Water Quantity ppt
Water Quantity ppt
Published on 08/02/2022
Introduction: Water quantity is the timing and total yield of water from a watershed, and is measured by total yield and peak flow over a specified period of time. Water quality is the suitability of water for drinking, recreational uses, and as habitat for aquatic organisms and other wildlife.
Importance and necessity of water supply scheme
General Importance of water
- No life can exist without water
- It is as essential for life as air is
- Two-third of human body is constituted of water
- Provides luxuries and comforts to human beings
Objectives/Necessity of protected water supply
- To supply safe and wholesome water to consumers
- To supply water in sufficient quantities
- To supply water at convenient points and timings
- To supply water at reasonable cost to the users
- To encourage personal and house hold cleanliness of users
Components of a protected water supply scheme
- Source of water
- Intakes
- Treatment
- Distribution
Water Demands/ Per Capita Demand
Definition:
- It is the amount of water required by one person per one day ( based on annual average)
- It includes the domestic use, industrial and commercial use, public use, wastes and thefts, fire demand etc.
Per capita demand
- If ‘Q’ is the total quantity of water required by various purposes by a town per year and ‘p’ is population of town, then per capita demand will be
Per capita demand = Q/ P x 365 litres/day
Variation in water demand
- The water demand is not constant through out
- There are wide variations in the use of water in different seasons, months, days and hours
- The variation depends on the general habits of people, climatic conditions and character of city such as industrial, Commercial and residential etc.
Types of variations in water demand
- Seasonal variations
- Monthly variations
- Daily variations
- Hourly variations
Water Quantity Estimation
The quantity of water required for municipal uses for which the water supply scheme has to be designed requires following data:
- Water consumption rate (Per Capita Demand in litres per day per head)
- Population to be served.
Quantity= Per capita demand x Population
Water Consumption Rate
- It is very difficult to precisely assess the quantity of water demanded by the public, since there are many variable factors affecting water consumption. The various types of water demands, which a city may have, may be broken into following classes:
Water Consumption for Various Purposes
- Domestic water demand
- Industrial demand
- Institution and commercial demand
- Demand for public use
- Fire demand
- Loses and wastes
Domestic water demand
- water required in the houses for drinking, bathing, cooking, washing etc.
- mainly depends upon the habits, social status, climatic conditions and customs of the people.
- As per IS: 1172-1963, under normal conditions, the domestic consumption of water in India is about 135 litres/day/capita.
The details of the domestic consumption are
- Drinking —————5 litres
- Cooking ————— 5 litres
- Bathing —————-55 litres
- Clothes washing ——20 litres
- Utensils washing ——10 litres
- House washing —— 10 litres
135 litres/day/capita
Industrial demand
- The water required in the industries mainly depends on the type of industries, which are existing in the city.
- The water required by factories, paper mills, Cloth mills, Cotton mills, Breweries, Sugar refineries etc. comes under industrial use.
- The quantity of water demand for industrial purpose is around 20 to 25% of the total demand of the city.
Institution and commercial demand
Universities, Institution, commercial buildings and commercial centres including office buildings, warehouses, stores, hotels, shopping centres, health centres, schools, temple, cinema houses, railway and bus stations etc. comes under this category.
Demand for public use
- Quantity of water required for public utility purposes such as for washing and sprinkling on roads, cleaning of sewers, watering of public parks, gardens, public fountains etc. comes under public demand.
- To meet the water demand for public use, provision of 5% of the total consumption is made designing the water works for a city.
Fire demand
During the fire breakdown large quantity of water is required for throwing it over the fire to extinguish it, therefore provision is made in the water work to supply sufficient quantity of water or keep as reserve in the water mains for this purpose.
- The quantity of water required for fire fighting is generally calculated by using different empirical formulae.
- For Indian conditions kuiching’s formula gives satisfactory results.
Q=3182 √p
Where ‘Q’ is quantity of water required in litres/min
‘P’ is population of town or city in thousands
Population Forecasting Methods
The various methods adopted for estimation future populations . The particular method to be adopted for a particular case or for a particular city depends largely on the factors discussed in the methods, and the selection is left to the discretion and intelligence of the designer
- Arithmetic Increase Method
- Geometric Increase Method
- Incremental Increase Method
- Decreasing Rate of Growth Method
- Simple Graphical Method
- Comparative Graphical Method
- The master plan method
Arithmetic Increase Method
- This method is based on the assumption that the population is increasing at a constant rate.
- The rate of change of population with time is constant. The population after ‘n’ decades can be determined by the formula
Pn = P + n.c where
P → population at present
n → No. of decades
c → Constant determined by the average of increase of ‘n’ decades
Geometric Increase Method
- This method is based on the assumption that the percentage increase in population from decade to decade remains constant.
- In this method the average percentage of growth of last few decades is determined.
- The population at the end of ‘n’ decades is calculated by- Pn = P {1+ IG/100} where
P → population at present
C → average percentage of growth of ‘n’ decades
Incremental Increase Method
- This method is improvement over the above two methods.
- The average increase in the population is determined by the arithmetical method and to this is added the average of the net incremental increase once for each future decade
Characteristics of surface water
- Physical and chemical character vary.
- Contain lot of sand.
- Lot silt and clay.
- Contain oxygen, algae, bacteria and other microbes.
- Proper treatment needed before use.
Characteristics of ground water
- Rich in mineral content.
- High iron content.
- Harder than surface water.
- Almost no treatment or only disinfection may require.