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A quick look at Water science

A quick look at Water science. Date : 31 July 2007 Time : 14.00 to 15.30 hrs. Venue : Aalankrita Resort, Hyderabad Topic : A quick look at Water science Faculty : Dr. S. V. Govardhan Das. Scheme of presentation. Earth’s Water Cycle or Hydrological cycle

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A quick look at Water science

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  1. A quick look at Water science Date : 31 July 2007Time : 14.00 to 15.30 hrs.Venue : Aalankrita Resort, HyderabadTopic : A quick look at Water scienceFaculty :Dr. S. V. Govardhan Das

  2. Scheme of presentation • Earth’s Water Cycle or Hydrological cycle • Factors controlling groundwater quantity • Factors controlling groundwater quality

  3. Factors controlling groundwater quantity • Geology • Rock type • Texture – Porosity • Permeability • Structure and Tectonics • Recharge rate • Aquifer type • Elevation • Rainfall • Well spacing • Human activity • Deforestation • Mining • Damming • Overdraft

  4. Factors controlling groundwater quantity Texture - Porosity

  5. Factors controlling groundwater quantity Permeability

  6. Factors controlling groundwater quantity Structure • Weathering • Fracturing • Magmatic activity • Folding • Faulting

  7. Factors controlling groundwater quantity Structure Weathering: • Soil • Loose material, above the parent rock • Formed over period of millions of years • Due to the action of geomorphic agents: • wind, • water, • sea action • temperature

  8. Factors controlling groundwater quantity Structure Fracturing • Layer between the weathered zone and parent rock • Tectonic activities • Magmatic activity • Volcanic activity • Increase/decrease in pressure regimes • Increase/decrease in thermal regimes

  9. Factors controlling groundwater quantity Aquifer type

  10. Factors controlling groundwater quantity Elevation • In case of unconfined/semi-confined aquifers • Higher elevations: recharge areas: more percolation • Low lying areas: discharge areas: base-flow • Very important in siting shallow dug-wells

  11. Factors controlling groundwater quantity Rainfall • Major source of groundwater recharge • Amount • Annual distribution • Temperature determines the percentage of evapotraspiration, percolation and run-off • Intensity • For producing run-off • For percolation • No. of rainy days

  12. Factors controlling groundwater quantity Recharge rate (Source: GEC 97)

  13. Factors controlling groundwater quantity Human activity:Deforestation • Cutting of trees exposes the soil • Natural action of geomorphic agents speeded up • Wind blows away soil at faster rates • Water takes away sediments at faster rates • Sea currents wash away the soil at faster rates • Soil heated up and cooled at faster rates • Loosening of soil material takes place at faster rates • Run-off at faster rates: Flash floods • Reduced percolation rate • Amount of percolation reduced

  14. Factors controlling groundwater quantity Human activity:Mining • Open cast mining augments recharge • Underground mining creates vacuums beneath ground • Land subsidence • Groundwater seeps into the mine: dangerous • Increased sub-surface runoff • Draining away of groundwater in adjoining areas • Major mining areas: weak structures collapse • Mild tremors: opening/closing of fractures • Drying up of fracture zones • Recharge of deep aquifer zones, directly • Upper aquifer zones in the vicinity go dry

  15. Factors controlling groundwater quantity Human activity: Damming • Dams are constructed across big rivers • Impoundment of water behind dam • Augments groundwater recharge process, in vicinity • Canal system (unlined): augments recharge, in vicinity • Water pressure can cause mild tremors • Mild tremors: opening/closing of fractures • Drying up of fracture zones • Recharge of deep aquifer zones, directly • Drying up of aquifers down stream • Land subsidence

  16. Factors controlling groundwater quantity Human activity: Overdraft • Lowering of water table • Increase in investment for tapping groundwater • Zone of Aeration increases • Base flows disappear making stream ephemeral • Drying up of fracture zones • Groundwater Mining • Mild tremors: opening/closing of fractures • Land subsidence • If the aquifer is artificially recharged mild tremors • Case of Vijayawada

  17. Factors controlling groundwater quantity Recharge – Draft – Balance

  18. Factors controlling groundwater quantity Recharge – Draft – Balance

  19. Factors controlling groundwater quantity Recharge – Draft – Balance

  20. Factors controlling groundwater quantity Recharge – Draft – Balance

  21. Factors controlling groundwater quantity Recharge – Draft – Balance

  22. Factors controlling groundwater quantity

  23. Factors controlling groundwater quality • Geology • Rock type • Texture – Porosity • Permeability • Structure • Leachability • Aquifer type • Human activity • Industrial pollution • Waste disposal • Sewage disposal • Fertilizer/pesticide/manure pits

  24. Thank U

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