Water Resources Full Notes
1. Intro
2. Scarcity of water
3. Conservation Methods
a. Dams
b. Rainwater harvesting
1. Introduction
--3/4 of the earth's surface is covered with water but the percentage of freshwater is very low.
They are mainly obtained from surface runoff and groundwater .
water keeps moving in a cycle called hydrological cycle also known as water cycle which ensure water to be a renewable resource.
Facts
√ 96.5% of total water are salt water which are not useable.
√ Only 2.5% are freshwater, even 70 % of this freshwater occurs as ice sheets and glaciers in Antarctica, Greenland and mountainous regions.
√ 30 % is stored as groundwater in the world's aquifers.
2. Scarcity of water
It refers to lack of quality and quantity of water in any particular region. These are following reasons for water scarcity.
a. Large and growing population
Due to rising population, need for water increases which leads to scarcity due to over consumption.
b. Irrigation
√ To feed large population, production of more food is required. And to facilitate higher food grain production, water resources are being overexploited to expand irrigated fields.
√ Using tubewells for irrigation can lower the groundwater levels.
c. Industries
√ After Independence many industries were set up in India, which also exerts pressure on freshwater resources.
d. Urban problem
√ In urban areas, groundwater pumping devices have contributed to the downfall of groundwater.
So far we have focused on the scarcity of water in terms of quantity, let us consider scarcity of water due to its bad quality.
Major reasons a. Pollution due to domestic, industrial wastes, chemical, pesticides and fertilisers.
Need for conservation
we should conserve our water resources : A. To safeguard ourself from health hazards B. To ensure food security. C. To prevent degradation of our natural resources
Conservation Methods
1. Dams
From ancient times we have been constructing dams.
For example :
• In the first century B.C., Sringaverapura near Allahabad had sophisticated water harvesting system channelling the flood water of the river Ganga.
• During the time of Chandragupta Maurya, dams, lakes and irrigation systems were extensively built
• In the 14th Century, the tank in Hauz Khas, Delhi was constructed by Iltutmish for supplying water to Siri Fort area.
Even in modern times it is being built, before we talk about it advantage or disadvantages let us first know what a dam is.
"A dam is a barrier across flowing water that slows down or directs the flow of water. It also results in creating a reservoir, lake or impoundment. "
It is also called temple of modern India by Pandit Jawaharlal Nehru.
Advantages
Traditionally it was only used for irrigation but today it is built for
A. Electricity generation
B. Irrigation. C. water supply for domestic and industrial uses. D. Flood controls. E. Recreation. F. Fish breeding
Hence dams are now referred to as multipurpose project .
For example - Bhakra Nangal Dam is used both for Hydel power generation and irrigation.
Integrated Water Resources Management
It refers to the management of water resources in a way where many uses of water are integrated with one another.
Disadvantages
A. Natural flow of water gets affected. B. It becomes difficult for aquatic fauna to migrate. C. It could submerge the existing vegetation and soil. D. It has caused large scale displacement of local community - That is why many new social movements like Narmada Bachao Andolan and Tehri Dam Andolan has started in India. E. This led to salinisation of the soil. F. Sharing of water is also causing conflicts among people. e. g:- Sabarmati Basin in Gujarat . G. It is also unsuccessful in controlling the floods.
Narmada Bachao Andolan
It is a NGO that mobilised people against Sardar Sarovar Dam built across Narmada river in Gujarat. Initially it focused on the trees that are submerged by dam. Recently they focused to get displaced people for rehabilitation
Rainwater Harvesting
Rainwater harvesting system was a better alternative system as compared to Dams.
In ancient times extraordinary tradition of water harvesting system was prevalent in India.
Guls/Kuls Diversion channel for agriculture in Western Himalayas. Rooftop Rainwater Harvesting. in Rajasthan. Inundation channel - in Bengal. Khadins (Jaisalmer) -- Fields that gets converted into rain fed storage structure. Tankas (Bikaner, Barmer) -- Built inside the main house or courtyard, used for drinking water . In the tankas rainwater is stored which was referred to as Palar Pani in these regions.
Bamboo pipe irrigation system - Meghalaya
Rainwater harvesting in decline
As plenty of water is available due to Indira canal, still some houses keep tank as they do not like the taste of tap water.
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