BOSTON — Leaders in the Massachusetts Senate are proposing a bill to help improve the state’s water infrastructure.

A 2012 report from a state commission found Massachusetts faces an approximate $21 billion shortfall over the next two decades to keep the state’s drinking and wastewater systems in adequate repair.

The Senate initiative unveiled Thursday would significantly increase the amount local communities can borrow at low interest rates from the state’s Water Pollution Abatement Trust to help improve and protect water supplies.

The bill’s sponsors say the measure would also create a “leak classification system” to make sure high-hazard leaks are fixed quickly while also encouraging renewable or “green infrastructure” water projects.

“This proposed legislation will address our water and wastewater infrastructure challenges and ensure that the commonwealth’s future will not be limited by our access to clean drinking water,” Senate President Therese Murray, D-Plymouth, said as she unveiled the bill.

Murray said the health of the state’s water infrastructure is also strongly linked to the health of the economy, citing residents getting sick, businesses closing and development stalling.

The push comes three years after a catastrophic water main break forced a “boil water order” for 2 million eastern Massachusetts residents. The 2010 break in the 10-foot pipe affected 30 cities and towns, including Boston.

Murray said the bill will go through the normal public hearing process with the joint legislative Committee on Environment, Natural Resources and Agriculture. She said she hopes the Senate can debate it before the end of November or when they meet again in formal sessions in January.