Final answer:
The water table is usually at its lowest elevation along valleys and is depicted as such in cross-sectional investigations like seismic sections.
Step-by-step explanation:
The elevation of the water table in an investigation is typically lowest along valleys, as it mimics the topography where the water table sinks with valleys and rises with hills. Specifically, in geographic terms, the water table is lowest at the elevation corresponding to the valley floor where it may discharge into streams. In the case of a cross-sectional investigation like a seismic section, the lowest point would likely be at the bottom of the depicted valley or basin.