Water Supply MCQ Quiz - Objective Question with Answer for Water Supply - Download Free PDF

Concept:

Reservoir Yield:

• It means the quantity of water which can be withdrawn from storage in the reservoir. Reservoir yield is determined by the rate of flow of the stream into the reservoir, losses due to evaporation from the reservoir surface, and the volume of water impounded in the reservoir 
• It is the amount of water that can be supplied by the reservoir in a specified interval of time.
• The specified time interval may vary from a day for a small distribution reservoir to a month or year for large conservation reservoirs.
• If we say that three million cubic meters of water can be supplied from a reservoir in a year then its yield is 3000000 m3/year.
•  The yield of the reservoir is dependent upon the inflow and thus varies from time to time.

Firm yield.

•  It is also known as Safe yield.
•  It is the maximum quantity of water that can be supplied from the reservoir with full guarantee during the worst dry period.

 Design Yield.

• The critical period for a reservoir is generally considered when natural flow in the reservoir is minimum.
• Hence a lower value than the guaranteed yield or safe yield may be taken for design purposes.
• This yield whose value is smaller than the safe or firm yield is known as design yield.
•  The value of design yield for a reservoir to be used for water supply is taken less than the safe yield.
•  In the case of reservoirs used for irrigation purpose, the design yield may be taken slightly more than the safe yield as crops can tolerate some deficiency of water during the exceptionally dry season

A Secondary Yield.

• The quantity of water available more than safe yield is known as secondary yield.
• This yield is available during a period of high inflows.
• This secondary yield of the reservoir can be used either to generate extra hydroelectric power or for irrigation of extra lands.

Average Yield.

•  The arithmetic average of the safe yield and the secondary yield considered for a number of years is known as average yield.
•  The storage capacity of the reservoir and its yield are very much interdependent.
• The water is stored in the reservoir to fulfill the safe yield requirements.
• If the capacity of the reservoir is more it can certainly provide more water and hence yield is more.
• The reservoirs are designed to meet specific water demands.

Explanation:

Trench Excavation 

• Purpose: Excavation of long, narrow trenches, usually deeper than they are wide.

• Common Use: Specifically for laying large pipelines, sewer lines, water lines, or other underground utilities.

• Support: Often involves shoring or trench boxes to prevent side collapses and ensure worker safety.

• Typical Depths: Can vary from shallow (for cables) to several meters (for large sewer lines).

Additional InformationMuck Excavation

• Purpose: Removal of waterlogged, soft, or unstable materials like mud, silt, and slush.

• Common Use: Often necessary in low-lying or marshy areas where water and soil mix.

• Challenge: The excavated material may not be reusable; it often needs to be transported away.

• Method: May involve dewatering and stabilization techniques before or during excavation.

Rock Excavation

• Purpose: Involves the removal of hard rock surfaces or boulders that cannot be removed with normal digging tools.

• Common Use: Found in hilly, mountainous areas or deep foundation works where bedrock is encountered.

• Method: Requires drilling, blasting, or the use of heavy machinery like breakers or jackhammers.

• Precaution: Safety is crucial due to flying debris and vibrations from blasting.

Open Excavation

• Purpose: Involves excavating a wide and shallow area, typically open to the atmosphere.

• Common Use: Used in foundation works, basements, tanks, roadways, and building sites.

• Advantages: Provides easy access for machinery and workers.

• Limitation: Requires a lot of space and may affect surrounding areas.

Explanation:

Groundwater:

• The groundwater supply is generally pure and safer, because the water before getting sorted in the underground reservoir, undergoes natural filtration during percolation through the soil pores
• This water is free from suspended impurities and organic matter but may contain greater amounts of dissolved salts, minerals, hardness, odours, and carbon dioxide.
• Since it is closed to the surface, will have less amount of dissolved oxygen in it.

∴ Groundwater ⇒ low organic content and low dissolved oxygen

Lake Water:

• Water in the lake is still and there is no circulation or movement of water molecules; Thus water at the surface will have a high amount of dissolved oxygen and very little D.O at the bottom
• All the particulates, pigments, and impurities settle down, and thus the bottom level water is highly contaminated and has silt and bacteria at the bottom.

∴ Lake Water ⇒ Has silt and bacteria at the bottom

River water:

• It is supposed to contain a high amount of organic matter; It has a lower content of such impurities due to the self-purification ability of pure water.
• Since it is open to the surface, will have a great amount of dissolved oxygen in it

Canal Water ⇒ Low organic content and high D.O.

Hence, only statement B is correct.

Explanation:

Coliforms/B. Coli/E.coli:

1. E-coli bacteria are a gram negative, non-spore forming and facultative aerobic bacteria.

2. These are harmless aerobic microorganisms which are found residing in the intestines of all warm blooded animals including human beings.

3. These are rod shaped non-pathogenic bacteria i.e. bacilli.

4. Their presence or absence in water indicates presence or absence of fecal pollution and hence, pathogens.

5. They are measured using:

a) Member Filter Technique,  b) Test Tube Method (MPN)

6. Safe limit for drinking water is < 1 coliforms colony per 100 ml of water. 

Explanation:

Methods of Supplying Water

The water can be supplied to the consumers by the two systems:

• A continuous system of water supply.
• Intermittent system of water supply.

Continuous system

• 24x7 supply is achieved when water is delivered continuously to every consumer of the service 24 hours a day, every day of the year, through a transmission and distribution system that is continuously full and under positive pressure.

Intermittent system:

• If plenty of water is not available, the supply of water is divided into zones & each zone is supplied with water for fixed hours in a day. As the water is supplied after intervals, it is called an intermittent system.
• Intermittent water supply is the supply system of water service through the pipe and delivering water to consumers for less than 24 hours in one day and it is adopted where the supply availability and/or the hydraulic capacities of the water supply system are too weak.

Ring system and controlled system are not the methods of water supplying sytem.

Explanation:

The odour characteristic is used for classifying odour of a given water sample as per IS 3025 (part-5) 1983 as follows:

1. Degrees of sweetness

2. Degrees of pungency

3. Degrees of smokiness

4. Degrees of Rottenness

Concept:

The population after n^th decade by using Arithmetic mean Method is given as:

\({P_n} = P + N\bar X\)

Where

P is the Present Population

N is no of decades of which population is to be calculated

X̅ is the average increase in population.

Calculation

\(\bar X = \frac{{9,000\; + \;7,000\; + \;12,000}}{3} = 9333.333\)

The population at end of 2011 i.e. after 3 decodes from 1981.

\({P_{{g_{011}}}} = 1,28,000 + 3 \times 9333.333\)

\({P_{{g_{011}}}} = 1,56,000\)

Explanation:

Various methods for population forecasting as suitable for that city, considering the growth pattern, are as follows:

1. Arithmetical increase method:

• In this method assumed that the population is increasing at a constant rate.
• This method is suitable for a large and old city with considerable development.

2. Geometrical increase method (or geometrical progression method):

• In this method, the percentage increase in population from decade to decade is assumed to remain constant. 
• This method gives higher values and hence should be applied for a young and rapidly increasing city, but only for a few decades.

3. Incremental increase method:

• This method is a modification of arithmetical increase method and it is suitable for an average size town under the normal condition where the growth rate is found to be in increasing order.

4. Logistic curve method:

• This method is used when the growth rate of the population due to births, deaths, and migrations takes place under normal situation and it is not subjected to any extraordinary changes like an epidemic, war, earthquake or any natural disaster, etc.

The different type of Valves and their purpose is given below in tabulated form:

Explanation

The design life and design discharge for different units in raw water are given below:

Note that

MDD (Maximum Daily Demand) = 2 × ADD ( Average Daily Demand)

Concepts:

Altitude valves are installed in the supply line to elevated tanks, basins, or reservoirs.   

The purpose of this valve is to admit water into the elevated tank until a present level is reached and to close at that point to prevent overflow and also holding the reservoir/elevated tank level constant.

Additional Information

The other different type of valves and their uses is given below:

Explanation

Water Requirement with Respect to Population as follows:

Concept:

Various methods for population forecasting as suitable for that city, considering the growth pattern, are as follows:

1. Arithmetical increase method:

• In this method assumed that the population is increasing at a constant rate.
• This method is suitable for a large and old city with considerable development.

2. Geometrical increase method (or geometrical progression method):

• In this method, the percentage increase in population from decade to decade is assumed to remain constant. 
• This method gives higher values and hence should be applied for a young and rapidly increasing city, but only for a few decades.

3. Incremental increase method:

• This method is a modification of the arithmetical increase method and it is suitable for an average size town under the normal condition where the growth rate is found to be in increasing order.

4. Exponential curve method

• It is a suitable method of estimating the future population by the end of the design period of the water supply scheme for a town or a city.

Concept:

Maximum hourly consumption:

It is generally taken as 150% of its average.

Therefore, maximum hourly consumption of the maximum day i.e. peak demand = 1.5 × average hourly consumption of maximum daily demand

= 1.5 × (maximum daily demand/24)

= 1.5 × (1.8 × annual average daily demand)/24

= 2.7 × annual average hourly demand

Calculation:

Given, 

Annual average daily demand = 48000 cubic meter

Maximum hourly demand = 2.7 × 48000/24 = 5400 cum/hour

Explanation:

IS 1172: 1993 is used for the basic requirements for water supply, drainage and sanitation

Important Points IS 456: 2000 - PLAIN AND REINFORCED CONCRETE - CODE OF PRACTICE 

IS 1035 (Part 32): Methods of Sampling and Test (Physical & Chemical) for water and wastewater

IS 10500 (2012): DRINKING WATER - SPECIFICATION

Additional InformationFrom IS 1172 (1993):

The following rates per capita per day may be considered the minimum for domestic and non-domestic needs:

1. For communities with a population of up to 20,000 and without a flushing system : 

a) water supply through standpost: 40 lpcd ( Min ) 

b) water supply through house service connection:  70 to 100 lpcd 

2. For communities with a population of 20,000 to 100,000 together with a full flushing system: 100 to 150 lpcd 

3. For communities with a population above 100000  together with a full flushing system: 150 to 200 lpcd