was flooded every winter, but an Act of Parliament was then obtained, to authorise the improvement and enclosure of of land. This was one of the largest areas enclosed in north Shropshire, and although the scheme was more costly and difficult than enclosing some of the dryer areas, the resultant land was more fertile, and so justified the cost. Below the large meander at Ruyton, where a narrow valley cuts through sandstone, the bed flows over boulder clay with some glacial debris, and becomes stony again. The lower section retains some of its natural features, including meanders and riffle-pool sequences, which provide habitat for fish. Much of the upper section has been heavily modified, with the river canalised to improve flow. Between 1985 and 1988, the river bed between Ruyton and Rednal was lowered by about , in order to improve the drainage of Baggy Moor. Water quality is affected by discharges from Sewage Treatment Plants, including one which reaches the river from Oswestry via the Common Brook, and another which discharged into the Tetchill Brook at Ellesmere prior to 1999. The sewage works has since been closed, and improvements have been made to sewage outfalls and storm drains. In addition the brook has been dredged to remove polluted silts, and field studies have subsequently revealed that the quality of the brook is improving, measured by the diversity of invertebrates found in it. In addition, water quality is affected by effluent from factories processing dairy products. These and the sewage works outfalls are generally well-regulated, but there have been some serious pollution incidents as a result of poor agricultural practice. The worst was in September 1985, when of pig slurry was discharged into the river, resulting in the destruction of all of the fish populations down to the River Severn. A tank containing the slurry burst, and around 100,000 fish died as a result of the pollution. Flow on the river is measured at three gauging stations. The furthest upstream is at Perry Farm, which uses a flat V triangular profile weir. That at Ruyton Bridge is a velocity area gauging station, while the final one is at Yeaton, where there is a Crump Profile weir. The catchment area above the Yeaton station is , which receives a mean rainfall of . This results in a mean flow of 30.4 million gallons per day (138.2 Mld), although a peak flow