14 DAY TRIAL // A new investigation conducted by the US Geological Survey has demonstrated that the amount of water flowing through rivers in the United States has experienced massive alterations for the worse over the past few decades.
The research is important because it highlights land and water management practices as the main factors responsible for this decline, which affects about 90 percent of all waters in the country.
Additionally, experts say that flow alterations is the primary reason why native river species are lost, and why the ecosystems around rivers degrade as a whole.
The USGS researchers say that there are many management schemes that affect water quality, including, but not limited to reservoirs, diversions, subsurface tile drains, groundwater withdrawals, wastewater inputs, and impervious surfaces, such as parking lots, sidewalks and roads.
“This USGS assessment provides the most geographically extensive analysis to date of stream flow alteration,” explains the Associate Director for Water at the Survey, Bill Werkheiser.
“Findings show the pervasiveness of stream flow alteration resulting from land and water management, the significant impact of altered stream flow on aquatic organisms, and the importance of considering this factor for sustaining and restoring the health of the nation's streams and ecosystems,” he adds.
One good example of how human activities jeopardize native species is the gradual disappearance of trout from fast-running, gravel-paved rivers, and the emergence of non-desirable species such as carp.
The new research also showed that species accustomed to fast-flowing water are gradually being replaced by fish that can more commonly be found in lakes and ponds rather than rivers.
“Altered river flows lead to the loss of native fish and invertebrate species whose survival and reproduction are tightly linked to specific flow conditions, explains USGS ecologist Daren Carlisle.
“These consequences can also affect water quality, recreational opportunities and the maintenance of sport fish populations,” adds the expert, who was the lead scientist on the investigation.
Scientists now believe that water management schemes should be thought through more carefully, so that they take into account all possible ramifications that they might have on ecosystems, biodiversity and the environment in general.
One of the primary goals of all water management schemes should be maintaining sufficiently clean and abundant waters to support fisheries and recreation opportunities.
“While this study provided the first, national assessment of flow alteration, focused studies within specific geographic regions will provide a better understanding of the ecological effects of altered stream flows, which can be more effectively applied to local water management challenges,” Carlisle concludes.