The US Environmental Protection Agency conducted a survey on quality of US rivers, indicating that majority of streams and rivers in the country are in “poor condition” for their inhabitants due to high levels of contamination and physical disturbances.
Hydrologists from the agency collected samples from around 2000 sites over the period between 2008 and 2009. They conducted various tests, establishing levels of mercury in fish flesh, faecal bacteria and nutrients from fertilizers as well as determining physical disturbances of the water bodies.
Around 40% of all rivers and streams were found to contain high levels of phosphorus, while 28% exceeded the limits for nitrate concentrations.
Phosphorus pollution has increased drastically since 2004, when nearly 53 % of all rivers were found to be in “good” condition for aquatic life. The current survey indicated that this number has now dropped to 34%.
In addition, nitrates, the main cause for algal blooms and oxygen depletion in rivers and streams, have been found to persist in the aquatic environment for decades, according to a new study.
The main reason for the increased levels of pollution, as stated by Neil Dubrovsky, a US Geological Survey hydrologist based in Sacramento, California, is the ignorance of farmers towards official guidance on fertilizer usage.