1. Everyone knows that the Mississippi is the largest river basin in North America, at 1.2 million square miles, gathering water from the Rocky Mountains to the Appalachians. But at 700,000 square miles, which river basin is the second-largest in North America?

2. This river in South America contains the world's highest uninterrupted waterfall, Angel Falls, which descends 3212 feet over a sheer cliff before the river continues.

3. In terms of pure length, where does the Amazon River rank in the world?

4. The Amazon carries an incredible amount of water to the sea each year. In terms of all water discharged into the ocean by rivers across the world, the Amazon is responsible for 20 percent of it all by itself. Which African river comes second, at a distant 4 percent?

5. This river contains the spectacular Victoria Falls, which is more than twice the height and width of Niagara Falls.

6. There is only one European river longer than 500 miles that flows into the Mediterranean Sea. Which is it?

7. Europe's longest river is the Volga, 2293 miles long, which flows through western Russia to the Caspian Sea. What is Europe's second-longest river, 1770 miles long, and what body of water does it flow into?

8. Which Asian river is the muddiest in the world, carrying 30 times more silt per cubic meter than the Nile? (Hint: In 1931 this river flooded, killing somewhere between one and two million people in the world's worst natural disaster in recorded history.)

9. Though it is not as muddy and concentrated as the river in the previous question, this Asian river carries the most sediment in the world in terms of raw numbers, discharging two billion tons of of it every year. (Hint: The delta at the mouth of this river is home to one of the last remaining populations of the endangered Bengal tiger.)

10. What is the name of the only major river system in Australia, the drainage area of which contains more than 80 percent of the country's irrigated farmland?