The Groundwater Pump is the advanced part of waterworks that permits an expansion of water grid deep into the landmass.
As the name implies, this pump can pull water straight out of ground, no need for adjacent ocean. It`s also producing two and half times more water per tick then Water Pump (without upgrades) and has better water storage.
However, all those advantages come with their own shortcomings. To begin with, this pump is eight times more expensive. Other disadvantage is that unlike the Water Pump, Groundwater Pump needs an adjacent Water Pipe or Water Pump in order to function - it can not pump water directly into adjacent generators or into other Groundwater pumps. It should be mentioned that Groundwater pumps can pump into Water Pumps and vice versa.
It should be mentioned that while the pumps share the capacity upgrade with all the other Water Works elements, the upgrades to pump production are separate.
An example on how a Groundwater Pump can be used in a complex grid.
An example of an advanced grid, stacking the output of several pumps.