Rudyard Lake is a man made reservoir and  is supplied from a feeder at the north end which runs from the river Dane.  At the south end the dam incorporates a ‘spillway’ which determines the maximum level of the water in the lake; when in use it provides a spectacular waterfall.  The outflow of water to the Caldon canal is controlled by valves in the two housings at the west end of the dam. On days when there is heavy usage of water by leisure craft on the canal system the flow of water can be increased by opening these valves.  There is a constant battle between the need to ensure the canals have adequate water while still keeping sufficient water in the lake for its sailing, yachting and fishing needs.  This is most critical in the late summer months when there has been periods of low rainfall.