Write critical notes on the following:
(a) Eutrophication
(b) Biological magnification
(c) Groundwater depletion and ways for its replenishment

 

(a) Eutrophication. The process of natural aging oflake because of the presence of excessive nuttrients. The excess of nutrients result in the increase in the population of aquatic organisms and thus decrease in the level of oxygen. The quality of the water is depleted and the temperature also increases.

(b) Biological magnification (Bio-magnification). The phenomenon in which the harmful pollutants (such as pesticides) enter the food chain and get concentrated more and more at each successive trophic level of organisms is called biological magnification.

This phenomenon is well known for mercury and DDT. Zooplankton (tiny floating animals) in the food chain, accumulated moderate levels of DDT. However, small fish, forming the next level of the food chain, must eat zooplankton several times their own weight and thus they accumulate more of DDT. In this manner, the concentration of DDT is magnified at successive trophic levels, starting with 0.003 ppb (ppb = parts per billion) in water it ultimately reached 25 ppm (ppm = parts per million) in fish-eating birds.

(c) Ground water depletion and ways for its replenishment.
The level of ground water has decreased in the recent years. The source of water supply is rapidly diminishing each year because of an increase in the population and water pollution. To meet the demand of water, water is withdrawn from water bodies such as ponds, rivers etc. As a result, the source of ground water is depleting. This is because the amount of groundwater being drawn for human use is more than the amount replaced by rainfall. Lack of vegetation cover also results in very small amounts of water seeping through the ground. An increase in water pollution is another factor that has reduced the availability of ground water.

Measures for replenishing ground water:-

i. Preventing over-exploitation of ground water

ii Optimizing water use and reducing water demand

ii Rain water harvesting

iv Preventing deforestation and plantation of more trees