Climate, Soil and Water Conservation of Rajasthan gk english notes

Comprehensive Study Guide: Climate and Soil of Rajasthan

For students preparing for competitive exams, a thorough understanding of Rajasthan's geography is essential. This guide covers the climate, soil types, and water conservation methods of the state in a simple, easy-to-read format

Climate Characteristics and Regions

Rajasthan is located in the subtropical zone. The Aravalli mountain ranges divide the state's climate into two distinct parts. The western region is a rain shadow area that receives very little rainfall, leading to an arid climate. In contrast, the eastern part of the Aravallis enjoys a humid climate with relatively uniform temperatures, higher humidity, and seasonal rainfall.

Key Characteristics

• Almost all of the state's rainfall occurs during the summer months (late June, July, and August) from the South-West monsoon winds.
• During winter, the north-western parts of Rajasthan receive very little rainfall from western disturbances originating in the Mediterranean Sea, which is locally called 'Mawath'.
• The annual average rainfall is approximately 58 cm.
• Rainfall timing and quantities are highly uncertain, frequently causing droughts and famines.
• Rainfall distribution is unequal; the south-eastern region receives heavy rain, while rainfall in the north-western area is negligible.

Climatic Regions by the Indian Meteorological Department

• Arid Climatic Region: Includes Jaisalmer, western Bikaner, western Barmer, and parts of Jodhpur, Ganganagar, and Phalodi. Average rainfall is 0-20 cm. Summer temperatures range from 34 to 40 degrees Celsius (sometimes reaching 48 to 49 degrees Celsius during the day), and winter temperatures fall between 12 and 16 degrees Celsius, often dropping below zero at night. Evaporation rates exceed rainfall. Vegetation is sparse and limited to thorny bushes. The region experiences dust storms and hot 'Loo' winds, causing pastoralists to lead a nomadic life.
• Semi-Arid Climatic Region: Covers Churu, Ganganagar, Hanumangarh, Jodhpur, Pali, Jalore, Sikar, Nagaur, and Jhunjhunu among others. Rainfall is 20-40 cm, with summer temperatures at 30 to 36 degrees Celsius and winter at 10 to 17 degrees Celsius. Features thorny bushes, Khejri, Babool, and grasses like Sewan and Leelan. Inland drainage causes the formation of saline water lakes.
• Sub-Humid Climatic Region: Found in Alwar, Jaipur, Ajmer, Bhilwara, and parts of Pali, Sikar, and Tonk. Rainfall is 40-60 cm. Temperatures are 28 to 34 degrees Celsius in summer and 12 to 18 degrees Celsius in winter. Supports deciduous trees like Neem, Babool, and Mango, and steppe vegetation suitable for wheat, barley, and mustard.
• Humid Climatic Region: Encompasses eastern and south-eastern areas like Bharatpur, Dholpur, Kota, Bundi, and Sawai Madhopur. Rainfall is 60-80 cm. Summer temperatures are 32 to 35 degrees Celsius and winters are 14 to 17 degrees Celsius. Features dense deciduous forests with Banyan, Peepal, and Neem, and hosts the Ranthambore and Keoladeo bird sanctuaries.
• Very Humid Climatic Region: Located in Jhalawar, Banswara, Dungarpur, Pratapgarh, and Mount Abu. It receives the highest average rainfall of 80-150 cm. Summers are 30 to 34 degrees Celsius (25 degrees Celsius in Mount Abu) and winters are 12 to 15 degrees Celsius (9 to 10 degrees Celsius in Mount Abu). Rich in monsoon savanna vegetation, including Teak, Mango, and Bamboo.

Factors and Reasons for Low Rainfall

The climate is influenced by latitudinal position, distance from the sea, mountain barriers, altitude, prevailing winds, and continentality. The state experiences three main seasons: Summer (March to mid-June), Winter (November to February), and Monsoon (mid-June to September).

The state experiences low rainfall due to three main geographical factors:

• The Bay of Bengal monsoon branch loses almost all of its moisture over the Ganga plains before reaching Rajasthan.
• The Arabian Sea monsoon winds blow parallel to the Aravalli mountain ranges, passing over the state without causing precipitation due to lack of obstruction.
• When monsoon winds enter the desert region, the intense heat decreases their humidity, preventing them from producing rain.

Global Climate Classifications

Koppen's Classification

Dr. Vladimir Koppen classified the state into these regions based on vegetation:

• Aw (Tropical Humid): Banswara, Dungarpur, Pratapgarh, and Mount Abu. Over 80 cm rainfall. Dense monsoon deciduous and savanna vegetation.
• Bshw (Semi-Arid/Steppe): Barmer, Jodhpur, Nagaur, Sikar, etc. Rainfall 20-40 cm, featuring thorny bushes and steppe vegetation.
• Bwhw (Tropical Arid): Jaisalmer, Bikaner, Ganganagar, and Churu. Rainfall 10-20 cm. Harsh climate with sand dunes, though the Indira Gandhi Canal has transformed the area. High evaporation rate.
• Cwg (Sub-Humid): Jaipur, Alwar, Bharatpur, Tonk, etc. Rainfall 60-80 cm, known for the Chambal river ravines.

Thornthwaite's Classification

• CA'w (Sub-Humid): Jhalawar, Baran, Kota, Banswara, Mount Abu.
• DA'w (Tropical Humid/Semi-Arid): Nagaur, Sikar, Jodhpur, Jaipur, Ajmer, Pali.
• DB'w (Semi-Arid Mixed): Ganganagar, Hanumangarh, Churu, Bikaner.
• EA'd (Tropical Arid): Jaisalmer, western Bikaner, western Barmer.

Trewartha's Classification

• Aw: Tropical humid region covering Jhalawar, Dungarpur, and Banswara.
• BSh: Tropical and sub-tropical steppe covering Jodhpur, Bikaner, Sikar, and Jaipur.
• BWh: Arid desert covering Jaisalmer, western Bikaner, and Barmer.
• CAW: Sub-tropical humid covering eastern and southern districts like Alwar, Bharatpur, and Bundi.

Traditional Soil Classification in Rajasthan

Soil Type	Region	Characteristics
Sandy/Balui Soil	Jaisalmer, Barmer, Bikaner, Jodhpur.	Large particles, low moisture retention. Low in nitrogen, high in calcium. Best for Kharif crops like Bajra, Moth, and Moong.
Red Loam	Udaipur, Dungarpur, Banswara, Chittorgarh.	Fine particles, great moisture retention. Low in nitrogen and phosphorus, high in iron and potash. Ideal for Maize.
Black Soil	Kota, Bundi, Baran, Jhalawar.	Fine particles, high moisture retention. Deficient in phosphate, rich in calcium and potash. Best for cotton and cash crops.
Mixed Red-Black	Udaipur, Chittorgarh, Bhilwara, Dungarpur.	Low in phosphate and nitrogen. Suitable for cotton and maize.
Mixed Red-Yellow	Sawai Madhopur, Bhilwara, Ajmer, Sirohi.	Low in nitrogen and calcium, rich in iron oxides.
Alluvial Soil	Alwar, Bharatpur, Dholpur, Jaipur (River plains).	Highly fertile, great water capacity. Perfect for wheat, rice, cotton, and tobacco.
Brown Soil	Tonk, Bundi, Bhilwara, Ajmer.	Lacks nitrogen and phosphorus. Found in the Banas river basin, good for agriculture.
Sirozem / Grey Desert	Pali, Nagaur, Jalore.	Yellow-brown color, low fertility. Lacks nitrogen and organic matter.
Saline Soil	Ganganagar, Bikaner, Barmer, Jalore.	Infertile due to high alkaline and saline elements. Naturally found in lowlands.
Mountainous Soil	Sirohi, Udaipur, Ajmer, Alwar hills.	Unsuitable for farming due to shallow soil depth.

Scientific Soil Classification (USDA)

The US Department of Agriculture system classifies the state's soils into five orders:

• Aridisols: Mineral soils found strictly in arid climates like Churu, Sikar, Nagaur, and Jodhpur. Key sub-orders include Orthids.
• Alfisols: Found in Jaipur, Alwar, Kota, and Udaipur. They possess medium to fully developed profiles with Argillic horizons, meaning they have a high clay percentage. The main sub-order is Ustalfs.
• Entisols: Covering most western districts, these are found across diverse climates. They are pale yellow-brown in color, and sub-orders include Psamments and Fluvents.
• Inceptisols: Found in semi-arid to humid regions like Sirohi, Pali, and Jaipur plains (never in purely dry climates). The main sub-order is Ustepts.
• Vertisols: Heavy clay soils located in Jhalawar, Baran, Kota, and Bundi. They exhibit all characteristics of clay soils and belong to the Usterts sub-order.

Soil Erosion and Conservation Methods

• Gully erosion (Avnalika) is highest along the Chambal river.
• Bihad (ravine) lands have the largest extent in Dholpur, followed by Sawai Madhopur and Karauli.
• Water erosion heavily impacts the southern and eastern districts.
• In the Aravalli hills, soil erosion is caused by deforestation, overgrazing, and unscientific farming.
• Wind erosion is the leading cause of soil degradation in the western desert, affecting the largest total land area in Rajasthan.
• Treating Salinity: Soil salinity is reduced using Rock Phosphate. Mixing weeds like Dhamasa (Tephrosia purpurea) and Subabool into the soil is also effective.
• Treating Alkalinity: Soil alkalinity is managed by plowing green manure crops like Guar and Dhaincha into the fields. Protecting earthworms and beneficial microbes is vital to maintain soil fertility.

Traditional Water Conservation Methods

• Sar: Natural depressions between desert sand dunes that collect rainwater to form ponds, such as Jasusar and Malusar.
• Johad (Nada): Raw and masonry wells built for water collection in the Shekhawati and Bangar regions.
• Bawdi: Ancient, large, stepped wells built for water storage and collection.
• Tanka: Rainwater cisterns built in forts and houses in Marwar and Shekhawati. This stored water is used year-round and is known as 'Palar Pani' or Kundi.
• Nadi: Traditional rainwater ponds very common in western Rajasthan villages.
• Toba: A water-collecting structure similar to a Nadi, but comparatively deeper.
• Khadin: Temporary, earthen dam-like ponds built at the bottom of slopes in Jaisalmer to harvest rainwater.
• Kui or Beri: Small wells constructed near ponds to collect filtered, seeped water for drinking purposes.

Important Geographical Facts for Exams

• Temperature Trends: Temperatures drop as you move from the north-western parts to the south-eastern parts of the state. The temperature also decreases by 1 degree Celsius for every 165 meters of altitude gained.
• Rainfall Extremes: The highest rainfall place is Mount Abu, and the highest rainfall district is Jhalawar. The minimum rainfall occurs in Jaisalmer. June is the hottest month, and January is the coldest.
• Purvaiya: South-East trade winds from the Indian Ocean turn into South-West monsoons after crossing the equator. The monsoon branch coming from the Bay of Bengal is locally called Purvaiya in Rajasthan.
• Loo: Extremely hot and dry winds blowing through the desert regions.
• Bhabhulya: Small, localized whirlwinds or cyclones.
• Frost (Pala): During winter, freezing winds from the northern mountains can drop night temperatures to the freezing point, turning water to ice and destroying crops.
• Relative humidity is at its lowest in March-April and reaches its maximum in July-August.
• Brown loam soil is predominantly found in the Luni basin.

Use the quick links below to navigate through the topics:

• Climate Characteristics and Regions
• Reasons for Low Rainfall
• Global Climate Classifications (Koppen, Thornthwaite, Trewartha)
• Traditional Soil Classification
• Scientific Soil Classification (USDA)
• Soil Erosion and Conservation
• Traditional Water Conservation Methods
• Important Geographical Facts