Before we begin, dust off the 8th grade science textbook and flip through its chapters.
Let’s get the basics right.
Aquatic water bodies can be classified into two groups based on the absence or presence of water flow – Lotic Waters and Lentic Waters.
Lotic aquatic systems refer to flowing water systems like rivers, springs or streams where there is constant movement of the water. Lentic aquatic systems refer to still water systems where the water contained within a space is more or less static such as lakes, ponds or even oceans. They generally do not have a downhill flow which is characteristic of the lotic water system.
To take care of our lakes’ health in the present, we need to turn the Earth’s geologic clock back to its origins when its crust was undergoing constant shifts. Lakes are more than mere collections of water spotting the Earth’s geography and they are not homogenous in variety.
On a larger level, lakes can be either naturally-formed or man-made. Peninsular India does not have naturally-formed lentic water bodies which are abundantly found in lakes in Canada and temperate regions; the still glass-like clear water of such lakes is strongly characteristic of the lentic systems formed by the melting of the glaciers.
However, peninsular India lacks such natural glacier-formed aquatic systems.
Our lakes are all man-made and are formed by impounding the water flow in valleys. As mentioned in a previous article, Bangalore’s valley-filled topography is the best for impounding the water flow to create lakes. We had also seen how the interconnectedness of the lakes belonging to the Bangalore lake basin produces an unfavorable situation where a specific lake’s polluted waters seep down to the neighboring lakes through underground common water channels.
It is bad enough that there are underground water channels multiplying the effects of water pollution. Unfortunately, the spread of toxins can happen above the ground too.
Upstream-Downstream, a strong linking factor
As the geography of the Bangalore terrain has many ups and downs, the water from lakes located on higher points naturally flows downstream to join the lower lakes. For instance, the water from Bellandur lake flows down to join Varthur to finally join the Dakshina Pinakini river basin. Bellandur’s frothing is infamous and needs no introduction. Its polluted water simply flows into Varthur, which has taken after its elder sibling Bellandur in frothing away to glory.
The upstream-downstream lay of the lakes is therefore crucial in taking efficient measures against pollution or related issues. Unless Bellandur is taken care of or the channels diverted from joining Varthur, it is futile to rejuvenate Varthur.
Such information might seem insignificant. But as responsible citizens, we need to understand that reviving lakes is not simply about clean-up drives or blindly joining lake activities. It requires us to critically understand where help is needed the most such as the upstream lakes.
The story does not end here.
Yet another route for interlinking? The Avians nod
Toxic waste and pollution-causing microbial organisms can also travel from one lake to another through winged visitors. Birds move from one water body to another in search of food and they are excellent carriers of matter, organic or inorganic. Micro-sized particles that are harmful to the aquatic life can be transported by the birds as they often stick to the body of the avians.
The birds can effectively transfer planktons (microorganisms) from one lake to another. Sometimes, it can also be toxic matter and that does not bode well for anyone. Given the proximity of the Bangalore lakes to one another, such transference is inevitable. Sometimes, it could be larger organisms that are moved across lakes like small fishes.
The intermixing of the aquatic life across Bangalore lakes can be understood as the phenomenon of metapopulation. Metapopulation refers to a group of populations that are dispersed across space but consist of same or closely related species which undergo some amount of interaction. The pockets of populations are known as subpopulations. Bangalore lakes can likely be said to contain metapopulation in terms of its aquatic life.
Given the interlinking of the Bangalore lakes though underwater channels, upstream-downstream flow and its interacting metapopulation, it is essential that we take action at the right place, at the right lakes, to revive the lakes in the most efficient manner.
We need to understand that the lakes are not isolated patches of water and that affecting one can have effects on a geographically far-off lake.
Join us on our journey Wake the Lake project, in holistically learning about our Bengaluru lakes and further reviving the dying ones.
We gratefully acknowledge the various inputs and insights provided by Dr. MB Krishna towards the formulation of this article. He is an ecologist, ornithologist and a lake conservationist.