Quantifying the hydrological connectivity of wetland ecosystems is crucial for their sustainable management. This study assessed the water balance of an Australian Sphagnum peatland via continuous monitoring of key hydrological parameters over four years (2017­–2021). Meteoric water inputs (rain and snow), evapotranspiration, changes in peat water storage (soil moisture and water table depth), groundwater contributions, and stream outflows were monitored or calculated over the four-year study period. Results showed a substantial groundwater contribution to the ecosystem, equivalent to 65% of total annual inputs. Groundwater inputs sustained stream outflows of 1.5 mm per day during periods without meteoric water input (i.e. summer dry periods), providing persistent surface wetness in this critical growing period. The continuous supply of groundwater to the peatland serves two important and interconnected environmental services. First, incoming groundwater enables the peatland water table to remain close to the surface, ensuring the persistence of the peatland vegetation during dry periods. Secondly, 94% of the peatland water balance (70% contributed from groundwater) leaves the peatland as streamflow, maintaining critical summer flows to downstream catchments. Climate change is predicted to increase the frequency and intensity of droughts in this region in the future, however, substantial groundwater contributions may provide more resilience to hydrologically intact peatlands in this region than what was previously thought.