The Environment Agency measure the water quality of the river systems in England. Each is given an overall ecological status, which may be one of five levels: high, good, moderate, poor and bad. There are several components that are used to determine this, including biological status, which looks at the quantity and varieties of invertebrates, angiosperms and fish. Chemical status, which compares the concentrations of various chemicals against known safe concentrations, is rated good or fail. The South Forty-Foot Drain is designated as "heavily modified", which means that the channels have been altered by human activity, and the criteria for this designation are defined by the Water Framework Directive. The water quality of the South Forty-Foot Drain was as follows in 2019. Reasons for the water quality being less than good include physical modification of the channel, which prevents the free movement of fish and other organisms along the waterway, discharge from sewage treatment works, and runoff from agricultural land. Like many waterways in the UK, the chemical status was rated as fail in 2019, due to the presence of polybrominated diphenyl ethers (PBDE) and mercury compounds, neither of which had previously been included in the assessment. Prior to 2019, there were issues with tributyltin compounds being discharged into the system, which also affected chemical status. See also Canals of Great Britain History of the British canal system Fens Waterways Link Bibliography References External links Canals in Lincolnshire Drainage canals in England Inland navigations