The River Ash is one of about 260 chalk rivers in the world, and the restoration project has included the creation of new gravel beds.
The trust said brown trout were already spawning on them.
In addition, monitoring carried out before and after the restoration found an increase in river invertebrates, including mayflies and stoneflies.
Sarah Perry, rivers recovery manager at the trust said: “Natural rivers, connected floodplains and healthy wetlands support biodiversity by providing places for wildlife to feed and breed.
“They also help water move through the landscape and can contribute to resilience against both flooding and drought.
“The scarce blue-tailed damselfly sightings along the River Ash offer a hopeful example of what these efforts can achieve.”
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