Background
The
river and the flood is the common and it is a special eco-system. It even
varies with the rivers depending upon its flow. The Mekong river in Cambodia
forms a special eco-system. Mekong forms a biggest lake in the delta and the
people cultivate rice depending upon the rise of the water levels in the lake.
If the river fails the whole densely populated Mekong delta in Cambodia will
fail. Likewise the Zambezi river in South central Africa forms a dry and wet
type ecosystem. The river is a seasonal river flows heavily in rainy season and
forms marshy eco-system. And in summer the river delta will become bone dry
with patches of ponds and will look like a desert. So, the deltas were a sensitive
eco-system connected with another richest and special eco-system called Mangroves
in India. Delta eco-system will as fertile as the Mangroves. The classical
example of mangroves in India lies over Sunderbans of West Bengal. So all these
fertility comes out of the fine materials washed from the weathering mountains
and the highlands in the catchment i.e. the Silt.
Silt – The Secret of the
deltas
The Silt is the nutrition for the delta bloom. Silt
nourishes the riverine eco-systems and supports the higher food chain animals
like Crocodiles. For example in the river Amaravathi, a tributary of Cauvery,
the inland Crocodiles were still existing. The silt is the base for the inland
fresh water eco-systems of rivers, ponds, lakes and even wells. The reddish or
the greyish alluviums carried over from the highlands and mountains make these
fresh water eco-systems very fertile. Such silt depositions in the delta is the
prime source for the nutrition in the cultivable wetlands. If it is properly
managed it will yield for endless generations. India is country that has been
blessed with such delta throughout its east coast from Bengal to Kumari.
Silt in the case of
Thanjavur delta
Thanjavur
is a town and head quarters of the district located 100 kilometres away from
the sea. It is located in the Cauvery river bed, where from she divides herself
in to many streams before draining in to the sea. She makes Thanjavur district
along with the new today’s Thiruvarur and Nagapattinam districts as a fertile
triangle. The beauty of the geography of the delta is that it travels with very
gentle slope of 3 feet for every 20 km. This facilitates the river Cauvery to
deposits the silt more in inland rather in to sea. The nature of the district
helps the silt harvesting unlike the other rivers of India including Ganges. The
Silt deposition very much high in the dividing point called Kallanai (Grand
Anicut), built before 1600 years. Below the anicut (dam) for few kilometers the
Colonial rulers described it as the Breast of the Delta.
The silt deposition
was aided by heavy floods from July to November in both the monsoons. The
flooding is the nature of that eco-system. The people and the cultivars of the
eco-system have evolves along with the flood nourished by the wonderful silt. The
historical fiction novel Ponniyin Selvan narrates the borders of the mighty
river Cauvery in the grandeur manner. In this fertile soil one of the greatest
dynasties of India have flourished and formed a greater civilization. Their
mightiness and the healthiness still existing in the form of hundreds of
temples. British called this land as the Fertile Crescent in their empire,
giving three harvests of rice a year.
The same is the reason that the British have invested a lot in expanding
the river for increasing their revenue. Such flourishment cannot be seen in any
South Indian rivers except Cauvery. For everything, the name goes to the Silt
of the mighty river.
Flood regulatory systems in
Cauvery
British, the colonial traders entered India with their
empire on the soils of Thanjavur in the Madras presidency. As described earlier
seeing the fertility of the land the hardworking people they have got an idea
and have not minded in investing huge money in building the dams and Canals to
expand the irrigation to increase the state’s revenue. British have seen the
flood damage as the huge loss and they have started working in the delta to
regulate the flood. They didn’t realize the problems until they have built few
dam in the river coarse.
Cauvery -Vennar regulators
and Upper Anicuts
The main river Cauvery divides herself before the city of
Trichy in to Kollidam or Coleroon river in to the north and the river Cauvery
in the south, flowing to the east remerges at the point called Kallanai (an
ancient dam built of clay and stone) forming the island of Srirangam. The South
stream of Cauvery again divide in to Vennar and Cauvery and travels to further
east forming the fertile crescent of Thanjavur. The excess water in the Cauvery
river was drained in the Kollidam through Ullar channel in the Kallanai.
Unfortunately, the silting up of the river bed in the Vennar and Cauvery have
diverted the maximum amount of water in to Ullar channel and to Kollidam. The
Kallanai didn’t serve the purpose completely.
Primarily in 1835, a dam called Upper Anicut was
constructed with the Iron weirs in the Kollidam river before Tirchy. It lead to
the huge erosion of the river bed and resulting in the deepening of the river
Cauvery and causing severe floods in the delta. Subsequently, to manage this
connecting the Southern bank another Upper anicut was extended in to Cauvery
and the river was brought under the total control. Even after that the colonial
administration were not able to control the flood through both the weirs and
have constructed a siphoning channel called 150 yards calingula, below the
Upper anicut before the Srirangam town, to regulate the floods in Cauvery.
In 1851, the investment was made to construct a regulator
in the Vennar-Cauvery bifurcation of Kallanai, with the Iron shutters avoiding
the silt deposition. The flood regulators were constructed in the next 50 years
through out the main streams of Cauvery in the delta and were managed by the
Public Works Department.
Flood embankments in Coleroon
The
flood control was very difficult for them even after the flood regulators and
they have built a 200 miles embankment in the river Kollidam (Coleroon) to hold
the excess amount of water safely in to sea, without flooding the northeastern
part of the districts. The revenue of the state was depleted by the flood
reliefs, which again made the state to go for further construction of the dams
in the upstream of Cauvery.
Mettur and other reservoirs in
Tamil Nadu
To control these flood the British administration have
decided to built the dams in the Cauvery’s catchment frontiers and have planned
for Mettur, Bhavanisagar and Amaravathi
dams in Cauvery and it s tributaries. In 1934, Sir Stanley have opened
the Mettur reservoir and named it as the Stanley reservoir. The other dam project
in Tamil nadu was carried out during the post-independence period.
Mysore – Madras River conflict
In
the midst of the Madras presidency’s dam projects, the Mysore state under
Mr.Krishnaraja Wodeiyar, the Raja of Mysore state went for a dam project of
holding 80 TMC in the upstream of Cauvery in 1892. The Madras presidency told
about their Mettur project and went for to the Court and the Court ordered
Mysore that it should get permissions from the Madras before any construction
of the dams and ordered to construct 11 TMC dam project instead of 80 TMC. But
the Mysore states violated the order and have planned for the latter. This is
the starting point of the Cauvery tribunal, which is still continuing after a
century.
Impact of Series of Anicuts on delta
The series construction of dams from Trichy to the
upstream of Cauvery in 19th
century leads to diminishing water to delta and the delta farmers have
to follow the turn system. The culture of transplanting the paddy by seeing the
freshes (i.e. the silty water after the onset of South-west monsoon) of the
Cauvery river have changed and the silt deposition has reduced. The farmers
have to wait for the dams to be opened. According to the people of Thanjavur in
the 19th Century and the district collector’s versus the delta have
started deteriorating after the construction of various dam in the Cauvery. If
it is properly studied the nightmare will be revealed.
Granary slowly shifted to Mandiya
The
construction of the upstream dams in Mysore state has lead to the cultivation
paddy in Mandiya district of Mysore in extensive manner. The following map
shows the Mandiya districts production of paddy equaling the delta districts.
Reservoirs of silt in 2011
The silt deprived Cauvery went to Thanjavur with
insufficient silt and have depositied them on river beds instead of the banks.
The most of the silts were harvested in the dam of the upstream.
Stanley Siltvoir and rised unsilted river
beds in the delta
In the mid-term Tamil nadu budget for 2011, Rs.475 Crores
have been allotted for desilting the river beds of Thanjavur delta to
facilitate the river flow. The Cauvery Delta farmers Association President
Mr.Ranganathan said in his budget review that some dozens of Rupees have to be
allotted for desilting the Stanley reservoir which contains 20 feet of silt in
it 120 feet capacity.
River weeds encroaching the rivers
The raised rivers beds have paved way for encroachment of
the river weeds using its dry spells, which again promotes the silt deposition
in the rivers and further rising the river beds. The weeds like Sedges,
Ipomoea, Kusha grass have encroached the upto the middle of the streams and
have paved the way for the floods in winter.
Ground water Irrigated Paddy
cultivation in the Delta
It may sound strange if it is told before 30 years. How
come the delta region will use ground water for a season of rice cultivation?
But we have achieved this with our effortless development works in a century.
Kuruvai farmers cultivate the paddy with ground water these days. Without that
there won’t be any Kuruvai crop in delta.
Research opening
The PWD spends huge amount every year for desilting the
rivers and channels and occasionally the dams. The desilted materials were
wasted on strengthening the bunds instead of using it in the field for
cropping. The agricultural department provides the fertilizers in subsidies to
the same farmers who leave the desilted materials on the bunds. With the free
electricity the Kuruvai crop is made possible by pumping ground water. The
charging minimum amounts for electricity may turn the governments aside. These
were the worst observe, which was the result of the above historical
developments of the bad governmental policies. The beauty and the fertility of
the delta have lost.
The PWD can sell the extra desilted materials for a
minimal cost to the farmers after strengthening the bunds. The proper desilting
in the time will avoid the ground water pumping for atleast few weeks and save
electricity. The desilting in time will also avoid or reduce the flood relief
funds and the crop losses. The proper study and the policy recommendation are
needed along with the proper functioning of PWD. The impacts of the dams cannot
be reversed, for which the time have to answer. However, the ecological and the
economical impacts of such constructions have to be studied in detail,
especially in the important rivers like Cauvery and it shall be used for future
projects of such kind.
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