'The first germ of life was developed by water and heat.' (Manusmriti - Book I, sloka 8, 9) From the very beginning the people of India know the importance of water. It is one of the five great elements among air, water, fire, earth, and ether. Water is also intermediate between all pervasive air and localized earth. These natural entities and forces have been worshiped in India as Gods since time immemorial. Perhaps it is not a sheer coincidence that the King of these Gods is Indra, the God of Rain. Clearly, ancient Indians were aware of the importance of rain and other hydrological variables for the society. The ancient Indian literature contains numerous references to hydrology and a reading of it suggests that those people knew the basic concepts of hydrological processes and measurements. Important concepts of modern hydrology are scattered in various verses of Vedas, Puranas, Meghmala, Mahabharat, Mayurchitraka, Vrhat Sanhita and other ancient Indian works. 'Yaapo divyaa utavaa sravanti khanitrimaa utavaa yaa swayarn jaa / samudraartha yaa soochayapaavakaasta aap devi iha mamavantu //' [Rig-Veda, VII 49.2] "The waters of the sky or those that flow (on earth), those that are dug out, or those that arise from themselves, those pure and clear waters that seek the ocean as their goal — Let the waters, who are goddesses, help me here and now." The texts categorically assert that there are innumerable rivers and that all are uniformly divine. They are said to have sprung from the celestial rivers that dwell in the form of clouds and rain in the atmosphere: The Vedic texts contain valuable references on hydrologic cycle. The most important concepts, on which the modern science of hydrology is founded, are scattered in Vedas in various verses which are in the form of hymns and prayers addressed to various deities. Likewise, other Sanskrit literature has valuable discourses regarding hydrology. Atisthanteenam viveshnanam kashthanam madhyaey nihitam shareeram, Bratrasya nidyam vi varantyapo deerghatam aashaydindrashatruha. [Rig-veda 1: 32:10] It says that the water is never stationary, but it continuously gets evaporated and due to smallness of particles we cannot see the up-going water particles. In the Varahamihira’s Vraht Sanhita (550 A.D.), three Chapters are devoted to hydrometeorology comprising Pregnancy of clouds (Chapter 21), Pregnancy of air (Chapter 22) and quantity of rainfall (Chapter 23). Slokas 1 and 2 of Dakargelam (Chapter 54 of Vraht Samhita) state the importance of science of ground water exploration which helps man to ascertain the existence of water. These are as follows: Dharmyam yashashyam va vadabhaytoham dakargalam yen jaloplabdhiha Punsam yathagdeshu shirastathaiva chhitavapi pronnatnimnasanstha. Ekayna vardayna rasayna chambhyashchyutam namasto vasudha vishayshanta Nana rastvam bahuvarnatam cha gatam pareekshyam chhititulyamayva. The water veins beneath the earth are like vein’s in the human body, some higher and some lower. The water falling from sky assumes various colors and tastes from differences in the nature of the earth. In Linga Purana a full-fledged chapter (I, 36) has been devoted to the science of hydrology. It scientifically explains evaporation, condensation, rainfall with suitable examples and says that the water cannot be destroyed; only its state is changed: Dandhaymanayshu charachayshu godhoombhootastvabha nishkramantee Ya ya oordhva mastraynayrita vai tastastvabhamyagnivayucha. Ato dhoomagnivatanam sanyogstavamuchyatay Vareeni varshteetyabhrambhrasyeshah sahastradrik. i.e. “after being heated by sun, water contained in most of the materials on earth gets converted to smoke (vapour) and ascends to sky with the air and subsequently gets converted to cloud. Thus the combination of smoke, fire and air is the cause of cloud formation. These clouds cause rainfall under the guidance of Lord Indra, having thousand eyes. Vayu (51. 14-15-16) states like this: Aadityapateetam suryaganeha somam sankramatay jalam Nadeebhirvayuyuktabhirlokadhanam pravartatay. Yatsomatstravatay surya tadbhayshvavatishthatay Megha vayunighatain visrajant jalam bhuvi. Evamutikshapyatay chaiva patatay cham punarjalam Na nashmu udkasyasti tadev parivartatay. i.e. the water evaporated by sun ascends to atmosphere through the capillarity of air, and there gets cooled and condensed. After formation of clouds it rains by the force of air. Thus, water is not lost in all these processes but gets converted from one form to other continuously. Verses of Rigveda (I, 27.6; I, 32.8): Vibhaktasi chitrabhano sindhoroorma upak aa Sagho dashushay chharasi. Nadam na bhinnamuya shayanam mano ruhana atim yantyapah Yashchidwatro mahina paryatishthattasamhih patsutah shirbbhoova. This verse explains that all water that goes to the sky with wind by the heat of Sun rays gets converted to clouds and then again after the penetration by sunrays it rains and gets stored into rivers, ponds, ocean, etc. Two verses (V, 54, 2 & V,55, 5) explain the cloud-bearing winds as the cause of rainfall, viz.: Pra vo marootaststavisha udnyavo vayovridho ashwayujah parijayah San vighuta dadhati vashati tritah swarntyapoivana parijayah. Udeeryatha marootah samudrato youam vrishtim varshyatha pureeshidam Na vo dastra up dasyanti dhanayvah shubam yatamanu ratha avratsat. o cloud bearing wind your troops are reach in water, they are strengtheners of life and are your strong bond, they shed water and augment food, and are harnessed with waves that wander far and special everywhere. Combining with lightning, the triple group (of wind, cloud and lightning) roars aloud and water fall upon the earth. All these facts are proven by modern science but it was discovered over more than 3,000 years ago in India.