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♤ In India, natural lakes (relatively few) mostly lie in the Himalayan region , the floodplains of Indus, Ganga and Brahmaputra.
♤ In the semi-arid and arid regions of western and peninsular India, tens of thousands of water bodies have been constructed over millennia.
♤ Lake ‘Sudarshan’ in Gujarat’s Girnar area was perhaps the oldest man-made lake in India, dating back to
300 BC.
♤ Lakes are also classified on the basis of their water chemistry. Based on the levels of salinity, they are known as Freshwater, Brackish or Saline lakes (similar to that of classification of aquatic ecosystem).
♤ On the basis of their nutrient content, they are categorized as Oligotrophic (very low nutrients), Mesotrophic (moderate nutrients) and Eutrophic (highly nutrient rich).
♤ Vast majority of lakes in India are either eutrophic or mesotrophic because of the nutrients derived from their surroundings or organic wastes entering them.
4.2.3. General Characteristics of Oligotrophic and eutrophic Lakes
Type of lake | |||
Sl.no | Parameter | Oligotrophic | Eutrophic |
1. | Aquatic plant production | Low | Eliminated due to Eutrophication |
2. | Aquatic animal production | Low | Eliminated due to Eutrophication |
3. | Aquatic plant nutrient flux | Low | High |
4. | Oxygen in the hypolimnion (bottom layer) | Present | Absent |
5. | Depth | Tend to be deeper | Tend to be shallower |
6. | Water quality for domestic & industrial uses | Good | Poor |
7. | Total salts or conductance | Usually lower | Sometimes higher |
8. | Number of plant and animal species | Many | Fewer |