompasses the total water necessity (from all sources, including rain) to ensure optimal growth and yield.
- **Option (c)** is incorrect because this describes 'Irrigation Requirement'. Irrigation requirement is the portion of the Crop Water Requirement that is not met by effective rainfall.
- **Option (d)** is incorrect because CWR refers to the biological need of the plant, regardless of whether the water source is groundwater, surface water, or precipitation.
Which type of traversing is best suited for an area with multiple obstacles?
A)
Open traverse
B)
Closed traverse
C)
Radial traverse
D)
Triangulation
In surveying, traversing is the process of establishing a series of connected lines.
1. **Closed Traverse (Option b):** A closed traverse starts and ends at the same point or connects two known points. This is the best choice for areas with multiple obstacles because the surveyor can 'navigate around' the obstacles by adjusting the path of the traverse. Furthermore, because it closes on itself, it allows for the calculation of the 'closing error,' enabling the surveyor to check for accuracy and distribute errors mathematically (using methods like Bowditch's rule), which is critical when the path is irregular due to obstacles.
2. **Open Traverse (Option a):** An open traverse does not return to the starting point or close on a known point. It is used for linear features like roads or rivers. It provides no way to check for cumulative errors, making it unreliable for complex areas with obstacles.
3. **Radial Traverse (Option c):** In a radial traverse, all lines are measured from a single central point. This is only feasible if the central point has a clear line of sight to all other points. If there are multiple obstacles, the line of sight is blocked, making this method impossible to implement.
4. **Triangulation (Option d):** While triangulation is a highly accurate method for large areas, it relies on the creation of a network of triangles. It requires clear inter-visibility between stations. In an area with many obstacles, establishing these clear lines of sight for a triangle network is significantly more difficult than simply 'walking' a closed traverse around the obstacles.
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 water input or increasing water removal.
- Option (a) 'Using well-planned irrigation techniques' (such as drip or sprinkler irrigation) prevents over-watering, thus preventing waterlogging.
- Option (b) 'Installing drainage systems' (such as surface or subsurface drains) allows excess water to exit the root zone, directly preventing waterlogging.
- Option (d) 'Using raised beds for planting' improves aeration and allows excess water to drain away from the plant roots into the furrows, preventing saturation of the root zone.
- 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 already prone to waterlogging, this practice does nothing to mitigate the physical condition of the soil and may lead to salinity or alkalinity issues in other crop cycles.
How does a total station improve accuracy in surveying compared to a theodolite?
A)
It reduces the need for manual calculations
B)
It can measure underground features
C)
It works without needing a reference point
D)
It automatically adjusts for atmospheric conditions
A Total Station is an electronic/optical instrument that integrates an Electronic Distance Meter (EDM) with a digital theodolite and an onboard microprocessor.
1. Why Option (a) is correct: In traditional theodolite surveying, the surveyor must manually read angles and measure distances (using a tape or chain), and then perform trigonometric calculations (like sine and cosine rules) to determine the coordinates (X, Y, Z) of a point. A Total Station performs these calculations automatically and instantaneously using its internal microprocessor, which significantly reduces human error associated with manual data recording and mathematical computation, thereby improving the overall accuracy and efficiency of the survey.
2. Why Option (b) is incorrect: Total Stations use light/infrared waves (EDM) which require a line-of-sight. They cannot penetrate the ground to measure underground features; that would require Ground Penetrating Radar (GPR) or seismic surveying.
3. Why Option (c) is incorrect: Every survey requires a reference point (benchmark or known station) to establish a coordinate system. A Total Station still needs a known starting point and orientation to provide absolute coordinates.
4. Why Option (d) is incorrect: While some high-end Total Stations allow the user to input atmospheric corrections (temperature and pressure) to adjust the EDM's speed of light calculations, they do not 'automatically' adjust for all atmospheric conditions without input or calibration; more importantly, this is a feature of the EDM component, whereas the primary systemic improvement over a theodolite is the integration of measurement and calculation.
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 to recharge groundwater. The 'effective' part is the remaining water that exceeds the infiltration capacity of the soil and flows over the land surface as surface runoff, which eventually reaches the stream or outlet.
Analysis of options:
- Option (a) is incorrect because total rainfall includes water that is lost to evaporation and interception.
- Option (b) is correct as it identifies the portion that actually contributes to the hydrological response (runoff) and the subsurface movement (infiltration/baseflow).
- Option (c) describes 'interception loss' or 'evaporation', not effective rainfall.
- Option (d) describes 'surface storage', which is a result of rainfall but not the definition of effective rainfall.
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 facility established at a specific point along a river or stream to monitor and measure the volume of water moving past that point over time.
1. **Streamflow and Discharge**: The primary objective of these stations is to determine the 'discharge' (Q), which is the volume of water flowing per unit of time (typically measured in m³/s or cusecs). Discharge is calculated using the formula Q = A × V, where A is the cross-sectional area of the channel and V is the average velocity of the flow.
2. **Why other options are incorrect**:
- **Option a (River velocity only)**: While velocity is measured at a gauging station, it is merely a component used to calculate the total discharge. Measuring velocity alone does not fulfill the primary purpose of gauging the stream's flow volume.
- **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 monitor the phreatic surface of an aquifer, not the surface flow of a stream.
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 based on the soil's hydraulic properties, specifically its infiltration rate and water-holding capacity.
1. **Infiltration Rate:** Sandy soils have high infiltration rates (water absorbs quickly). If a surface irrigation method like flood or furrow irrigation is used on sandy soil, the water will seep deep into the ground before it can reach the end of the field, leading to massive water waste and uneven distribution. In such cases, drip or sprinkler irrigation is preferred.
2. **Water Retention:** Clayey soils have low infiltration rates and high water retention. Using high-volume surface irrigation on clay can lead to waterlogging and anaerobic conditions for roots.
Evaluating the options:
- **Option a** is correct because it accurately describes how soil permeability (absorption speed) dictates the efficiency of the irrigation method.
- **Option b** is incorrect because different soils react differently to water application (e.g., flood irrigation is inefficient in sand).
- **Option c** is incorrect because soil type affects both the biological growth of the crop and the physical movement of water (hydraulics).
- **Option d** is incorrect because while water availability is a factor, it is not the *only* factor; soil type, topography, and crop type are equally critical.
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 triangulation and traversing.
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 (unless it is a Total Station, which is a combination of a theodolite and an EDM).
4. **Why Option (d) is incorrect:** Capturing digital data with automated processing describes a Total Station or GPS/GNSS receiver. A traditional theodolite is an optical instrument requiring manual readings.
If the flow in an irrigation canal is subcritical, what does it indicate?
A)
The flow is slow and controlled by downstream conditions
B)
The flow is fast and controlled by upstream conditions
C)
The canal is in supercritical flow
D)
The flow is always uniform
In fluid mechanics, flow is classified based on the Froude Number (Fr), where Fr = v / √(gD).
1. Subcritical Flow (Fr < 1): This occurs when the flow velocity is low (slow) relative to the wave speed. In this regime, disturbances (waves) can travel upstream. Consequently, the water level and flow characteristics are influenced by downstream conditions (e.g., a weir, a gate, or a narrowing downstream). This is typical for most irrigation canals to prevent erosion of the canal bed.
2. Supercritical Flow (Fr > 1): This occurs when the flow velocity is high (fast). Disturbances cannot travel upstream; therefore, the flow is controlled by upstream conditions (e.g., the slope of the channel or the headwater level).
Evaluating the options:
- Option (a) is correct because subcritical flow is characterized by low velocity and downstream control.
- Option (b) describes supercritical flow.
- Option (c) is a contradiction; subcritical flow cannot be supercritical flow.
- Option (d) is incorrect because subcritical flow can be either uniform or non-uniform (varied flow).
Which of the following best describes a catchment area?
A)
A low-lying region with high rainfall
B)
An area where rainfall is completely absorbed
C)
A region from which all precipitation drains into a common outlet
D)
A part of a river prone to flooding
Step-by-step reasoning:
1. Definition: In hydrology, a catchment area (also known as a drainage basin or watershed) is the entire geographical area from which surface runoff and groundwater flow into a single point, such as a river, lake, or reservoir (the common outlet).
2. Analysis of Option (a): A low-lying region with high rainfall describes a specific climatic or topographic condition, not the functional definition of a catchment.
3. Analysis of Option (b): An area where rainfall is completely absorbed describes a region with high infiltration or a 'sink,' whereas a catchment is defined by the movement of water toward an outlet.
4. Analysis of Option (c): This aligns perfectly with the scientific definition. The boundaries of a catchment are defined by topographic ridges (divides) that direct all precipitation within that boundary toward a common exit point.
5. Analysis of Option (d): A part of a river prone to flooding describes a 'floodplain,' which is a feature within a catchment, but not the catchment area itself.
Why are clayey soils more prone to waterlogging compared to sandy soils?
A)
Clayey soils have larger pore spaces
B)
Clayey soils allow faster infiltration
C)
Clayey soils have lower permeability
D)
Clayey soils absorb more oxygen
Waterlogging occurs when the soil becomes saturated and water cannot drain away efficiently. The ability of soil to transmit water is known as permeability (or hydraulic conductivity).
1. **Clayey Soils:** These soils consist of very fine particles that pack closely together. While they have a high total porosity (more total void space), the individual pores are microscopic (micropores). These small pores create high friction and capillary forces that significantly restrict the movement of water, resulting in low permeability. Consequently, water accumulates in the root zone, leading to waterlogging.
2. **Sandy Soils:** These consist of larger particles with larger interconnected spaces (macropores). This allows water to move rapidly through the soil profile via gravity, resulting in high permeability and a lower risk of waterlogging.
Evaluating the options:
- **Option a** is incorrect because clayey soils have smaller individual pore spaces (micropores) compared to sandy soils.
- **Option b** is incorrect because clayey soils have much slower infiltration rates due to their fine texture.
- **Option d** is incorrect because waterlogging actually displaces oxygen from the soil, leading to anaerobic conditions; clayey soils do not 'absorb more oxygen' to prevent waterlogging.
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
In canal engineering, 'side slope canals' refers to the standard trapezoidal cross-section used for most unlined canals. The major disadvantage of this design, particularly when constructed in pervious soils, is the large wetted perimeter relative to the flow area. Because the water is in direct contact with the soil along the side slopes and the bed, there is a significant amount of water loss through seepage into the ground. To mitigate this, lining (such as concrete or LDPE) is often required.
Evaluating other options:
- (a) High construction cost: Side slope (trapezoidal) canals are generally the most economical to excavate compared to complex reinforced structures.
- (c) Prone to landslides: While slope stability is a design consideration, it is a failure mode rather than a general 'major disadvantage' of the canal type itself, provided the slope is designed according to the angle of repose of the soil.
- (d) Requires pumping stations: Pumping stations are required based on the topography (lift irrigation) and the head of the water source, not based on the cross-sectional shape (side slopes) of the canal.
Which crop season in India typically requires the highest irrigation?
A)
Kharif
B)
Rabi
C)
Zaid
D)
Monsoon
In India, crop seasons are primarily categorized based on the monsoon cycle.
1. **Kharif Season (June to October):** These are monsoon crops (e.g., rice, maize, cotton). Since they are grown during the period of heaviest rainfall in India, they rely heavily on precipitation, and while irrigation is used to supplement rainfall, the overall external irrigation requirement is lower than in the dry season.
2. **Rabi Season (November to April):** These are winter crops (e.g., wheat, mustard, barley). This season coincides with the dry winter and spring months when there is very little to no rainfall. Consequently, these crops are almost entirely dependent on artificial irrigation (canals, tube wells, etc.) to meet their water requirements.
3. **Zaid Season (March to June):** This is a short summer season (e.g., watermelon, cucumber). While these crops require irrigation due to high temperatures, the total volume of water required for the entire Zaid season is significantly less than that of the primary Rabi season due to the shorter duration and smaller scale of cultivation.
4. **Monsoon:** This is a climatic period, not a distinct crop season separate from Kharif.
Therefore, because the Rabi season occurs during the driest part of the year, it typically requires the highest amount of irrigation.
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 tracks the discharge (Q) of a stream over a period of time (t).
2. Analysis of Options:
- Option (a) describes a 'water table fluctuation' or 'piezometric head' plot, not a hydrograph.
- Option (b) correctly identifies the relationship between stream flow (discharge) and time.
- Option (c) describes a 'hyetograph', which is a plot of rainfall intensity versus time.
- Option (d) describes soil moisture profiles or monitoring, which is a different parameter of the hydrological cycle.
3. Conclusion: Since a hydrograph measures the response of a catchment to a rainfall event by plotting the resulting streamflow, option (b) is the correct technical definition.