Environment Agency officers have helped plant more than 500 new trees along the River Gipping to help restore it.
The aim of the partnership project with Suffolk Wildlife Trust is to improve river habitat diversity and the water quality.
The work is needed to meet water quality requirements and to help the river adapt to the changing climate.
This winter officers planted 528 trees over a five-kilometre stretch along the river.
Four kilometres were downstream of Needham Market and more than one kilometre on the Somersham Watercourse at Little Blakenham.
The trees will provide increased shading for the river, which will benefit the ecology.
Naomi Boyle, Environment Agency Project Manager for the project, said: “Shading will help lessen the effects of our changing climate by helping to keep the river cool in summer.
“This has big benefits for fish, invertebrate populations and water voles.
“It is also expected that shading will help control vigorous plant growth within the river channels at some locations reducing the need to carry out costly in channel vegetation clearance.
“In time the tree roots will help to stabilise the river banks leading to less sediment entering the water which will help improve water quality.
“The roots will also provide vital habitats for fish as will low hanging branches trailing into the watercourse.”