It can be augmented by the water being replaced from other systems. Draw a longitudinal section of your model. Use arrows to indicate where water is discharged from the model. Label the arrows with the process terms. Plants absorb groundwater and use it to make food through photosynthesis.
Excess water is transpired back into the atmosphere as part of the hydrologic cycle.
Animals drink water and excrete excess water as liquid waste, some of which evaporates back into the atmosphere. Living tissue of both plants and animals is mostly water. When the organisms die, some of the water evaporates back into the atmosphere as part of the drying process. More groundwater would be brought to the surface and discharged. It could dry up the groundwater system.