Birmingham [UK], October 21 : According to a recent study, our rivers are heating up due to decreased water flows and rising atmospheric temperatures, which are posing serious problems for society, ecosystems, and aquatic life.
The study was published in the journal, 'Hydrological Processes'.
A key regulator of all the physical, chemical, and biological activities in rivers is water temperature. For species like fish who are unable to control their own body temperatures, it is especially crucial. The health of individuals using rivers for industrial, household, and recreational purposes depends on their temperature.
Three main factorsatmospheric energy inputs, physical habitat influences (such as shading and river channel shapes controlling flow), and the contributions of various water sourceshave been identified by scientists as being responsible for river water temperature increases during droughts. In the summer, groundwater tends to cool rivers.
The study showed that the main contributor to elevated river water temperatures is probably intense shortwave radiation during hot and dry periods.
In times of drought, the combination of this with dropping water levels and volumes as well as reduced flow rates will cause the water to warm up more quickly. The authors stress that in some cases, cooling effects from evaporation, channel shadowing, and groundwater inputs can balance out high temperatures.
Co-author David Hannah, Professor of Hydrology and UNESCO Chair in Water Sciences at the University of Birmingham, commented, "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 - including recreating natural channel forms and reconnecting groundwaters - could help to offset high thermal extremes during droughts if interventions are well targeted."
The researchers noted that more holistic, catchment-wide approaches to river restoration are required that consider how high river water temperature extremes can be offset while delivering other environmental and ecological benefits. The study authors call for new scientific approaches examining how the processes operating across the three mechanisms they have identified interact - helping to better inform models capable of estimating where and when high river thermal extremes are likely to occur during droughts.
Lead author Dr James White, from the University of Birmingham, commented: "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."
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