US Geological Survey / by Daren M. Carlisle, et al.
[From Press Release] A new USGS report describes how the health of our Nation’s streams is being degraded by streamflow modifications and elevated levels of nutrients and pesticides.
The national assessment of stream health was unprecedented in the breadth of the measurements—including assessments of multiple biological communities as well as streamflow modifications and measurements of over 100 chemical constituents in water and streambed sediments…
To assess ecological health, USGS scientists examined the relationship of the condition of three biological communities (algae, macroinvertebrates, and fish) to man-made changes in streamflow characteristics and water quality. The ability of a stream to support these biological communities is a direct measure of stream health.
Stream health was reduced at the vast majority of streams assessed in agricultural and urban areas. In these areas, at least one of the three aquatic communities was altered at 83 percent of the streams assessed.
In contrast, nearly one in five streams in agricultural and urban areas was in relatively good health, signaling that it is possible to maintain stream health in watersheds with substantial land and water-use development…