United Nations General Assembly President Volkan Bozkir said last week that the lack of safe drinking water for 2.2 billion people worldwide is a "moral failure," in a stark warning days before World Water Day on Monday.

In a new interview, Oscar-winning actor and water equity philanthropist Matt Damon said the solution requires a wave of private sector investment to scale up the model of micro-finance, which has already delivered both water access for tens of millions and reliable returns for investors.

He called on major investors to help put an end to the water crisis before climate change makes the task even more difficult.

"All we're trying to do is get the attention of the heavy hitters to come into this space," says Damon, who co-founded the nonprofit organization Water.org in 2009 and WaterEquity in 2017. "There is so much low-hanging fruit here — and this model really, really works."

Water.org has disbursed 7.2 million loans totaling $2.6 billion, which have improved water access for 33 million people, according to its website.

'The problem contains its own solution'

Since 2002, worldwide micro-finance has grown dramatically. That year, 68 million borrowers benefitted from such loans; in 2013 that figure had risen to 211 million, according to a report released in 2015 by the Microcredit Summit Campaign.

Gary White, the CEO and co-founder of both Water.org and WaterEquity, pointed to the example of a Kenyan farmer named Alice who was paying $60 per month to a water vendor in order to nourish her crops. Instead, she took out a $20 per month loan from a Water.org partner, which will allow her to build a water tank in a well.

"Now she can pocket $40 a month and if you look at that multiplied by millions, this actually becomes an investment opportunity," says White, who noted that the rate of repayment on such loans is 99%. "If we can connect the capital markets to people like Alice, they still get immense value."

"In many ways, this problem contains its own solution if we can draw in the finance," he adds

Damon and White spoke to Yahoo Finance Editor-in-Chief Andy Serwer in an episode of “Influencers with Andy Serwer,” a weekly interview series with leaders in business, politics, and entertainment.

Damon kicked off his water philanthropy with the launch of H2O Africa in 2006, while working on a documentary called "Running the Sahara," which profiled three men who attempted to traverse the Sahara Dessert.

At a Clinton Global Initiative meeting two years later, Damon met White, who nearly two decades earlier had founded WaterPartners International, an organization that sought to alleviate the water crisis in Latin America, Barron's reported. The two began to discuss the possibility of a partnership, and Water.org was founded a year later.