It would depend on the use.
What you are showing in your picture is not considered a pila in Central America, and this has become a point of confusion.
Pila may be a recipient of potable water from a natural source, but the main use is for washing clothes or cleaning pots and dishes.
An actual pila looks like this...
A pila has 2 basins, one for storing fresh water, and another with ridges for scrubbing clothes. Pretty much all homes have one here, or failing that, a public pila...
In Guatemala, pilón is not generally used (only means big pila).
It is not for animals to drink out of.
Animals drink from an abrevadero, and is "trough" in English.
Cisterna, or cistern,
: an artificial reservoir (such as an underground tank) for storing liquids and especially water (such as rainwater)
...is a deposit of water in the ground, or at a higher level than the house to provide water by gravity in lieu of a pump, but usually covered. It is used for most household purposes.
Note that cisterna has another name--tanque, or tank.
It was suggested:
(from French réservoir – a "tank") is, most commonly, an enlarged natural or artificial lake, pond or impoundment created using a dam or lock to store water.
The best word for pila would be...pila. I do not think there is better word. Asking for this word in English is like asking for a better word for "taco", or "burrito".
...and, what you are showing in your picture is not considered a pila in Central America, and is a point of confusion.
It is either a cistern, or reservoir.