Water is admitted to the river through sluice gates at the upstream end of the channel near Taplow. This is normally controlled by measurements of the water levels below Boulters Lock and the estimated flow of the Thames at the Datchet gauging station near Windsor. The first serious test of the new structure occurred during the flooding of early January 2003, and revealed a number of defects in the design. With both the Boulters Lock levels and the Datchet flow indicating that the channel was needed, the Taplow sluices were opened briefly on 1 January, but were then shut again until 4 January, by which time the Boulters Lock levels were above the target levels, and the flow at Datchet was some 320 cubic metres per second, 140 cubic metres per second above the recommended flow. A subsequent investigation revealed that the Environment Agency had known there were defects in the channel since November 2002, and this had been a major factor in not operating it correctly.