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.
There is also a fluid ounce, 1/128 of a US gallon, about 29.57 mL and an Imperial fluid ounce, 1/160 of an Imperial gallon, about 28.41 mL. A (US) gallon of water weighs about 8.34 lb at temperature of maximum density (4 C) and gasoline floats on water because it weighs less, around 6.2 lb/gallon.