This would depend on numerous factors - including, which waterfall, time of year etc.
About 500,000 gallons of water
Water flowing over a cliff will form a waterfall.
over 1,000 gallons
977,554 gallons
When a river flows over a cliff, it is called a waterfall. This occurs when the river encounters a sudden drop in elevation, creating a dramatic cascade of water. Waterfalls are commonly formed by erosion and can vary in size and height.
river
150 000 American gallons flow over every second.
Over 8 millions gallons
By how many gallons of water are used over a set time period.
over 9000 roughly...
More then over 1,000,000,000,000,0
Waterfall.