Why water artificial turf on sports ground prior to use?
Most artificial pitches are either “sand-based” or “water-based”. Sand-based pitches are either dressed or filled with sand in order to stabilise the pile and keep it upright. They are cheap but they have the disadvantage of being very rough if you fall on them (you get a very bad carpet burn). Water-based pitches use a layer of water to separate out the pile. They tend to be more expensive to install but are much nicer to fall on as you don’t get a really bad burn/cut filled with sand. It’s likely to be one of these pitches that you saw being watered. More recently long pile or “rubber-crumb” pitches have started to be installed that use small bits of rubber to separate the pile. Rubber tends to be better for football and training whereas the sand is better for club hockey. Water based is pretty versatile for all but is nearly always used for an international hockey match.
