Bengaluru was once known as a windy city, a pensioner’s paradise. Bengaluru’s IT industry boom, followed by the fast-growing startup ecosystem, fueled migration into the city. The population of the city is expected to grow by 30 million by 2025, according to a report. More people mean more corporate buildings, residential complexes and new road constructions. Construction projects require cement and cement guzzles water. For every 1 Sq. Mt of wall construction, an average of 350 litres of water gets consumed. Obviously, such large-scale urbanization cannot happen without leaving an imprint on the environment.
Bengaluru’s tank water system was established in the 4th C.E; because of the city's elevation gradient, the city's natural depressions acted as water reservoirs that filled up during the rainy season. An elaborate network of interconnected lakes and rich groundwater levels were more than sufficient for the city. Till 2007 groundwater levels were maintained at a satisfactory level, but development projects due to a high influx of migrants have depleted the water levels, and major lakes have dried up. Many building projects broke the interconnected lake ecosystem worsening the situation of the already drying up lakes. In 2017 the composite water management report by NITI Ayog predicted that Bengaluru would run out of water by 2020. It is estimated that by 2031 the water demand would rise to 37.9 TMC, while the supply would stand at 26.68 TMC further exacerbating the deficit.
The Bengaluru Water Supply and Sewerage Board (BWSSB) solved the problem initially by establishing a pipeline taking 14750 tmcft of water from the Kaveri River. By 2050 the temperature is expected to rise by 1.40C, and the frequency of droughts is expected to increase to 1 in 5 years from 1 in 20 years. Such events will affect the water levels of Kaveri drastically. Dr Kshithij Urs, former executive director of Greenpeace India, says, “What we don’t realise is that we’re fortunate not to have experienced a shortage in the rainfall over the years. Because if the Cauvery misses a single monsoon, Bengaluru will run out of water within the next six months and that’s the reality”.
The government realizes the impending threat and is working towards diversifying Bengaluru’s water resource supply. It has made rainwater harvesting compulsory in Bengaluru. According to the Karnataka Legislative Assembly law buildings built on sites measuring 60x 40 feet or more need to harvest and use rainwater for internal purposes. Large buildings will have to install a dual piping system for storage and supply of water to toilets, gardens and washrooms using rainwater. The law exempts old houses which might not be fit for retrofitting. Despite a mandatory law, the government saw less compliance; to tackle this issue, the government conducted awareness programs at the municipality level and even established the M. Vishweshwarayya “Rain Water Harvesting Theme Park”. It uses working models to explain different types of rainwater harvesting like Rooftop harvesting, Runoff harvesting(landscapes, parks, stormwater drains, roads, etc.) and Natural storage and collection through lakes and tanks.
Bengaluru receives an average of 800mm of rainfall every year. Studies show that by rainwater harvesting and treating sewage water, Bengaluru city can yield up to 31 TMCft water supply. Wastewater treatment can fill up the lakes, enhance biodiversity, and provide water to farmers for cultivation. Such projects are already being undertaken at Kolar and Chintamani and need to be expanded to other areas. By 2040, it is projected that 560 MLD of water will come from wastewater treatment facilities. Another problem that remains unaddressed is water wastage; according to a report city, 30% of water is lost due to leaking water tankers, old pipelines, poor city planning, and inefficient water management. We as citizens should recognize the problem and be conscious of our water usage.