The Karnataka State Pollution Control Board (KSPCB) has flagged concerns about lakes in Bengaluru losing aquatic life.
A water quality analysis of lakes in Bengaluru undertaken by the KSPCB has noted the deteriorating conditions of lakes that are unsuitable for aquatic life, ie, fish.
According to the report, the water in 32 Lakes of Bengaluru was found to be unfit for aquatic ecosystems. It was fit only for irrigation and industrial purposes.
KSPCB official K Sudhakar told South First, “Under the National Water Monitoring Program, the KSPCB conducts monthly tests of 106 lakes across Bengaluru city. Out of these, 32 lakes have been found in a bad condition.”
He added: “The entry of sewage water on a constant basis is one of the prime factors behind the lakes’ waters testing as Category E.”
The current categorisation of water in lakes — not just in Bengaluru or Karnataka but the whole of India — stands thus:
The parameters taken into consideration during the testing of lake waters include Biological Oxygen Demand (BOD), Dissolved Oxygen (DO), the pH value of the water, solid wastes, conductivity, salinity, and turbidity.
The eight lakes in Bengaluru whose water tested as Category E for the month of April are the Kaikondrahalli Lake, Singasandra Lake, Gangondanahalli Lake, Doddabidirukallu Lake, Bandematta Tank, Shivpura Tank, Kalkere Lake, and Varthur Lake.
Bruhat Bengaluru Mahanagara Palike (BBMP) Lake Department Assistant Executive Engineer Shivalingappa Savukar denied receiving the KSPCB report on lakes.
He told South First, “We have not received any report on the condition of lakes by the KSPCB. However, deterioration of water quality was reported in the past few months and we are preparing to act on it.”
Raghavendra Pachhapur, a programme manager for Action Aid, has been relentlessly flagging concerns on the condition of lakes in Bengaluru.
Raghavendra told South First, “The recent report of the KSPCB is a worrisome indicator about the grave loss of aquatic longevity of the lakes. Many of them being reported the Category E proves that sewage inflow into the lakes is taking place at a rampant pace and civic bodies are less bothered about it.”
Huge expense on lakes
The expenditure by the BBMP, the custodian civic body of lakes in Bengaluru, has been crores of rupees. However, many lakes are losing their capacity to sustain an aquatic ecosystem despite that.
As per Savukar, the expenditure on lake development varies. A lake that covers less area involves an approximate expenditure of ₹1-2 crore, whereas lakes spread over a large area need ₹5 crore, or even more.
To get an idea of the expenditure involved in lake development, South First accessed a Detailed Project Report (DPR) of a lake.
The cost involved in the development of the Doddakallasandra Lake, as per the DPR accessed, was ₹5.93 crore.
The development included the lake bed, Mainbund, Ringbund, wetland formation, sewage diversion drain, silt trap, fencing, walkway, overhead tank, access control display board, toilet room, a foot bridge, and a yoga platform.
Despite the expenditure, Doddakallasandra Lake falls under Category D. Worse, it has a high dissolved oxygen level, making it unfit for its aquatic life.
Karnataka announced in June a grant of ₹200 crore to the BBMP to restore 67 lakes in Bengaluru and its outskirts.
As per BBMP official data, there are 167 lakes in BBMP custody.
Lakes in severe conditions must be dealt with immediately, demanded Action Aid's Raghavendra.
He told South First, “The BBMP must visit 32 lakes classified under Category E and investigate if there are any live polluting streams running into the lake, and arrest the pollution immediately.”
He added, “It is worrying that the water quality in the lakes of Bengaluru is not adequate for the sustenance of wildlife or fish.”
Recent fish kills in Bengaluru
Bengaluru witnessed a total of eight instances of fish kill — also known as fish die-off — within the first seven months of 2022. In the last five years, instances of fish kill were 32.
The highest number of fish deaths occurred in 2022.
As per Raghavendra, the region and time of occurrence of fish kill have not remained specific.
However, the major reasons behind it are the entry of sewage and the discharge of chemical wastes into the lakes.
The first spell of monsoon was also one of the probable reasons for the fish kill.
The rain brings additional pollutants through widespread run-off into the lakes, providing even more organic matter for microorganisms to break down by consuming the oxygen dissolved in water.
Additional factors that lead to mass deaths of fish include the sudden change of temperature of the lake water during seasonal transitions and high algal growth that subsequently causes the depletion of oxygen.