HOT TOPICS
SPOTLIGHT AGENCIES
Relevance of Lakes in Bangalore
Written By psaram42 - 29 September, 2009
Bangalore lakes Water environment Analysis Others Everything else RWH
The topology of the city of Bangalore located at 3000 feet above sea level runs into three valleys
- Hebbal valley in which river Arkavati flows and terminates before reaching any sea.
- Rishbhavati valley which drains in to river Cauvery
- Belandur / Vartur Valley which drains into Thenna Peryar river also known Dakshina Pinakini
The three valleys on which the present Bangalore extends is important in the context of storm water drain network of the city. These three valley SWD networks collect the rain water to feed the lakes, interspersed all along. The relevance of lakes when built in 17th century was for drinking water as well as irrigation of agricultural lands.
The situation in 21st century is such that the lakes agricultural relevance is absent. The lake water being stagnant and perennial tends to loose the freshness and become devoid of marine life and hence not potable. As a direct consequence, the drinking water needs are met by river Cauvery, at a considerable investment cost and recurring power bills. This is the underlying reason for the disappearance of many lakes and neglect of those surviving.
The present relevance of the surviving lakes is thus
- nostalgia,
- entertainment
- environment
- Lung space
- Ground Water charging
All the four points above are important for not loosing any more lakes. It can be safely concluded that it is important to preserve the surviving lakes with the points 3, 4 above in particular. I am of the opinion that the lakes are not efficient enough for point 5 above.
It is pointed out that the drinking water is not finding a place in the relevance list above. I would rather go for RWH at residential level for the drinking water needs.
COMMENTS
Ok Sir,
we should use your thread to understand lakes etc. of bangalore. shall we try to restrict all discussion to this thread?
AFAIK, neither belandur nor hebbal are man made. In anycase why do i sense a tiraskaara for man made lakes? isnt it awesome that even without satellites and other advanced scientific knowledge, people knew exactly where to put the lakes?
the point is this. lakes sit in locations that are topographically crucial. they are where they are for a reason. those spots are crucial. we may not be able to do much to control the flows in and out of the lakes today. but i dont forsee, how we can engineer the topography of greater bangalore even a 1000 years from now.
please expand more on
I am of the opinion that the lakes are not efficient enough for point 5 above.
Stagnant lakes are deleterious to any ecosystem. Perennial lakes are not so useful to aqua culture. Thus the maintenance of Perennial lakes is not economical.
psaram42 - 30 September, 2009 - 03:16
@TSBhata
The lakes relevance in the context of ground water charging is what I had in mind while on the subject of lakes and their relevance. Hence Point number 5. Yes it is confusing to any body reading my post above.
What I had in mind was why transport the rain water from point A, where it falls to the lake point B and charge the ground water there? Why not charge the ground water at the nearest location where it touches the ground level? This charging can continue while the water travels over the ground. [There are porous Tar and concrete specially made for such applications.] Similarly why pump water back to homes for drinking water needs from the lakes? Why not capture and use in situ? Our town planning concepts have to be suitably modified as we go along.
The RWH regulations that are about to be finalized are trying to make RWH / Ground water charging mandatory for all Bangalore properties 2400 sq ft [site] area and above. The concept of transporting the rain water from point A to B is negated.
Now the concept is keep the pure rain water for drinking rest charge the ground. Only surplus goes to other uses.
thampan - 29 September, 2009 - 12:56
http://parisaramahiti.kar.nic.in/lakes.html
Extract from http://parisaramahiti.kar.nic.in/role.html
The lakes in Bangalore, which are scattered and placed in all vantage areas, have an important role in recharge of groundwater. .........
But, with the decrease in number of lakes year by year, the recharge of groundwater has steadily declined to a very great extent.
The terrain of Bangaiore is such that the water flows out on sloping land, but does not infiltrate quickly into the surface soil horizon. This phenomenon of water repellency is due to crusting of surface soils devoid of vegetation. If this runoff water is not trapped and groundwater aquifers not recharged, the scenario would indeed become bleak.
================================
I am not contesting the usefulness of local recharging, IMHO both (local recharging and lakes ) can co exist.
psaram42 - 29 September, 2009 - 12:56
Being a non lakes person I learnt a few things at the ESG Seminar. I will try and answer your query in a manner a blind person explaining about light to another blind person. I think it was prof Ravindra who talked about perennial lakes disadvantage. I too was surprised about the statement. I got the picture when he explained to me when I queried him during lunch break. Stagnant water that is exposed sun light as in lakes is at a risk of growth of harmful algae, suffocating aqua life. Fish, Insects and other aqua life are essential for the health of lake water. I believe that lakes should dry up and refill in an annual cycle. This will help the insects to procreate in a similar cycle of the rainy and dry seasons. These are insects which take care of sewage human and cattle.
There are people who would be glad to rejuvenate stagnant lakes. However it is economical to have seasonal lakes.
Importance aquatic ecosystem in the context of Lakes
psaram42 - 30 August, 2011 - 06:01
The Wiki article talks about what are aquatic ecosystems and its role in many important environmental functions.
“
An aquatic ecosystem is an ecosystem located in water bodies. Communities of organisms that are dependent on each other and on their environment live in aquatic ecosystems. The two main types of aquatic ecosystems are marine ecosystems and freshwater ecosystems.[1]
An ecosystem is a natural unit consisting of all plants, animals and micro-organisms (biotic factors) in an area functioning together with all of the physical (abiotic) factors of the environment. Ecosystems can be permanent or temporary. An ecosystem is a unit of interdependent organisms which share the same habitat. Ecosystems usually form a number of food webs. [1]”
The important point to understand is that fresh water ecosystems are slowly / rapidly moving towards wet lands. Stagnant lakes are deleterious to any ecosystem. Perennial lakes are not so useful to aqua culture. Thus the maintenance of Perennial lakes is not economical.
It is important that the lakes are full during rainy season June to Novenmber and are only wet lands or even dry (Partially) at other time.
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