Environmental Engineering Reference
In-Depth Information
Alterations in Physico-chemical Parameters
of Water and Aquatic Diversity at Maneri-
Bhali Phase I Dam Site on River Ganges
in District Uttarkashi, Uttarakhand
Madhu Thapliyal, Poonam Tiwari, and Ashish Thapliyal
Rivers and lakes comprise approximately 0.009 % of earth's water but they harbour
about 43 % of fish biodiversity (Nelson 2006 ; Helfman 2007 ). These fresh water
systems also support various zoo-planktons and phyto-planktons which are
important bio-indicators of an ecosystem. Greatest threats to freshwater ecosystems
globally are: anthropogenic activities that cause habitat degradation, fragmentation,
and loss; flow modifications; translocation of species outside their native ranges;
over exploitation and pollution. Humans appropriate fresh water globally for direct
consumption, crop irrigation, hydro-electric energy production and other purposes.
The direct and indirect competition with humans for limited freshwater resources is
largely why fishes and other aquatic organisms are among the most imperiled faunas
on earth (Baxter 1977 ; Leidy and Moyle 1998 ; Duncan and Lockwood 2001 ).
Blocking the rivers/streams by construction of dams converts it into slow flow-
ing lentil aquatic ecosystem. Benefits of impounding rivers are: flood control,
hydro power generation, navigation, water supply, fishery etc. However, major
drawbacks of construction of dams which exists in relation to aquatic flora and
fauna are: blockage to fish migration, efficiency of fish passes, reduction in flood
plain fish production etc. Impacts of dams can be grouped into direct and indirect
effects. Direct effects include: (i) Physical barriers and preventing passage of
migrating fish to their usual breeding, rearing, and feeding grounds. This results
in massive failure of recruitment and eventual extinction of stock. The blank niche
so created may be filled by the undesirable species. (ii) Change in physico-chemical
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