Whitewater Valley Conservation Society

Tag: River Whitewater

  • Riverfly surveys review

    WVCS has been advised by Wildfish to publicise and promote the unique and valuable archive which has been gained as a result of the capture of the 2017-2019 data as well as the most recent 2025 survey.

    Changes in the ecology  of any river the tend to take place gradually, apart from major pollution incidents, and since our data spans 9 years, we are able to recognise such changes and take steps to address them.

    When looking at changes, weather patterns are obviously important and even the differences between Spring and Autumn (in the latter any pollutants have a greater impact) need to be carefully considered.

    The 2017-2019 surveys , in some locations, show that the biometric reading  of  a river suffering from the following:

    • Nutrients
    • Chemicals
    • Sediments
    • Silt
    • Phosphates

    Clearly identification of source of these pollutants would help to address them.

    Survey data suggests there tends to be greater diversity working downstream from the source, which could of course be affected as the river flow increases naturally and of course where the R Hart join the Whitewater, just beyond Holdshott  Farm.

    The constant reference to the presence of American Crayfish, throughout the river, and their potentially detrimental impact, excavating the banks creating additional silt, munching through invertebrates on the river bed prompts the suggestion that Wildfish and WVCS should obtain suggestions or approval how to reduce the numbers in the river.

    Family :    Gammaridae.

    Shrimp are detritivores feeding on organic matter. Shrimp numbers may vary due to pollution. However, we should also keep in mind that numbers will naturally vary within a river, e.g. that an area of river with lots of leaf litter would naturally have more shrimp.  Larger individuals are thought to be more sensitive to pollution.  So if you do a sample and find all very small shrimp this can be suggestive of an issue.

    Comparison between 2017/9 and 2025

    The comparison between 2017-19 and 2025 surveys can be found here.

    Water Quality

    The most notable difference is an average decline in siltation pressure relative to River Census 2019-2019 data. So pressure looks to have reduced in 2025.

    Flow and phosphorus stress sees to have reduced.

    Minimal change to organic enrichment, slight increase in chemical impact.

    Invertebrate community

    On average, for both the total invertebrate and riverfly communities, diversity seems to be lower while abundance is higher in the 2025 data.

    Family level metrics support the view diversity is reduced in 2025 but suggests the “quality” (proportion of higher scoring taxa) has increased.

    But saying the river has ‘improved’ from our original survey is a little bold given we’ve only just restarted the monitoring. It’s important to capture the full picture before trend comparisons will be more representative of the actual situation.

    The comparison 2017/9 to 2025 should be reviewed by committee, although it is still very early days.

    In an email accompanying the comparison between 2025 and 2017-2019, WildFish further commented:

    Looking at the last graph (abundance), the almost disappearance of beetles, molluscs and caddisflies in the majority of sites is concerning. The “surprising” increase in the abundance of mayflies might be related to more tolerant families (like Baetidae) at the expense of more sensitive families (like Heptageniidae).

    The decrease in the abundance of molluscs, caddisflies and flies in Borough Court might be related to the increase in Signal crayfish numbers, as they predate on them. Reduced pea clam (Sphaeriidae sp) and NZ mud snail (P. antipodarum) numbers would drive the change in PSI scores – so the interpretation challenge is:

    1. Has sediment pressure reduced so we’re seeing fewer sediment tolerant molluscs, or

    2. Have signal crayfish munched the molluscs and that has driven the reduction in PSI impact score

    (or 3. a bit of both…)? 

    It’s a tricky one to untangle with these more simple comparisons!

    WVCS has asked if WildFish could provide us with updated biometric numbers expected in a chalk stream such as the Whitewater, to serve as comparison and reference.

  • Sewage spillages into the River Whitewater

    Sewage spillages into the River Whitewater

    Thames Water Holt Lane sewage discharge map
    Thames Water Holt Lane sewage discharge map

    Constructor damage to pipeline at Sainsbury’s site, North East Hook

    The Whitewater Valley Preservation Society (WVPS) expressed concerns when the development of 500 houses on a site in North East Hook, adjacent to the roundabout on the A30, was first considered by Hart District Council.

    The main reason for our concerns was the fact that the entire site sits on a slope (the West side of the river valley) which exposes the river not only to run-off from construction but, once built and sold, problems with the sewage generated by the site, given the lie of the land.

    During the construction phase, there were indeed incidents of pollution to the river, despite assurances from Hart, and now the entire sewage system is reliant upon pumping of effluent into tanks on the site when the Thames Water network cannot handle the flow.

    Whilst touring various pumping stations susceptible to sewage discharge recorded on the Thames Water sewage discharge map, WVPS committee member John Fleming, visited Holt Lane. Here it was apparent that flooding was occurring in the field next to the River Whitewater.   A Thames Water engineer informed Mr Fleming that builders on the Sainsbury’s site had damaged a sewage pipe carrying effluent to the storage tank on site. Thus putting all of the houses at risk of flooding with sewage effluent from the damaged pipeline.

    The only solution available to Thames Water was to divert many tankers to the location of the damaged pipe, to collect the effluent and transport it to the Holt Lane storage tanks.

    Holt Lane pumping station links into the system leading to Hartley Wintney treatment works, but at times of heavy rainfall, the system is overwhelmed and effluent must be stored until capacity is available.

    Since Holt Lane is known to need tankers to avoid having to discharge into the river, in these heavy rainfall conditions, the problem at Hook will inevitably lead to discharge into the Whitewater.

    WVPS Chairman, Candy Burnyeat, and Mr Fleming feel this is sufficiently important for members to be informed and to write to the new Chief Executives of Hart and the Environment Agency.

    WVPS believes there should be a full investigation into and report on the damage caused to the river, and actions proposed to alleviate the environmental impact on its chalk stream ecology.

    The working of the current system and its reliance on holding tanks, especially in view of the changing climate and therefore weather patterns, should be the subject of an urgent review. There is a need to increase the capacity of the wastewater system to Hartley Wintney, thereby removing the constant danger of effluent discharging into to River Whitewater.