This is not one question but I can help out with some general definitions.
"Water table" is an ambiguous term. It can be a perched water table or the "piezometric" surface which can be thought of as a regional water table. Hydrogeologists can use the terms interchangeably. The general concept for a water table is that it is "unconfined" meaning that it does not have an impermable unit (clay, shale, etc.) above it.
If an aquifer is confined, the measured water level is called the potentiometric surface, which is generally above the actual pemeable layer due to the pressure of the overlying materials. The pressure can be significant causing the water level to rise a great distance above the aquifer, even above the ground surface(artesian well).
Head is simply the measured water level or elevation. If a well is placed into saturated material, the measured water level is the head. The differences in head create the potential for flow to occur from areas of higher head to those with lower head.
Except for being visible on the surface, prone to evaporation, and vulnerable to contamination, surface water only has one basic difference with groundwater to a hydrogeologist making flow calculations. Instead of being contained in a medium such as sand that has 35% pore space and limited permeability, water can be thought of as having 100% pore space and unlimited permeability. Otherwise surface water heads are handled similar to groundwater heads in flow calculations.
Surface water can be perched such as in a lined pond or connected to the groundwater table such as an unlined gravel pit pond. Head can be measured the same way in a pond based on the elevation of the water surface.
If the water level in the pond is higher than the water level in an aquifer, there will be potential for flow from the pond to the aquifer (leak). The opposite is also true (spring).
I have several water table ponds. We finally had some rain recently and you can see the initial increase in water levels directly from rain to the pond surface, followed by several days of groundwater recharge to the pond as a result of increased head from the rising water table due to infiltration of rain in the drainage basin. The opposite occurs during evaporation, which lowers the water table in the vicinity of the pond. Liners just slow down the process.
Theo, in your case where groundwater is so deep, the surface water you refer to is most likely all perched water so your position is correct. It wouldn't necessarily stand up at my place, where those same post holes are right into the water table. The water table at my property fell almost 4-feet this summer as did my ponds but they are always connected with the aquifer unless it falls 12-feet where it would be below the pond bottom. Keep in mind that even clays have limited permeability so differences in head will cause flow through the clay, however, it is very slow (by the way, hope the Bucks pound the skunks this Saturday).
There are also capillary effects due to surface tension that cause soil moisture in a thin zone above the water table but I don't think that was the question.
Crisw, you will probably need professional help to calculate your water budget. To really do it right, you balance all of the water input/output of the drainage basin, not just your pond (precipitation, groundwater recharge, runoff, etc.) minus the outflow (evapotranspiration, streamflow, seepage,well withdrawals,stream discharge, etc).
A simplified approach can be made if you know the annual precipitation, pan evaporation rate, aquifer thickness, permeability, and water level in the aquifer. Digging a water table pond can have negative effects that can get you trouble with upgradient users.
There should be someone at the loccal NRCS office who can help. The easiest way to figure it out is to investigate other pond projects near you. Practical experience in your area may prevent you from wasting money on a no brainer.
