Entering the basement
To lower themselves into their cellar basement is a scary thing for Zlata and her mother, because they are pretty phobic about rats and mice, and they know that rats and mice live in the basement. But by the time the shelling starts, they are happy to be there, among the rats and mice. So the basement is a symbol for the re-prioritization that war brought their family. From now on, comfort simply cannot be obeyed if they are to survive the invasion.
The father getting water
When the father gets water for his family, it is a picture of his conquering his fear through love, because his commitment to do the best for Zlata and his wife make him willing to enter the battlefield, and his journey is rewarded with a boon—his family can live for another day in their basement. His sacrifice is painful every time he makes it, but after all, this is a picture of love.
The mother getting water
The mother didn't even want to enter the basement to sacrifice her mental comfort, but when bombs stole her mental comfort away, she saw the situation in crystal clarity. When the father became injured, and the family still needed supplies for survival, the mother instantly knew it was her responsibility. She must literally follow her husband's example of sacrifice, so both of them independently share this same adventure—head on into the war and then back to the basement with water.
The motif of growth and learning
When the Serbs target the schools, that means Zlata's studies have to be done in private, in the safety of their dark cellar. That means that instead of being surrounded by her friends, she learns alone, and she has to make her own sacrifice to keep investing in her future. That's scary and hard, though, because it makes her face her impending fear that maybe they will all be slaughtered by the enemy. This happens in many other ways throughout the book, because the war affects every aspect of her life, so as she grows up, she learns all life's lessons with death looming on the horizon—not exactly a walk in the park.
The motif of luxury and necessity
Water goes from being a thing the family takes for granted to something entirely different in a matter of only days or weeks. Before, water was a free resource, basically. But after warfare limited what they were able to do in a day, the luxuries of water excess became clear: If they wanted to shower, they'd have to shower with water they were willing to die for. No water to flush the toilet. No water in the sinks. No water in storage. If they wanted to survive, they would have to make little daily journeys into the war-filled overworld to get it. Water shows the advantage that privilege adds, and it shows the absolute desperation of war and poverty.
