The law of conservation of mass states that in a chemical reaction mass can neither be created nor destroyed. Similarly, the law of conservation of energy states that the amount of energy in an isolated system is conserved ie. the amount of energy can neither be created nor destroyed, but instead changes form.
Trough my nebourhood it starts in the local pond when the sun hits it evaportes and then it will make clouds then it rains next it flows trough the sewers and it will make it back to the pond