{"id":121,"date":"2019-03-07T06:52:56","date_gmt":"2019-03-07T06:52:56","guid":{"rendered":"http:\/\/esp04.epgpbooks.inflibnet.ac.in\/?post_type=chapter&p=121"},"modified":"2019-03-13T11:09:42","modified_gmt":"2019-03-13T11:09:42","slug":"10-hydrogeology-and-hydrologic-cycle","status":"publish","type":"chapter","link":"https:\/\/ebooks.inflibnet.ac.in\/esp04\/chapter\/10-hydrogeology-and-hydrologic-cycle\/","title":{"rendered":"Hydrogeology and Hydrologic cycle"},"content":{"raw":"1-\u00a0\u00a0 INTRODUCTION:<\/strong>\r\n\r\n \r\n

Air is a mixture of gases. The principal AMONG the gases are Nitrogen (78% by volume), Oxygen (21% by volume), Argon (0.95% by volume), Carbon dioxide (0.034% by volume) and a variable amount of water vapour. The amount of water vapour in the lower range of the atmosphere can vary over a wide range from about 0.05 % to almost 4% by volume.<\/p>\r\n\"\"<\/a>\r\n\r\nFig 1 <\/strong>Pie Diagram Showing Distribution Of Gases in Atmosphere\r\n\r\n \r\n\r\n \r\n

The water vapour present in the air is an important causative factor for the formation of mist, fog, clouds, rain or snow. The carbon dioxide plays a role in plant life and overall climate of the earth. Presence of ozone in the atmosphere in the altitude ranging between 20 to 30kms above the earth\u2019s surface absorbs all the ultraviolet radiation from the sun, where otherwise it would have been detrimental to plant and animal life. The atmosphere, particularly with water vapour and carbon dioxide change the incoming solar radiation, reaches both the land and ocean at the earth\u2019s surface. With the increase in carbon dioxide content the radiation would be more and the earth become warmer. P.R. Pisharoty, a pioneer in Indian Meteorology has in his book \u2018Meteorology for the Indian Farmers\u2019 (Special Publication, Indian Space Research Organisation, Bengaluru, September, 1986) has comprehensively dealt about the solar radiation, its interaction with the atmosphere, structure of the atmosphere and the variations of pressure and temperature with altitude. He has outlined how horizontal pressure differences on a rotating earth, primarily caused by temperature differences, generate winds. He also has described the physics of clouds and rain or snow. He has given an outline of different weather systems which has regional impact.<\/p>\r\n\"\"<\/a>\r\n\r\nFig 2 <\/strong>Conversion of Solar radiation into heat energy\r\n\r\n \r\n

Water in the planet earth, occurring in liquid, solid and gaseous status, displays varied degree of motion. The hydrological cycle, also known as \u2018water cycle\u2019 defines the movement of water and storage of water in earth. Agriculture is strongly dependent upon weather. Human survival is dependent on water availability. Seasons impart a rhythm to life of the earth. The sequence of events in \u2018hydrologic cycle\u2019 appears to be simplistic. But, in reality, the hydrologic cycle is a vast and complicated cycle which involves a large number of paths of varying time scale. It is a continuous recirculating cycle. It has neither a beginning nor an end (Subramanya, 2013).<\/p>\r\n \r\n\r\n2-<\/strong>\u00a0\u00a0 OBJECTIVES<\/strong>\r\n\r\n \r\n

    \r\n \t
  1. Explain stages of Hydrological cycle<\/li>\r\n \t
  2. Describes the various factors effecting Hydrological cycle<\/li>\r\n \t
  3. Narrating the importance of Hydrological cycle<\/li>\r\n \t
  4. Describes the movement and circulation of water on earth<\/li>\r\n<\/ol>\r\n \r\n\r\n3-<\/strong>\u00a0\u00a0\u00a0\u00a0 CONCEPT MAP<\/strong>\r\n\r\n \r\n\r\nThe components of the hydrological cycle Evaporation -- Condensation--Precipitation--Run-off\r\n\r\n\"\"<\/a>\r\n\r\n\"\"<\/a>\r\n\r\n4-<\/strong>\u00a0\u00a0 DESCRIPTIONS<\/strong>\r\n\r\n \r\n\r\n4-1 Hydrological cycle<\/strong>\r\n\r\n \r\n

    The hydrologic Cycle begins with the evaporation of water from oceans and lakes. Evaporation is the change of water form from a liquid stage to a gaseous one. The largest movement of water in the \u2018water cycle\u2019 is the evaporation of water from the oceans. Evaporation of water from the warm surface of oceanic body results in increased amount of moisture in the colder\/ drier air immediately above. As water vapour moves up, it gets cooled and condenses into clouds. Condensation is the change of water form from gaseous form into liquid form. Condensation occurs in atmosphere when warm air raises, cools and loses its capacity to hold water vapour. When, water vapour condenses it becomes \u2018droplets\u2019 in the cloud .The upward motion that generate clouds can be the result of \u2018convection\u2019 in unstable air. Convection is the result that happens when the land surface is hot; the overlying air\u00a0 which warms up becomes less dense than the air in the surrounding parts and attains motion in a vertical direction. When surface winds are deflected by friction towards the centre of the low pressure surface, it would result in \u2018extra tropical cyclones\u2019. Surface convergence can generate rising motion, leading into condensation of water vapour.<\/p>\r\n \r\n\r\n\"\"<\/a>\r\n\r\nFig 4 <\/strong>Hydrological cycle And distribution\r\n\r\n \r\n\r\n \r\n

    The huge quantity of evaporated water, in one form or the other, moves around the globe until it returns to surface as \u2018precipitation\u2019. The precipitation\u00a0 is the primary natural mechanism of water transportation from the atmosphere to the surface of the earth. It may include rain, hail, snow and freezing rain. While much of the clouds get back into the oceans and lakes as rain, some part of it when driven by wind on to the land, precipitate into rain, snow hail etc. A well-developed \u2018extra tropical cyclone\u2019 can generate any or all forms of precipitation. With continued evaporation, water\u00a0 vapour in the cold part of atmosphere condenses to form ice crystals. It is said that the atmosphere keeps water for an average of 9 days before it releases it down as rain.<\/p>\r\n\"\"<\/a>\r\n

    The boundary between air masses (front) can either be warm, cold or stationary. In case of \u2018cold front\u2019, a colder, denser air mass lifts the warm moist air ahead of it. As the air rises, it cools and the moisture in it condenses to produce clouds and precipitation. Due to steep slope of a cold front, vigorous rising motion leads to formation of showers and occasionally severe thunderstorm. In the case of \u2018warm front\u2019, the warm, less dense air lifts up the colder air ahead. Again, the air cools and its moisture condenses to form clouds. Precipitation that develops in advance of a surface warm front is typically steady and wide spread than precipitation associated with a cold front.<\/p>\r\n \r\n\r\n\"\"<\/a>\r\n\r\nInputs <\/strong>into the drainage basin include:\r\n\r\n \r\n