Patrons of D.C.’s top restaurants face many options when deciding what kind of water to drink. But whether your preferred glass is bottled, filtered, sparkling or tap, you will have an extra charitable choice this week.

More than 70 Washington restaurants, including a number on Capitol Hill, have joined UNICEF’s Tap Project, which was launched in New York City last year. Participating venues ask diners to add $1 to their tab to cover the cost of the tap water they usually drink for free. The money is donated to a UNICEF fund used to provide clean, safe drinking water to children in developing nations.

Organizers hope the grass-roots approach of the weeklong, nationwide drive will raise awareness and funds to address the world’s growing water supply crisis. Even the smallest contributions can have a large impact, they say: $1 provides a child with clean water for 40 days.

“We are overwhelmed at the numbers of volunteers, industry leaders and restaurants that have pledged to make the Tap Project a success this year,” said Caryl Stern, president and CEO of the U.S. Fund for UNICEF, in a statement. “It simply underscores the widespread desire to work together to provide clean and safe water to millions of children.”

Ann Cashion, co-owner of Johnny’s Half Shell, said she and her partner became involved with Tap after a fellow D.C. restaurant proprietor directed her to the project’s Web site.

“I guess I hadn’t really realized that not having clean water was such a big issue,” Cashion said. “I didn’t realize it was as lethal as it is. What we’re really hoping is that we’ll be able to explain [the issues to] people tableside and they’ll choose to donate because of that.”

Cashion said Johnny’s hopes to tap into its Capitol Hill clientele to recruit at least 1,000 participants by the end of the week.

“I think we have a good shot at having a higher participation rate than other restaurants because, presumably, we’re serving people who think about helping the world all the time,” she said.

The Tap Project runs March 16-22. For more information and a complete list of participating restaurants, visit tapproject.org.

—Torey Van Oot