Types of water demand | Formula to Calculate

Water demand is the quantity of water required for living beings living in a country, city, or urban area. Calculation of water demand is very important for designing structures like reservoirs, dams, canals, etc.

Types of water demand

  • Domestic demand
  • Livestock demand
  • Commercial demand
  • Public or municipal demand
  • Industrial demand
  • Fire fighting demand
  • Loss and wastage

A) Domestic Demand

It includes the quantity of water required in the houses for drinking, bathing, cooking, washing, etc.

Domestic water demand is about 55%-60% of total water consumption.

For design purposes in Nepal

1For urban or fully plumbed house113 lpcd
2For semi-urban or partially plumped houses (No sewerage System)65 lpcd
3For a rural areas with public tap stands45 lpcd

B) Livestock Demand (20% of domestic demand)

The quantity of water required for domestic animals and birds is called livestock demand. Generally, it is considered only in rural areas while calculating the total demand.

Different types of livestock demand are as follows.

Big animals (Cow, Buffalo, Horses) 45 liter/animal/day

Small animals (Goat,Dog, Rabbit) 20 liter / per animal/day

Poultry (Birds, Chickens, Duck) 0.2 liter/birds/day

C) Commercial/Industrial demand

The water demand for commercial and institutional-like hospitals, hotels, schools, restaurants, cinema halls, offices, colleges etc depends upon the types and nature of the city. It also depends upon the future planning of the city. It covers 5% to 10% of total demand.

The commercial/Institutional demand in Nepal is generally taken as,

1.Hospital / Health post / Clinics With bed without bed    500 ltr/bed/day 2500 ltr/hos/day
2.School BoardersDay scholar  65 ltr/student/day 10 ltr/student/day
3.Hotel With bed without bed  200 ltr/bed/day 500-1000 ltr/day
4.Restaurants/Tea stall500-1000 Ltr/day
5.Office500-1000 Ltr/Day

D) Public/Municipal demand

It includes washing and sprinkling on road, cleaning sewers, watering public parks, gardens, etc. It covers (5-10)% of total demand. This demand is only considered in the urban water supply system.

The different types of municipal demand are as shown in the table below.

  1. For public parks – 1.4 liter/m2 /day
  2. For street washing 1-1.5 liter/m2 /day
  3. For sewer cleaning – 4.5 liter/m2 /day
  4. For Garden and Sports – 3.5 liter/m2 /day

E) Industrial demand

It is commonly considered in urban areas It depends upon the types, size and number of industries. Normally, 20%-25% of total demand is taken for industrial demand.

F) Firefighting demand

It is the water required for firefighting purposes. A provision should be made for a modern public water supply scheme. It is not considered in Nepal.

This demand is for,

  • Short-circuiting
  • Fire catching material
  • Explosion
  • Bad intention of criminal.

Different empirical formulas are used for calculating fire demand.

1) National Board of fire underwater’s formula.

Where Q is quantity of water in liter per minutes.

And P is population in thousand.

2) Freeman’s formula

Where Q is quantity of water in liter per minutes.

And P is population in thousand.

3) Kuilchings Formula

Where Q is quantity of water in liter per minutes.

And P is population in thousand.

4) Boston’s Formula

Where Q is quantity of water in liter per minutes.

And P is population in thousand.

5) Indian water supply manual (1976 Formula)

Where Q is quantity of water meter cube per day.

And P is population in thousand.

G) Loss and wastage

All the water which goes in the distribution pipe does not reach the consumers due to,

  • Defective pipe joints
  • Cracked and broken pipes
  • Faulty valves and fittings
  • Consumers keep open their taps or public taps even when they are not using the water and allow continuous wastage of water.
  • Unauthorized and illegal connection.

While estimating the total requirement of water in a town, allowance for these losses and wastage should also be done.

Generally, an allowance of 15% of the total quantity of water is made to compensate for losses thefts, and wastage of water.

Factors affecting the demand of water

1) Climate condition

The quantity of water required in better and dry places is more and less in colder areas.

2) Size and type of community

Bigger size have more demand and vice versa.

3) Living standard of people

Higher the living standard higher while being the demand.

4) Quality of water

The quality of water demand will be more and vice versa

5) Pressure in the supply

The higher the pressure loss will be and the demand is higher

6) System of supply

Less demand in case of an intermittent system hi demand in case of a continuous system.

6) Cost of water

If the cost of water is higher demand will be lower.

7) Metering system

The use of water matter lesser is the demand.

8) Sewerage system

If a sewerage system is provided in the community water required for flushing and cleaning increases the demand

9) Age of the community

In newly city, the demand is higher due to the construction.

10) Availability of local sources

The availability of local sources lowers the demand.

11) Education and awareness of people

12) Socio-economics factors

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