Reduced water flows and rising atmospheric temperatures on rivers is of utmost concern and the changes are posing significant challenges to aquatic life, ecosystems, and society as a whole, according to a recent study. The study published in the journal ‘Hydrological Processes’ emphasize the far-reaching consequences of this environmental shift, affecting not only aquatic organisms but also human health and various activities that rely on river.
FOCUS OF THE STUDY
River water temperature holds a crucial role in a range of physical, chemical, and biological processes. It is especially critical for fish, which lack the ability to self-regulate their body temperatures.
Beyond its ecological significance, river temperature is also vital for human well-being, industrial operations, household needs, and recreational pursuits. The study identifies three key mechanisms driving the increase in river water temperatures during DROUGHTS: atmospheric energy inputs, physical habitat factors like shading and river channel shapes influencing flow, and the impact of various WATER sources. Groundwater, for instance, tends to cool rivers during the summer.
The study underscores that during hot and dry periods, intense shortwave radiation is likely the most substantial contributor to elevated river water temperatures. Coupled with decreasing water levels and volumes, as well as slower flow rates during droughts, rivers warm more rapidly. Nonetheless, the study’s authors stress that cooling effects from groundwater inputs, channel shading, and evaporation can mitigate high temperatures in specific circumstances.
Co-author David Hannah, Professor of Hydrology and UNESCO Chair in Water Sciences at the University of Birmingham, warns, “Rising river water temperatures can have significant and often detrimental implications for aquatic life, impacting both individual species and entire ecosystems. 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. However, certain management interventions, such as riverside planting and river restoration initiatives, could help offset high thermal extremes during droughts if interventions are well targeted.”
NEED FOR HOLISTIC APPROACHES
The researchers advocate for more comprehensive, catchment-wide strategies for river restoration. These approaches should consider how high river water temperature extremes can be counteracted while delivering other ecological benefits. They call for new scientific methods to examine the interactions between the three mechanisms they’ve identified. This will aid in the development of models capable of estimating when and where high water thermal extremes are likely to occur during droughts, ultimately assisting water managers in mitigating and adapting to these challenges.
Lead author Dr. James White, from the University of Birmingham, highlights the study’s significance, saying, “Our 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.”