WASHINGTON — Scott Harrison knows his charity has funded nearly 7,000 clean water projects in some of the poorest areas of the world in the past six years. But how many of those wells are still flowing with drinking water months or years later is a tough question to answer.

His organization, called Charity: Water, has funded projects in 20 countries. It says it is committed to spending 100 percent of each donation in the field to help reach some of the 800 million people who don’t have clean water and resort to drinking from swamps, unhealthy ponds, or polluted rivers.