The Sumbar (also Sari-su, Sara-su and Ṣáríṣú) is a fast flowing river in southern Turkmenistan and northern Iran. It a tributary of the Atrek. The name Sari-su means yellow water in Turkic languages, but is applied to a number of other rivers as well. It used to be an area for Caspian tigers[1] in Turkmenistan, until the last individual was killed in January 1954.