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.
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Importance aquatic ecosystem in the context of Lakes
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.
Lakes
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
Ground Water Charging
@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.
lakes of bangalore
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.
Perennial Lakes
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.
All lakes are man made / Manipulated
Let alone Bellandur or Hebbal. . Especially the Bellandur Lake the extent of which is 350 acres could hardly be natural or virgin without manual interferences. There is an embankment over which the water flows, heading towards Varthur lake. The valleys are however natural. In B lake there is a huge natural wet land, being actively encroached upon.
Bellandure lake Outlet water discharging to Vartur canal
Lakes past and present
@ TS Bahatta,
There was no intension of belittling ancient civilizations in this thread. It was only to analyze the reasons of unfortunate neglect and misuse of the surviving lakes of Bangalore. The relevance of lakes is apparently an ever changing phenomenon of generations after generations.
I do not think there was a need for satellites to locate the ideal place to build embankments, to hold back flowing water to create artificial lakes in olden days. People living in the area could easily see the course of the flowing water as water as any liquid can find its own level, when it rains heavily. The ideal location for building an embankment is the throat of a valley where the water flow could be visibly deep enough. This can be identified on ground especially when it is an agricultural field uninhibited by human dwellings, unlike as in modern day cities. Bangalore is no exception.
The point I would like to make is huge lakes like Bellandur Lake are a blessing and need to be protected and developed optimally. Ecologically preserving the lakes is a specialized task where in educational institutions like IISc are contributing to certain extent, apart from others. As our drinking water needs can be met by RWH the relevance of lakes in present day context is for lung space, bird, fish etc. RWH is going to be mandatory for house holds built on sites of area 2400 sq ft and above.
@Thampan
Obviously lakes also recharge ground water. This is an added benefit. The point made here is that lake water in present day conditions is not potable and does not support aqua life. It is necessary to work towards making it ecologically beneficial.
Bangalore's filthy Lakes and Anchetti village in TN
Thanks a million
Beautifully written and I am glad someone has taken the trouble of tracing the chain of Lakes. Pity indeed that there is not a single soul in BBMP / BWSSB etc who feel for the Lakes and would take some positive initiative to sve them.
Lakes indeed are largely God given phenominas and we should not neglect it at any cost.
BTW, I am not very sure Lakes are meant to recharge groundwater table. If that be so water at the base of the lake would be continuously infiltrating to sub-soil levels and on the top it would be depleting correspondingly. I think when water stagnates for long periods of time it tends to convert the topography into clay which as everyone knows, is highly impervious. While I do not discount that fact that some water does get naturally infiltrated, to make infiltration and recharging of groundwater table as the main natural reason for the lake's very existence in the first place, appears to be somewhat simplistic.
Whatever be the reason, a concerted effort must be mounted to save, clean and maintain a pleasant, green environs all around it. Let us all work towards that.
RKC
development & maintenance of lakes
ssheragu
there has been a lot discussions on lakes; I heard that not only in Bangalore but even in my place Hassan many lakes have disappeared; they have been been gobbled by the land mafia;
Does the Lake Development Authority have jurisdiction only in Bnagalore but all over the state; if not which is the agency forprotection of lakes in other places;
can any one provide information on the same
many thanks
Srinath Heragu
washed away
loads of interesting stuff. will get back. van beurle saar thanks. but i find it really amusing whenever TN lectures KA on polluting waters. let us know what they do to cauvery. how much vaigai etc still flows, how many of the old lakes in cauvery basin, TN still exist and what sort of purification coimbatooru, tiruppuru , erodu, etc etc do and so on. how many notices did tn give to itself?
ofcourse, two wrongs dont make a right. but it will take two rights to make one right. they should also do their part, no? why should all the clean water (11tmcs) be flushed from ka, just so as to clean up after tn in its merry ways?