Pollution in small dams misjudged
With more plastic than fish expected in oceans by ’50, a global attempt is being made to curb marine pollution
A first-of-its-kind research article said small dams across rivers have been misjudged to not have environmental impact as opposed to large dams in India. The article focuses on the Western Ghats.
The article was written by PhD student and graduate assistant Suman Jumani of the soil and water sciences department of the University of Florida in collaboration with Wildlife Conservation Society, ATREE and National Centre for Biological Sciences.
The report states: “Small hydropower projects have disrupted the longitudinal, lateral and vertical connectivity of rivers, altered physicochemical characteristics, blocked sediment and nutrient transport, obstructed fish migration, and encouraged fish invasion.”
Two dammed tributaries and one undammed tributary of the Nethravati river in Karnataka was selected for the study.
Flow alterations were caused by small dams which caused the width and depth of the streams to be diminished drastically.
Lead author Jumani said, “The report talks about how dewatering causes community shifts by selectively favouring “eurytopic” fish which can tolerate ecological changes over “rheophilic” fish that are adapted to flowing river waters. The varying flow also causes decline in fishery yields.”
Speaking about displacement, Ms Jumani told this newspaper: “There have been a few instances where small hydroelectric projects (SHPs) have caused significant submergence leading to rehabilitation activity. For example, the allotted Kukke Stage-1 SHP on the Nethravti river would submerge over 700 acres of forest and agricultural land.”
With reduced stream flows, water temperatures would soar higher, and dissolved oxygen levels would fall lower.
“We collected fish from the dammed and dammed parts of the Nethravati river and identified the same standard taxonomic keys. We knew that the chemical and biological process on which the fish are dependent on would alter in case of SHPs,” she said.
“More generalist and not specialist species of fish that are unique to rivers were found with native species being driven to extinction,” she said. She also stated that fish species’ richness can bounce back with flow restoration.
“By restoring river flows, we reduce habitat fragmentation and allow sediment, nutrients and aquatic plants and animals to move freely,” Ms Jumani said.
The tagline, “If you can’t reuse it, refuse it” has gone viral with a call for citizens to be alert to ensure that water bodies are safe. With more plastic than fish is expected in oceans by 2050, a global attempt is being made to curb marine pollution.