What was found
DURING DESCENT THROUGH FL200 ECAM INDICATED LOSS OF GREEN HYDRAULIC QUANTITY BELOW RED DOT. HYD RESV LOW. COMPLIED WITH ECAM AND QRH. PERFORMED MANUAL GEAR EXTENSION AND LANDED WITH NO FURTHER ISSUES. AFTER THE GEAR WAS EXTENDED GREEN HYDRAULIC SYSTEM RESTORED TO FULL CAPACITY. AMM 12-12-29-00 AMM: 32-33-00-02, AMM: 20-23-16-00. R & R LT NOTCH FLAP RETURN LINE O-RING, IAW MM 20-23-00-00, 20-23-16-00, 29-00-00-04, CYCLED SLATS REF MM 27-80-00. OPS & LEAK CHKD NORMAL AMM 25-66-20-02-01. REINSTALLED THE DECOMPRESSION PANELS THAT WERE REMOVED TO GAIN ACCESS TO THE NOTCH FLAPS TO ACCOMPLISH MX TASKS IAW AMM 25-66-20-02-01 FWD CARGO COMPARTMENT DECOMPRESSION PANELS - MAINTENANCE PRACTICES. A/C TO CONTINUE.