Most large stock water troughs can hold about 100-180 gallons. Some, depending on the brand name and shape of the trough, can hold anywhere from 150-200 gallons.
You haven't told us how long the trough is, or how deep the water is in it. If it's full to the rim ... 2-ft deep ... then there's 44.88 gallons for every foot of the trough's length.
700 gallons
It depends on what type of water heater do you have. For a gas-heater, 75 gallons is considered large. For the electric heater, 120 gallons is considered large.
A trough is something that contains food or water. A small animal might be fed from a bowl; a large animal needs a bigger food container. That's a trough. A visual: you know how in movies set in the American West, after a fight, somebody ends up in the water container the horses were drinking out of? That's a water trough.
To calculate the volume of an 8' x 3' x 2' stock tank, multiply the dimensions: 8 feet × 3 feet × 2 feet = 48 cubic feet. Since there are 7.48 gallons in a cubic foot, the total volume in gallons is 48 cubic feet × 7.48 gallons/cubic foot = approximately 359.04 gallons. Therefore, the stock tank holds about 359 gallons of water.
The question is not very specific. There are many kinds of water tankers. A water tanker truck, of the largest 18 wheeler kind, can carry about 30 tons of water. Which is about 8000 gallons.
At least 6 gallons!
It depends on the context. For a single person's daily use, 15 gallons is a lot of water. However, compared to industrial or agricultural water usage, 15 gallons may not be considered a large amount.
Helps if you bury it in the ground for a few months first, so the insects can work on it for a while. I use a large stock pot and 5-6 gallons of water when I'm boiling shark jaws.
60 billion gallons
With 20,000 gallons of water, you could fill a swimming pool, water a large garden or agricultural crop, provide drinking water for a small community for a short period of time, or support industrial processes that require a large amount of water.
There was a deep trough where the lake water emptied into the river.Scientists have been looking for rare fish in the deep underwater trough.