Keeping Rivers Cool is a four year (2012-2016) Environment Agency led climate change adaptation project focused on using trees to keep rivers cool. This approach aims to address the pressures of climate change on freshwater ecosystems. The targeted catchments have been the Wye, Hampshire Avon, Tyne, Ribble, Frome and the Tywi.
Evidence indicates that some salmon and trout populations in England and Wales are under stress from climate change, with some rivers reaching above the lethal limit for salmonids in recent hot, dry summers. It has been shown that riparian trees can help reduce local stream temperatures on hot summer days. Summer mean and maximum water temperatures are on average 2-3ºC lower in shaded versus open rivers.
The Environment Agency has been working with charitable trusts such as the Woodland Trust and the Rivers Trusts to plant trees and install riparian fencing in appropriate sites. The approach aims to create a mosaic of tree cover along riparian banks, rather than a blanket cover which could have a negative impact on other aspects of river ecology.
To support the identification of key areas to target and increase riparian shade, LiDAR (Light Detection And Ranging) data for England and Wales is used to produce accurate maps of riparian tree distribution, indicating where the gaps are. The measure of incoming solar radiation indicates the likely amount of shade created by the landscape as well as shading caused by existing vegetation.
It is recognised that riparian shading is not a stand-alone measure to managing warming in rivers, but it is a low-risk reversible action and a good start to keeping rivers cool.