When studying medieval cities, along with the complex issues, including the structure, defense system, localization of cities according to written sources, identifying economic districts, is the study of the ancient irrigation system. Although the city of Syganak is mentioned in Arabic and Persian sources of the 10th century, we can find data on the irrigation system of the city in the work of the 16th century “Mikhman-name-iy” by Bukhara Fazlallah ibn Ruzbikhan. The waqf letters discovered by V.V. Bartold mention rivers near the city of Syganak and canals drawn from the Syrdarya. Data on the irrigation of Syganak are contained in the “Book of the Big Drawing”, “Drawing Book of Siberia” by S. Remezov. In Soviet times, E.I. Ageeva and G.I. Patsevich, V.N. Groshev drew attention to the issues of the irrigation system of Syganak. S. Zholdasbaev, who studied the city of Syganak for many years, paid special attention to the origin of the name of the canal Tuman aryk, derived from the Syr Darya. In this article, the authors drew attention to a controversial issue related to the location of the medieval city of Syganak. In some sources, the city is located on the right bank, in others – on the left bank of the Syrdarya River. Some researchers, relying on these sources, suggest that another city, Syganak, is mentioned in written sources. Our field studies have shown that the Syr Darya had several old channels in the vicinity of the city of Syganak. The discovery of these channels confirms that at one time the city was located on the left bank of the Syr Darya. The Sarysu and Shu rivers from Central Kazakhstan and Semirechye at the northwestern end of Karatau flowed into these old channels. Also, in the course of research along the ancient canals, several medieval cities and settlements of the cities of the Syr Darya were identified. The article provides information about ditches, derived from the Syr Darya, also provides data on the rivers originating in the southern part of Karatau, about their ancient names. The authors reveal that the toponymic names of Kyrash, Toktamys, Kelte-Shalkiya, Arystandy, Mynbulak found in vakuf charters have retained their names to this day.