Both sides struggled to find their attacking game in a scoreless first quarter.
It was the Spanish who began to build momentum when a Laura Barrios penalty corner was well saved by Irish goalkeeper Lizzie Murphy.
The home side continued to dominate in the second quarter and were rewarded with a pair of goals.
After Murphy denied Marta Segu twice, she was beaten with a shot she will have been disappointed not to save. Out of nothing a reverse stick effort from a tight angle by Alvarez went off the inside of her pad and into the net.
Ireland responded well to going behind. They had plenty of possession leading up to the Spanish goal but had failed to create any chances of note.
That changed when a Niamh Carey pounced on a loose ball, only to see her shot turned aside by Clara Perez in the Spanish goal.
The crucial second goal came in the last minute of the first half.
Lola Riera’s shot from a penalty corner found the back board and Spain had a two-goal cushion heading to the break.