Water Demand: Complete Guide to 6 Types of Water Demand

Introduction

Water demand estimation is very important for planning and running water supply systems. As the population increases and lifestyles change, the need for water also grows. In India, agriculture uses more than 80% of the total water, but due to urbanization and industrial growth, domestic, commercial, and institutional water demand is also rising quickly. (For example, in the Delhi-NCR region, the per capita water demand has increased in the last ten years.)

In this article, we will explain the main types of water demand, simple formulas used for estimation, and some modern approaches, such as forecasting methods and real-time monitoring.

Water Demand

Estimation of water demand is a key factor in designing an efficient water supply system. In India, agriculture alone consumes more than 80% of available water, while the remaining portion is utilized to meet domestic, industrial, and other demands. The improvement of lifestyle and associated industrial development of a nation push up the per capita demand for water.

Types of Water Demand

Water demand can be divided into several categories depending on the purpose of use. The main types, with typical IS references, are:

Domestic Water Demand

This includes water for drinking, cooking, bathing, washing, cleaning, and gardening. Typical values used for design (subject to local variation) are: 135–200 lpcd, depending on lifestyle and facilities. IS:1172–1993 (Code of basic requirements for water supply, drainage, and sanitation) and CPHEEO manuals are commonly used for guidance.

Industrial Water Demand

Water required by industries (textile, paper, chemical, etc.) varies widely by industry type, production scale, and reuse practices. Industry-specific standards and CPHEEO guidelines are normally referred to for design values.

Institutional and Commercial Water Demand

This includes schools, colleges, offices, hotels, restaurants, hospitals, railway stations, and airports. Typical design values given in the table below:

Public Water Demand

Public uses like parks, street washing, public fountains, and community uses are covered under municipal / CPHEEO guidance. Values depend on the area of parks, planting density, and municipal policies.

Fire Fighting Demand

Fire demand is estimated using empirical approaches and firefighting standards (Kuchling’s, Buston’s rules, and local fire codes). Always follow local fire authority requirements and IS guidance where applicable.

Water Losses and Unaccounted-for Water

Transmission, distribution losses, leakages, and illegal connections typically account for 10–20% (or more) of supply. CPHEEO and water utilities publish recommended targets for reduction and acceptable levels. On average, a per capita demand of 20 lpcd is usually considered to be enough to meet such commercial and institutional water requirements. Institutional and commercial water demand may be as high as 50 lpcd for highly commercial cities. Some of them are listed below:

Demand for Public Uses: 

This includes water requirements for Park gardening, washing of roads, etc. A nominal amount not exceeding 5% of total consumption may be provided to achieve this demand. Around 10 lpcd is usually added to this account while computing the total water consumption for the cities or towns.

Water Demands for Fire: 

The quantity of water required for extinguishing fire is not very large. For the total amount of water consumption for a city of 50 lakhs population, it hardly comes out to around 1 lpcd water required for fire demand, but this water should be easily available and always kept stored in a storage reservoir, as the quantity of water required is a very less duration. 

There are many empirical formulas for estimating the water required for the Fire demand, Such as Kuchling’s formula, Freeman’s formula, Buston’s formula, etc.

Water required to compensate for losses in theft and wastage: 

This includes the water lost in leakage due to bad plumbing or damaged meters, stolen water due to unauthorized water connections, and other losses and wastage. These losses should be taken into account while estimating the total requirement of water, even in the best-managed water work. The amount may be as high as 15% of total consumption, which is nearly 55 lpcd.

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Conclusion

Water demand is one of the most important factors in designing and managing water supply systems. Understanding its different types—domestic, industrial, institutional, public, fire, and losses—helps engineers and planners estimate requirements more accurately. By following standards such as IS:1172–1993 and CPHEEO guidelines, water supply projects can be designed to meet present as well as future needs. Proper estimation and planning ensure sustainable use of water resources and a reliable supply for communities.

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