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The Ahr river valley once looked like
this – a changing natural landscape,

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home to many different
plant and animal species.

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Then floods in July of 2021 severely 
damaged the ecosystem here.

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This team of four young scientists
visits the river regularly.

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They're all part of a 
project involving universities

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in the German cities 
of Trier and Koblenz.

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The researchers are
studying the bed of the Ahr.

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The aquatic organisms living in 
and on it say a lot about how well

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the ecosystem is recovering from
the flood and its aftermath.

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"We gather samples with
what's called kick sampling.

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You plant the scoop net in a relatively 
stable position in the ground,

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then stomp on the
bed really hard for a while.

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All the animals – which live mainly on, 
in or under the stones – are swept up.

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That's where the current in
the water comes in handy.

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It flushes them right into the net."

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The team usually catches small invertebrates 
like worms, snails and insect larvae.

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Before the flood, the Ahr was
known for its rich biodiversity.

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"Immediately after the
flood it collapsed completely.

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Many species disappeared, and 
biodiversity hasn't bounced back fully.

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We're not seeing that yet.

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But that's what this project is about –
monitoring how things develop."

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To find out which habitats are
recovering and how well,

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the team takes samples at 
a number of points in the river.

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They also monitor water quality,
which is closely linked to the

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well-being of the river's fauna.

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Nutrients that promote the
growth of algae are one parameter.

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They leaked from wastewater systems
heavily damaged by the flooding.

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"Untreated wastewater was
discharged into the river.

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And that wastewater
contained a lot of nutrients.

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We now want to investigate in 
more detail how things will develop

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over the next few years."

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Those investigations are carried out 
in a lab at the University of Koblenz.

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Here, the team calculates
levels of compounds like

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 phosphates, nitrates 
and ammonium.

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If a water sample turns dark blue, 
it contains too many of them.

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The project is scheduled to run for six years,

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and is meant to provide scientific 
support for any restoration measures.

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But it's still early days.

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The team head to the river every two
weeks to check its water quality.

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Any changes are
thus registered quickly.

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"For example, when earthworks 
are dug out to build a new bridge,

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it can quickly cloud the water, or 
set free nutrients or pollutants

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 that may have accumulated 
there during the flood.

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Then the work releases
and mobilizes them again."

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High levels of nutrients 
can harm aquatic life-forms.

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Because when lots of algae grows 
and subsequently decomposes,

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oxygen and water levels drop.

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And that has consequences for
the animals that inhabit the river.

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In a lab at the Trier University 
of  Applied Sciences,

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the young researchers 
therefore also analyze

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how many invertebrate microorganisms 
are found in the samples.

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Under the microscope, the team 
sorts the animals into different groups

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and determines species –
like this mayfly larva.

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"Individual species are
highly adapted to their environment.

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This means that when we find certain
species, that indicates particularly

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good water quality, for example.
Because they need oxygen-rich water."

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The initial results show that some 
species are already repopulating the Ahr.

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In the future, recommendations will
also be made on how recovery and

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conservation efforts can best be
streamlined and optimized –

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with one eye on other 
extreme weather events.

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"The project also looks at construction work 
from a biological and ecological perspective.

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This means, for instance, that if the
weather turns very dry in the future,

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plans should incorporate a residual 
channel where water always flows,

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where species that depend 
on water could survive."

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And conservation plans for other rivers will 
also benefit from the findings on the Ahr.

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