Possible meanings are 1) "foot" is a metonymy that represents the hard work of walking to carry water to the fields. AT: "worked hard to water it" or 2) they would use their feet to turn a water wheel that supplied water to the fields. (See: [[rc://en/ta/man/translate/figs-metonymy]])
The land receiving and absorbing a lot of rain is spoken of as if the land were drinking the water. AT: "the rain from the sky gives it plenty of water" (See: [[rc://en/ta/man/translate/figs-personification]])
Here the two extremes "beginning" and "end" are used together to mean the entire year. AT: "continuously throughout the entire year" (See: [[rc://en/ta/man/translate/figs-merism]])