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.
20 gallons
7615 Gallons
12,345 gallons
If the container is 3ft x 3ft x 9ft, the answer is 81 cubic ft. There are approximately 607.5 gallons of water.
704.5 gallons (approx).
Approx 4892 Imperial gallons.
Trough is usually associated with low tide. During low tide, the water level is at its lowest, exposing more of the shore.
Not enough information. If it is a rectangular shape, you need to multiply length x width x height. The answer will be in cubic feet, which you would then have to convert to gallons (which is a great example of the benefits of the SI).
There are 907.9202769 feet2 of water, but you will have to convert that into gallons.
20 gallons
7615 Gallons
1056 GALLONS
50,000 gallons
12,345 gallons
74.42 gallons.
Approx 2.1 Imperial gallons = 2.5 US gallons.
4745 gallons Best estimate I have.