Importance of Water
Water is the essence of life. Humans, animals, and plants require water for their survival. Seventy- one percent of the surface of the earth is covered by water. Five percent of water loss in the body causes degradation of muscle strength and endurance. 10% reduction in water leads to delirium and blurred vision and 20% reduction in water leads to death.
Functions of water in the human body:
- It moisturizes the air in the lungs and joints
- It helps in metabolism
- It protects our vital organs
- It transports oxygen and nutrients into cells
- It regulates human body temperature
- It helps to absorb nutrients
Importance of Water supply Engineering:
- Necessity of life
- Prevention of land pollution
- Aesthetic appearance
1. Pure and Impure Water
Water which does not contain any other substances except Hydrogen and Oxygen is said to be pure water. Pure water is note actually suitable for drinking as it lacks vital minerals required for human growth. Pure water is used in laboratories and medical purposes and is obtained by the special method of distillation.
Water that contains other substances as mineral salts, organisms, gases except hydrogen and oxygen is called impure water. The water that is used for drinking is impure water, but impurities should not be excessive to cause an adverse effect on human health.
2. Portable and Wholesome Water
Water that is safe for drinking by humans and other animals is called potable water. It is also called safe water.
Water that is practically clear, colourless, odourless, palatable, sparkling and reasonably free from objectionable chemical salts in solution and from microscopic organisms in suspension is called wholesome water.
- Biological quality: Including the levels of bacteria and viruses.
- Chemical quality: Including the levels of metals, pesticides, solvents and hydrocarbons.
- Physical quality: Including colour, taste and odour.
3. Polluted and Contaminated Water
The water that contains excessive impurities such as minerals, salts, gases, and microorganisms is called polluted water. The polluted water is not generally clean and wholesome. The water that contains microorganisms such as bacteria, viruses, protozoa, and worms is called as contaminated water. It is non potable and must not be used for drinking purposes.
The process of supplying potable water from source to consumers through the network of pipes, reservoir, and other appurtenances is known as water supply system or water supply scheme.
Historical Development of Water Supply System:
- Digging of shallow wells was the earliest innovation beyond rivers, lakes, and springs.
- Brick lined wells were built by city dwellers in the Indus River basin as early as 2500 BC and wells almost 500m deep are known to have been used in ancient China.
- Use of cast iron pipes with joints started in the 19thcentury.
- Stone spouts were introduced to the Kathmandu valley during the Lichhavi period, in the fifth to seventh centuries.
- There are 118 stone spouts in Kathmandu, 103 in Bhaktapur and 48 in Patan.
- Bir Dhara System was commissioned in 1895 A.D.
- Pani Goshowara Adda was established.
- Department of Water Supply and Sewerage (DWSS) were formally established in 1972.
1.4 Water Supply Sector Institutions in Nepal
1.5 Objectives of Water Supply System:
- Qualitative water supply (safe, wholesome and potable water)
- Quantitative water supply
- Efficient water supplies scheme
- Affordable water supply
- Accessible water supply
- Reliable water supply
- Water supply for industrial, commercial and domestic purposes.
- Collection of water
- Transmission of water
- Treatment of water
- Distribution of water
The layout of water supply system and its component extending from the water source to the consumer areas is called schematic diagram of a water supply system.
Intake > Sedimentation Tank > Disinfection > Distribution
Fig: Rural water supply scheme
Intake > Reservoir > Sedimentation Tank > Sedimentation with coagulation > Filtration > Disinfection > Hardening/Softening > Aeration > Storage tank > Distribution
Fig: Urban water supply scheme