Environmental Engineering Reference
In-Depth Information
and biological parameters upstream and downstream as well as in surrounding
environment and also causes fluctuations in planktonic, crustacean and molluscan
fauna (the natural fish food) and (iii) Mortality or damage to fishes in a number of
ways including abrasion against rough surfaces, turbine blade mangling, rapid
pressure changes, water shearing effects and nitrogen super saturation in the still-
ing basin.
The indirect effects include: (i) Thermal stratification of reservoirs in warm
season which can result in de-oxygenation of the hypo-limnion. Cool and/or
anoxic water discharged from the hypo-limnion can severely reduce water quality
downstream and negatively impact fish stock and fisheries. Fish may be elimi-
nated from the river as far downstream from the dam as de-oxygenation persists.
(ii) Sediment released from the reservoir can hasten turbidity which can create
severe problems for the downstream flora and fauna. (iii) Sediments trapped in the
reservoir may be contaminated with pesticides and industrial chemicals from
catchment sources and residues can enter the reservoir food chain and make fish
poisonous. (iv) Change in fish biodiversity and stock abundance over time. (v)
Extensive de-oxygenation and acidification may occur due to rotting of sub-
merged vegetation in reservoirs which may result in the extensive kill of the origi-
nal riverine population in the lower layers of water (Heppner and Loague
2009
;
Ziegeweid et al.
2008
; Burlakova and Karatayev
2007
; Mérona et al.
2005
; Todd
et al.
2005
; Turner and Erskine
2005
; Santucci et al.
2005
; Johnson et al.
2004
;
Park et al.
2004
; Taylor et al. 2001).
The Garhwal Himalayan region, located in middle Himalaya in India, harbours
many endemic species and is known as a global hotspot for biodiversity (Fig.
1a
).
This region also has an extensive network of fresh water rivers and streams
(Fig.
1b
). According to estimates, there are approximately 10 major rivers in
Garhwal region of Uttarakhand that supports some 60-70 species of fishes within
a short radius of 200 miles (Badola
2009
). These fresh water systems are also
known to harbour a wealth of benthic fauna and flora. These river systems of
Garhwal Himalaya are being used extensively to generate hydro-electric projects
by construction of dams. In Uttarkashi district, there are about 18 proposed hydro-
electric projects within a span of 100 km on river Bhagirathi (Fig.
1a
) out of which
five major dams under construction (Dabrani, Lohari-Nag, Pala, Maneri and
Asiganga) are in district Uttarkashi. It is surprising to see that these many dams/
barrages exist within such a short distance and there have been no initiatives to
conserve/manage/monitor the aquatic fresh water biodiversity. Water from the res-
ervoirs of these dams is channelized through tunnels to power houses located at
distant part somewhere downstream causing drastically reduced water levels in
river between dam wall and power house (Fig.
2a, b
). There has been no base line
data effect of these drastically reduced water levels on aquatic biodiversity (flora
and fauna) of the region including that in Uttarkashi district. During this study,
efforts were made to investigate various parameters including variation in aquatic
flora and fauna, changes in physico-chemical parameters of water in river before
and after the dams on river Bhagirathi at Maneri Bhali Phase I hydro-electric power
project, Uttarkashi district.
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