India accounts for about 2.45 per cent of world’s surface area, 4 per cent of the world’s water resources and about 16 per cent of world’s population. The total water available from precipitation in the country in a year is about 4,000 cubic km. The availability from surface water and replenishable groundwater is 1,869 cubic km. Out of this only 60 per cent can be put to beneficial uses. Thus, the total utilisable water resource in the country is only 1,122 cubic km.
RIVER SYSTEM IN INDIA
The Indus River Systems:
The Ganga River System
The Brahmaputra Rivers System:
• Brahmaputra rises in Tibet, east of Mansarovar Lake very close to the sources of the Indus and the Sutlej.
• In Tibet, it is known by the name, Tsang Po.
• It is slightly longer than the Indus, and most of its course lies in Tibet.
• It flows eastwards parallel to the Himalayas to its south.
• When it reaches mountain peak of Namcha Barwa (7757 m), it takes a ‘U’ twin and makes a 5500 m deep gorge.
• Then it enters India in Arunachal Pradesh through a gorge. Here it is called the Dihang and it is joined by the Dibang, the Lohit, the Kenula and numerous other tributaries to form the Brahmaputra in Assam.
• In Tibet Tsang Po river carries a smaller volume of water and less silt as it is a comparatively dry and hard rocked area.
• In India it passes through a region, which receives a huge amount of rainfall. The result is that the river carries a large volume of water and considerable amount of silt.
• The Brahmaputra has a braided channel in its entire length in Assam, with numerous riverine islands.
• Every year during the rainy season, Brahmaputra River floods its banks and causes widespread devastation in Assam and Bangladesh.
• The river also shifts its channels during rainy season every year.
Peninsular River system
The drainage systems of the Peninsular and extra Peninsular regions differ from each other. The main differences in their drainage systems are given below:
DATA ON DIFFERENT WATER RESOURCES OF INDIA
Surface Water Resource
• The main source of surface water is precipitation.
• About 20 percent part of the precipitation evaporates and mixes with the environment.
• The large part of surface water is found in rivers, riverlets, ponds and lakes. Remaining water flows into the seas, oceans. Water found on the surface is called surface water.
• About two-third of the total surface water flows into three major rivers of the country – Indus, Ganges and Brahmaputras. The water storage capacity of reservoirs constructed in India so far is about 17,400 billion cubic metres.
• The storage capacity of usable water in the Ganges basin is the maximum, but in spite of maximum annual flow, the storage capacity of usable water is the least in Brahmaputras basin.
• The storage capacity in Godavari, Krishna, Mahanadi and Indus is sufficient.
• If storage capacity of usable water is seen in terms of ratio, then of Tapi river basin is 97 percent.
Ground Water Resources
• The total Annual Replenishable ground water resources of the Country have been estimated as 431 billion cubic meter (BCM).
• Keeping 35 BCM for natural discharge, the net annual ground water availability for the entire Country is 396 BCM.
• The Annual ground water draft is 243 BCM out of which 221 BCM is for irrigation use and 22 BCM is for domestic & industrial use.
• The groundwater utilisation is very high in the states of Punjab, Haryana, Rajasthan, and Tamil Nadu.
• However, there are States like Chhattisgarh, Odisha, Kerala, etc., which utilise only a small proportion of their groundwater potentials. States like Gujarat, Uttar Pradesh, Bihar, Tripura and Maharashtra are utilising their ground water resources at a moderate rate.
• If the present trend continues, the demands for water would need the supplies. And such situation, will be detrimental to development, and can cause social upheaval and disruptions.
Lagoons and Backwaters
• India has a vast coastline and the coast is very indented in some states.
• Due to this, a number of lagoons and lakes have formed.
• The States like Kerala, Odisha and West Bengal have vast surface water resources in these lagoons and lakes.
• Although, water is generally brackish in these water-bodies, it is used for fishing and irrigating certain varieties of paddy crops, coconut, etc.
Inland Water Resources
• Inland water resources include streams (rivers), canals, lakes, ponds and wet lands.
• These resources’ offer several services to man which include:
1. Domestic water supply:
• Inland water resources cater to the domestic needs of man for drinking, cooking, bathing, cleaning, watering plants, and crops.
• The water should be pure, free from bacteria and other contaminants (salts, sediments, etc.), taste, smell, and colour.
2. Industrial water supply:
• Industrial plants require water in more quantities than for domestic purposes. Water is needed in-industries for producing steam, for condensing steam, for solution chemical, for humidifiers and refrigerators, for cooling hot Metals, for washing coke; for the manufacture of acids and alkalies in chemical industries, and for washing and dying of hides, etc.
• Water often gets contaminated when it comes from mining areas.
• Rivers, lakes and ponds are sources of inland fishery.
• The Ganga, Sutlej, Mahanadi, etc. in India and many other rivers provide fish for local consumption.
4. Irrigation of Crops:
• In India, various means of irrigation-Canals, wells and tube wells, tanks, are extensively used.
• Selection of crops is largely determined by the availability of water for irrigation.
• Navigation in rivers, canals and lakes is determined by a number of factors including : (i) the direction of river flow, (ii) geographical location of water bodies, (iii) extent of the water body, (iv) amount of water in rivers or lakes, (v) depth and width of water, (vi) meandering of rivers, (vii) swift flow of the stream, (viii) rocks, sand bars etc. in the river channels, (ix) rapids and waterfalls on the rivers, (x) weather conditions and floods, (xi) shifting of river channels, (xii) landing places.
6. Generation of Steam Power and Hydro-electricity:
• Steam power is generated from water to drive machines of plants and locomotives. This steam power is used to generate thermal electricity for plants.
• Hydro-electricity is the cheapest and the cleanest of all the sources of power.
• Besides, it is a renewable and inexhaustible resource.
• A major advantage of hydro-electricity is its utility in decentralization of industries, while the use of coal favours the centralization of industries which creates ninny adverse environmental effects.
7. Availability of minerals:
• Some lakes provide minerals such as salts, potassium etc.
• The Sambhar Lake, the Pachpadra Lake and the Lunkaransar in Rajasthan are sources of salt production in India.
Irrigation in India
• Indian agriculture depends on the monsoon for its water requirement. Even if the monsoon is normal all the places need not get sufficient rainfall, some place may get high rainfall, or some places get very low rainfall as in Rajasthan, Punjab, Haryana, etc.
• The early or delayed withdrawal of monsoon affects the cropping pattern. In the dry period after monsoon, crops cannot be raised without irrigation.
• So irrigation becomes indispensable in India as many people directly or indirectly still depends on agriculture for their subsistence.
• The sources of irrigation can be divided into four categories viz. Canals, Wells, Tanks and other Channels.
• Wells: Wells and tube wells account about 55.9% of the total irrigation, derives water from underground sources, so it is a widely distributed source of irrigation. The major states where well irrigation is utilised are Punjab, UP, Rajasthan, Gujarat, Maharastra, MP and TN.
• Canals: Canals account 31.7% of the total irrigation, it uses surface water from rivers and becomes a principal source of irrigation in India. UP has a good network of canals followed by Punjab, Haryana and Andra Pradesh.
• Tanks: Tanks account 5.9% of the total irrigation, mainly found in peninsular India, most of them are small in size and due to high evaporation, it supplies water only for one crop in year. TN, Karnataka, AP and Orissa tops in tank irrigation.
• Other sources: The other sources of irrigation include as small dams like ahars and pynes in Bihar, spring channels of TN, water holes in flood plains, etc account for 6.4 of the total irrigation.
Distribution of Irrigated Areas
a) The percentage of irrigated land varies from state to state. It varies from state to state with lowest being in Mizoram (6.4 per cent) and highest in Punjab (92.9 per cent).
b) Punjab is at the top in proportion of irrigated area followed by Haryana, U.P., Bihar, Jharkhand, Jammu and Kashmir. Manipur in the north east region irrigate more than 40 per cent of their net cropped area.
• For the better utilization of the total potential the irrigation schemes have been divided into-
(1) Major Projects: Cultivable command area of more than 10,000 hectare, (including canal irrigation).
(2) Medium Project: Cultivable command area between 2000 and 10000 hectare.
(3) Minor Projects: Cultivable command area less than 2000 hectare, include mainly well-irrigation.
(4) Micro Projects: Drip irrigation and the use of sprinklers.
Major Dams of India
Definition of forests by
• All lands which are more than 1 hectare in area and with a Canopy density of more than 10% irrespective of the ownership and legal status is called Forest Cover.
• The forest ecosystem has two components- the non-living (abiotic) and the living (biotic) component.
• Climate, soil types are part of the non-living component and the living component includes plants, animals and other life forms.
Forest Resource of India
• The total forest and tree cover is 79.42 million hectare, which is 24.16 percent of the total geographical area.
• The total carbon stock in the country’s forest is estimated to be 7, 044 million tones, an increase of 103 million tonnes, which is an increase of 1.48 in percentage terms over the previous assessments.
• According to the Report, the maximum increase in forest cover has been observed in Tamil Nadu – 2, 501 sq km, followed by Kerala – 1, 317 sq km and Jammu & Kashmir – 450 sq km.
• Madhya Pradesh has the largest forest cover of 77, 462 sq km in the country, followed by Arunachal Pradesh, with a forest cover of 67, 248 sq km and Chhattisgarh – 55, 586 sq km.
• Mizoram, with 88.93 percentage of forest cover has the highest forest cover in percentage terms, followed by Lakshadweep with 84.56 per cent.
• The states where forest cover has decreased substantially are Mizoram , Telangana, Uttarakhand, Nagaland, Arunachal Pradesh.
• In world’s total mangrove vegetation, India’s share stands at 3%. Currently Mangrove cover in India is 4740 km² which is 0.14 % of the country’s geographical area. Sundarbans in West Bengal accounts for almost half of the total area. As compared to 2013 there is a net increase of 112 sq km in the mangrove cover.
Role of Forests
• Plants provide habitat to different types of organisms. Birds build their nests on the branches of trees, animals and birds live in the hollows, insects and other organisms live in various parts of the plant.
• Forests act as hydrologic flow modulators. Plants provide a protective canopy that lessens the impact of raindrops on the soil, thereby reducing soil erosion. Roots help to hold the soil in place. They provide shade which prevents the soil to become too dry. Thus increases the soil moisture holding capacity.
• Forests help in maintaining microclimate of the area. Plants clean the air, cool it on hot days, conserve heat at night, and act as excellent sound absorbers. Transpiration from the forests affects the relative humidity and precipitation in a place. Forests clean the environment by muffling noises, buffering strong winds and stopping dust and gases.
• The layer of leaves that fall around the tree prevents runoff and allows the water to percolate into the soil. Thus helping in ground water recharge.
• Dead plants decompose to form humus, organic matter that holds the water and provides nutrients to the soil.
• Through the process of photosynthesis, forests renew the oxygen supply in the atmosphere by absorbing atmospheric CO2 and moderating the greenhouse effect.
• Forest play an important role in maintaining water cycle of the area.
• Some species of trees have the ability to return nitrogen to the soil through root decomposition or fallen leaves. Such trees are planted to increase the nitrogen content of the soil.
• Forests also helps in the process of soil formation by causing weathering of rock.
• The play vital role in maintaining healthy watershed.
• It provides forest food which has great medicinal value and used by local people in respective season.
Classification of natural vegetation in India
A. Tropical Wet Evergreen forests
• These are the typical rain forests of India.
• Annual rainfall: above 250 cm.
• Mean annual temperature: 27°C.
• Dry season is very brief.
• Western Ghats, parts of Karnataka (Anamalai Hills, Coorg, Mysore Plateau), Cachar and Brahmaputra valley of Assam and Andaman-Nicobar islands.
B. Tropical Moist Semi-evergreen forests
• These forests are intermediate between the evergreen and the deciduous forms.
• Annual rainfall: between 200-250 cm.
• Mean annual temperature: 26°C.
• Some trees shed their leaves for brief periods in winter and spring.
• Western Ghats, parts of upper Assam, Bengal, Bihar, Orissa and Andamans.
C. Tropical Moist Deciduous forests
• Annual rainfall: 150-200 cm.
• Drought period is for 1-2 months.
• Eastern side of Western Ghats, Chhota Nagpur, Khasi Hills and a narrow belt along the foothills of Himalayas.
• Based on dominant species, they are generally of 3 types: Sandal, Teak and Sal forests.
D. Littoral and Swamp forests
• They are subdivided into 3 years: beach, tidal and fresh water swamp forests.
(a) Beach forests
• These are distributed all along the sandy sea beaches and sandy flats of river deltas.
(b) Tidal forests
• These grow over the deltas of various rivers, creeks along the coast and swampy margins of islands.
• The plants often have prop roots with well developed pneumatophores for support and aeration.
(c) Fresh Water Swamp forests
• They grow in depressions where rain-water or swollen river-water collects for some period.
• Elephant grass (Typha species) is quite common in these forests.
E. Tropical Dry Deciduous forests
• They cover about 40% of total land in India.
• Annual rainfall: 75-125 cm.
• Dry season extends for about 6 months.
• They spread from foot of Himalayas to extreme South (except Western Ghats, Rajasthan, Kashmir, Bengal and other Eastern States).
F. Tropical Thorn forests
• They occur on rocky substrata.
• Annual rainfall: 25-75 cm.
• The vegetation is dominated by Acacia and Euphorbia (thorny plants).
• Punjab, Haryana, Rajasthan, Gujarat, Delhi, Bundelkhand part of Uttar Pradesh, parts of Madhya Pradesh, Maharashtra and Tamil Nadu.
G. Tropical Dry Evergreen forests
• They receive rain from retreating monsoon.
• Parts of Andhra Pradesh and Tamil Nadu.
H. Montane Subtropical forests
• These are intermediate between tropical and temperate forest and therefore, exhibit mixed vegetation of both types.
• They are divisible into three sub-types:
(a) Broad-leaved hill forests: Nilgiri and Palni Hills of South, Mahableshwar and other areas of Maharashtra, Mout Abu, Pachmarhi in M.P., Parasnath in Bihar, kalimpong and Darjeeling.
(b) Pine forests: Foothills of Himalayas and in the East over Khasi, Naga, Manipur and Lushai hills.
(c) Dry evergreen forests: Shiwalik Hills, Punjab, Haryana, Himachal Pradesh and Jammu and Kashmir.
I. Montane Temperate forests
• These forests develop at a height of 1700 metres in the hills of both North and South.
• They are not humid.
• They are of three types:
(a) Montane wet temperate forests: these are found in both North and South. The Southern wet temperate forests are called Shoals. They occur in Nilgiris, Annamalai, Palni, Tinnevelly hills of both Tamil Nadu and Kerala.
(b) Himalayan moist temperate Forests: Western and central Himalayas.
(c) Himalayan Dry temperate Forests: Inner Himalayas.
J. Sub-Alpine forests
• They are found throughout Himalayas till the timber line.
• It spreads from Ladakh in west to Arunachal Pradesh in East.
• Annual rainfall is less than 65 cm.
• Snowfall occurs for several weeks in a year.
• It has two types of forests: Silver fir-Birch Forest and Birch-Rhododendron Forest.
K. Alpine forest
• These are found above the timber line and upto snow line in Himalayas.
• Rainfall is almost absent.
• Snowfall is common.
• The vegetation is commonly known as elfin scrub (short stems; branches come out of soil and creep along the ground and form tangled masses).
• This vegetation is divided into four types: moist alpine scrub, dry alpine scrub, alpine stony deserts and alpine meadows.
L. Grassland Vegetation
• Natural grasslands are hardly present in India but have developed secondarily by the sestruction of forests. This is known as secondary development.
• Indian grasslands are of three major types:
(i) Xerophilous (North-West India under semi-desert conditions).
(ii) Mesophilous (Savannahs) are typical of moist deciduous forests of UP.
(iii) Hygrophilous (Wet Savannahs).
M. Desert Vegetation
• Rainfall is scanty, infrequent and irregular (10cm)
• The vegetation cover is sparse.
• Vegetation is of thorn forest type.
• Natural vegetation contributes to productivity of trees like Khejri (Prosopis cineraria).
(Note: Issues related to deforestation will be covered in Environmental section)
The utilization of land depends upon physical factors like topography, soil and climate as well as upon human factors such as the density of population duration of occupation of the area, land tenure and technical levels of the people.
LAND USE IN INDIA
The major land uses in India are:
Net sown Area
• Agriculture land means cultivated area, it includes net cropped area and fallow lands. Cropped area in the year under consideration in called net sown area.
• India stands seventh in the world in terms of total geographical area but second in terms of cultivated land.
• Net shown Area is about 46%.
• Percentage wise Punjab and Haryana are highest and Arunachal Pradesh is Lowest (3.2% )
• The net sown area and the area sown more than once together are called gross cultivated area.
• This includes all land classified either as forest under any legal enactment, or administered as forest, whether State-owned or private, and whether wooded or maintained as potential forest land.
• The area of crops raised in the forest and grazing lands or areas open for grazing within the forests remain included under the “forest area”.
Area under Non-agricultural Uses
• This includes all land occupied by buildings, roads and railways or under water, e.g. rivers and canals, and other land put to uses other than agriculture.
Barren and Un-culturable Land
• This includes all land covered by mountains, deserts, etc.
• Land which cannot be brought under cultivation except at an exorbitant cost is classified as unculturable whether such land is in isolated blocks or within cultivated holdings.
Permanent Pasture and other Grazing Land
• This includes all grazing land whether it is permanent pasture/meadows or not.
• Village common grazing land is included under this category.
Land under Miscellaneous Tree Crops, etc.
• This includes all cultivable land which is not included in ‘Net area sown’ but is put to some agricultural use.
• Land under trees, thatching grasses, bamboo bushes and other groves for fuel, etc. which are not included under ‘Orchards’ are classified under this category.
Culturable Waste Land
• This includes land available for cultivation, whether taken up or not taken up for cultivation once, but not cultivated during the last five years or more in succession including the current year for some reason or the other .
• Such land may be either fallow or covered with shrubs and jungles which are not put to any use.
Fallow Lands other than Current Fallows
• This includes all land which was taken up for cultivation but is temporarily out of cultivation for a period of not less than one year and not more than five years.
• This represents cropped area which is kept fallow during the current year.
LAND CAPABILITY CONCEPT
• Land capability classification shows, in a general way, the suitability of soils for most kinds of field crops. Crops that require special management are excluded.
• The soils are grouped according to their limitations for field crops, the risk of damage if they are used for crops, and the way they respond to management.
• The classification is as follows:
Class 1 soils have slight limitations that restrict their use.
Class 2 soils have moderate limitations that restrict the choice of plants or that require moderate conservation practices.
Class 3 soils have severe limitations that restrict the choice of plants or that require special conservation practices, or both.
Class 4 soils have very severe limitations that restrict the choice of plants or that require very careful management, or both.
Class 5 soils are subject to little or no erosion but have other limitations, impractical to remove, that restrict their use mainly to pasture, rangeland, forestland, or wildlife habitat.
Class 6 soils have severe limitations that make them generally unsuitable for cultivation and that restrict their use mainly to pasture, rangeland, forestland, or wildlife habitat.
Class 7 soils have very severe limitations that make them unsuitable for cultivation and that restrict their use mainly to grazing, forestland, or wildlife habitat.
Class 8 soils and miscellaneous areas have limitations that preclude commercial plant production and that restrict their use to recreational purposes, wildlife habitat, watershed, or esthetic purposes.
(Note: Issues related to land degradation will be covered in Environmental section)