River Water Quality

The quality of water in a chalk stream is one of it’s key attributes. Rainwater that falls in the catchment percolates through the chalk, emerging through fissures to create springs of pure, naturally filtered crystal clearwater of a constant temperature. How far up the catchment the springs will run is driven by the level of groundwater in the aquifer.

But of course, not all the water in our chalk streams is derived from spring sources. When it rains, surface water that can’t be absorbed into the ground will progress over the surface towards valley bottoms, either naturally or through drainage. Along the way that water can pick up chemicals and pollutants from the land, either agricultural or urban in origin and these all contribute to a cocktail mix of organic and synthetic chemicals entering the natural environment that gradually builds up within the chalk stream eco-system

Another source of water in our rivers is that which is discharged from sewage treatment works directly into the river. This water has been treated (in most cases) to the required standards, which are controlled by licence and monitored by the Environment Agency. Occasionally spills of raw sewage directly into the river do happen. To what extent this occurs and its legality is the subject of great public attention (Panorama, The Guardian, The Times) through the campaigning work of many, including pioneering work by WINDRUSH Wasp that introduces machine learning to the analysis of Water Company performance.

For the last couple of years the The Rivers Trust have compiled publicly available data on sewage spills, published through the ‘Is my river fit to play in?’ interactive site (2019 version, 2020 version). The figures for our catchment showing an increase in raw sewage discharges from Thames Water’s Sewage Treatment Works of over 300% across the catchment as a whole, which with increasing demands on the infrastructure through further development, are likely continue and increase.

A further addition was the Chalk Stream Restoration Strategy which was published last autumn. Within its appendices are tables of the country’s chalk streams by catchment, giving a high level of overview of river quality and the sewage treatment works that flow into them.

The illustration above shows the table for the Thames/Lee catchment, broken down into the individual sub catchments, ours being Rib upper, Rib lower and Quin. The letter designation indicates the type of chalk stream, ours being A/D – a combination of …..
Group A: classic slope-face chalk streams. These are streams that rise directly from the chalk, flow over chalk and then in some cases – usually in their lower reaches – over younger tertiary (sand and clay) deposits. This group would include the majority of the Hampshire-basin streams and the majority of those that flow into the Thames basin. Most of the iconic chalk- streams like the Itchen or Test or Kennet are in this group. Group A can be sub-divided into slope-face streams that flow from and largely across chalk (eg Chess) and those that rise from chalk but mostly flow over tertiary outcrops (eg Wandle).
as well as …..
Group D: Pleistocene ice-impacted chalk streams can fall into any one of the above categories but these streams rise from chalk that was directly impacted by major glacial action during the Pleistocene. This group would include the northern Chiltern streams and the East Anglian, Lincolnshire and Yorkshire streams. Group D could be further subdivided into streams that flow from chalk over glacial outwash deposits (the Wensum) and those that flow from chalk onto older (pre-glacial) river deposits, such as the pre-glacial Bytham River which flowed eastwards from the Midlands across Norfolk and emptied into the North Sea north of Lowestoft: the streams that lie between the Chilterns and Norfolk.

The final column lists, to the best of author’s (Charles Rangeley-Wilson) knowledge’, the sewage treatment works located within the sub-catchments and whether they remove phosphates as part of their treatment process. Unfortunately this indicates that apparently only Standon is certain to currently employ this treatment within our catchment.

Alongside these new resources is the Environment Agency Catchment Data Explorer which gives access to testing and analysis data on a wide range of measures. Links to the individual pages for our catchment can be found on our Links page here).

The quality of the water in the River Rib and River Quin remains a significant, continuing and deteriorating problem, alongside the abstraction of the groundwater that feeds them. Friends of the Rib & Quin will continue to campaign on this issue alongside employing it’s own water quality monitoring to add further data and weight to the case for improved water infrastructure in parallel to development and measures to directly protect our precious chalk streams.