In hot water
The holy Ganges river in India is covered with floating trash and ash from corpses cremated on its banks. Thousands of kilometers away in Malaysia, the Sungai Kim Kim river, tainted by chemical waste, poisons children with its noxious fumes.
Such pollution is visible and visceral, but humans also directly pollute waterways in hidden and equally insidious ways—like discharging heated water that comes from thermal power plants into the environment. Over time, such thermal pollution tips the balance of our underwater ecosystems as fish and amphibians migrate to cooler regions and microbes flourish in warmer water, using up the dissolved oxygen.
Now, a team of researchers from the Chinese Academy of Sciences has come up with a model to quantify the impact such anthropogenic—that is, human-induced—heat emissions have on river temperatures worldwide. The scientists incorporated a large-scale scheme for computing river water temperature into a river routing model coupled to a global land surface model, allowing them to simulate river flows and show changes in water temperatures over the past 30 years.
Running the model on the Tianhe-1 supercomputer, the study found that water temperatures in tropical rivers increased the most, about 0.5°C per decade from 1981 to 2010. In Asia, power plants alone increased local river temperatures by about 60 percent.
“Climate change warmed river water, and anthropogenic heat emission further made the temperature increase,” the researchers concluded. “The rivers, even climate, are gradually being dominated by humans.”
