SEGURA (anc. Tader), a river of south-eastern Spain about 150 m. long. It is formed by the confluence of three head-streams, one of which rises on the northern versant of La Sagra (7875 ft.), a mountain in Granada, while the other two spring from the Sierra de Segura, in Jaen. From the junction of these three streams below Yeste the river winds in an easterly and south-easterly direction past the towns of Cieza and Archena to Murcia. Thence it trends N.E. and passing Orihuela falls into the Mediterranean 19 m. S.W. of Alicante. Its chief tributaries are the Mundo and Arroyo del Jua on the left, and the Caravaca, Quipar and Sangonera on the right. It is only navigable by small sailing-vessels, even in its estuary, but its waters are extensively utilized for irrigation.