Great Himalayas, Himalayan Rivers, Indian Climate & Soils

Posted on Feb 8, 2026 in Geography

Great Himalayas (Himadri): Structure and Features

The Great Himalayas, also known as the Himadri, form the northernmost and loftiest range of the Himalayan mountain system. They are characterized by their immense height, continuity, and rugged terrain.

1. Structure of the Great Himalayas

The geological structure of the Himadri is a result of the ongoing collision between the Indian and Eurasian tectonic plates.

• Rock Composition: The core of the Great Himalayas is primarily composed of Archaean rocks like granite, gneiss, and schist. These crystalline rocks are often overlain by metamorphosed sediments, such as limestone, which are remnants of the ancient Tethys Sea floor.
• Asymmetrical Folds: Due to the intense compressional forces of the plate collision, the mountain folds are asymmetrical. The southern slopes are very steep, while the northern slopes descend more gently toward the Tibetan Plateau.
• Continuity: It is the most continuous range in the world, stretching approximately 2,400–2,500 km from the Indus Gorge in the west (Nanga Parbat) to the Brahmaputra Gorge in the east (Namcha Barwa).
• Syntaxial Bends: At both ends of the range, the mountains take sharp southward turns known as syntaxial bends.

2. Relief Features

The relief of the Himadri is among the most dramatic on Earth, featuring extreme altitudinal variations.

• Average Elevation: The range maintains an average elevation of about 6,100 meters above sea level. It contains almost all the world’s highest peaks, including Mount Everest (8,848 m) and Kanchenjunga (8,586 m).
• Topography: The relief is “highly dissected,” meaning it is deeply cut by erosion into jagged peaks and deep valleys. The “hogback” topography—long, steep-sided ridges—is a defining feature of its slopes.
• Glaciation: Because the range is perennially snowbound, it is the source of numerous massive glaciers, such as the Gangotri and Yamunotri, which feed the major perennial rivers of North India.
• Gorges: Despite their height, several rivers (like the Indus and Sutlej) have cut through the range, creating deep, vertical V-shaped gorges, proving that these rivers existed before the mountains reached their current height (antecedent drainage).

Hydrology of Himalayan Rivers and Regime

The hydrological regime of Himalayan rivers (such as the Indus, Ganga, and Brahmaputra) refers to the seasonal variation in their water discharge (the volume of water flowing through the river). Unlike Peninsular rivers, which are purely rain-fed, Himalayan rivers are perennial, meaning they flow year-round due to a dual supply of water: snow/glacial melt and monsoon rainfall.

1. Sources of Water Supply

The regime is characterized by two distinct recharge periods:

• Glacial/Snow Melt (March–June): As temperatures rise in spring and summer, glaciers and snowcaps in the higher altitudes melt. This ensures that the rivers maintain a significant flow even during the dry summer months before the rains arrive.
• Monsoon Rainfall (July–September): During the Southwest Monsoon, the Himalayan region receives heavy precipitation. This causes the rivers to swell significantly, often reaching their peak discharge levels.

2. Seasonal Discharge Patterns

The flow of these rivers follows a predictable annual cycle:

• Winter (December–February): This is the low-flow period. Precipitation in the mountains occurs as snow, which does not immediately contribute to river flow. Groundwater (baseflow) is the primary source during this time.
• Pre-Monsoon (March–May): Discharge begins to increase as the seasonal snow at lower altitudes starts to melt.
• Monsoon (June–September): This is the peak-flow period. The combination of high-intensity rainfall and continued glacial melt leads to maximum discharge.
• Post-Monsoon (October–November): Discharge steadily decreases as the rains retreat and temperatures drop, slowing down the glacial melt.

Most Himalayan rivers carry about 70–80% of their annual volume during these four months, often leading to floods in the plains.

3. Regional Variations

The regime varies from west to east across the Himalayan range:

• Western Rivers (e.g., Indus): These are more dependent on snowmelt and “Western Disturbances” (winter storms). Glacial melt can contribute up to 40–50% of the annual flow.
• Eastern Rivers (e.g., Brahmaputra): These are heavily influenced by the Monsoon. Because the Eastern Himalayas receive much higher rainfall, the monsoonal “surge” in discharge is much more dramatic compared to the Western rivers.

4. Himalayan vs. Peninsular Regimes

Summary comparison:

Climate of India: Monsoon and Regional Diversity

The climate of India is primarily described as a Tropical Monsoon type. Despite this broad classification, India’s vast size and varied relief (from the high Himalayas to the coastal plains) create significant regional diversity.

Key Climatic Characteristics

The climatic characteristics of India are defined by the following key features:

1. The Monsoon System (Seasonal Reversal of Winds)

• Southwest Monsoon (June–September): Moisture-laden winds blow from the Indian Ocean toward the land, bringing over 75% to 80% of India’s annual rainfall.
• Northeast Monsoon (October–December): As the land cools, winds reverse and blow from the land toward the sea. These are generally dry, except when they pick up moisture from the Bay of Bengal and bring rain to the Coromandel Coast (Tamil Nadu).

2. Plurality of Seasons

The India Meteorological Department (IMD) recognizes four official seasons:

• Winter (December–February): Characterized by clear skies and pleasant weather. Northern India experiences cold conditions (often below 10°C) due to Western Disturbances from the Mediterranean.
• Summer/Pre-Monsoon (March–May): Temperatures rise sharply, often exceeding 40°C in the interiors. Hot, dry winds called “loo” are common in the northern plains.
• Monsoon/Rainy Season (June–September): The period of heavy downpour and high humidity.
• Post-Monsoon/Retreating Monsoon (October–November): A transition period where the monsoon withdraws, often characterized by “October Heat” (high temperature and humidity).

3. Regional Diversity and Extremes

India exhibits sharp climatic contrasts across its geography:

• Temperature Extremes: While the Thar Desert in Rajasthan may record temperatures above 50°C in summer, the Dras sector in Ladakh can drop to -45°C in winter.
• Rainfall Extremes: Mawsynram and Cherrapunji in Meghalaya are among the wettest places on Earth (over 1,000 cm annually), while parts of western Rajasthan receive less than 15 cm.

4. Major Influencing Factors

• The Himalayas: Act as a giant climatic divide. They block the frigid cold winds from Central Asia (keeping India warmer than other regions at the same latitude) and trap the monsoon winds, forcing them to shed rain over the subcontinent.
• Latitude: The Tropic of Cancer passes through the middle of India. The southern half lies in the Tropical Zone (consistently warm), while the northern half is in the Sub-tropical/Temperate Zone (larger seasonal variations).
• Distance from the Sea: Coastal areas (like Mumbai and Chennai) have an equable/maritime climate with little temperature variation. In contrast, interior areas (like Delhi) have a continental climate with extreme heat and cold.

5. Climatic Regions (Köppen Classification)

Geographers and climatologists often use Köppen’s scheme to divide India into specific zones:

• Amw (Monsoon type): Western coast (short dry season).
• BWhw (Hot Desert): Western Rajasthan.
• Cwg (Humid Subtropical): Most of the Northern Plains (dry winters).
• E (Polar): Higher reaches of the Himalayas.

Soil Conservation: Necessity and Methods

Soil conservation is the prevention of soil loss from erosion or reduced fertility caused by over-usage, acidification, salinization, or other chemical soil contamination. Given that it takes centuries to form just one inch of topsoil, conservation is vital for food security and environmental stability.

1. Necessity of Soil Conservation

• Food Security: Fertile topsoil is the primary medium for growing food. Conservation ensures long-term agricultural productivity.
• Water Quality: Soil erosion causes sedimentation in rivers and reservoirs, leading to water pollution and reduced storage capacity of dams.
• Flood Control: Healthy soil acts like a sponge, absorbing rainwater. Eroded or compacted land increases surface runoff, which triggers flash floods.
• Climate Regulation: Soil is a massive carbon sink. Proper management prevents the release of carbon dioxide into the atmosphere, helping mitigate global warming.
• Economic Stability: For an agrarian economy like India, soil degradation leads to lower yields and increased costs for chemical fertilizers, trapping farmers in debt.

2. Methods of Soil Conservation

Methods are generally classified into Biological (Agronomic) and Mechanical (Engineering) measures.

A. Biological / Agronomic Methods

These methods use vegetation and farming techniques to protect the soil surface.

• Contour Ploughing: Plowing along the natural contours of a slope rather than up and down. This creates “natural dams” that slow down water flow.
• Strip Cropping: Growing different crops (e.g., a cover crop like clover and a row crop like corn) in alternating strips to break the force of wind and water.
• Cover Cropping: Planting fast-growing crops (like legumes or grasses) during the off-season to ensure the soil is never left bare and exposed to erosion.
• Crop Rotation: Alternating different types of crops in the same area to prevent nutrient depletion and improve soil structure.
• Mulching: Covering bare soil with organic matter (straw, leaves) to retain moisture and prevent rain from washing away the topsoil.
• Shelterbelts (Windbreaks): Planting rows of trees or shrubs at right angles to the prevailing wind direction, especially in arid regions like Rajasthan, to reduce wind erosion.

B. Mechanical / Engineering Methods

These are structural interventions used on steeper slopes or where erosion is severe.

• Terracing: Cutting “steps” into steep hillsides (common in the Himalayas). This reduces the length of the slope and prevents water from gaining enough speed to erode the soil.
• Contour Bunding: Constructing small earthen embankments (bunds) across the slope to intercept runoff and encourage water to soak into the ground.
• Check Dams: Small barriers built across gullies or small streams to slow down water velocity and trap sediment.
• Gully Plugging: Using stones, sandbags, or vegetation to fill up small gullies, preventing them from expanding into large ravines.