Editing Old Bedford River (section)

==Water quality==
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 [[invertebrate]]s, [[angiosperm]]s and fish. Chemical status, which compares the concentrations of various chemicals against known safe concentrations, is rated good or fail.<ref>{{cite web |url=http://environment.data.gov.uk/catchment-planning/help/glossary |website=Catchment Data Explorer |title=Glossary (see Biological quality element; Chemical status; and Ecological status) |publisher=Environment Agency |access-date=15 May 2017}}</ref>

The water quality of the Old Bedford River and River Delph, which includes the Ouse Washes, was as follows in 2019.
{| class="wikitable"
|-
! Section !! Ecological Status !! Chemical Status !! Length !! Catchment !! Channel
|-
| {{waterqual_title |desc=Old Bedford River / River Delph (inc The Hundred Foot Washes) |asset=GB205033000060 |access-date=23 December 2021}} 
| {{Waterqual mod}}
| {{waterqual_fail}} 
| {{convert|18.8|mi}}
| {{convert|8.15|sqmi}}
| artificial
|}
The water quality in the river has deteriorated since 2014, when it was rated good for ecological status. This is partly due to the fact that dissolved oxygen levels are now included in the assessment. Other reasons for the quality being less than good are low flow and physical modification of the channel, which is managed for flood protection. Both of these factors affect fish populations within the river. Like most rivers in the UK, the chemical status changed from good to fail in 2019, due to the presence of polybrominated diphenyl ethers (PBDE), perfluorooctane sulphonate (PFOS) and mercury compounds, none of which had previously been included in the assessment.<ref>{{cite web |url=https://environment.data.gov.uk/catchment-planning/help/usage#chemical-status |archive-url=https://web.archive.org/web/20240314040920/https://environment.data.gov.uk/catchment-planning/help/usage#chemical-status |archive-date=14 March 2024 |url-status=live |title=Chemical Status |publisher=Environment Agency |year=2023}}</ref>