Test: Hydrology & Irrigation - Civil Engineering (CE) MCQ

• Less length of the weir: When the weir is aligned at right angles to the main river current, it ensures that the length of the weir is minimized. This is important as a shorter weir is easier to construct and maintain.



• Better discharging capacity: Aligning the weir at right angles helps in maximizing the discharging capacity of the weir. This allows for efficient regulation of water flow and prevents flooding.



• Economical: By aligning the weir at right angles to the main river current, it becomes more cost-effective to build and operate. This is because it optimizes the flow of water and reduces the overall construction and maintenance costs.

Therefore, aligning the weir at right angles to the direction of the main river current is beneficial in terms of efficiency, cost-effectiveness, and overall functionality.

• A hydrograph is a plot that shows the relationship between stream flow and time.

• Time: The x-axis of a hydrograph represents time, usually in hours, days, or months.


• Stream flow: The y-axis of a hydrograph represents the flow rate of a river or stream, usually measured in cubic feet per second (cfs) or cubic meters per second (cms).

• Precipitation events: Peaks on a hydrograph represent periods of increased stream flow, typically caused by rainfall or snowmelt.


• Base flow: The base flow of a hydrograph represents the normal, sustained flow of a river or stream during dry periods.


• Recession limb: The recession limb of a hydrograph shows the gradual decrease in stream flow after a peak event.

• Flood forecasting: Hydrographs can be used to predict and prepare for potential flooding events based on precipitation and stream flow data.


• Water resource management: Hydrographs help water resource managers understand the availability and distribution of water in rivers and streams.

• Glacis fall: A glacis fall is a type of spillway where the water flows over a sloping surface with a baffle platform and a baffle wall to dissipate energy.


• Straight Glacis Type Fall: This type of glacis fall has a straight slope without any curves or bends in the design.


• Baffle Platform and Baffle Wall: The presence of a baffle platform and a baffle wall helps in reducing the velocity of water and dissipating energy to prevent erosion and damage downstream.


• Inglis Fall: A straight glacis type fall with a baffle platform and a baffle wall is commonly known as an Inglis fall in hydraulic engineering terminology.


• Vertical Drop-Fall, Glacis Fall, Montague Type Fall: These terms do not specifically refer to the described design of a straight glacis type fall with a baffle platform and a baffle wall, making them incorrect choices in this context.

• Source of Water: Flow irrigation is done from canals, which are man-made waterways that divert water from rivers or reservoirs to irrigate agricultural land.


• Gravity Flow: Water from canals flows by gravity to the fields, providing a constant and consistent water supply for crops.


• Efficiency: Canals are a traditional and efficient method of flow irrigation, ensuring that water reaches a large area of land without the need for pumps or other equipment.


• Community Use: Canals often serve multiple farms or communities, allowing for the sharing of water resources and promoting cooperation among farmers.

• Wells: Wells can also be used for flow irrigation by pumping water from underground sources to the fields. However, this method may require more energy and maintenance compared to canals.


• Tube Wells: Tube wells are another source of flow irrigation, where water is extracted from deep underground aquifers using a tube well system. This method is commonly used in areas where surface water sources are limited.


• None of the Above: If flow irrigation is not done from canals, wells, or tube wells, then other sources such as rivers, reservoirs, or lakes may be used depending on the availability of water resources in the region.

• River Discharge: The meander pattern of a river is primarily developed by the dominant discharge of the river.


• Dominant Discharge: Dominant discharge refers to the average flow of water in a river over a period of time. It is the key factor that shapes the meander pattern as it determines the erosional and depositional processes along the river channel.


• Erosional Processes: The dominant discharge of a river influences erosion along its banks, causing the formation of curves or bends known as meanders. The erosional processes are more pronounced on the outer bank of a meander bend due to higher flow velocity.


• Depositional Processes: On the inner bank of a meander bend, deposition occurs as the flow velocity decreases, leading to the formation of point bars. This continuous erosion and deposition process results in the development of a meander pattern over time.


• Migration of Meanders: Meanders may migrate over time due to changes in discharge, sediment load, or other factors. This migration can lead to the formation of oxbow lakes and cutoff meanders.

Therefore, the dominant discharge of a river plays a crucial role in shaping the meander pattern by influencing erosion, deposition, and the overall morphological evolution of the river channel.

• Water-logging: Over irrigation can lead to water-logging in the soil, which occurs when the soil becomes saturated with water and excess water cannot drain away. This can deprive plant roots of oxygen, leading to root rot and ultimately plant death.



• Wilting: While it may seem contradictory, over irrigation can actually lead to wilting in plants. This is because water-logged soil can prevent roots from absorbing water and nutrients effectively, causing plants to wilt due to lack of proper hydration.



• Fertility: Over irrigation can also leach nutrients from the soil, leading to a decrease in soil fertility. This can impact plant growth and productivity, as essential nutrients are washed away with excess water.



• None of the above: This option is incorrect, as over irrigation can indeed lead to various negative effects on plants and soil health.

Therefore, it is important to practice proper irrigation techniques and avoid over watering to ensure optimal plant growth and soil health.

• Load factor: Load factor is the ratio of average load to the peak load. It gives an indication of how efficiently the plant is being utilized.


• Plant factor: Plant factor is the ratio of the average load to the installed capacity of the plant. It indicates how effectively the installed capacity of the plant is being utilized.


• Utilization factor: Utilization factor is the ratio of actual energy produced by the plant to the maximum possible energy that could have been produced during a given period. It shows the efficiency of the plant in converting its capacity into actual output.


• When the reserve capacity of the plant is zero, the ratio of the average load to the installed capacity will be equal to both the load factor and the plant factor.


• Therefore, the correct answer is Both (A) and (B).

• Definition: Superfluous water is the excess water that drains out of the soil due to gravity.


• Also Known As: Superfluous water is also known as gravitational water.


• Characteristics: This type of water is not available for plant uptake as it moves rapidly through the soil profile.


• Role in Soil: Gravitational water helps in leaching out excess salts and other harmful substances from the soil.


• Importance: Proper drainage of superfluous water is essential to prevent waterlogging and improve soil aeration.

• Evaporation: Evaporation is the process by which water changes from a liquid to a gas or vapor. It occurs when heat is applied to the water surface, causing the water molecules to gain enough energy to escape into the air.


• Reducing Evaporation: To reduce evaporation, a barrier can be created on the water surface to prevent water molecules from escaping into the air.


• Cetyl Alcohol: Cetyl alcohol is a waxy substance that can be applied to the water surface to create a barrier that reduces evaporation.


• Suitability: Cetyl alcohol is suitable for reducing evaporation because of its waxy nature, which forms a protective layer on the water surface, preventing water molecules from escaping into the air.


• Effectiveness: Cetyl alcohol is effective in reducing evaporation and can help conserve water in various applications such as reservoirs, ponds, and swimming pools.

Field Capacity:

• Field capacity refers to the moisture content of the soil after free drainage has removed most of the gravity water.


• It is the maximum amount of water held by the soil against the force of gravity.


• At field capacity, the soil is neither saturated nor dried out, making it ideal for plant growth.


• This is the point where plants can easily access water and nutrients from the soil.


• Field capacity is an important parameter for determining irrigation schedules and managing water resources efficiently.