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Semiarid saline streams are uncommon and hence are seldom studied. Moreover, most studies on filamentous algae have been carried out in permanent freshwaters. Seventeen waterbodies from ephemeral streams of semiarid south-eastern Spain (’ramblas’) were surveyed from a botanical, phycological and ecological point of view over a four-year period. Gradients of environmental conditions ranged from fresh to saline water (0.27 to 47 mS cm(-1)), from ephemeral to permanent and from pools to streams. Most of the sites were springs or streams that appeared in certain reaches as a result of the upwelling of groundwater. In total, 47 species of submerged macrophytes and macroalgae were recorded, with 1-18 species per site. The most diverse orders were Zygnematales, Oedogoniales and Charales, although the importance and diversification of Vaucheriales in some places was also of note. Multivariate analysis identified salinity as the main factor explaining species distribution. Conductivity ranges for species were compared with other saline habitats such as saline lakes, saltmarshes or coastal lagoons. Finally, this study broadens the ecological range of some taxa and highlights the ecological importance of these kinds of systems for the preservation of biodiversity in arid lands.