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Past Questions — 2025
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
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 of flow.
Step 1: Calculate the cross-sectional area (A) for a 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).
Discharge (Q) = Area (A) × Velocity (V)
Q = 3.6 m² × 1.5 m/s = 5.4 m³/s
Comparing this result to the given options:
- Option (a) 4.9 m³/s is incorrect.
- Option (b) 5.4 m³/s matches our calculation.
- Option (c) 5.6 m³/s is incorrect.
- Option (d) 5.1 m³/s is incorrect.
A canal supplies 0.2 cumecs of water to a field continuously for 8 hours. Determine the volume of water supplied.
A)
5760 m³
B)
3600 m³
C)
4800 m³
D)
6000 m³
To determine the total volume of water supplied, we use the formula: Volume = Discharge × Time.
1. **Identify the given values:**
- Discharge (Q) = 0.2 cumecs. 'Cumec' stands for cubic meters per second (m³/s).
- Time (t) = 8 hours.
2. **Convert time into seconds:**
Since the discharge is given per second, the time must be converted to seconds to maintain unit consistency.
- 1 hour = 60 minutes
- 1 minute = 60 seconds
- Therefore, 8 hours = 8 × 60 × 60 = 28,800 seconds.
3. **Calculate the Volume (V):**
- V = Q × t
- V = 0.2 m³/s × 28,800 s
- V = 5,760 m³
Comparing this result to the options:
- Option (a) 5760 m³ matches our calculation.
- Option (b) 3600 m³ is incorrect.
- Option (c) 4800 m³ is incorrect.
- Option (d) 6000 m³ is incorrect.
The main source of irrigation in India is-
A)
Wells
B)
Canals
C)
Rainwater
D)
Lakes
In India, groundwater is the primary source of irrigation. This category includes both open wells and tube wells. According to data from the Ministry of Jal Shakti and various agricultural reports, groundwater (wells) accounts for approximately 60% to 65% of the total irrigated area in India, surpassing surface water sources.
Analysis of options:
- a. Wells: Correct. Tube wells and open wells are the most widely used irrigation methods across most Indian states due to their accessibility and reliability.
- b. Canals: Incorrect. While canals are a significant source of irrigation (especially in Northern India), they cover a smaller percentage of the total irrigated area compared to wells.
- c. Rainwater: Incorrect. Rainwater is the basis for 'rain-fed' agriculture, but by definition, 'irrigation' refers to the artificial application of water to land, making rainwater a source of moisture rather than a source of irrigation.
- d. Lakes: Incorrect. Lakes are not used as a primary systemic source of irrigation on a national scale in India.
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 = A / P, where A is the cross-sectional area and P is the wetted perimeter.
1. **Given Data:**
- Bottom width (b) = 6 m
- Depth (h) = 3 m
- Side slope (m) = 1 (Horizontal:Vertical = 1:1)
2. **Calculate 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 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 = 6 + 8.4852 = 14.4852 m
4. **Calculate 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.
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 horizontal and vertical planes.
1. Why Option (a) is correct: The fundamental design of a theodolite consists of a telescope mounted on two perpendicular axes (horizontal and vertical), allowing the surveyor to measure horizontal angles (for triangulation and traversing) and vertical angles (for determining heights or slopes) with very high accuracy.
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 defining function compared to a level.
3. Why Option (c) is incorrect: Measuring distances directly is the function of a tape, chain, or Electronic Distance Meter (EDM). 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 survey system. A traditional theodolite is an optical instrument used for manual readings.
What is the primary focus of hydrology?
A)
Study of ocean currents
B)
Study of groundwater only
C)
Study of movement, distribution, and quality of water on Earth
D)
Study of air pressure and weather patterns
Hydrology is defined as the science that deals with the occurrence, circulation, distribution, and properties of water on Earth and its atmosphere. This includes the study of the hydrological cycle (precipitation, evaporation, transpiration, runoff, and infiltration), surface water (rivers, lakes), and groundwater.
Analysis of other options:
- Option (a) is incorrect because the study of ocean currents is specifically called 'Oceanography'.
- Option (b) is incorrect because groundwater is only one component of hydrology; the field also encompasses surface water and atmospheric water.
- Option (d) is incorrect because the study of air pressure and weather patterns is 'Meteorology'.
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 introduces significant errors if ignored. Therefore, geodetic surveying is necessary to maintain high precision over large distances.
Analysis of other options:
- Option (a) is incorrect because geodetic surveying is significantly more complex than plane surveying due to the advanced mathematics and instrumentation required.
- Option (c) is incorrect because geodetic surveying usually increases costs due to the need for specialized equipment (like GPS/GNSS) and expert personnel.
- Option (d) is incorrect because levelling is still a fundamental requirement for determining elevations, regardless of whether the horizontal control is plane or geodetic.
Using Dicken’s formula, estimate the peak discharge if the catchment area is 500 km² and the Dicken’s coefficient (C) is 25.
A)
1565 m³/s
B)
2643 m³/s
C)
2547 m³/s
D)
3070 m³/s
Option B is correct: 2643 m³/s.
The most common type of error in levelling is:
A)
Instrumental error
B)
Gross error
C)
Collimation error
D)
Systematic error
In levelling, errors are generally classified into three categories: Instrumental, Personal (Gross), and Natural. Among these, the most common and significant instrumental error encountered in the field is the Collimation Error.
1. Collimation Error: This occurs when the line of sight (line of collimation) is not perfectly horizontal when the instrument is levelled. It is the most frequent error because the instrument can easily be knocked out of adjustment during transport or use. It is typically corrected by keeping the backsight and foresight distances equal or by using the two-peg test.
2. Instrumental Error (Option a): This is a broad category. While collimation error is a type of instrumental error, 'Collimation error' is the specific, most common type within this category.
3. Gross Error (Option b): These are caused by human carelessness (e.g., misreading a staff or recording a wrong value). While they happen, they are not 'systematic' or 'common' in the technical sense of instrument behavior.
4. Systematic Error (Option d): This is a general classification of errors that follow a mathematical or physical law (including collimation error). However, the question asks for the 'most common type', and in the context of levelling, the specific answer is the collimation error.
What is the primary benefit of using GPS in surveying?
A)
It eliminates the need for fieldwork
B)
It provides high-accuracy elevation measurements
C)
It allows real-time positioning with minimal effort
D)
It replaces all traditional surveying techniques
Step-by-step reasoning:
1. Analysis of GPS (Global Positioning System): GPS is a satellite-based navigation system that allows a receiver to determine its absolute position (latitude, longitude, and altitude) anywhere on Earth.
2. Evaluating Option (a): GPS does not eliminate fieldwork; a surveyor must still physically go to the site to place the receiver on the specific point being measured.
3. Evaluating Option (b): While GPS provides elevation, traditional leveling (using a dumpy level or auto-level) is significantly more accurate for vertical measurements than standard GPS, which often has a higher margin of error in the Z-axis (vertical) compared to the X and Y axes.
4. Evaluating Option (c): This is the primary benefit. GPS allows for 'Real-Time Kinematic' (RTK) positioning, enabling surveyors to obtain coordinates instantly without the need for complex manual chaining or triangulation between points, drastically reducing the effort and time required for establishing control points.
5. Evaluating Option (d): GPS does not replace all traditional techniques. For example, in dense forests or urban canyons (where satellite signals are blocked), traditional methods like Total Station or Theodolite surveying are still essential.
Conclusion: The most accurate primary benefit among the choices is the ability to achieve real-time positioning with significantly reduced manual effort compared to traditional traverse methods.
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
Sprinkler irrigation is a pressurized irrigation system. To evaluate the options:
1. **Suitable for undulating terrain (Option a):** This is an advantage. Unlike surface irrigation, which requires precise land leveling, sprinklers can be used on uneven or sloping ground without causing massive runoff.
2. **Efficient water distribution (Option b):** This is an advantage. Sprinklers allow for precise control over the amount of water applied, reducing wastage compared to flood irrigation.
3. **Reduces soil erosion (Option c):** This is generally an advantage compared to furrow or flood irrigation on slopes, as it prevents the concentrated flow of water that strips topsoil (provided the application rate does not exceed the soil's infiltration rate).
4. **Low initial investment cost (Option d):** This is NOT an advantage; it is a major disadvantage. Sprinkler systems require significant capital for pumps, piping, nozzles, and control valves, making the initial setup cost much higher than traditional surface irrigation methods.
Therefore, option 'd' is the correct answer as it describes a disadvantage, not an advantage.
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.
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.
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.
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 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.
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 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 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.
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'.
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.
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.
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.
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%
Step-by-step calculation:
1. **Definitions**:
- **Gross Command Area (GCA)**: The total area that can be irrigated by a canal system, including both culturable and non-culturable land (such as roads, settlements, and forests).
- **Culturable Command Area (CCA)**: The portion of the GCA that is fit for cultivation.
- **Intensity of Irrigation**: The percentage of the CCA that is actually irrigated during a specific crop season.
2. **Formula**:
In the context of basic irrigation planning where the actual area irrigated is not separately specified, the intensity of irrigation is often calculated as the ratio of the Culturable Command Area (CCA) to the Gross Command Area (GCA) to determine the proportion of the total area that is cultivable.
Intensity of Irrigation (%) = (CCA / GCA) × 100
3. **Substitution**:
Given GCA = 5000 hectares
Given CCA = 4000 hectares
Intensity = (4000 / 5000) × 100
Intensity = 0.8 × 100 = 80%
Therefore, the intensity of irrigation is 80%. Option (a) is correct, while options (b), (c), and (d) are mathematically incorrect based on the provided values.
Which of the following is a disadvantage of flood irrigation?
A)
High efficiency
B)
High water loss due to evaporation
C)
Uniform water distribution
D)
Cost-effectiveness
Flood irrigation is a surface irrigation method where water is applied to the entire field or a specific area by flooding it.
1. Why Option (b) is correct: Because water is spread over a large surface area and often remains stagnant for periods, it is highly susceptible to evaporation and deep percolation. This leads to low water-use efficiency compared to drip or sprinkler irrigation.
2. Why Option (a) is incorrect: Flood irrigation has very low efficiency (often 40-60%) because a significant amount of water is lost before it reaches the root zone.
3. Why Option (c) is incorrect: Water distribution in flood irrigation is typically non-uniform; the area closest to the water inlet usually receives more water than the far end of the field.
4. Why Option (d) is incorrect: While flood irrigation is often considered 'cost-effective' in terms of initial capital investment (low technology/equipment cost), the question asks for a 'disadvantage'. Cost-effectiveness is generally viewed as an advantage, not a disadvantage.