Ripple Effect is working with local
volunteers to monitor water quality and pollution across 13–15 sites
along three, 10km stretches of the Upper River Medway, including the
Grom and Eridge Stream. You can explore all our monitoring locations and
data on our interactive map -
just click on a site and scroll to see what we’ve found.
Each month, our citizen scientists test for key indicators of water health: ammonia, phosphate, conductivity, and temperature. We aim for surveys to be carried out on the same Monday between 10am and 2pm, helping us capture consistent data and spot pollution incidents.
We also use the Riverfly
method to assess ecological health. Volunteers carry out a “kick sample”
in the riverbed, identifying and counting eight groups of freshwater
invertebrates. These creatures vary in their tolerance to pollution, so
their presence or absence helps us calculate a water quality score.
This figure shows the ammonia concentration (ppm) recorded at
each monitoring site this month.
To interpret the figure:
This figure shows the phosphate concentration (ppm) recorded
at each monitoring site this month.
To interpret the figure:
This figure shows the conductivity (μS/cm) recorded at each
monitoring site this month.
To interpret the figure:
This figure shows the ARMI (Anglers’ Riverfly Monitoring
Initiative) score for each site surveyed this month. The score is based
on the number of freshwater invertebrates found from eight indicator
groups, which vary in their tolerance to pollution. It provides a useful
snapshot of ecological water quality.
Sites that are monitored regularly (at least 10 times over 12 months) are assigned a trigger level. If a site’s ARMI score falls below this threshold, it may indicate a problem. To confirm this, a follow-up survey must be carried out within 48 hours. If the schore is verified, the Environment Agency (EA) must be notified so an investigation can be launched.
For reference:
This figure shows the total number of invertebrates recorded at each monitoring site, broken down by the eight Riverfly indicator groups (or ‘taxa’). Each coloured segment in the stacked bars represents the abundance of a different group, helping us understand not just how many invertebrates were found, but which types.
These groups vary in their tolerance to pollution, so their relative abundance gives us insight into the ecological health of each site. A diverse mix with pollution-sensitive groups suggests good water quality, while dominance by tolerant groups may indicate stress or pollution.
Use this figure to:
Conductivity is a measure of water quality and
is affected by the presence of dissolved solids such as those from
sewage effluent. Conductivity naturally varies between 150 and 500
μs/cm; above this range could indicate water not suitable for certain
species. A sudden change may indicate the onset of a polluting
discharge.
Phosphate is a common constituent
of fertilisers, manure, industrial effluent, and organic wastes in
sewage. In excess it can cause a reduction in dissolved oxygen in
rivers, caused by excessive algal growth. Without dissolved oxygen in
the water, aquatic animals cannot survive.
Ammonia is an important natural resource in nature, but
high levels can be toxic, causing lower reproduction and growth or
death. It can be discharged into rivers from a range of sources
including agricultural fertilisers and sewage effluent. It’s important
to measure temperature at same time as this can impact the levels found
in freshwater. Concentrations in unpolluted rivers range from 0.2 to 1.0
ppm. Tests with a reading of 3.0 ppm or above should be repeated to
confirm, then reported to the EA.
Riverfly ARMI scores are determined by
collecting the animals from the river in a net following a standardised
protocol, identifying 8 specific groups of animals (insect larvae and
freshwater shrimp), and counting how many there are in each group. The
score has been validated as a reliable measure to monitor changes in
water health.