How much water is on Earth?
The large blue drop represents all of Earth’s water. Diameter is about 860 miles, volume about 332,500,000 cubic miles (1,386,000,000 cubic kilometers.)
The smaller blue drop represents the world’s liquid fresh water. Diameter is about 169.5 miles (272.8 kilometers,) volume 2,551,100 mi3 (10,633,450 km3,) of which 99 percent is groundwater, much of it not accessible to humans.
The smallest blue dot, diameter only 34.9 miles (56.2 kilometers,) volume 22,339 mi3 (93,113 km3) represents fresh water in all the lakes and rivers on the planet. The water life needs every day comes from these precious surface-water sources.

Source: ga.water.usgs.gov/edu/2010/gallery/global-water-volume.html

How many people live on Earth?
About 7,080,461,690, says US census.
United States population today numbers 313,722,191 (Mon, April 22, 2013, 8:45am PST).
One year ago, on Earth Day 2012, there were 313,465,631 people in USA.
Sources: www.census.gov/popclock/ and www.census.gov/popclock/

What about growth?

Forty years after the release of the groundbreaking study, were the concerns about overpopulation and the environment correct? Mark Strauss tackles growth for the Smithsonian magazine, April 2012. Australian physicist Graham Turner revisited The Limits to Growth (1972) and compared real-world data from 1970 to 2000 with the business-as-usual scenario. Turner, senior research scientist at CSIRO Ecosystem Sciences (previously Sustainable Ecosystems), Canberra ACT, Australia found the predictions nearly matched the facts. “There is a very clear warning bell being rung here,” he says. “We are not on a sustainable trajectory.”

Prosperity without Growth, is it possible?

Tim Jackson, economics commissioner on the UK government’s Sustainable Development Commission, says yes in his book, Prosperity without Growth: Economics for a Finite Planet. He also says, "Questioning growth is deemed to be the act of lunatics, idealists and revolutionaries."

More: 15 Facts About Our Plane for Earth Day, Bad Astronomy