The seventh (and last) day of Sukkot is called Hoshana Rabbah (the Great Salvation), a climactic day of praise to [HaShem] that was viewed by the rabbis as following the sequence of Yom Kippur. Rosh Hashanah judgement is presented, Yom Kippur judgement is sealed, Hoshana Rabbah judgement is delivered.
On the seventh day of the feast, the Temple water-pouring ceremony, which is performed each morning throughout the week, takes on great importance. Jewish tradition holds that it is on this day that G-d decides whether there will be rain for the next year’s crops. Instead of three silver-trumpet blasts, there are seven sets of three blasts.Rather than one circuit around the altar, the priests make seven circuits. It is during this ceremony that Yeshua stands up and shouts, “If anyone is thirsty, he should come to Me and drink!..."
This is also when the Torah Scrolls are "rewound" to Genesis