Due to the status of Aravalli mountain range, the amount of rainfall in the eastern districts of the state remains high. But in the western districts, the level of rainfall is very low because here, the Aravalli mountain range lies parallel to the monsoon, therefore it remains unable in stopping the monsoon here and so the monsoon proceeds ahead, without causing rainfall here. In the western part of Rajasthan, about 61 per cent of the total surface area is deserted.