Tuesday, October 29, 2013

Natural resources: Water resources - Use and Over-use





NATURAL RESOURCES:

Natural resources are the sources which are useful to man or those than be transformed into a useful product. Natural resources are of two types:
  1. Renewable resources and
  2. Non-renewable resources
WATER RESOURCES:
 Water is the most abundant, inexhaustible renewable resource. It covers 70%  of the globe in the form of oceans, rivers, lakes, etc. Of this 70%, only 3% is available as freshwater. From this 3%, roughly 2% is frozen in polar icecaps and only a fraction of the remaining 1% is used as drinking water (potable). 90% of the water is utilized for agricultural purposes in India.

USE OF SURFACE AND GROUND WATER
Consumptive use: In such uses, water is completely utilized  and cannot be reused.
Ex: Domestic, industrial and irrigation
Non-consumptive use:In such uses,water is not completely utilized and is reused
Ex: Hydropower plant

Other uses:
  1. Water is used for domestic purposes like drinking, bathing, cooking, washing. etc.
  2. Water is used in commercial establishments like hotels, theaters, educational institutions, offices, etc.
  3. Almost 60-70% of fresh water is used for irrigation
  4. 20-30% of water is used for industrial operations by refineries, iron & steel industries, paper & pulp industries, etc.
  5. Water plays a key role in sculpting the earths surface, moderating climate and diluting pollutants.
OVER-UTILIZATION OF SURFACE & GROUND WATER
The rapid increase in population and industrial growth led to severe demand on water resources. After using all available surface water resources to the maximum, human beings began using groundwater to meet their needs.
  1. The increased extraction of groundwater far in excess of the natural recharge led to decreased groundwater level. The erratic and inadequate rainfall caused reduction in storage of water in reservoirs. This also led to decrease of groundwater.
  2. Building construction activities seal permeable soil zone and reduce the area for percolation of rainwater thereby increasing surface runoff.
  3. If groundwater withdrawal rate is higher than recharge rate, sediments in aquifers get compacted resulting in sinking of overlaying land surface. This is called land subsidence which leads to structural damage in buildings, fracture in pipes and reverses the flow of canals leading to tidal flooding.
  4. Over-utilization of groundwater in arid and semi-arid regions for agriculture disturbs equilibrium of reservoir in the region causing problems like lowering of water table and decreased pressure in aquifers coupled with changes in speed and direction of water flow.
  5. Over utilization of groundwater in coastal areas leads to rapid intrusion of salt water from the sea thereby rendering it unusable for drinking and agriculture.
  6. Over-utilization of groundwater lads  to decrease in water level thereby causing earthquake, landslides and famine. 
  7. Over-utilization of groundwater leads to drying-up of dug wells as well as bore wells.
  8. Due to excess use of groundwater near agricultural fields, agricultural water that contains nitrogen as a fertilizer percolates rapidly and pollutes the groundwater thereby rendering the water unfit for potable use by infants. (Nitrate concentration exceeding 45 mg/L).

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