Envis Centre, Ministry of Environment & Forest, Govt. of India

Printed Date: Thursday, September 24, 2020

Water Resource

 

Photo Source: Brahnaputraboard.in

 

WATER RESOURCE:

 

Assam is endowed with enormous water resources. The large perennial rivers and other water bodies with the rich aquifer speak about vastness of its water resource. Surface water is available in the forms of river, stream, lake, swamps, pond etc. The ground water is available at low to moderate depth almost in entire state. Although there is seasonal and regional variation in the availability of water resources, the annual availability of water resource remain almost same. In the last few decades the use of water has been growing at a fast rate, which is more than twice the rate of the increase of human population. The consumption of water has increased due to the increase of human population as well as the diversification of human activities. With the increase of per capita consumption of water in domestic, agricultural and industrial sectors, cause the reduction of potential per capita availability of water. Moreover, it may cause the deterioration of water quality to a great extent.

 

Surface Water:

Apart from the rain water received, the state is endowed with number of perennial rivers and lake locally known as beel. The state is drained by the dance networks of two river system, viz the Brahmaputra and the Barak. These rivers have large number of tributaries joining them from both the banks. There are about 73 important tributaries of the Brahmaputra river and 11 tributaries of Barak river. The vast potential surface water resource of the state is not yet properly utilized in the state. In the last few decades, the rate of consumption of water in the agricultural sector, industrial sector and in the urban centers has been increased significantly. The discharges of untreated domestic wastewater, industrial wastewater, run of from the agricultural fields and the urban sewage water posing threat to the water bodies of the state.

 

Irrigation:

Agriculture constitutes the largest share of water consumption amongst various uses followed by the domestic and industrial uses. The gross irrigation potential created up to March 2002 through govt. irrigation schemes in Assam was 5,13,341.00 hectare (includes both irrigation from surface water and ground water) against the irrigation potential of 240406.17 hectare in 1987. This indicates the increasing trend of water utilization in agricultural sector.

Apart from irrigation, the second most beneficial uses of water are drinking, cooking, bathing, washing, etc. – domestic use. More than 75 per cent population of the state are living in the rural area and due to certain factors the direct use of river water is limited in the state. The ground water is the main source of water for most of the rural population of the state. The per capita abstraction would therefore be small and may be estimated at 25 liter per day.

Urban areas are generally provided with organized water supply. Cities and town located near the river usually depend on the river for their source of water. This hold good for the Brahmaputra basin too. With the steady growth of urban centers in the river basins of the state, the water abstraction for the domestic consumption is one of the major constituents of the water consumption. The table no 3.2 show the district wise water consumption by the urban people in the state. It may be mentioned here that there is usually combination sources i. e. directly from river or through tube wells. The estimate is based on a gross of per capita average demand of 150 liter per day, although local variation and variation among the various groups of users are expected. The share of water consume in the industrial sector is increasing in last two decades with the growth of industries in the state. Water is mainly use in the industries for cooling and washing purposes and after use it is generally drained out to the natural water bodies either after treatment or without treatment. He waste water generated by the posing a threat to the water environment.

 

Besides the river, another important source of surface water is the wetlands of the state. There are about 3513 numbers of wetlands of different size and shape in the state. The total area under different categories of wetland in Assam is about 1012.32 sq km during the pre monsoon season. It constitutes 1.29 percent of the total geographical area of the state. Of the total wetlands, 1367 inland wetlands suffer due to the problem of invasion by aquatic weeds and need ameliorative steps for conservation. Out of this, 656 are swampy/marshy areas, 366 ox-bow lakes/cut-off meanders, 193 lakes/ponds, 133 water-logged, 13 tanks and 3 reservoirs. The wetlands of the state are facing serious threat from the human society. The large-scale encroachment, over fishing in wetlands, filing up of wetlands for other uses and dumping of wastes in the wetlands are some of the human activities causing serious damage to the wetland ecosystem.

 

Like the surface water bodies, the pressure on the ground water is increasing in the state. The rate of groundwater extraction in the state has been increase by many folds in last decade of for irrigation through shallow tube wells. Unscientific dumping of municipal solid and industrial wastes on the ground and in the water body is increasing with the population growth. The excessive extraction of ground water especially for the irrigation and in densely settled areas for the domestic consumption the water table in winter season goes down beyond the reach of low and medium depth dug wells and tube wells and thereby causing water crises in some areas of the state. The situation is quite common in the parts of the Guwahati city in winter months.

 

River System

 

Brahmaputra River System:

The Brahmaputra is one of the biggest rivers of the world. The Brahmaputra basin covers an area of 5,80,000 Sq. Km of which 1,94,413 Sq. Km falls in India. In India, the basin lies in the states of Arunachal Pradesh, Assam, Nagaland, Meghalaya, Sikkim and West Bengal. Brahmaputra is a perennial river, feed by snow as well as by rain.

 

The Brahmaputra rolls down the plain of Assam east to west for a distance of 640 km up to Bangladesh border. Through its course, the river receives innumerable tributaries (about 73) coming out of the northern, northeastern and the southern hill ranges. The mighty river with a well-knit network of tributaries drains an area of 56,480 Sq. Km of the state accounting for 72 per cent of its total geographical area. Most of the right bank tributaries of Brahmaputra are snow as well rain feed and are perennial. Although the left bank tributaries is mainly rain feed but perennial in nature.

 

It is the fourth largest river in the world in term of average water discharge at the mouth with a flow of 19,830 m3s-1. The river carries 82 per cent of its annual flow during the rainy season (May through October). The maximum discharge of the river at Pandu (in Guwahati) on 23-08-62 was 72794 m3s-1 and the minimum discharge at the same point on 20-02-68 was 1757 m3s-1. The mean annual flood discharge and dry season discharge of the river at Pandu is 51156 m3s-1and 4420 m3s-1 respectively. The discharge per unit area of basin at Pandu is 0.03 m3s-1.

 

 

Right Bank Tributaries of the Brahmaputra River and their annual discharge

 

Left Bank Tributaries of the Brahmaputra River and their annual discharge 

 

ii) The Barak River System:

Barak is the second largest river system in the North East India as well as in Assam. The river with a total length of 900 km from source to mouth drains an area of 52,000 sq. km. In India and traverses a distance of 532 km up to the Indo-Bangla border. Like Brahmaputra, the Barak is also a perennial river of the state. The important north bank tributaries of Barak river are Jiri, Siri, Madhura, Jatinga and Larang, while the important south bank tributaries include sonai, Ghagra, katakhal, Dhaleswari, Singla and Longai. The flows of the rivers in Assam decrease considerably during the dry season. They maintained pick flow in summer rainy months.

 

Wetlands

 

The valley of the river Brahmaputra with its innumerable fresh water lakes (locally called beel), or ox-bow lakes (era suti), marshy tracts and seasonally flooded plains and hundreds of riverine sand_bars and islands was, till recently, an ideal wetland eco-system which contained specialised wetland animals like the fresh water dolphin, dugong and the great Indian one-horned rhino and reptiles like the crocodile, the winter monitor lizard and few species of turtles. All these creatures are either extinct or highly endangered at present. With the progressive destruction of the Brahmaputra valley wetlands since the advent of the British, along with these animals and others, we have lost yet another spectacular natural beauty - the hundreds of thousands of water birds all along the 800 km. of the river running through the plains of Assam.

 

The destruction of the Brahmaputra valley wetland system started with the arrival of the water hyacinth from Central America more than a century ago. Extensive growth of this fast growing weed can cut out sun light from the micro flora and also produces faster eutrophication by slowing down water current and depositing debris at the bottom. The second phase of enhanced eutrophication took place with the raising of earthen bunds along the banks of almost the entire length of the river and many of its tributaries after the 1950 earthquake. These artificial levees cut off, to a great extent, the periodic flushing out of the wetlands by the monsoon flood. The third and the final onslaught on the wetlands has taken place with the arrival of the human settlers in the sand bars and the minor riverine islands, mostly in the lower Assam. This has turned the wetlands into agricultural zones rich in rice and vegetables but totally denuded of wild_life. With the vanished wetlands, gone also are the rich supplies of fish, a compulsory item of the Assamese menu and a good source of protein for the rural mass. In spite of the presence of the mighty Brahmaputra, its numerous tributaries, and the large number of wetlands, Assam today imports 0.20 lakh tonnes of fish an anually to satisfy the domestic market. Out of this, 0.14 lakh tonnes is consumed in Assam. The total fish production from Assam's wetlands is 1.55 lakh tonnes per year. Thus, a total of 1.69 lakh tonnes of fish is supplied from imports as well as local wetlands. The total demand for fish in the state, on the other hand, is estimated at 2.21 lakh tonnes per year, 6.68 percent of which met by imports from other states (source : Directorate of Fisheries, Government of Assam). As a result, there is a deficit of 0.52 lakh tonnes of fish every year and consequently the price of fish has rocketed up to such a height that the poor man simply cannot afford to buy it even once in a week. The production potential of wetlands in the state is estimated at 400-500 kg/ha/year after development. The progressive short supply of fish in Assam is a direct consequence of mismanagement and neglect of its wetland eco-system.

 

It is therefore felt to be an imperative need to conserve these wetlands and protect their unique biodiversity. If properly managed, the wetlands are going to be a source of immense wealth for this state leading also to enrichment of the quality of its environment.

 

Lakes / Ponds :

In Assam, there are 690 lakes and ponds as recorded through the study. These lakes /ponds cover an area of 15494.00 ha which constitutes 0.20 percent of the total geographical area of the state and 15.30 percent of the total area under wetlands. The smallest of them measures 2.50 ha while the largest one has 882.50 ha of areal coverage. Majority of this type of wetlands have water with low turbidity. An analysis of aquatic vegetation in these lakes / ponds indicates that most of them have no vegetation or are partially vegetated. Highest number of lakes / ponds are observed in Golaghat district (113 number) followed by Dhubri (73 number) and Nagaon (68 number) districts. But areawise, the highest area under this category is observed in Kamrup district (15705.00 ha) followed by Nagaon (2175.50 ha) and Dhubri (1816.50 ha) districts. Some of the important wetlands under this category are Deepar beel in Kamrup district, Dhir beel in Dhubri district, Tamaranga beel and Dalani beel in Bongaigaon district.

 

Ox-bow Lakes / Cut-off Meanders:

A total 861 number of ox-bow lakes/cut-off meanders are observed throughout the state of Assam, covering an area of 15460.60 ha which constitutes 0.20 percent of the total geographical area of the state and 15.27 percent of the total area under wetlands. The smallest of them measures 5.0 ha while the largest one has 582.50 ha of areal coverage. Majority of this type of wetlands have water with low turbidity. An analysis of aquatic vegetation in these ox-bow lakes / cut-off meanders indicates that most of them are either without vegetation or partially vegetated. Highest number of ox-bow lakes / cut-off meanders are observed in Golaghat district (104 number) followed by Nagaon district (71 number) and Dhubri district (68 number). But area wise, the highest area under this category is observed in Morigaon district (2143.00 ha) followed by Nagaon (1746.00 ha) and Golaghat (1563.00 ha) districts. Some of the important wetlands under this category are Morikolong and Patoli beel in Nagaon district, Mer beel in Golaghat district and Guruajan in Morigaon district.

 

In Assam, a total of 1125 number of waterlogged areas are observed which are distributed unevenly covering an area of 23431.50 ha which constitutes 0.30 percent of the total geographical area of the state and 23.15 percent of the total area under wetlands. The smallest of them is 2.5 ha while the largest one has 3010.00 ha of areal coverage. Majority of this type of wetlands have low turbidity. An analysis of aquatic vegetation in these wate-logged areas indicates that most of them are free from aquatic vegetation. Highest number of water(c)logged areas are observed in Cachar district (231 number) followed by Nagaon district (138 number) and Sonitpur district (110 number). But area wise, the highest area under this category is observed in Cachar district (4869.50 ha) followed by Karimganj (4667.00 ha) and Nagaon (2559.50 ha) districts. Some of the important wetlands under this category are Son beel in Karimganj district and Raumari beel in Darrang district.

 

These water-logged areas play significant role in the region’s economy as they are present in large numbers in the rural areas containing good amount of fishes and other aquatic fauna and providing habitat to a variety of migratory as well as domestic birds. Besides they have remarkable potential for supplying irrigation water to the nearby agricultural fields during the dry periods. There are some waterlogged areas which can be developed for recreational purposes and as tourist spots such as the Son beel in Karimganj district.

 

Swampy/Marshy areas:

These swampy/marshy areas constitute another major group of wetlands in Assam. These are identifiable on satellite imagery by their reddish tone indicating the presence of vegetation, associated with dark blue tone inferring to the presence of water and their occurrence in the low lying areas. Due to the presence of varied quantities of minerals in the water, these swampy/marshy areas are either moderately or highly turbid. In most cases, there is no feeder channel to control the inflow or outflow of water.

 

In Assam, as many as 712 number of swampy/marshy areas have been identified from satellite data which cover an area of 43433.50 ha constituting 0.55 percent of the total geographical area of the state and 42.91 percent of the total area under wetlands. The smallest of them is 2.5 ha while the largest one has 1350.00 ha of areal coverage. Majority of this type of wetlands are with low turbidity. An analysis of aquatic vegetation in these lakes / ponds indicates that most of them are partially vegetated. Highest number of swampy/marshy areas are observed in Kamrup district (155 number) followed by Nagaon (92 number) and Goalpara (68 number) districts. But area wise, the highest area under this category is observed in Kamrup district (8109.50 ha) followed by Morigaon (7051.00 ha) and Nagaon (4764.50 ha) districts. Some of the important wetlands under this category are Nandan-Sonai beel in Morigaon district, Batha beel in Darrang district and Urpad beel in Goalpara district.

 

Unlike the water-logged areas, the swampy/marshy areas don’t have much contribution to the state's economy. But with the help of proper developmental schemes by converting them into utilizable form, these may boost up the economy of the state to a significant level.

 

Reservoirs:

Reservoirs are artificial impoundments of water for irrigation, flood control, municipal water supplies, hydro-electric power generation and so forth. There are as many as 10 number of reservoirs covering an area of 2662.5 ha which constitutes 0.03 percent of the total geographical area of the state and 2.63 percent of the total area under wetlands. The smallest of them covers 17.50 ha while the largest one has 930.00 ha of areal coverage. Majority of this type of wetlands contains water with low turbidity. An analysis of aquatic vegetation in these reservoirs indicates that most of them are either free from vegetation or partially vegetated. Highest number of reservoirs is observed in N.C.Hills district (4 nos.) followed by Golaghat and Nalbari districts (2 nos. each). But area wise, the highest area under this category is observed in N.C.Hills district (2365.00 ha) followed by Kamrup (220.00 ha) and Golaghat (37.50 ha) districts. Some of the important wetlands under this category are Garampani and Umrangsu in N.C.Hills district.

 

Tanks:

Assam has several thousands of family owned small size tanks, these have not entered into reckoning as far as this report is concerned because of the scale factor. In Assam, a total of 115 number of tanks are identified from satellite data. These tanks occupy an area of 749.00 ha which constitutes 0.01 percent of the total geographical area of the state and 0.74 percent of the total area under wetlands. The smallest of them covers 2.5 ha while the largest one has 55.00 ha of areal coverage. Majority of this type of wetlands have low turbidity. An analysis of aquatic vegetation in these tanks indicates that most of them are free from vegetation. Highest number of tanks are observed in Sibsagar district (20 number) followed by Kamrup (18 number) and Sonitpur (16 number). But area wise, the highest area under this category is observed in Sibsagar district (267.00 ha) followed by Sonitpur (83.50 ha) and Kamrup (80.00 ha) districts. Some of the important wetlands under this category are Gaurisagar Pukhuri, Sibsagar Pukhuri and Joysagar Pukhuri in Sibsagar district. Besides providing water to the people of the nearby areas, these tanks can also be used for rearing fishes and raising plantation crops like coconut, arecanut, cashewnut etc. along the sides of the ponds. Ornamental gardens can also be developed on the banks of the ponds.

 

Ground Water Resource:

Assam is one of the rich states of the country in term of the ground water development potentiality. The entire Brahmaputra valley, covering more than 70 per cent of the total geographical area of the state, contain prolific aquifer system with water table lying within 5 m of land surface. The Barak valley also has a good potentiality for the development of ground water. The present stage ground water development even in the Brahmaputra valley, the most populous part of the state, is nothing but in a nascent stage.

Based on the recommendation of the Ground Water Estimation Committee, Ministry of Irrigation, March 1984, the recoverable recharge of ground water in Assam as worked out by the Central Ground Water Board, to about 2 million hectare metre per year. With the present ground water resource available to be utilized, it is estimated that an additional area of about 14 lakh hectare of net area sown can be brought under irrigation. Besides the irrigational use, ground water forms the most common form source of domestic use water in the state. The lifting of ground water through dug wells, tube wells, shallow tube wells and deep tube wells for irrigation, domestic and industrial use is very common in the state. Table below shows the Ground water distribution in Assam.

 

Water Pollution

 

The problem of water pollution is rampant in all thickly populated areas. Water does possess a self-cleaning property. The problem intensifies with the addition of pollutants in our water-ways from many sources like wastes from reactors, laboratories, hospitals and fallout from nuclear explosions, domestic wastes from the cities and towns, chemical wastes from factories and industrial units, etc. 90% of water pollution is due to human waste, which gives rise to such diseases as intestinal infection, hookworms, cholera, typhoid, infectious hepatitis, etc. chemicals like DDT, Parathion, lindane, etc contribute a great deal to water pollution.

To prevent water pollution, the discharge of effluents from the industries as well as the use of DDT should be controlled. All domestic waste should be properly treated before discharging it into the water bodies. Acid rain can be prevented by reducing the emission of oxides of sulphur and nitrogen from power plants, fertiliser plants, etc.

 

Engineering (Flood Control Department Service Rules 1981)

The Assam Embankment and Drainage Act, 1953

The Assam Embankment and Drainage Act, 1960

The Assam Ground Water Control and Regulation Act, 2012

The Assam Irrigation Act, 1983 (1)

The Assam Irrigation Act, 1983

The Assam Irrigation Rules, 1997

The Assam Irrigation Water Users Act, 2004

 

 

Source:

Water Resource Department

Irrigation and Water Resources Development

Brahmaputra Board 

 

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