sentences:  New field drainage work on farms in the 18th and 19th centuries had dramatic effects on water courses, most often recorded through complaints by millers that they could no longer get enough water to turn their mills waterwheels.The weir at Dalgarven on the River Garnock is made of boulders which are carefully placed and locked together to create a natural millpond to supply a good head of water to the wheel through the lade.The weir is built on a natural dyke across the Garnock at this point, its existence being carefully exploited by the monks of Kilwinning Abbey who chose the site for Dalgarven Mill.