What was found
DURING CRUISE THE LEFT HYDRAULIC RESERVOIR LOW QUANTITY/PRESSURE LIGHT ILLUMINATED. AT TOP OF DESCENT THE HYDRAULIC PRESSURE LIGHTS ON THE ENGINE AND ELECTRIC PUMPS ILLUMINATED. DECLARED YELLOW EMERGENCY AND USED ALTERNATE GEAR AND FLAPS EXTENSION. AIRCRAFT LANDED WITHOUT INCIDENT AND WAS TOWED TO THE GATE. FOUND THE CASE DRAIN FILTER ASSEMBLY LEAKING. REMOVED AND REPLACED FILTER ASSEMBLY, REPLENISHED FLUIDS, OPERATIONALLY CHECKED AND RETURNED TO SERVICE.