Is this Poison Hemlock? There is a lot of this growing in standing water near a drainage route and spring. It looks similar to water or poison hemlock. ![picture of plant](

This is most likely water cress ( _Nasturtium officinale_ ), which is in the cabbage family (Brassicaceae).

This is a water dwelling species that has white flowers and leaves in a pinnately compound form and flowers in clusters.

In contrast, hemlock ( _Conium maculatum_ ) has its flowers in distinct umbels (umbrella shape), and the leaves are also pinnate, but deeply divided and lacy in appearance as opposed to the intact and lightly toothed edges on watercress.

Here's a picture of hemlock leaf from Iowa State University, contrast it to the ones in your question:

!hemlock