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.
Fresh water is take 39.2 degrees Fahrenheit . 1 gallon of fresh water is about 8.36 pounds (Gallon of water weigh calculator). For US: 128 ounces to a gallon, about 30 g/ounce (memory says 29.6g/oz but I would not trust my life on it.)