Study examines factors influencing amount of carbon in large US rivers
According to a new study conducted by a team of researchers at the U.S. Geological Survey (USGS), the movement of carbon in the Colorado and Missouri Rivers follows different patterns but is governed by a combination of natural factors and human activities.
The research, published in the Journal of Geophysical Research - Biogeosciences, reveals that the difference is noticeable in downstream patterns. In the Missouri River, levels of carbon steadily rose downstream until it joined the Mississippi River, whereas the amount of carbon decreased in the lower Colorado River. Scientists believe that the difference could be put down to varying degrees of precipitation and evaporation, as well as to the variety of human activities taking place at the Colorado River that divert significant amounts of water.
Looking at headwater and upstream sites on the rivers, the study found that the level of carbon depended on seasonal precipitation and variations in temperature. In upstream waters the variation in carbon concentration is larger, due to fluctuations in the seasonal input of organic materials found in both rivers, the study said. As water moves downstream, reservoirs and dams interfere with the connection between watersheds and the river and makes carbon levels less susceptible to variation and more independent of temperature and precipitation changes.
The study gives an important insight into aquatic carbon cycling in water-stressed areas, where research on freshwater carbon cycling has been less common. It aims to provide an understanding of the importance of freshwater ecosystems as part of the broader carbon cycle, USGS noted in a press release.