Alberca is not pool
I have realized that alberca is the translation for pool when actually the real translation would be piscina. Worldwide the word alberca is not recognized as pool, it is barely recognized as a water tank for irrigation. Proof: http://goo.gl/7F6nh while piscina is recognized as a pool on every spanish speaking country (including mexico) http://goo.gl/7F6nh . Although in some parts of mexico it is recognized as a pool but we cannot consider mexico as all the speaking countries. It only as 113Mil people while if we add the four countries which come after Mexico in population (that call a pool a piscina), Spain 46mil, Colombia 44mil, Argentina 41mil and peru 29mil we get a much bigger number that the people who call it alberca. I even find it discriminatory to consider that spanish is how mexicans make it although the site portrays spanish whith a spanish flag. And another point, the word piscina is over alberca, alberca is recognized in mexico while piscina is recognized worldwide and mexicans understand piscina but other spanish speaking people dont understand alberca. Ergo, piscina>alberca, therefore that word should be used
The word frequency ranks are piscina 2367, piscinas 19106, alberca 47009 and the plural alberca does not show up in the top 50,000 most frequent words in Spanish subtitles. Lower numbers equal more frequent usage. I've not researched if that file was derived from Spanish subtitles from one region. But clearly "piscina" is probably the word a beginner should learn first.
Yes I could imagine my Uruguayan and Argentinian friends looking at me oddly if I told them, "voy a nadar en mi alberca". I think it is fair and interesting to use colloquialisms from different parts of the Spanish-speaking world, but it would be nice if when you clicked on the word, it would give you some background (ie predominately used as a term for 'pool' in Mexico and Central America).
Alberca is usually a big water container excavated in the grown to collect water from the rain.