Of course, the main influence on streamflow is precipitation runoff in the watershed. Rainfall causes rivers to rise, and a river can even rise if it only rains very far up in the watershed-remember that water that falls in a watershed will eventually drain by the outflow point.
One US gallon of water weighs 133.526464 ounces. The calculations for that answer are below: 1 gallon = 8.345404 pounds 1 pound = 16 ounces 8.345404 X 16 = 133.526464.
That much water weighs about 3,500 pounds (1 gallon weighs around 8.3 pounds, depending on its temperature), while seven people with an average weight of 185 pounds have a combined weight of 1,295 pounds.