Management And Natural Resource of Class 10
Water is renewable resource. Like air, water is vital to life since for all physiological activities of plants and animals, it is essential. Water is mainly present in two forms :
- Surface water
- Ground water.
Keeping in mind importance of agriculture for economy of India, water resources are of great significance.
TYPES OF WATER RESOURCES
Water resources can be classified into two types i.e.
- Fresh water resources
- Salt water resources
Fresh Water Resources
Fresh water resources range from ponds to lakes and large rivers.It has following characteristics:
- Fresh water is exhaustible, however it is being made available again by oceans through hydrological cycle.
- 77.2 percent of fresh water is stored in glaciers and ice caps and 22.4 percent is ground water and soil moisture. Remaining 0.36 percent is found in lakes, rivers, streams and swamps etc. Out of total water evaporated from oceans 90 per cent falls to the oceans and remaining 10 per cent falls on the land. This water is utilised by various terrestrial ecosystems.
- Fresh water is essential for life on earth as well as for survival of human race.
- The total water in hydrosphere is 1.4 billion cubic kilometers (km)3. Total 97% is ocean water. The ocean water cannot be consumed by human beings. Remaining three percent (fresh water) is available for human consumption.
- The water resources in India have an average run off in river system of 1,869 km3 and 432 km3 ground water.
Fresh water is obtained by following three types of natural resources :
- Rain water
- Surface water
- Ground water
Rain water. India gets near about 3 trillion m3 of water from rainfall (or precipitation which amounts for 105-117 cm. annually).In India, intensity of annual rainfall differs in different zones. Following four zones have been identified :
Wet zone. In this region, rainfall is very high (more than 200 cm.).
Intermediate zone. This is a zone with heavy rainfall (100—200 cm.).
Semi—arid zone. Region with moderate rainfall (50—100 cm.).
Arid zone. Region with very low rainfall (20—50 cm)
Surface water. India has plenty of rivers, lakes, streams and ponds. In India, surface flow of water takes place through 14 major river systems like Ganga, Godavri, Bahmani, Cauvery, Brahmaputra etc.
Ground water. Water which percolates into the ground through air spaces of soil.
Zone of Saturation :When porous soil is saturated with water at certain level below soil surface, it is called as zone of saturation.
Water table. The upper level of zone of saturation is called water table.
Water level. Water table is exhibited with reference to the mean sea level. Vertical distance from a place on the surface to the water table is called water level.
Ground water is useful in:
- It provides soil moisture for plant growth.
It is commonly used for human consumption.
It supplements water in streams.
This water is used by human beings for drinking, cooking, bathing, cleaning etc.
Fresh water is also required for various types of industries.
It is required for irrigation purpose (agriculture).
It is required for construction of buildings.
It is required for transportation, hydel power etc.
Salt Water Resources
India has a very long coast line hence, it has a large source of salt water of seas and oceans.
Oceans can be used in following aspects:
Mineral concentrates in the form of mineral nodules can be used for the source of various minerals.
To build offshore terminals for ships etc.
As a source of food and other edible animals mainly fishes.
Shells of mollusks are source of calcium and quicklime.s.
For the production of many useful products such as algin, agar, carrageenan, diatomitic etc.
It is used for commercial navigation and shipping.
For generating power from sea tides
Pearls produced by pearl oysters form valuable jewellery.
As a source of edible sea weeds as many brown algae (keips) etc.
For the extraction of common salt.
Planning floating cities on the ocean surface is under way.
Dams are the large water storing bodies usually built by the government agencies. This stored water is then allowed to flow downstream at the desired rate.
A dam built across a river
Usefulness of dams for the society
The dams are useful to the society in the following ways :
(a) Water stored in a dam is used for irrigation through a network of canals. It ensures round the year water supply to the crop fields and help raise agricultural production. For example, the Indira Gandhi canal has brought greenery to considerable area of Rajasthan.
(b) Dams ensure continuous water supply to the people in towns and cities through pipelines after suitable treatment.
(c) The falling of water from the dam is used for generating electricity. The electricity thus produced is called hydro electricity.Purposes for building a dam :
- Generation of electricity
- Control of flood which either stops or slows the amount of water in the river.
Criticism about large dams :
- Social problems : They displace large number of farmers and tribals.
- Economic problems : They consume huge amount of public money without proportionate benefit.
- Environmental problems. As they cause deforestation and loss of biological diversity
Problems created by dams:
(a) Social problems:
(i) Mismanagement of the water has largely led to the benefits being cornered by a few people. There is no equitable distribution of water, thus people close to the source grow water intensive crops like sugarcane and rice while people farther downstream do not get any water.
(ii) A large number of human settlements are submerged in the water of large reservoir formed by the dam and many people are rendered homeless. It is therefore necessary that these people are given adequate compensation by the government for rehabilitation so as to start their life afresh.
(b) Environmental problems:
(i) The construction of dams on the rivers has contributed to deforestation and loss of biodiversity.
(ii) A large variety of flora and fauna get submerged in the water of large reservoir formed by the dam which disturbs the ecological balance.
(c) Economic problems: A huge amount of public money is spent without proportionate benefits.
MANAGEMENT AND CONSERVATION OF WATER RESOURCES
(i) Integrated water-shed plan for drinking, irrigation and industrial uses.
(ii) Flood control
(iii) Transfer of surplus water to water deficit basins by inter-linking of rivers.
(iv) Hydrogeological survey to identify over-exploited areas.
(v) Artificial recharging of the ground water.
(vi) Mass awareness programmes through public or private agencies.
(vii)Dams: They are massive barriers built across rivers and streams to confine and utilize the flow of water for human purposes such as irrigation and generation of electricity.
- Large dams can also ensure the storage of adequate water.
- Canal system leading from dams transfer large quantity of water upto great distances, e.g., Indira Gandhi Canal of Rajasthan brought greenery to considerable areas.
Missuse of Water Distribution:
Due to mismanagement in distribution of water, the benefit of constructing a dam goes to few people only. For example, people close to the water source grow water intensive crop like sugarcane and rice while people farther downstream do not get any water. This resulted in discontentment among the people who have been displaced by building of dam.
(i) Watershed management : It means scientific conservation of soil and water to increase the biomass production.
- Watershed management not only increases the production and income of the watershed community but also overcomes drought and flood.
- It increases the life of downstream dams and reservoirs.
(ii) Water harvesting : It means capturing rainwater where it falls or capturing the runoff water in a local area and taking measures to keep the water clean by not allowing polluting activities to take place.
Techniques of water harvesting :
Water harvesting techniques are mainly location specific. It is an age - old concept in India.
- Khadins, tanks and nadis in Rajasthan.
- Bandharas and tals in Maharashtra
- Ahars and Pynes in Bihar
- Kulhs in Himanchal Pradesh
- Ponds in kandi belt of Jammu.
- Eris (tanks) in Tamil Nadu.
- Surangams in Kerala.
- Kattas in Karnataka.
- Due to own control of the local population over exploitation of the local water resources is reduced.
Some of the water harvesting techniques are:
- Capturing of runoff water roof tops.
- Capturing of runoff water from local catchments.
- Capturing seasonal flood water from local streams.
Benefits of water harvesting :
- Provide drinking water.
- Provide irrigation water.
- Increase in ground water resources.
- Reduces storm water discharge, urban flood and overloading of sewage treatment plants.
Advantages of ground water:
- It does not evaporate.
- It spreads out to recharge wells.
- It provides moisture for vegetation.
- It does not provide breeding grounds for mosquitoes.
- It is relatively protected from contamination by human and animal waste.
Traditional water harvesting system :
- The water harvesting structures are mainly crescent shaped.
- Monsoon rains fill ponds behind the structures.
- The large structure hold water throughout the year while most dry up after monsoon.
- The main purpose of this system is to recharge the ground water and not to hold surface water.
Advantages of water harvesting system: The various advantages of water harvesting system are:
- The water stored in ground does not evaporate.
- The water stored in ground spreads out to recharge wells and provides moisture for crops.
- The water stored in ground does not promote breeding of mosquitoes.
- The water stored in ground is protected from contamination by human and animal wastes.
- The water stored in ground is utilized for the benefit of the local population.