Physical map of La Guajira
The northern part of the department consists of arid plains called the Guajira-Barranquilla xeric scrub caused by the rain shadow of the Sierra Nevada de Santa Marta, which rise to 5,775 metres (18,947 ft) in the south. The Sinú Valley dry forests lie in between. In the far south are the headwaters of the Cesar River which flow south towards the Magdalena River.
The Ranchería River, which also rises in the Sierra Nevada de Santa Marta, crosses the Guajira Peninsula from south to north and flows through the Valley of Upar and into the Caribbean sea. The Serranía del Perijá and the Montes de Oca lie in the southeastern part of the department, bordering Venezuela.
The department was divided into three subregions based on geographical characteristics: Upper-, Middle-, and Southern Guajira. The Upper Guajira covers the northernmost part of the peninsula, with mostly scarce semi-desertic vegetation, and containing only an isolated low altitude mountain range, the Serranía de Macuira (865 m above sea level). The Middle Guajira region is mostly flat, with hills in some areas, presenting also an arid environment. The Southern Guajira covers the region of the Montes de Oca and the Serranía del Perijá mountain ranges on the border with Venezuela, and the valley formed with the Sierra Nevada de Santa Marta mountain range. Southern Guajira has more wetlands and rivers.