Everything You Need To Know About Water Demand & Its Types

Water demand refers to the total volume of water required by users for various purposes, including residential, agricultural, and industrial uses, as well as any losses incurred within the water supply system.

When planning and designing a water supply scheme, the engineer must first assess the amount of water required by the public.

In fact, the first study aims to consider the demand, and then, secondly, to find sources that can fulfil that demand.

The following quantities are therefore assessed and recorded:

• The total yearly demand
• The annual rate of demand
• The fluctuation (variation) in demand

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Various Types of Water Demand

Water demand may be broken down into the following classes:

Domestic Water Demand

Domestic water demand refers to the water required in private buildings for various purposes, including drinking, cooking, bathing, lawn sprinkling, gardening, and sanitary purposes.

Industrial Water Demand

Represents the water demand of industries, which are either existing or are likely to be started in future in the city for which the supply is planned.

A separate provision is made to meet the water demand of large enterprises. Their requirement has to be approximated based on the nature and magnitude of each industry.

The potential for industrial expansion should be investigated, so that the availability of water supply may attract such industries and add to the economic prosperity of the community.

Institutional and Commercial Water Demand

Institutions such as hospitals, hotels, restaurants, schools, colleges, railway stations, offices, and factories should be considered in the water supply planning.

The quantity will vary depending on the nature of the city and the number and types of commercial establishments and institutions present within it.

Demand for Public Use

Includes the quantity of water required for public utility purposes, e.g., watering of public parks, gardening, washing, and sprinkling on the roads, public fountains, etc.

Fire Demand

Fire hydrants are typically installed in the water at intervals of about 100-150 meters apart, and firefighting pumps are immediately connected to them by fire brigade personnel as soon as a fire breaks out.

Demand for Compensation for Losses in Theft and Wastes

This includes water lost in:

• Leakage due to bad plumbing
• Damaged water meter
• Stolen water due to unauthorised water connections, etc

This amount may be estimated to be at most 15% of the total consumption.

The Per Capita Demand

Per capita demand refers to the annual average amount of water required by one person, encompassing domestic, commercial, industrial, public, and other uses, as well as waste and theft.

Factors Affecting Per Capita Demand

• Size of the city: It is large for a city of its size, compared to smaller towns. A massive amount of water is required for maintaining clean and healthy environments, as these are often associated with sewered, commercial, and industrial activities.
• Climatic Conditions: Hotter and summer places require more water due to increased bathing, cleaning, the use of air coolers and air conditioning, sprinkling in lawns and gardens, and other similar activities. Similarly, in icy places, more water may be required because people keep taps open to prevent pipe freezing, and there may be increased leakage from pipe joints, as metals contract in cold temperatures.
• Types of Gentry and Habits of people: Rich and upper-class communities consume more water due to their wealthier living standards.
• Industrial and Commercial Activities: The increased pressures at a particular location lead to significant increases in water consumption.
• Quality of Water Supplies: A good quality of water will encourage people to use it instead of other sources, such as private wells.
• Pressure in the distribution system: For high pressure, more water is used because people in the upper storey will use water freely, as compared to the case when water is scarce to them.
• Cost of Water: If the water rate is high, a lesser quantity may be consumed. This may not result in significant savings, as affluent and wealthy individuals are relatively unaffected by these changes. But generally, the more costly the water, the lower the rate of demand.
• Billing system: For unmetered (flat-rate) services, people generally don’t practice economy in water usage, whereas for metered supplies, people use only as much water as required.

Factors Affecting Losses and Wastes

The following are factors affecting losses and wastes:

• Water-Tight Joints: Joints in the water mains and pipes leak due to bad plumbing. To avoid this, careful and better plumbing with constant maintenance is needed to keep the joints water-tight. Moreover, periodic checks of meters should be done to ensure that they do not leak.
• Pressure in the Distribution System: High pressure leads to higher leakage. To avoid this leakage, keep the pressure in the pipes to the minimum possible value.
• System of Supply: Leakage losses are reduced in an intermittent supply system. However, people generally waste more water by emptying old stored water and also by leaving their taps open.
• Metering: Metered supplies have reduced wastage because people become more mindful of their water usage, as they are charged for the volume of water they consume.
• Unauthorised Connections: Must be detected and checked by heavily punishing the defaulters to minimise losses.

Demand Variations

There are wide variations in water use across different seasons, months, days, hours, and even minutes of the hour.

Seasonal Variations

It occurs due to the larger use of water in the summer season, lesser use in the winter and much less in the rainy season.

Additionally, due to the seasonal use of water in industries, such as the processing of cash crops during harvesting, there is a need for water.

The maximum rate of demand during the summer is to be considered when designing pipe mains and other connected works.

Daily Variations

Reflect household and industrial activities. The nighttime flow (excluding industrial consumption) generally represents the magnitude of losses and waste, as there is no appreciable domestic consumption during this time.

FAQs On Water Demand

Conclusion on Water Demand & Its Types

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