A321 Captain reported normal flight operations until about FL250 when we received caution messages on the ECAM HYD G RSVR LO LVL; G ENG 1 PUMP LO PR; G SYS LO PR. The flight crew performed an air turn back and precautionary landing at departure airport.

Narrative

Events that surrounded Aircraft X from ZZZ to ZZZ1. We pushed off the Gate on time and had a normal flight operation until about FL250 when we received a caution message on the ECAM 'HYD: G Rsvr lo LVL; G ENG 1 PUMP LO PR; G SYS LO PR'. A decision was made to stop climb at FL270 and to remain on course for the time being to assess the situation. We complied with the ECAM procedure and also the QRH. After further assessment of the situation I transferred the controls to the First Officer so I could advise the company; flight attendants; and also the passengers. I then called the Dispatcher via SATCOM and asked to be connected as well to Maintenance. I explained the situation and we jointly; in the interest of safety; made the decision to return back to ZZZ. Referencing the QRH we had a sufficient stopping margin to safely land overweight on Runway XXL in ZZZ. Once that decision was made I then called the inflight crew to advise them of the diversion and explained that this will be a code yellow. Information given was that we had lost our green hydraulic system and will be on the ground back in ZZZ in about 25 minutes. After speaking to the flight attendants; I then made a PA to the passengers to advise them of the situation and what to expect. Once that was all complete both the First Officer and I came up with our 'game plan' for returning to ZZZ. We then requested priority handling and advised ATC of our hydraulic failure. Per SOP we completed the overweight landing QRH and also referenced the diversion guide material. The HYD G RSVR LO LVL QRH lead us into the alternate gear extension which we accomplished successfully. After we landed and exited the Runway I stopped the aircraft on Taxiway 1 and set the parking brake. I requested crash and rescue for an inspection of the aircraft for any indication of hot spots; excessive brake temperatures; or smoke before we proceed to the Gate. I made a PA to the passengers not to be alarmed by emergency vehicles around the aircraft as it's a normal procedure after an event like this. Once at the Gate; the parking brake was set and the parking checklist was completed. During the parking checklist; the First Officer and I could smell hydraulic fluid in the flight deck. Once Maintenance came on board and asked about the event we explained to him what happened; and he verified that there was little hydraulic fluid left in the reservoir. A post flight walk around was performed to confirm if any visible hydraulic fluid was coming from the aircraft. During our inspection we observed hydraulic fluid leaking from the back of the number 1 engine; under the belly of the aircraft; and also pooling of fluid on the Ramp as well. After the event; operations advised us of a tail swap to take our customer to ZZZ1. The First Officer and I made a self assessment of fitness to continue and with coordination with crew services determined we were legal. The subsequent flight was complicated uneventfully and landed safely at the destination 'ZZZ1' approximately 3 hrs behind schedule without further issue.