(VinePair) - We get it — wine regions are special, and not just because the fruits of their labor have lent a happy buzz to imbibers for millennia. A wealth of intricate details combine to make these hallowed regions perfect for grape growing. Sunshine, soil, and water are the basic ingredients, but the rivers that criss-cross most famed areas also play a critical and oft-overlooked role.

Beyond providing postcard-worthy backdrops, these curvaceous flows moderate severe climates across Europe and the New World, which is important because most wine regions exist in harsh, or marginalized areas. From the chilly Mosel Valley to the scorching Ribera del Duero in central Spain, vines thrive thanks to the influence of major rivers, and it’s not because they provide irrigation. In fact, it’s likely that without these rivers the vines there would produce average swill instead of legendary elixirs.

If not irrigation, then what? Drinkers have chemistry to thank in this case. Because liquid water maintains its temperature longer than air, rivers are able to act as both heat reservoirs and cooling agents in the valleys they’ve carved over thousands of years. This science is the same reason outdoor pools stay warm longer than the air after sunset, and why seaside areas have more consistent temperatures than their nearby inland counterparts.

When it comes to fine wine, these moderating influences are paramount because they allow grapes to ripen while retaining vital acidity, either by adding heat or cold. A combination of sugar and acid in grapes is what allows a finished wine to taste “balanced,” i.e. not overly dominated by oak, fruit flavors, astringent tannins, or tart acidity. When most professionals analyze a wine — from a celebrated locale or otherwise — this sense of balance and terroir is what they’re searching for, and what gives a wine a high value, and higher price on shelves and menus. A prime location near a major river makes this balance easier to achieve, since rivers tame climates and limit vintage variation as a result. In short, rivers counteract the most brutal elements of a region’s climate and give winemakers better crops to work with every season.