Riverside planting, recreating natural channels and reconnecting groundwater links could help offset high thermal extremes caused by climate change in rivers, a new study recommends.
The study led by the University of Birmingham, along with the University of Nottingham and the Scottish Government’s Marine Directorate, highlights that intense shortwave radiation during hot and dry periods is likely to be the biggest factor in high river water temperatures.
This factor, combined with declining water levels and volumes, and slower flow velocities during droughts, will warm up rivers more quickly, it says.
However, cooling effects from groundwater inputs, channel shading and evaporation can offset high temperatures in certain circumstances, the study published in the scientific journal Hydrological Processes says.
The scientists have identified three primary mechanisms that drive river water temperature increases during droughts.
These are: atmospheric energy inputs; physical habitat influences (shading and river channel shapes controlling flow); and the contributions of different water sources – groundwater tends to cool rivers in summer.
“Rising river water temperatures can have significant and often detrimental implications for aquatic life, impacting both individual species and entire ecosystems,” the study’s co-author, David Hannah, professor of hydrology and UNESCO chair in water sciences at the University of Birmingham, said.
“Drought conditions often coincide with high atmospheric temperatures, and such trends will become more intense and frequent with climate change - with major implications for river water temperatures due to the combination of intense solar radiation and lower (and slower) water flows,” he said.
“However, certain management interventions such as riverside planting and river restoration initiatives – including recreating natural channel forms and reconnecting groundwaters – could help to offset high thermal extremes during droughts if interventions are well targeted,” he said.
Lead author Dr James White, from the University of Birmingham, said the work “ highlights critical future research questions that will help us to better model river water temperature dynamics during droughts – helping river managers to work out how thermal extremes could be better managed through mitigation and adaptation strategies”.
The research was supported by the British Environment Agency, and the paper is here
