Is the Rother safe for swimming?

Our Freshwater Watch (FWW) Group now has seven members and will, very soon, cover survey sites from a stone’s throw from Petersfield all the way into Midhurst. It has also brought us new members as it has proved to be a topic close to many people’s hearts. FWW is a global scheme organised by Earthwatch. Read more about it here.

Having now carried out several river surveys and trained others to do the same I am impressed at how well designed the scheme is, allowing the non-specialist to confidently record a wide range of information about the river. Any queries that I had since my initial training I found covered in their 35 page manual, or I have emailed them about and received friendly and full responses.

Learning to interpret our results is a separate learning curve but at all of our survey sites the river has had good clarity (very low turbidity, in the jargon!), plenty of plants growing well both within and around it, no algae, lots of damselflies, very little litter, no foam or slurry or oily sheen. Phosphate and Nitrate levels have been a little variable giving individual surveys results that are between ‘very good ecological status’ and ‘moderate ecological status’. They are at a level that indicates further monitoring would be useful.  It will be interesting to see how these readings change over the course of a year, or following different weather conditions (particularly droughts or significant rain). It is a pity we were not up and running when slurry was clearly visible just east of Rogate, as those readings might have been particularly interesting.

Knowing what to make of the Phosphate and Nitrate levels we have been recording on our Freshwater Watch (FWW) surveys has led to me extending my vocabulary and getting my head around quite a few new TLAs (three letter acronyms!) such as NVZ (Nitrate Vulnerable Zone), WFD (Water Framework Directive), EDM (Event Duration Monitoring) and lots of STWs (Sewage Treatment Works). Apparently, ‘eutrophication’ means when there are too many nutrients, predominantly Phosphorous (P) and Nitrogen (N) in the water which can result in excessive growth of plants and algae. That extra growth can limit light penetration and can have a negative impact on the local ecology. Eutrophication also increases the cost of abstraction and treatment of drinking water and can have a negative impact on recreational use of waterways and on angling.

On a FWW survey we measure Phosphorous and Nitrogen by carrying out a chemical test on the river water for Phosphates and Nitrates.  Inevitably these riverside tests cannot be as accurate as tests carried out in a laboratory, but they are indicative of the levels and can flag up a need for a river to be further investigated.

It is still very early days for this project and we do not have enough results yet to be able to draw any firm conclusions, but it is interesting that, so far, Phosphate levels are significantly lower near Petersfield, but higher from Haben Bridge and onwards.  We will need to see if this finding is replicated in future months. We have had no particularly high phosphate readings but they are high enough to justify our regular surveying as we develop our understanding of how healthy our river is.  By comparison the Nitrate levels have proved to be fairly consistent, but once again, at a level that warrants ongoing monitoring. Once our surveys have passed a quality control process they will be visible to all here.

According to the Rivers Trusts map, there are three places where a water company has a permit to discharge into the River Rother or one of its tributaries between Petersfield and Midhurst, one near Petersfield, then at Rogate, then at Trotton. The first two have recorded multiple storm overflow spills (a total of 330 and 323 hours of spilling respectively during 2021). The fact that the Trotton one has no such records could indeed mean that there have been no spills there, or it could be that there is no Event Duration Monitor (EDM) fitted there as yet.  Water companies have pledged to fit EDMs to all pipes that discharge into waterways by 2023, so we should have better insight after that.

Understanding Phosphorous Levels

This section on Phosphorous is based on information taken from the Environment Agency’s publication ‘Phosphorus and freshwater eutrophication: challenges for the water environment’ October 2021.

‘Phosphorus is the most common cause of water quality failures under the WFD in England because it is the number one reason for water bodies not achieving good ecological status’ (page 5). The Water Framework Directive (WFD) sets standards for levels of Phosphate and Nitrate which are considered to result in a good ecological status. Some 55% of assessed river water bodies fail the current WFD Phosphorous standard (page 5).  This standard is not a simple figure that can then be easily compared to the figures we are recording on our River Rother surveys, it works on annual mean concentrations, allowing for other variables such as alkalinity and even altitude. When we upload our data to the database we get instant, automatic feedback which has so far told us our results indicate either ‘moderate ecological status’ or ‘very good ecological status’ at different points long the river, on different days.

There are 2 main sources of Phosphorous in our rivers, sewage and agricultural run-off. Some of the Phosphorous in our rivers coming from agriculture is ‘legacy’ Phosphorous from when agricultural fertilisers were used particularly liberally and  included significantly higher amounts of Phosphorous which was in the 1980s so, even if no more fertiliser were added to that land there would still be Phosphorous leaching out for years, if not decades, to come. Historically detergents were also a major source of Phosphorous in our waterways.

A shocking statement from the above document says, ‘Over 40% of UK soils are over-fertilised, with soil P levels above the agronomic optimum’ (page 7).  ‘The new environmental land management scheme (ELMS), now proposed, will be an important future mechanism for reducing diffuse pollution from agriculture’ (page 8)

However, the dominant source of Phosphorous in rivers is from sewage effluent, around 60-80% (page 13). The amount of Phosphorous in sewage could be reduced by people eating less meat (pp 33, 34) but I was left unsure if this related directly to meat consumption or was caused by fertilisers used in the growing of crops that would then be fed to animals for meat production.  Reducing the amount of untreated sewage entering our rivers remains paramount.

Understanding Nitrogen Levels

This interactive map shows that the River Rother forms a dividing line with the area north of it classified as a Nitrate Vulnerable Zone (NVZ), but the area south of it, as far as the Downs, not being so.  The same map shows that all of the Rother valley between Petersfield and Midhurst is a drinking water safeguard zone wrt surface water. I presume this relates to the fact that drinking water is extracted from the river further down, near its confluence with the River Arun.

[If reading up about Nitrate levels in rivers it is worth noting that there are 2 different units commonly used. 1 mg/L NO3-N (the unit used in FWW surveys) being the same concentration as 4.4mg/L NO3.]

Information in the rest of this section is taken from the Environment Agency report ‘Nitrates: challenges for the water environment’ October 2021.

High Nitrate levels are an issue due to eutrophiciation, impact on ecosystems and the need to keep levels in drinking water below the standard set by the World Health Organisation (p5). Although our interest is in river water rather than groundwater, it is worth noting that ‘Groundwater is a major source of drinking water supply and nearly 30% of groundwater used for that purpose in England must now be blended, treated, or replaced in order to meet tap water nitrate standards’ (p3).  Treating drinking water to remove Nitrates is expensive, the cost of which would inevitably be borne by us as the consumers.

The story for Nitrates in rivers bears many similarities to that of Phosphates. Once again it is agriculture and sewage effluent that are the main sources but wrt to Nitrates agriculture is responsible for arounds 70% and sewage around 25-30% (p3) with the increase in use of fertilisers in the 1980s once again being responsible for a marked increase in Nitrates in water bodies (pp 4,5). Concentrations of Nitrates tend to be higher in areas like ours which are drier and with more arable farming than in the north (p3).

55% of England is designated as a Nitrate Vulnerable Zone (p4). ‘Areas of land that drain into waters that are polluted or threatened by nitrate, and which contribute to nitrate pollution, are currently designated as Nitrate Vulnerable Zones (NVZs) [. . . ] Farmers with land in these areas must follow statutory management requirements to tackle nitrate loss’ (p 19).  Inadequate slurry storage can be an issue as it can act to prevent the efficient and timely use of slurries (p 20).

Since the year 2000 Nitrate levels had been gently declining but in recent years a slight increase has been seen (p8). The previous steady decline is thought to likely be due to reduced levels of use of Nitrogen based fertiliser and reduced livestock levels (p15). ‘However, recent changes in farming practice and the growth of anaerobic digestion have meant that more materials are now being spread on land, some of which would previously have gone to landfill.’ (p 17)

Climate change is predicted to exacerbate Nitrate issues due to more frequent storms increasing Nitrate moving from land to water ways and hotter summers will increase the amount of eutrophication.

The governments proposed Environmental Land Management Scheme (ELMS) has the potential to act to reduce Nitrate levels as would increased use of cover crops but this document also proposes ‘applying N below the economic rate’ (p22) which begs the question of how such economic loses would be compensated.

Besides ELMS there are other schemes, either voluntary or incentive programmes, which act to reduce Nitrate input from agriculture, such as Environmental Stewardship Schemes, farm Nutrient Management Plans and Catchment Sensitive Farming (CSF).  ‘62% of farm holdings in England have implemented at least half of the CSF farm specific recommendations’ (p22).

 There are no quick fixes for either Nitrates or Phosphates in rivers from agricultural sources but more informed agricultural practices should have an impact over time.  The same chemicals entering our waterways from sewage treatment plants could be significantly reduced by reducing (ideally removing) the incidence of raw sewage entering our rivers but inevitably population increase will lead to more sewage.

ERA’s FWW Group’s current focus is to amass a bank of data and develop our understanding of what that data means.  This will include developing links with other organisations, such as Arun and Rother River Trust, the Environment Agency,  Southern Water and others. The project has running costs of around £250 per annum which must also be planned for. (Donations always welcome!)

The good news is that our lovely River Rother is not doing too badly at the time of writing – long may this state of affairs continue!