Updated: February 26, 2018 11:34:05 am
Earlier this month, a BBC report listed 11 world cities that were “most likely to run out of drinking water”, and put Bengaluru at number 2, behind only São Paulo, Brazil. The report mentioned the acute shortage of water in Cape Town in South Africa, where people are now being rationed 50 litres daily, and which many fear could become the first major city to run dry in the modern era. Other cities on the list of the most vulnerable were Beijing, Cairo, Jakarta, Moscow, Istanbul, Mexico City, London, Tokyo and Miami.
The report noted that more than half of Bengaluru’s drinking water is wasted due to “antiquated plumbing”, 85% of the city’s lakes “had water that could only be used for irrigation and industrial cooling”, and “not a single lake had suitable water for drinking or bathing”.
The Bangalore Water Supply and Sewerage Board (BWSSB) — the state agency managing water supply and sewage disposal — was quick to respond. It suggested that the report was alarmist, was based on old data, and was “far from the factual situation”.
So, how serious is the drinking water crisis in Bengaluru?
Present situation, future projection
The Supreme Court has recently allocated a larger share of Cauvery water for Bengaluru’s nearly 10 million people, but there is little doubt that the city’s water resources must be managed more efficiently.
Bengaluru originally had multiple sources of water supply in the form of over 200 lakes, abundant groundwater, and supplies from reservoirs and tanks in the Arkavathi river basin — the Hesaraghatta Lake in the north and the Thippagondanahalli Reservoir in the west. These sources are all but dead now due to the depletion of catchment areas in the wake of uncontrolled infrastructure expansion. This makes Bengaluru critically dependent on the Cauvery — some 100 km away, and now the principal source of the city’s drinking water — and the monsoon. Residents get 65 litres per capita per day (lpcd) on average, less than half the ideal amount of 150 lpcd. Of the 270 thousand million cubic feet (tmc ft) of water that was earlier allocated to Karnataka from the Cauvery, 17.64 tmc ft was used every year for the city’s drinking water needs. This share has now increased by 4.75 tmc ft.
At 150 lpcd, Bengaluru’s current requirement of water, given its population, is estimated to be 24 tmc ft per annum. This is expected to rise to 30 tmc ft by 2025. Without considering the 4.75 tmc ft increase in allocation, water supply to the city is short by at least 6 tmc ft per annum. Against a requirement of 1,400 million litres per day (mld), it gets only 1,250 mld.
According to the BWSSB’s projection, Bengaluru, with a population of 11 million in 2021, will require 27 tmc ft of water at the rate of 2,100 mld to ensure 150 lpcd of water for residents; by 2031, when the population is 14 million, these numbers will rise to 37 tmc ft and 2,900 mld. The availability of water in many of the city’s poorer areas is currently estimated to be as low as 40-45 lpcd. At its present installed capacity, the Cauvery Water Supply Scheme cannot meet the needs of 110 villages, which cover 225 sq km of the 800 sq km of the Bengaluru region. A new scheme currently under implementation will supply 6.45 tmc ft in the first phase and 3.55 tmc ft in the second phase, which will provide drinking water from the Cauvery to all areas in the city, the BWSSB says.
Continuing depletion of sources
The proliferation of borewells, especially in the core city areas, has led to a massive depletion of groundwater. Only about 70 of the 272 lakes in and around the city from four decades ago survive. The government has reclaimed dozens of lakes for bus stands, stadiums, and housing complexes, and real estate firms have been the major beneficiaries of land allotment on lakeshores. Garbage and sewage have poisoned lakes, and the concretisation of catchment areas has choked inlet channels.
“Bangalore is… a ‘groundwater quality hotspot’ due to exploitation of groundwater beyond rechargeable limits. This has resulted in increasing number of semi-critical, critical, overexploited and overdeveloped regions emerging in many watersheds… The groundwater quality (has) deteriorated with high presence of iron, fluoride, nitrate and conductivity with drastic decline in water table,” a study by a researcher at the Centre for Economic Studies and Policy at the Bengaluru-based Institute for Social and Economic Change (ISEC), noted back in 2013. (‘Sustainable Urban Habitats and Urban Water Supply: Accounting for Unaccounted for Water in Bangalore City’: Krishna Raj, Current Urban Studies, Volume 1, No. 4, 2013) As much as 207,000 million litres of groundwater was being extracted per annum in Bengaluru, against an annual recharge of only 81,100 million litres per year, the study said.
There’s cushion, and a plan
In its response to the BBC report, the BWSSB said it would be able to provide adequate water to the city for the next decade by effectively using current supplies, tapping into rainwater sources, and recycling wastewater. “Solutions… are in terms of both supply management and the demand management,… and citizens of Bengaluru need not have to worry about this BBC report,” it said. The government had tied up with the Japan International Cooperation Agency for a Rs 5,500 crore loan, of which Rs 4,500 crore would be used to bring 10 tmc ft of additional water from the Cauvery to Bengaluru city, the BWSSB said. “The project will be started in… 2019 and commissioned by 2023”, increasing the availability of Cauvery water from “1,400 mld to 2,175 mld”.
Bengaluru has some cushion because the Cauvery is perennial, and the city gets a decent amount of rainfall every year, which can be utilised to meet drinking water needs and recharge the groundwater table. Meteorological data of the last 100 years show the city receives an average annual rainfall of 929 mm over 57 rainy days, which, experts say, is a good source of rainwater harvesting across the city’s 800 sq km expanse and 2 million properties.
“Cauvery water supply at the tap end in Bangalore is 2,50,057 million litres (685 MLD after losses). Rooftop rainwater harvesting can provide 2,04,380 million litres, groundwater available through rainwater harvesting will be 1,85,800 million litres and the facilities of waste water treatment plants can provide 1,89,800 million litres, totaling to 3,07,048 ML or 841 MLD,” A R Shivakumar, principal scientific officer at the Karnataka State Council of Science and Technology, wrote in a paper published last month. (‘Sustainable Water Supply Strategy for Bangalore — A Model for Emerging Cities in India’: A R Shivakumar, International Journal of Science, Technology and Society, Vol 6, Issue 1, January 2018)
“The ‘New Water’ available at consumer end from the three sources (rain water harvesting, groundwater and waste water treatment plants) will be 509 MLD, which is almost equivalent to the current water supply at the tap end” from the Cauvery river, Shivakumar has written.
In the end though, as BWSSB said in its response to the BBC report: “Great responsibility lies with the citizens of Bengaluru to use water judiciously and to save water. Rampant exploitation of groundwater should be avoided and rainwater harvesting should be undertaken in a way to replenish the groundwater.”
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