sentences:  On spring tides, this gave around 7 hours of operation, which gradually decreased as the tides reduced, and at neap tides, the operation of the mill was entirely dependent on the flow from the upper river.Rankins, the millers, objected to plans by the Great Eastern Railway to build a dam and reservoirs in Rochford, as it would damage their operation, but a single reservoir was authorised in 1904.The river channels are designated as "heavily modified" from their natural state by the Environment Agency, who measure the water quality.