Water assists the digestive system to break down food, and the water within the bloodstream carries those nutrients to all parts of the body. This represents the mission of all Jewish women: to bring the well of living water - Torah - to nourish all segments of the Jewish people, even those who totally lack knowledge of it. Thus we find that, while still in Egypt, Miriam devoted herself to small children, and her heroic efforts led to the annulment of Pharoah's decree against children. Consequently, it was in her merit that the well water came, since water represents the universal dissemination of Torah.
Thus, when a mother, sister or teacher educates a child, we witness the modern-day "living waters of Miriam" sustaining the Jewish people in exile, making it possible to go peacefully throughout our current "sojourn" in the "desert" of exile.
In addition to providing water to drink, Miriam's well also made it possible for the mitzvah of taharas hamishpachah [family purity] to be fulfilled. There was no other source of water in the desert, so Miriam's well served as a mikvah, enabling children to be born throughout the forty years.
The custom of drawing water on Motzei Shabbat [to draw from the well of Miriam] is cited in the Alter Rebbe's Shulchan Aruch. This appears to suggest that it is applicable today; however, this was not a custom practiced in the House of the Chabad Rebbeim. In any case, it certainly applies to all of us spiritually: studying this law about Miriam's well influences the whole week, that it may be a healthy week in both spiritual and physical terms.
Source: Gutnick Chumash: Based on various Sichos of the Lubavitcher Rebbe