Groundwater is dynamic. In fact, such discharge accounts for the base flow of all perennial streams. You may have wondered how many streams can still have running water after weeks of dry summer weather. The answer is that the stream is being replenished by groundwater. To make the hydrologic cycle even more interesting, surface waters can recharge groundwater, especially during and immediately after precipitation events.
Aquifers underlie and cross watershed boundaries.
We therefore need to monitor on both a watershed and an aquifer basis.