Parch

Parch is a Mercury class Utility Psynergy introduced in Golden Sun: The Lost Age that costs 2 Psynergy Points. It is learned by Piers when the party reaches the end of the Aqua Rock dungeon and interacts with the magic tablet there. Piers can use Parch to "Evaporate standing water." This effectively remove small bodies of water within dungeon-style environments. Like most Utility Psynergies, Parch is required to complete the game, particularly to enter Tundaria Tower. It is also needed to get to the Ulysses and Coatlicue summon tablets, as well as obtaining the Mercury Djinni Steam.

Using Parch on flowing water will yield an effect that indicates it evaporating water, but it has no actual effect. This is most likely meant to show that some water is evaporated, but more water simply takes its place. This can be assumed to be the reason it is, as its description says, only effective on standing water.