outer areas peripheral areas regions expected dh report lack feeder challenging season vital role poor condition reduce reliance highrisk wards iisc scientists banjara layout nri layout groundlevel reservoir science iisc indian institute city facing 80 critical wards increased availability recharge groundwater cauvery stage groundwater experts study shows bwssb formed water daily groundwater levels drop dangerously summer groundwater levels years intense summer face water crisis subfeeder lines lakes distribution challenges persist jakkur heavily rely piped water availability groundwater levels predicted bengalurus groundwater levels drop dangerously low cauvery water connections dwindling groundwater reserves comprehensive study conducted bwssb urged residents sewerage board bwssb bengalurus water scarcity bangalore water supply worrying water crisis subfeeder linesaction plan special task force brought global attention stalled leaving residents sewage treatment plant horamavu ramamurthy nagar