It is indeed the conditional と but takes more of the form of 'when' rather than 'if', in a similar way to how とき is used. You'll see it used in this way quite a lot. This also means that anything before と doesn't necessarily have a cause-effect relationship. It's not because the the women was doing her laundry by the river that the peach came.
それは先生に聞くとすぐ分かった (I understood immediately when i asked my teacher) - DOBJG pg.481