DEFINITION • Water is indispensable natural resource on this earth on which all life depends . • 97% of earth’s surface is covered by water . • Water is a unique resource.
Unique features of water • 1) it exist as a liquid over a wide range of temperature that is from 0-100 c . • 2) it is an excellent solvent for several nutrients. thus, it can serve as a very good carrier of nutrient including oxygen , which are essential for life. • 3)due to high surface tension and cohesion it can easily rise through great heights through the truck even in the tallest of the trees like sequoia. • It as the highest specific heat –warms up-cools down very slowly. • High latent heat of vaporization-due to this property only water provides cooling effect ex: freezers
HYDROLOGICAL CYCLE • The water we use keeps on cycling endlessly through the environment ,which we call as HYDROLOGICAL CYCLE.
Every year about 1.4 inch thick layer of water evaporates from the oceans more than 90% of which returns to the ocean through the hydrological cycle. • Global distribution of water resources is quite uneven depending upon several geographic factors . • Water –moist surfaces –evaporates-falls again-on to the earth-form of rain or snow-the same water re use by living organisms.(driving force is solar energy). • Plants –absorb water –soil-release into environment(by the mechanism of transpiration.
WATER USE AND OVER EXPLOITATION • Water is an essential for life. • Most of the life processes takes place in the water contained in the body . • water used by humans is of two types • 1. WATER WITHDRAWAL (taking water from ground water or surface water) • 2. WATER CONSUMPTION(water which is taken but not returned for re use ) • Globally 60% of water with drawn is consumed on the rest lost through avaporation. • Globally 70% of water with drawn is used for agriculture. • Globally 25% used water for Industries
Water –a precious natural resource water(90% Earth) Precious (97% Salt Water, 3% Fresh ) Drinking, Irrigation, Domestic Industries-causing pollution – ground water – unfit for consumption Finally by 2024 – 2/3 world population –will be suffering from acute water storage.
GROUND WATER • Much greater in volume than either lakes or streams • Non-renewable in our lifetime • About 9.86%of the total fresh water resources is in the form of ground water and35-50 times that of surface water supplies. • A layer of sediment or rock – highly permeable – contains water – known as Aquifer
What is an aquifer? • Geologic formation that possesses porosity and permeability
A layer of sediment or rock that is highly permeable and contains water is called an aquifer . • Aquifer may be two types • 1.UNCONFINED • 2.CONFINED
Water Table • Surface below which pores and fractures of rocks and overburden are water filled
Distribution of Waterhttp://ga.water.usgs.gov/edu/waterdistribution.html (1997 data)
EFFECTS OF GROUND WATER USAGE • Subsidence : when ground water withdrawal is more than its recharge rate the sedements in the aquifer get compacted ,a phenomenon is known as ground subsidense . • Lowering of water table :mining of ground water is done extensively in arid and semi arid regions for irrigating crop fields. • Water logging:when excessive irrigation is done with brackish water it raises the water table gradually leading to water logging and salinity problems .
SURFACE WATER • The water coming through precipitation when does not percolate down into the ground or does not return to the atmosphere as evaporation or transpiration loss assume the form of the streams ,lakes ,ponds ,wet lands or artificial reservoirs known as surface water .
FLOODS • When does flooding occur? When surface run-of exceeds a normal stream channel’s capacity and water spreads out onto the flood plain.
DROUGHTS • When annual rain fall is below normal and less than evaporation drought conditions are created .
DAMS • The dams have tremendous potential for economic upliftment and growth. • They can help in checking floods and famines ,generates electricity and reduce water and power shortage.
Some Dams • Aswan High Dam
Environmental Problems due to dams • Displacement of tribal people • Loss of forests, flora and fauna • Changes in fisheries and the spawning grounds • Siltation and sedimentation of reservoirs • Loss of non-forest land • Stagnation and water logging near reservoir • Breeding of vectors and spread of vector-borne diseases • Reservoir induced seismicity (RIS) causing earthquakes • Growth of aquatic weeds • Microclimatic changes
The downstream impacts include the following. • Water logging and salinity due to over irrigation. • Micro-climatic changes • Reduced water and silt deposition in river 4. • flash floods. • Salt water intrusion at river mouth • Loss of land fertility along the river since the sediments carrying nutrients get deposited in the reservoir • Outbreak of vector-borne diseases like malaria