Well, as a geologist, I would say there will be some correlation, but the only thing that will effect the water level is the tide effect. Tides are caused by gravitational attraction of water towards the moon, meaning as the Earth rotates there is a bulge of water always pointing twards the moon. There's also a smaller bulge on the other side of the planet as that water is less attracted to the moon. So, for each 24 hour period, there's approximately 2 tides (slightly less as the moon is at the same time slowly orbiting Earth). There is also a small effect caused by the sun, which operates in exactly the same way but ona smaller scale. I see no reason why groundwater shouldn't be effected the same way as oceanic water, so your best bet is to look at local high tide times (if you're anywhere near the coast. If not try and find a tide time for something on the same longitude). The actual phases of the moon may show a slight variation, as at New moon and Full moon the moon tide will be closest to the solar tide, so there should be an additive effect. Again, local tide tables should help.
