Rajasthan is a state of vast geographical area. Due to this large area, there are inequalities in annual rainfall seen all over Rajasthan. These inequalities of rainfall are on regional level. Due to internal conditions of Rajasthan, there is very little rainfall in the state. In the eastern parts of Aravalli range, there is sufficient annual rainfall. But in the western part of Aravalli range, rainfall is very less.
On the basis of rainfall in the state, Rajasthan has been divided into 5 zones:
1. Regions with more than 100 cm rainfall: In these regions of Rajasthan, the annual average rainfall is found to be more than 100 cm. In this category, districts such as Sirohi, (Mount Abu), western Udaipur, Rajsamand, south-western Bhilwara etc. are included.
2. Regions with 75 to 100 cm rainfall: The annual average rainfall is from 75 to 100 cm in these regions. The districts of Jhalawar, southern Kota, eastern part of Chittorgarh, Pratapgarh, Banswara, Dungarpur (western part), central region of Udaipur, central .and southern Bhilwara, eastern regions of Sirohi and Pali and central part of Rajsamand are included in this zone.
3. Regions with 50 to 75 cm rainfall: In this zone, the districts such as south – eastern and eastern areas of Jalore, central Pali, Ajmer, Jaipur, Dausa, Alwar, Bharatpur, Dholpur, Karauli, Sawai Madhopur, Tonk, Bundi, Baran, Kota and Bhilwara are included.
4. Regions with 25 to 50 cm rainfall: The average annual rainfall between 25 cm to 50 cm is seen in the districts of Jhunjhunu, Sikar, Nagaur, Jodhpur, (western part), most parts of Jalore, Pali, Ajmer, and westerm parts of Jaipur.
5. Regions with less than 25 cm rainfall: Under this category, the districts of Sri Ganganagar, Hanumangarh, Bikaner, Jaisalmer, Phalodi Tehsil of Jodhpur, Barmer and western regions of Nagaur are included.