The highlands of Andalucia are full of springs that give birth to major and minor waterways. Streams and tributaries flow together, aided by winter rainfall and the resultant heightened water table, forming rivers irrigating land and dammed to create reservoirs. The reservoirs service households, swimming pools and the coastal golf courses and tourist industry. During periods when winter rainfall is low for several consecutive years, demand on the reservoirs exceeds the water that fills them with notable changes in landscape around the man-made lakes.

The northern frontier of Andalucia is marked by the Sierra Morena Mountains, which separate the Castilian plain to the north and the Guadalquivir River basin to the south. To the west, the Guadiana River separates Andalucia from Portugal. To the south, the waters of the Atlantic Ocean wash the shores of Huelva and Cadiz provinces, while the Mediterranean meets the coast in the provinces of Cadiz, Malaga, Granada and Almeria. In the east, Andalucia´s frontiers are marked by the Mediterranean coast of Almeria and the Levante area of eastern Spain.

The rivers that flow to the Mediterranean are relatively short with less water than those that run to the Atlantic. The rivers that flow into the Atlantic are larger with copious amounts of waters. The region's most important river is the Guadalquivir and its tributaries: the Guadalimar, the Guadiana Menor and the Genil.

The Guadalquivir River has created a long and fertile valley which shares its name. Along with one of its tributaries, the Genil, it is Andalucia’s fundamental physical axis. From its source in the Sierra de Cazorla Mountains to the east, through to its mouth in the west alongside the marshes of the Donana National Park, the Guadalquivir is a source of life for the landscapes it crosses. The Guadalquivir also runs through central areas of Cordoba and Seville cities. In the latter the Isla Magica theme park stands on an island, the Isla la Cartija, in the river.

The major river basins in Andalucia, shown on the larger map, are:
The Guadalquivir as discussed, which flows out to the Atlantic dividing the Atlantic basins.
The Atlantic basins which to the north are the Guadiana and to the south theGuadalete-Barbate.
The Mediterranean basin known as the Cuenca del Sur (southern basin).