Drought Conditions: The Risks Posed By Higher River Temperatures
Last year saw the driest July since 1935, with drought conditions declared for much of the country off the back of soaring temperatures and below-average rainfall for every month except for February.
These drought conditions persisted well into this year, with the National Drought Group (NDG) warning back in February that England was just “one hot dry spell away from severe drought conditions”.
Fast forward a few months and record-breaking heatwave-level temperatures were seen in June, prompting the NDG to take action to ensure water supplies remained resilient in the face of increasing pressure.
How do droughts happen?
Drought conditions can arise when long periods of very low rainfall create water shortages, either localised or nationwide. Without typical monthly rainfall levels and when faced with extreme temperatures, reserve water supplies start to dwindle, with plants and crops dying as a result. If this period of dry weather continues, it can turn into drought.
As temperatures continue to rise in the face of climate change, it’s likely that we’ll face extreme weather events like heatwaves more often, increasing the chances of drought conditions as a result.
In line with extremes of heat and more frequent droughts, reduced water flows and rising atmospheric temperatures look set to heat up rivers around the world, with a new study suggesting that this will create some serious challenges for ecosystems, aquatic life and human society.
Carried out by the University of Birmingham, the University of Nottingham and the Scottish Government’s Marine Directorate, the study found that intense shortwave radiation during periods of hot dry weather is likely to be the biggest contributing factor to high river water temperatures.
Where these waterways are concerned, water temperature is one of the most important controls for all physical, chemical and biological processes.
Fish, for example, are unable to regulate their own body temperature so rely on the rivers to help them in this regard. Furthermore, warm water contains less oxygen than cool water, so if the temperature increases beyond a certain point, fish populations will be affected.
It’s not just fish that will be affected, however, and river temperature is also essential for maintaining human health, as well as supporting industrial, domestic and recreational uses.
There are three primary mechanisms that have been identified as the main drivers for river water temperature hikes during periods of drought: atmospheric energy inputs, contributions from different water sources and physical habitat influences (such as the shape of the river channel, which controls flow).
When combined with slower flow velocities and declining water levels and volumes, the intense shortwave radiation we see during hot, dry weather warms water up more quickly. However, high temperatures can be offset in some circumstances by the likes of groundwater inputs, evaporation and channel shading, which can have cooling effects.
It was concluded that more holistic approaches to river restoration are required catchment-wide to determine how high extremes of water temperature can be offset, while delivering other benefits for the environment and local biodiversity.
A call was also issued by the study authors to examine how the processes across the three identified mechanisms interact, which will help to inform estimations of where and when these extremes are likely to occur during droughts.
Commenting on the findings, David Hannah – co-author of the report and professor of hydrology and UNESCO chair in water sciences at Birmingham University – said: “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.”
Drought and water scarcity
The state of the UK’s rivers are often headline news these days, with drought and pollution wreaking havoc around the country and water quality taking a serious dive as a result.
Drought does naturally occur when temperatures climb and rainfall drops, but freshwater resources are now being placed under significant strain because of climate change and population growth, with water stress and scarcity an ever-present reality for many around the world right now.
Water abstraction from rivers and the underground aquifers that keep them full takes place at an increasingly unsustainable rate, with demand outstripping supply in many parts of the country. What’s more, changes that are now being seen in rainfall patterns mean that many rivers and waterways will start seeing a noticeable decline in flow.
When there’s less water flowing through, pollution concentrations will increase, driving up temperatures even more and having a significant impact on freshwater ecosystems.
For businesses and the general public, one of the best ways to go about protecting the nation’s rivers is to reduce water usage and consumption. Water suppliers often abstract water straight from the river source, water that is then treated before being used domestically and commercially.
If less water is used, abstraction rates can be reduced, helping to shore up supplies, build resilience into the water network and protect the natural environment at the same time.
Businesses, in particular, can make a big impact when it comes to protecting freshwater resources. Gaining an in-depth understanding of your water footprint is a great first place to begin, accounting for all the water you use across your entire operational base and right across the entire supply chain.
If you’d like to find out how you could go about saving water (and saving money!), get in touch with the SwitchWaterSupplier.com team today to see how we can help.