Can you reuse the runoff water? Definitely if it's just from the soil. But once you start adding in nutrients....better not. Depending on the style of nutrients you use, that can even be iffy to give to other plants in the garden, salt build ups, nitrates etc. Etc. If you're all organic though it can be used safely.
*there's an area in California that has to have all the garden water shipped in because there used to be a flower farm that used all sorts of bad nutrients and now it's leached into all the ground water for a several mile radius.🤯