Drainage part 1

 

Hello inquisitive people. Drainage system of India is vast and diverse just like India’s physiography and population and most of us find it knotty. Don’t worry we are here to make it simple and enthralling for you. Drainage would be covered in three blogs. This is part one that would cover basics.

  Drainage

Terms of significance:-

Drainage: - It refers to river system of an area.

Drainage basin: - The area drained by a single river system is referred to as drainage basin. For e.g.:- All the areas drained by Ganga or the areas Ganga passes through would be regarded as drainage basin of Ganga.

Water divide: - An upland or mountain that separates two neighboring drainage basins is called a water divide. Ambala is an example of water divide. It separated the Indus and the Ganges.

Confluence: - A place where streams merge.

Tributary: - A branch of river that flows into main stream.

Distributary: - The branches originating from tributaries are distributaries.

Watershed: - An area diving two parallel flowing rivers is called a watershed. It is smaller in size than water divide.

Delta: - It is more or less flat area of alluvium at the mouth of the river where sediments brought by the river get deposited. E.g.:- Sunder ban delta.

Eastury: - It is a V shaped valley of a river at its mouth where tides flow in and out and where fresh water and sea water mix. E.g.:- Narmada and Tapi.

Catchment area: - A river drains the water collected from a specific area, which is called its ‘catchment area’.

Drainage pattern:-

While flowing, rivers form various patterns. Some important drainage patterns are:-

          I.            Dendrtitic: - Drainage pattern resembling the branches of a tree is known as dendritic pattern. E.g. rivers of northern plains.

       II.            Radial: - When a river originates from a hill and flows in all directions, it is called radial pattern. E.g. Amarkantak range rivers.

    III.            Trellis: - When primary tributaries of a river flow parallel to each other and secondary tributaries join them at right angle.

   IV.            Centripetal: - When the rivers discharge its water from all directions in a lake or depression, it is centripetal drainage pattern.

Drainage system in India:-

Drainage system in India can be divided on three bases.

On the basis of discharge of water river drainage can be divided into:-

       I.            Arabian sea drainage:-

    II.            Bay of Bengal drainage:-

These are separated from each other by Delhi ridge, Aravalis and Sahyadris. Around about 77% drainage is oriented toward Bay of Bengal and 23% is oriented towards Arabian Sea.

On the basis of size of watershed, drainage can be divided into:-

       I.            Major river basins

    II.            Medium river basins

 III.            Minor river basins

Major river basins cover an area of more than 20000 sq. Km, medium river basins cover an area between 2000 and 20000 sq. Km and minor river basins cover an area of less than 2000 sq km.

On the basis of mode of origin, nature and characteristics, drainage can be divided into:-

       I.            Himalayan drainage system

    II.            Peninsular drainage system

We shall be discussing these two in detail in next two blogs.

Difference between Himalayan and Peninsular drainage:-

 

Role of rivers in economy:-

       I.            Development of civilizations: - Rivers have helped in development of major civilizations such as Indus valley civilization, Aztec etc.

    II.            Development for agriculture: - The soil deposits of rivers have proved to be the most fertile for agriculture. Moreover rivers help in irrigation also.

 III.            Settlement: - Most of the large cities are located on the banks of rivers such as Haridwar, Prayagraj, and Varanasi etc.

 IV.            Industrial development: - Many industries are set up along rivers as a coolant and for hydroelectricity generation.

    V.            Transportation means: - Rivers provide primary channel for inland transportation.

River regimes:-

The pattern of flow of river water through its channel over a year is known as its regime. It varies from season to season and river to river and even from one part of the river to other. The discharge is the volume of water flowing in a river measured over time. It is measured in cusecs (cubic feet per second) or cumecs (cubic meters per second). This value tells us about regime of a river.

Extent of usability of river water:-

The diverse nature of Himalayan and Peninsular rivers poses a problem to the water availability in various parts of the country. Rains cause thrift in the regimes of the Himalayan Rivers resulting into floods many a times. Since peninsular rivers are seasonal, they completely depend upon rains and if there is lack of rains, a drought like condition is created in southern part. There is need of managing river water through river linkage so that extra water from flood causing rivers can be diverted to river deficit areas and balance can be maintained. But river linkage isn’t a cinch. It requires huge sum of money, teams of engineers and foremost, calculated planning. There lie mountains of challenges before governments for River linkage. Foremost is the undulating topography of India. Other reasons are:-

§  No availability in sufficient quantity.

§  River pollution.

§  Load of silt in the river water.

§  Uneven seasonal flow of water.

§  River disputes between states.

§  Shrinking of channels due to the extension of settlements.

River pollution:-

River pollution is a major environmental issue in India. We all are familiar with its causes. The largest source of river pollution is untreated sewage; other sources are industrial effluents being discharged into rivers, solid waste of animals. People of rural areas still use banks of the rivers for domestic activities such as cleaning, bathing, washing etc. This affects not only the quality of water but also the self cleansing capacity of the river. For e.g. river Ganga is capable of diluting and assimilating pollution loads within 20 km of large cities. But it is polluted at a much larger rate due to industrialization and urbanization. Many action plans one of which is GAP (Ganga Action Plan) are launched by state and centre governments to ensure the quality of river water. NRCD (National River Conservation Directorate) layouts the action plans and provide with funds to the government for this purpose.