"An Historical Atlas of Central Asia" written by Yuri Bregel. This is stated on Page no 67 of this book.

Khorezm is one of the main agricultural regions of Central Asia (cf. map 1). It occupies the lower basin of the Amu-Darya, including its delta, and it is relatively isolated from the rest of Central Asia by two great deserts, the Qïzïl-qum from the east and the north, and the Qara-qum from the south and the west; northwest of Khorezm is the Üst-Yurt steppe plateau, as dry as a desert. Agriculture based on artificial irrigation developed in Khorezm at least by the early 1st millenium B.C. Irrigation in Khorezm has been based on a single natural source: the Amu-Darya river. This river changed its course many times, because of both natural causes and human activity. Especially frequent were the changes in the course of the river branches that formed the lower delta of the Amu-Darya, downstream from the city of Khoja-eli. The Mongol invasion in the 13th century caused the destruction of sedentary life on the right bank of the Amu-Darya; it was only partially revived in the 19th century, and for more than five centuries sedentary civilization existed in Khorezm almost entirely on the left bank of the Amu-Darya. The military campaigns of Timur in the late 14th century also caused the destruction of irrigation systems and sedentary life in Khorezm. At the time when Khorezm was conquered by the Özbeks under the #Arabshahids (early 16th century; see map 25) the great majority of its sedentary population was concentrated in the southern part of the country, with its cities of Khiva, Hazarasp, and Khanqah, and the conquerors began to sedentarize only slowly.
The arrival in Khorezm of new nomadic groups by the middle of the 17th century (see map 28) required a redistribution of land among the Özbek tribes, which was carried out by Abu’l-Ghazi Khan. It seems that important new canals were built under this khan and his son, Anusha. The political situation in Khorezm during much of the 18th century was not favorable for the expansion of the irrigation system. Such an expansion took place only under the rulers of the Qongrat dynasty, and it was connected with the resettlement of a number of nomadic and semi-nomadic tribes within this region: the deportation of part of the Aral Özbeks to the south of the khanate; the deportation of the Qaraqalpaqs to the Aral delta; and the migration of several Turkmen tribes to Khorezm.
Thus, much of the irrigation system that existed in the middle and northern parts of Khorezm under the Qongrats was of a relatively recent origin. Two cultural regions could be distinguished in Khorezm from at least the early 18th century: Besh Qala (lit. “Five cities”), the south of the country, and Aral, the Amu-Darya delta. The five cities included Khiva, Hazarasp, Urgench, Khanqah, and Shahabad.
The predominant ethnic group in the south (both in the cities and the countryside) was the Sarts, the Turkicized descendants of the ancient Khorezmians, while Aral was divided between the mostly nomadic Özbeks and the Qaraqalpaqs. Özbeks also settled in the southern part of the country, especially near Khiva and Hazarasp, along the left bank of the Amu-Darya from Qïpchaq to Gurlen, and, in the 1840s, south of Köhne-Urgench across the Daryalïq. In the mid19th century the Turkmens, who formed about one quarter of the total population, were settled mostly in the western regions of the oasis of Khorezm, from Aq-Saray in the south to Köhne-Urgench and Qïzïlcha-qala in the north. Other, smaller, ethnic groups included the Jamshidis (in 1842-1855), and the Tajiks deported from the Khanate of Bukhara during the Khorezmian raids. Qazaqs, mostly from the Junior Horde, nomadized on their winter pastures in the Qïzïl-qum and on the Üst-Yurt plateau along the edges of Khorezm.