about reservoir

2.  Eco-degradation of reservoir has been on the increase due
to the rapid of industrialization, poor environment
management in the catchment and variety of others
factors.
 The environmental degradation in reservoir is caused
mainly by the waste discharge from industrial, municipal
and agricultural sources and the thermal power plants.

3. Reservoir Name of river Sources of pollution
Getalsud subarnarekha Heavy engineering,
chemicals and sewage
Gandhisagar Chambal Textile, chemicals, trade
effulents from indore,
Ujjain and kota
Tungabhadra Tungabhadra Paper iron and steel,
rayon, chemicals and
sewage
G. B. pantsagar Rend Thermal power plants,
coal washery, chemicals
Bhavanisagar Bhavani Viscouse factory effulent
Hussainsagar Musa Trade effulents and
sewage from Hyderabad
city
Hirakud Mahanadi Paper mill
Byramangala vrishabhavati Industrial effulents and city
sewage.

4.  A number of reservoir has been selected as sites for thermal power
plants due to their utility as perennial source of water supply and
disposal point for heated effluents.
 Thermal power generation capacity of the country has been
registering a steady growth of 8% per annum & by the turn of
century the installed capacity is expected to reach 84000MW.
 Various thermal plants in the country are estimated to generate 10
billion m³ of hot water (40 ̊C to 50 ̊C) and 17 million ton of fly ash
every year. (Fly ash is known to contain heavy metals such as
Zn(6%),Ba(12.2%) , Cu(1.3%),As(0.02%) and Mn(0.23%) which
may find their way to the nearest rivers stretch or reservoir.

5.  The main ecological consequences of heated water discharged into the aquatic
ecosystem are increase in water temperature change in chemical composition
and change in metabolism and life history of aquatic communities. The heated
discharge may elevate the water temperature by 8 ̊to10 ̊C which may cause
mortality of fish and fish food organisms.
 Temperature above 40 ̊C has been reported to the negatively affect the plankton
and benthic communities. Generally fishes avoid heated effluents discharge
points by swimming away to safer places.
 However the reproduction of fish is affected due deposition of fly ash in the
marginal areas of the river/reservoir which act as their breeding grounds.

6.  A no. of reservoir contiguous to towns and cities face threat from sewage pollution.
 The major adverse impact of sewage pollution can be assessed from deoxygenation,
high BOD, rapid eutrophication and accumulation of heavy metals in the environment.
Sharp fall in the dissolved oxygenation, in water puts the biotic communities under
severe stress.
 Apart from affecting the organism at lower trophic levels, intensive rate of pollution
from municipal sources often causes direct fish kill, especially in small reservoirs
where the problem gets aggravated due to reduced water flow.
 owing to increased use of synthetic detergent for domestic purpose, their incidence in
sewage effluents are on the increase. synthetic detergent being absorbed into the body
system of fish impair their growth and reproductive capacity. Detergent mixed with oil
may be 60 times more toxic than the oil alone. Synergistic action of detergents with
insecticides has also been recorded. Its sub-lethal concentration causes thinning &
elongation of respiratory epithelial cells. Sodium lauryl sulphate is more toxic to
freshwater teleosts, compare to alkyl benzene sulphonate (13-60 mg/l).

7. wastes emanating from an array of industries such as chemical plants, textile
mills, heavy engineering plants, paper mills, iron & steel factories, rayons etc. cause pollution
hazard in Indian reservoirs. Effluence from the kanoria chemicals discharge into Rihand
reservoir are alikaline ( pH 9.2) & high in total alkalinity (4770 mg/l), specific conductivity
(12816 umhos), chlorides (5173 mg/l) & free chlorine (1924 mg/l) these wastes have shown
several toxic effects on phyto & zoo plankton. Direct fish kills have also been reported in
this reservoir due to high chlorine wastes.
Discharge of industrial wastes consisting of dissolved & insoluble solids, free
chlorine & lime of mettur chemical factory into the surplus water channel of stanley reservoir
is reported to have resulted in large scale mortality of carps & catfishes in summer.
Non biodegradbale & persistent types of pollutants like heavy metal, chlorinated
hydrocarbon pesticides, oil components having high boiling points & radionuclides get more
concentrated at higher trophic level through biomagnefication & pose threat to human health.
Discharge of effluents into the up stream can throw up a chemical barrier for
breeding migration of economic carps, apart from causing considerable mortality to spawn &
hatchling .
C) Industrial Effluents

8. There are two general classes of effects of pollutants on water uses. Some of
dramatic effects of toxicity, including fish kills are often well publicized. But the other
class of effuxion which involves continuous chronic sub lethal degradation needs a
more demanding consideration. This goes unnoticed except by ecologist, taxonomist &
by fishermen. It is in the form of reduction in the rate of reproduction by aquatic
species or subtle changes in the food chain pattern on which the fish population
depend.
Domestic wastes also contain a variety of chemicals, detergents & organic
load. Unfortunately the impact of these toxicants on the biotic communities is very
complex & our knowledge in this regard is inadequate.
To prevent ecosystem from gradual degradation, we must provide criteria that
will protect the entire life cycle of desirable species as well as the food chain on which
these species depend. A significant reduction in available food or reproductive success
will result in a condition similar to that after a fish kill.
Chronic effects of effluents discharge

9. Hazardous & toxic substances such as pesticides & heavy metals are carried to the reservoirs
through the effluents & the rain washings from the catchments. These substances are highly persistent
& there by contaminate the entire biogeochemical cycle of static systems like reservoirs .
Pesticides residues have been detected in the riverine ecosystem in all the river basin of the
country. High levels of BHC , methyl parathion, endosulfan & DDT & their biomagnification in biotic
communities like plankton, benthos & fish have been reported from Cauvery, Ganga & Yamuna rivers.
However such observations from reservoirs are rare.
The significant presences of residues of different
isomers of BHC & DDT & it’s metabolites (DDT, DDD)
in fish & plankton of Rihand reservoir is already recorded.
D) Pesticides & Heavy Metals

10. Excessive siltation leading to drastic decrease in the water holding capacity & even damage to
concrete hydraulic structures is a common problem in reservoirs.
Siltation also hampers the productivity of water body by affecting the life processes of biotic
communities. Erosion of top soil in the catchment area is the manmade factor that leads to increased
sediment load in the river. Vegetation cover on the slopes act as an adherent of top soil during the
surface run off. Removal of forest cover through logging, grazing,
road construction or for urban needs makes the soilsusceptible
to erosion.
Apart from diminishing of WHC of the reservoirs &
cutting it’s life, siltation also affects the biota by blanketing the
benthic & periphytic community. It also hampers the
recruitments by destroying the breeding ground & retards
E) Siltation