The rivers in Andalusia (lotic epicontinental waters)
A network that connects territories and transports the resource that is the source of life and biodiversity.
The hydrographic network of Andalusia is organized mainly around the depression of the Guadalquivir river that flows into the Atlantic Ocean. Curiously, there is some controversy about the location of its spring, officially located in the Sierra de Cazorla (Jaén). Its main tributaries are the Guadiana Menor, Genil and Guadalimar rivers.
The Atlantic basin also receives the Guadiana river, which flows north of Andalusia and borders Portugal and the Odiel, Guadalete and Barbate rivers. The Mediterranean basin has shorter rivers: Guadiaro, Guadalhorce, Guadalfeo, Andarax, Almanzora and Segura.
Andalusia is characterized by a semi-arid Mediterranean climate that causes a strong evaporation of water in the middle and upper reaches. Our region is distinguished by the numerical importance of temporary streams and ramblas (the latter only drain rainwater). Even so, the lower reaches of the main rivers are permanent.
It is worth noting the omnipresence of reservoirs built throughout the hydrographic network. This results in huge reservoirs of water used for irrigation agriculture and which have also generated gigantic benefits to the construction sector. In these artificial lakes, populations of invading exotic fish thrive to the detriment of native species found in Mediterranean rivers.
Oleander (Nerium oleander), with its magnificent flowering, are spontaneous shrubs typical of the banks of temporary rivers in Andalusia.
Meander of the Genil river upstream of a dam: the clogging of the river bed has allowed the development of aquatic vegetation of interest.
The chemistry of the Tinto is one of the strangest and most fascinating river in all of Europe.
Flood on the Guadalquivir in the city of Cordoba and its famous thousand-year-old Roman bridge.
Some of them stand out especially for their naturalness and biological interest: the Guadiaro basin, with the Genal and Hozgarganta rivers; several streams of the Costa del Sol; the Pedroches stream next to the city of Córdoba, and some others. Mention an extraordinary river, the Tinto, characterized by its very acidic waters of pH 2, where only rugs of extremophilic bacteria can develop. No less interesting are the salty streams of the Guadalquivir depression, which also constitute a very scarce sample in the European continent and host an important biodiversity of endemic water beetles. These streams are usually better preserved because the salinity of its waters and its boundaries limits agriculture.
Native fish, many of them endemic, are especially adapted to the conditions of temporary streams; benthic invertebrates that turn out to be bioindicators of water quality; abundant dragonflies in the middle sections running waters, although the interesting Faded pincertail (Onychogomphus costae) appears mainly in the lower sections. Among vertebrates, it is worth noting the otter (Lutra lutra), is increasingly more common, and riverine passerine birds such as the western olivaceous warbler (Iduna opaca) and the penduline tit (Remiz pendulina). As for the headwaters of the streams, they offer very good pools for the breeding of amphibians and especially salamanders (Salamandra salamandra).
2007: a full year of studying aquatic insects (+200 days in the field) on the best and the worst streams in Andalusia.
Pool at a temporary Mediterranean river
During the summer period, a drying phase characterizes the middle streams and the heads of Mediterranean rivers and streams. Here, the Hozgarganta River. The deepest and impermeable zones of the minor bed conserve water and form basins, veritable oases for aquatic fauna and flora, in particular rare dragonflies.