Climate and Drainage System of India

The climate of India is described as Tropical Monsoon Climate. Monsoon is an Arabic term which indicates seasonal changes in the distribution pattern of:

  • Atmosphere Pressure
  • Temperature
  • Rainfall
  • The direction of Wind

Climate of India

Based on the seasonal distribution of these four parameters, the climate of India is divided into the following climate:

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Although the Great Plains of India are located in the Sub-Tropical Zone, the Indian climate is called Tropical which indicates its hot and humid conditions with seasonal rainfall. The topicality of India has been contributed by the following two physiographic factors:

  1. Himalayan Mountains – North of the Great Plains
  2. Indian Peninsula – Surrounded by sea from three sides

In the winter season, extremely cold Polar winds are prevented by the Himalayan mountain ranges from flowing into the Great Plains of India. Thus, winters are short & mild.

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During summers, Southern Western Monsoon winds which are Tropical hot and humid winds flow to the Great Plains of India and generate rainfall under the influence of the Orographic Effect of the Himalaya with their inflow into the Great Plains, hot & humid.

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Summer

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Southwest Monsoon Season

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The Southern Western season starts in the last week of May or the first week of June which is when there is a burst of monsoon. The heaviest rainfall is seen in the Andaman & Nicobar Islands and the North European Hills due to the Bay of Bengal branch, the windward side of Western Ghats due to the Arabian Sea branch.

Retreating Monsoon

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Basic Terms related to Drainage System

Catchment Area (Or) Basin Area the area in which a river drains its water collected from a specific source

Command Area is the area around the dam, where the benefits of the dam, such as irrigation water, electricity, etc., reach. Govt. runs various Command Area development programs nearby almost all big & small Dams.

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Antecedent Rivers: These are rivers that are older than the physical barrier it cuts through. For instance, all rivers originating from Tibet is older than the Himalayas. These rivers thus originate before the shape is formed (Tibet is older than the Himalayas). Antecedent rivers are those rivers that originate before its slope or gradient.

Consequent Rivers are those rivers that originate only after the formation of its slope. All Peninsular rivers and their drainage system emerge only after the formation of landforms that created a slope towards the sea. (Deccan Plateau is the geologically oldest landform in India.)

V-Shaped Valley: In conditions of high altitude, high slope and flow are over soft rocks, then steep, deep and narrow valley is formed due to Vertical Erosion. Such valleys are V-shaped valleys.

Climate of India
V-shaped Valley

Meander: These soft rocks are easily eroded resulting in the serpentine Flow pattern of the river. These are called Meanders. E.g: v-shaped valleys and meanders are seen predominantly in the Himalayan Rivers.

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Lateral Erosion: If the flow is over hard rocks, the banks are eroded and the valleys formed are wide and shallow. This erosion of banks alone is called lateral erosion. Here meanders are restricted. E.g: peninsular Rivers of India. [Hard rocks resist erosion; the metamorphic rocks of the Peninsular are highly resistant to erosion by its hardness]

Climate of India
Illustration of Lateral Erosion

The drainage system of India

Based on origin, drainage s/m of India is divided into two categories:

  1. The Himalayan drainage system which contains Indus, Ganga, Brahmaputra, and their tributaries. The basin or catchment area of Ganga is the largest in India. The Himalayan drainage system is Antecedent in nature as these rivers are older than the Himalayan mountain ranges. Indus, Brahmaputra, Sutlej, and Arun-Kosi originate from Tibet and cut across the Himalayan mountain ranges to flow into the plains.

Himalayan rivers have perennial flow. Their valleys are deep due to the vertical erosion. With perennial flow and deep valleys, in the Himalayan course, these rivers are useful for Hydro Power Production and in plains for Navigation.

Climate of India
Classification of India Drainage System

Himalayan rivers form Meanders as their flow is serpentine.

  1. Peninsular Rivers: Based on the flow of the river, peninsular rivers are classified as under.
  • East flowing peninsular rivers
  • West flowing Peninsular rivers
  • Inland Drainage

East Flowing Peninsular Rivers: Mahanadi (Odisha), Godavari, Krishna (A.P) & Kaveri (T.N.). The Godavari has the largest basin and it is the second-largest basin of India after Ganga. So it is called as Dakshinganga.

These rivers are consequent. Their flow is south-east along the slope of Indian Peninsular. These rivers are seasonal as their flow is over hard metamorphic rocks. With low altitude and slope, these rivers are involved in lateral erosion. With lateral erosion, their valleys are wide and shallow.

With seasonal flow and wide and shallow valleys, these rivers are neither useful for hydric power nor navigation. Formations of meanders are restricted.

West Flowing Peninsular Rivers: Narmada and Tapi are the important west-flowing rivers. These rivers flow into rift valleys which are linear, deep, narrow, and steep (which is why their course is almost like a straight line). Rift valleys are formed due to the Down faulting of rocks (Endogenetic Forces). This is why their flow is opposite to the slope of the Peninsula [the slope of the Indian is south-east ward]. Narmada is the longest west flowing river.

Inland Drainage System: If the ultimate flow of water is not to the sea, it is called an Inland Drainage System. Luni forms an inland drainage system. Its flow is into the Rann Of Kutch in Gujarat. The Rann of Kutch is a saline and marshy area.