Amelioration is when water is added to a must in an effort to dilute the concentration of grape sugars. High sugar levels bring the potentials of high alcohol levels and fermentations that have difficulty completing to full dryness. High sugar levels are more common in areas like California, where sunshine is plentiful, grapes easily mature to full ripeness, and winemaking trends have shifted toward longer hang times for the fruit before harvesting.

Although there is a concern about dilution of the wine, it is important to note that most of the high sugar level in very ripe grapes is due to dehydration and adding water back merely restores the balance that was in the grapes.