GANGA 47th Issue | Page 8
deposition in the reservoir and leading to
systems. Channel erosion of rivers has its
downstream erosion of these sedimentary
own set of consequences. The eroded
depositional environments. While the rate of
channel could create a lower water table
sedimentations varies for each dam and each
level in the affected area.
reservoir, eventually all reservoirs develop a
© Effects on Humans:-
reduced water-storage capacity due to the
Whilst reservoirs are helpful to humans,
exchange of storage space for sediments.
they may also be harmful as well. Reservoir
Diminished storage capacity results in
can
decreased ability to produce hydroelectric
mosquitoes’ particularly in tropical region
power, reduced availability of water for
where
irrigation, and if left unaddressed, may
advantage of the slow flowing water to
ultimately result in the expiration of the
breed.
dams and rivers.
Dams and reservoir require relocation of
(b) Riverine & Coastal erosion:-
potentially large human populations, if they
As all dams, results in reduced sediments
are constructed close to residential areas.
load downstream, a dammed river is said to
Breaking of dams due to natural disasters
be “hungry” for sediment. Because the rate
like earthquake may cause catastrophic
of deposition of sediments is greatly reduced
damage to the downstream communities.
since there is less to deposit, but the rate of
Dams & Reservoirs may impact on earth’s
e rosion nearly constant, the water flow
climate. Warm climate reservoirs generate
erodes the river shores and river bed,
methane, a greenhouse gas, when the
threatening shoreline ecosystems, deepening
reservoirs are stratified in which the bottom
the river bed, and narrowing the river over
layers are anoxic (i.e. they lack oxygen),
time. This leads to a compromised water
leading to degradation of biomass through
table, reduced water levels, homogenization
anaerobic processes. Hydroelectric dams are
of the river flow and thus reduced ecosystem
the number one source of methane gas
variability, reduced support for wild life, and
emissions caused by humans which impact
reduced amount of sediment, reaching
more to climate change than carbon dioxide.
become
mosquito
breeding
and
grounds
snails
can
for
take
coastal plains and deltas. This prompts
coastal erosion, as beaches are unable to
replenish what waves erode without the
Editor- Sujit Choudhury, Published by
IRBMS (© Integrated River Basin
Management Society)
sediment deposition of supporting river
8
Integrated River Basin Management Society