Urban Lakes
Urban waterbodies are an inherent part
of Indian culture. They served a variety of purposes. In the
dry central and Southern India--that fall in the rain shadow
region--they stored rainwater and ensured supply for domestic
use and for agriculture. They also helped in recharging groundwater.
In cities enjoying perennial river sources and high rainfall
they served as flood cushions, and as in the case of Kolkata,
acted as a resource recovery area, releasing nitrogen, inactivating
phosphates, removing toxins and treating wastewater.
And they were taken care of by the local
people, who desilted, cleaned and recharged the lakes and
tanks, as a part of their regular chores. But all this changed
after the government took over management of public lands
in cities.
Why lakes die
Eutrophication: Industral effluents,
run-off from agricultural fields, refuse and sewage are dumped
into lakes. Domestic wastes like food remnants, soaps, detergents
and sewage break down and release nutrients. Microscopic organisms
ingest these and live off them. Following ingestion of carbonic
elements, carbon dioxide is released, while some of the elements
are converted into nitrates and phosphates. This is called oxidising
and uses up a lot of oxygen (O2). Thus, depleted levels of dissolved
O2 in water leads to a situation where other aquatic lifeforms
cannot survive.
Siltation: Water flowing into a lake brings
silt. Increased deforestation loosens the top soil, which
finds its way into lakes. Some of the silt is washed out when
the lake overflows. However, the outflow of silt does not
always match the inflow and the silt settles at the bottom
of the lake.
Tourism: Refuse and sewer water pour into
the lake from hotels constructed on its banks. Mechanised
pleasure boats create noise and leave traces of oil on the
waters.
Read also:
|
