Transcript Water Harvesting in Eastern Coastal Plains (Orissa, AP, TN)

Water Harvesting in Eastern
Coastal Plains (Orissa, AP, TN)
Sangati CPR Working group
Area of focus
• Between Eastern ghats
and Bay of Bengal
• Rainfall range: 10003000mm
• Subdivisions:
– Mahanadi delta
– Southern AP plains
– Krishna and Godavari
deltas
– Kanyakumari coast
– Sandy littorals
– Madras/Coromandel coast
Role of Water Harvesting
• Study by an organization known as PROGRESS
• Area of focus: drainage basin of a few tributaries
of Krishna river
• Elevation difference between mouth of basin and
topmost point: 290m
– Heavy runoff
• Main rainfall: July and August
• Rainfall in 1988-90: ~900mm per year
• Yet soil was moisture-deficient (drought
conditions)
Role of Water Harvesting
• Study over two years with:
– Water-absorbing cropping techniques
• Intercropping, organic farming, etc.
– Water harvesting
• Runoff conserved through interconnected water structures, so that
overflow in one gets collected in another
• 170 structures, covering 4% of the basin area
– Harvested 25% of total rainfall
• Conclusions of study:
– Drought is not because of lack of rainfall but because of
mismanagement of existing rainfall
– Traditional water structures if revitalized can harvest 75% of the
runoff
– Worst-affected by lack of over-reliance on individual wells (as
opposed to tanks) are the small farmers. Leads to the usual
cycle of indebtedness
Orissa, AP
• Area: Mahanadi delta, Palar basin
• Tanks, percolations tanks, etc.
Tamil Nadu
• Drought-prone state
• Artificial irrigation imperative
• Classic example: Tanjore
– “For the most part, the soil is naturally poor,
and it is irrigation alone which makes the
province such a scene of fertility” (British
irrigation authority)
• Annual Rainfall: 750-1000mm – NE
monsoon, 250mm – SW monsoon
Anicuts
• Small to medium size dams
– Length: 329m, width: 12-18m, depth: 4.5m
• Mainly around the Cauvery delta to channel
water
• Silting/scouring of the riverbed was a problem
(not carefully engineered to prevent this)
• Prevented by controlling the water flow into the
Cauvery delta, by constructing centralized
“regulators” or kallanais at the head of the
Cauvery delta in Srirangam
• Serpentine structure for kallanai to resist floods
better
Eris
• Ancient tanks
• Approximately one-third of the
irrigated area of Tamil Nadu is
watered by eris (tanks).
• Eris have played several important
roles in maintaining ecological
harmony as flood-control systems,
preventing soil erosion and wastage
of runoff during periods of heavy
rainfall, and recharging the
groundwater in the surrounding
areas.
• The presence of eris provided an
appropriate micro-climate for the
local areas. Without eris, paddy
cultivation would have been
impossible.
History of Eris
• Till the British arrived, local communities
maintained eris.
• Historical data from Chengalpattu district
indicates that in the 18th century about 4-5 per
cent of the gross produce of each village was
allocated to maintain eris and other irrigation
structures.
• The early British rule saw the enormous
expropriation of village resources by the state
– Eris managed by centralized Public Works
Department
– Led to the poor maintenance and degeneration of eris
Oorani
• Smaller tanks (compared to eris)
containing just enough water to
cultivate the few acres of land
dependent on them.
• Major source of water for drinking and
domestic use where groundwater not
sufficient
• Generally excavated to depths ranging
from 2-5 m below ground.
• In many cases, rehabilitation of
neglected village tanks saves
approximately 365 hours or 45 working
days per household
– Which is the total time spent each year
to fetch water from neighboring villages.
• Especially applicable where
groundwater is saline
Kudimaramath
• Voluntary labor undertaken by village
communities traditionally to maintain the eris /
ooranis
–
–
–
–
Checking the growth of weeds on tank bunds
Clearing away underwood from tank bunds
Clearing out deposits/silt
Blocking breaches through ring bunds
• Came to an end when the British forced eris
under PWD
– Eri maintenance was contracted out, leading to the
usual cycle of negligence, corruption, etc.
Decline of tank irrigation in TN
• Old records: 39000 tanks in TN!
• Sharp decline, esp. in North Arcot, South Arcot and
Chengalpattu
• Traditional Irrigation Institutions (TIIs) that perform
maintenance have reduced in effectiveness
– Centralization of tank maintenance
– Emergence of wells and electricity, also leading to cuts in
payments of maintenance workers
– Transfer of land / redistribution of land means more owners of
land, more castes own land
• Caste-based factions of TIIs, more people means less effectiveness
– Many tanks in TN are fed by an anicut system; Palar anicut
system supplies water to 317 tanks in N. Arcot and Chengalpattu
• Here, the tanks close to the head have more effective TIIs, tailreach tanks are less effective
Chennai
• Annual rainfall: 1200mm, which is sufficient
• Lack of facilities to store this water
• Current capacity: 100 million cu. M, or ~2700 million cu.
Ft. or ~76,356 million liters
– 124 tanks, plus 39 temple tanks (or kulams) (?)
• 5.5% of Madras Metropolitan area
– Include tanks in Cholavaram and Red Hills which are used only
for domestic needs (~28000 million liters)
• Rough demand: ~283 million liters a day, or ~100,000
million liters a year
• Clearly, the current capacity to store rain water needs to
be fully utilized!
– RWH crucial!
Chennai
• However, traditional temple tanks (and other
tanks too) have degenerated
– Storm-water courses that refill these tanks have
disappeared
– Water runs off into the sea
• Slum resettlements on tank and lake beds
– “When World Bank gave TNHB Rs. 600 crore as aid
for slum improvement schemes, we had no land to
implement them on. Hence, we had to think of tank
beds” (deputy planner, MMDA)
• As a result, ground-water depletion heavy
– Salt water front of the sea has advanced by 800m in
20 years (10-year old data, probably even worse now)