Young Brunette Girl Wearing A Red Necklace Near The Old Wooden Watermill

Largely unaffected from the turbulent political events following the demise of the Western Roman Empire, the importance of watermilling continued to grow under the new Germanic lords. The sharp rise in numbers of documented early medieval watermills coincided with the appearance of new documentary genres (legal codes, monastic charters, hagiography) which were more inclined to address such a relatively mundane device than the ancient urban-centered literary class had been. This partly explains the relative abundance of medieval literary references to watermills compared to former times. Also, through Thirlage, they formed part of the feudal system and its associated bureaucracy.
Nevertheless, the quantitative growth of medieval evidence appears to be more than a mere reflection of the changing nature of surviving sources: by Carolingian times, references to watermills in the Frankish Realm had become "innumerable", and at the time of the compilation of the Domesday Book (1086), there were 5,624 watermills in England alone, only 2% of which have not been located by modern archeological surveys. Later research estimates a less conservative number of 6,082, and it has been pointed out that this should be considered a minimum as the northern reaches of England were never properly recorded. In 1300, this number had risen to between 10,000 and 15,000. By the early 7th century, watermills were well established in Ireland, and began to spread from the former territory of the empire into the non-romanized parts of Germany a century later. The introduction of the ship mill and tide mill in the 6th century, both of which yet unattested for the ancient period, allowed for a flexible response to the changing water-level of rivers and the Atlantic Ocean, thus demonstrating the technological innovativeness of early medieval watermillers.
+ Tide mills
In recent years, a number of new archaeological finds has consecutively pushed back the date of the earliest tide mills, all of which were discovered on the Irish coast: A 6th century vertical-wheeled tide mill was located at Killoteran near Waterford. A twin flume horizontal-wheeled tide mill dating to c. 630 was excavated on Little Island. Alongside it, another tide mill was found which was powered by a vertical undershot wheel. The Nendrum Monastery mill from 787 was situated on an island in Strangford Lough in Northern Ireland. Its millstones are 830mm in diameter and the horizontal wheel is estimated to have developed 7—8 hp at its peak. Remains of an earlier mill dated at 619 were also found at the site.