Drinking-Water Warming Risks Due to Temperature Rise

An article in Science Daily says that Germany’s Rappbode reservoir, the largest drinking reservoir in Germany, is at risk of warming due to climate change, which could present new water management challenges.

A global temperature increase of 4 to 6 degrees Celsius by 2100 will also increase water temperature, creating new challenges to reservoir water management.

A group of researchers led by Dr. Karsten Rinke examines the possible implications and challenges of this reservoir’s rising temperature. They observed that in the summer, the reservoir’s water surface has already increased by about 4 degrees and have demonstrated that this trend will continue in the coming years.

The researchers based their projections on the three representative concentration pathways (RCPs):  RCP 2.6, RCP 6, and RCP 8.5. 

These RCPs show various trajectories of GHG concentrations in the atmosphere, which the IPCC adopted to describe and model different climate futures depending on whether emissions are abated or will continue to increase in the coming years and decades.

The latter, RCP 8.5, a worst-case scenario in which emissions continue to rise throughout the 21^st century, will increase the water temperature by .5 degrees every decade or about 4 degrees by 2100.  

However, drinking water is usually drawn out from the bottom of the reservoir, which is 50 meters deep. Temperatures at that level could reach up to 8 degrees.

The consequences of increased water temperatures would speed up “biological metabolic processes,” which will increase oxygen consumption, but warmer water cannot absorb as much oxygen.

“Potential consequences include intensified dissolution of nutrients and dissolved metals from the sediment, algae growth and an increase in blue-green algae”

According to the article, increased temperature will also increase the risk of contamination from the substances released from sediments and significant bacterial growth.

When this happens, water treatment efforts will likely increase, resulting in higher demands for treatment capacity. Operators are not helpless to deal with rising water temperatures, though; they can use downstream discharge to cool down the surface or near-surface water.

Although operators have solutions to various water challenges, when the air temperature increases to 6 degrees, it will be impossible to prevent the reservoir’s deep waters from heating up.

In addition, other consequences of climate change, like dry seasons, present another challenge to reservoir management.

The article says keeping deep waters in the reservoir cold will be in the best interest of drinking water suppliers and reservoir management operators. To do this, ambitious climate policies that limit global warming will be necessary.

To read the journal, click the link below:

PHOTO CREDIT: By Bermicourt – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=17250567