The Phoenix City Council has approved a measure to help safeguard water supplies against a future Colorado River shortage.

The unanimous vote Tuesday sets up what is called the Colorado River Resiliency Fund. With about $5.5 million to work with each year, city officials will be able store unused river water in underground facilities and join in sharing wells with local utilities. The fund might also be used during a shortage to lease water from other users and to beef up conservation efforts.

Money for the resiliency fund will come from refinancing water department debt. The city said it won’t affect water rates this year.