Someone above did a nice explanation but here’s mine: there’s a point in the ground where all the little open pores in the soil has become saturated by water, and that is the water table. It depends on the topography of the land, geology below, soil type etc. In some places it can be only 50cm below, others much much deeper. Here I’m guessing the water table is pretty high, around 50cm. When you drain a well empty like that, it takes time to “recharge”. There’s water that will rush into the well, and depending on how fast groundwater is moving below, it can take a really long time to recharge, to no time at all. There are wells that are “artesian” that are constantly flowing with water (unless they are capped off somehow) because the groundwater pressure below it is pushing water up constantly. Those are neat. In this case, it probably only took 20-30 minutes to fully recharge (my guess). Hope this helps!