Bengaluru, Mar 23 (IANS): Karnataka would soon amend the law to make usage of harvested rainwater mandatory for all buildings in this tech city, an official said on Monday.

"The Bengaluru Water Supply and Sewerage Board (BWSSB) Act will soon be amended to mandate all buildings across the city to compulsorily harvest and use rainwater by installing a dual-pipe system," said the official after the cabinet approved the amendment bill earlier in the day.

As the budget session of the state legislature is underway, there was no official briefing after the cabinet meeting.

Located over 3,000 feet above sea level, Bengaluru depends heavily on the Cauvery river for water supply to its 1.2-crore denizens.

Rainwater harvesting has been made mandatory for all new houses and office buildings across the city to meet the need and reduce dependency on rivers and groundwater.

"The rainwater can be stored and used for gardening, washrooms and the like to judiciously use the river water for drinking and cooking," added the official.

Meanwhile, marking 'World Water Day', the state government on Monday signed an agreement with multi-business conglomerate ITC Ltd to develop a watershed in 10-lakh acres of land across the southern state in three years.

"The partnership agreement is part of the state government's 'watershed development for drought-proofing programme, which aims at covering 1.16-million acres of watershed area in 29 of the 31 districts across the state," said an official statement.