During the Akyathlon, we were able to run through farms above Mount Sto. Tomas in Benguet and I noticed this hole covered with plastic that was full of water.
If my analytical skills are correct, this was constructed to catch the dew in the early morning and the drops of water from frequent drizzles. The water is being used to water the surrounding vegetations.
Too bad, I was racing that time and I couldn’t find a nearby farmer to ask what it’s use was. Let’s just hope I am correct.