Argentina is one of the largest wine-producing nations, during the past few years there has been a dramatic improvement in quality. The vineyards stretch for more than 2000 kilometres, for the most part along the eastern flanks of the Andes, from Salta in the north to Río Negro in the south. The climate is ideal for the production of wine, with hail being an occasional problem. The vineyards rely on melt water from the Andes, either in the river valleys or in subterranean aquifers. Increased planting is taking place at higher altitudes of cooler climate grape varieties.