UNDERSHOT DRIVEN WATER MILLS AND WATER RAISING DEVICES IN OTTOMAN ANATOLIA
Atilla Bir & Mahmut Kayral
For about two thousand years water was the main source for milling and other industrial purposes. The oldest known water wheel used for grinding corn existing in Cebeira (near the present day Niksar) in the Kingdom Mithridates was described by the historian Strabo about the first century BC. Water mills need high and constant flow rates to operate. In this region of Anatolia , river flow rates were high and constant all throughout the year.
Water wheels are generally classified into two categories according to the position of their axles. These are: a) vertical axled water wheels, b) horizontal axled water wheels. Due to technical difficulties vertical axled water wheels were not frequently used, thus they were not found in archeological excavations. On the other hand, horizontal axled water wheels using gear wheels to transfer the movement to the vertical mill stone axle were mostly preferred. However, the gears caused a great loss of efficiency.
Water wheels are also classified as undershot and overshot water wheels. The wheel type to be used depends on the flow rate and speed of the river. The undershot driven water wheels are used in rivers having abundant and constant flow rates. The more efficient overshot driven wheels need higher settlement costs and are preferable in rivers having low and varying flow rates.
In this article two types of undershot driven horizontal axled water wheels used in Anatolia during the Ottoman period are studied. The first type is mounted on boats or rafts and is driven by river currents. These wheels are generally established at river turns where water speed is high or at roadsides near bridges to ease the transportation of wheat and flour. This mobile type of wheels have superiority over fixed types since they are not much affected by the changes in river beds. The second type called noria (dolap in Turkish) is an undershot driven water raising device which is usually built on rivers with high flow rates. However, throughout antiquity and the middle ages, these wheels were also driven by human or animal power to raise water from low rate rivers. Norias continued to be used until the end of the 19th century.
In this article, the technical properties such as efficiency, flow rate, capacity, rotation frequency, height of water elevation and irrigation distance of the two types of water wheels are calculated. Pictures and photographs of these 19th century Anatolian devices are annexed to the article.