Groundwater Externalities of Surface Irrigation Transfers in Krishna Delta

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Groundwater Externalities of Surface Irrigation
Transfers in Krishna Delta

• Bharat R Sharma,
• KVGK Rao,
• Anupama Sharma, 
• Jean-Philippe Venot

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Polavaram Vijayawada Link

• Godavari Water Disputes Tribunal (GWDT) award
  stipulates diversion of 2265 Mm3 (80 TMC) of
  Godavari waters from the Polavaram project to
  Krishna river above Prakasam barrage at
  Vijayawada.
• The Right Main Canal (Polavaram Vijayawada
  Link) will be 174 km long and is envisaged to
  provide irrigation to a CCA of about 1.40 lakh ha
  besides transfer of 2265 Mm3 of Godavari waters
  to Krishna.
• National Water Development Agency (NWDA) in its
  analysis in 1999 had found the link as viable.

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Krishna Delta
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Source GWD, Vijayawada
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Krishna Delta Irrigation System

• Irrigation canals take off from Prakasam Barrage
  at Vijayawada
• Existing command is 5.236 lakh ha.
• Eastern main canals command is 2.948 lakh ha in
  Krishna and WG Districts.
• The Western main canal serves an ayacut of 2.284
  lakh ha in Guntur and Prakasam Districts.

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Climate Topography

• Krishna Delta receives an average rainfall of
  about 1000 to 1100 mm. Southwest monsoon
  contributes 63 and northeast monsoon 28 of this
  total respectively.
• Cyclonic storms hit the coast during northeast
  monsoon season.
• The topography of the delta is very flat with
  very little drainage network. In most of the area
  the irrigation canal network serves as drainage
  network also.
• Low lying areas prone to submergence by the sea
  and middle reaches of delta prone to water
  stagnation
• Kolleru Lake, largest fresh water lake and a
  declared wildlife sanctuary and spread in an area
  of 90,132 ha, is also part of the Delta and
  receives canal return flow and drainage water
  from the Delta in addition to run-offs of small
  rivulets from Eastern Ghats.

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Krishna A Closed Basin

• Since the 1850s, the Krishna basin has seen an
  increasing mobilization of its water resources
  and a dramatic development of irrigation.
• This has led to the progressive decline of river
  flows and to closure of the river basin almost
  all available water is depleted with none
  remaining untapped.
• The discharge to the ocean has dramatically
  declined as consumptive water uses increased from
  71 to 92 of the basin net inflow between
  1955/1965 and 1990/2000.
• Impacted the availability and time of release of
  canal water to the Delta.

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Water Development in the Krishna Basin
Long history of irrigation development and
decreasing discharge to the ocean Warnings of
Closure Enhanced by recognition of
Environmental Water Requirements

• Before 1965
• Average at 57 Km3/yr
• After 1965
• Decrease by about 0.8 Km3/yr
• In 2000 11 Km3/yr
• Between 2001 and 2004
• 0.75 Km3/yr

Decreasing discharge into the Krishna delta
canals Until 2000 6.15 Km3/yr 2001-2004
4.8 Km3/yr
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Water Utilization - Krishna Delta 1996-97 to
2003-04
Source ICAD Department, Vijayawada
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Monthly Water Utilization in 1996 -97
and 2003-04
Source ICAD Department, Vijayawada
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Water Release Dates to Krishna Delta from
1996-2005
Source ICAD Department, Vijayawada
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Agriculture and Irrigation

• Agriculture and fisheries are the main farm land
  based activities in the delta. About 58 of the
  delta land is under agriculture .
• About 33,000 ha area has been developed for
  shrimp farming. Another 74409 ha has been taken
  up freshwater fish production in Krishna District
  
• Mangrove forest area occupies about 18,000 ha.
• Most of the wasteland, which is saline, and
  mangrove area have been converted to aquaculture.
• Main crop in monsoon season in Delta is rice
  occupies about 4,21,189 ha.
• In rabi rice is covered 1,15,764 ha in tail end.
• Sugarcane is grown in 15,596 ha.
• Black gram and green gram are grown in residual
  moisture after harvest of Khariff rice in
  2,43,991 ha.
• About 6 of the area in tail end Mandals has been
  left fallow in rabi season may be due to high
  soil salinity and insufficient water supply.

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Irrigated Area
Source ICAD Department, Vijayawada
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Average Yields of Paddy in Krishna Delta
Source ICAD Department, Vijayawada
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Mandalwise paddy yield in 2003
Source ICAD Department, Vijayawada
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Mandalwise Kharif and Rabi Crop yields in Krishna
Delta
Rice
Rice
Rice
Rice
Rice
Rice
B.G
B.G
Source Farm Survey
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Yield black gram vs date of sowing
Source APWAM Project, ANGRAU, Bapatla
Area under black gram Green gram 2,44, 000 ha
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Average Net Returns in Krishna Delta
Source Farm Survey
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Reduction in Rice Production in tail end area
due to reduced canal supplies.
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Groundwater Net Irrigated Area (Ha) in the
Eastern Delta
Source Chief Planning Officer, Krishna,
Machilipatnam.
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Groundwater Quality
Source GWD, Vijayawada
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Groundwater Development Status
Source GWD, Vijayawada
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Depth of tubewell pump capacity in different
Mandals
Source Farm Survey
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Impact on groundwater

• The impact of canal supplies on groundwater is
  very rapid.
• The comparison of electrical conductance of
  shallow aquifers in 2003 with those of 1976 show
  that the saline water -fresh water interface has
  moved inland in the eastern delta and certain
  fresh water zones within regional saline areas
  are no more present. Similar land-ward movement
  of the saline water - fresh water interface is
  observed in the western delta also.
• The boundary between fresh and saline water lies
  in the upper aquifers all of which are unconfined
  at some place or the other. Hence, any change in
  water level is likely to disturb this interface
  and up-coning of saline water can occur wherever
  hydraulic continuity with sea exists and that is
  likely to leave a permanent imprint on
  groundwater quality in the area.
• There is a need to understand the effects of poor
  flows in Krishna River and the canal network in
  terms of water quality and ecology of the river
  system

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Threats to the Krishna Delta Environment
Groundwater Salinization
Canal and river flows are central for groundwater
recharge
GoAP. (2003). Freshwater-saline water
interrelationhip in the multi-aquifer system of
the Krishna delta. RD project Abridged version.
Groundwater department, GoAP Hyderabad.
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Threats to the Krishna Delta Environment
Groundwater Salinization
Inland migration of Saline/Freshwater interface
some ag wells tap saline water
Post Monsoon 1976
Post Monsoon 2002
Water Contamination Urban, Industrial and
Aquaculture Effluents
GoAP. (2007). Presentation on the nature of
coastal alluvial aquifer in the Krishna delta.
Presentation held by the Department of
Groundwater at International Water Management
Institute Workshop on Groundwater Externalities.
September, 5th of 2006, Hyderabad.
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Soil Salinity

• About 25,000 ha is suffering from soil salinity
  and alkalinity.
• Most of the effected area is located in the
  coastal zone. Their formation is in marine
  environment and salts impregnate in soils and
  groundwater.
• Their use for agriculture depends on availability
  of adequate fresh water to flush out the salts,
  which is done by repeated flooding and drainage,
  and to grow rice crop with a continuous
  submergence to keep the rootzone free from salts.

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Source GWD, Vijayawada
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Uppugunduru Pilot Area Rice Crop Yields in
Relation to Salinity
Source AP Water Management Project, Bapatla
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Yield of black gram vs soil salinity
Source APWAM Project, ANGRAU, Bapatla
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Cost of coping measures for soil salinity
Rice crop in saline area requires about 25 more
water for flushing of salts.
Source Farm Survey
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Projections using the 2D ModelNIH Study

• To study the response of fresh-saline water
  interface to
• delayed canal supplies, and
• increased gw draft during a typical deficient
  rainfall period.
• Deficient rainfall year 2002-03
• (actual average rainfall in Krishna District was
  573.8 mm against a normal value of 1033.0 mm)
• Extended deficient period four years

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Variation in water table and GW salt
concentration in Avanigadda
Fall in water table (m)
Rise in gw salt concentration (g/l)
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Variation in water table and GW salt
concentration in Mopidevi
Fall in water table (m)
Rise in gw salt concentration (g/l)
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Variation in water table and GW salt
concentration in a freshwater zone in Koduru
Fall in water table (m)
Rise in gw salt concentration (g/l)
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Findings

• Freshwater in shallow aquifer zone is vulnerable
  to contamination from saltwater in lower aquifer
  zone because of susceptibility of saltwater front
  to vertical hydraulic gradients that get
  accentuated due to large gw drafts.
• Changes in salinity levels during a typical
  deficient rainfall period - Mandals located
  towards the coastline like Mopidevi, Avanigadda,
  Koduru and Nagayalanka exhibit an increase in gw
  salinity when the canal water supply is reduced
  and gw draft is more during extended periods of
  deficient rainfall.
• Since the salinity in the delta varies both
  areally and with depth, the rise in salt
  concentration in wells (e.g. Mopidevi) is not
  uniform for similar decline in the water table.

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Findings

• In case of intermediate aquifer in which the
  salinity levels are higher, the rise in salinity
  due to reduction in net recharge is not
  appreciable during the short simulation time
  period of four years.
• Saltwater front is slow to respond to variations
  in the water table elevation.
• It would take longer time before the effects
  become significant at the regional-scale.

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Adverse Impacts of Low River/Canal Flows

• Agriculture
• Reduction in rice production in tail end Mandals
  more than 50 and 25 in middle reaches - About
  Rs 500 crores
• Rabi rice crop not taken in 1.20 lakh ha About
  Rs.150 crores
• Reduction in black gram production in 2,44,000 ha
  by about 5 q/ha About Rs. 150 crores
• Loss of indirect benefits social costs could be
  very significant
• Long term effects may be more severe.

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Land Use Krishna Delta
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Threats to the Krishna Delta Environment
Aquaculture and Ecosystem Degradation

• Development of brackish and fresh water
  aquaculture in the coastal area and Kolleru lake
  region since the 1970s
• Increasing pollution due to heavy loaded
  pollutants from aquaculture ponds
• Declining Areas of Mangroves
• Drying up of the Kolleru Ramsar area (encroached
  by ponds)

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Impacts of the Polavaram-Vijayawada Link
Total Transfer 2,265 Mm3/yr - A Partial response?

• Allocation of 1,236 Mm3/yr to stabilize Krishna
  Delta agriculture
• Need for understanding how this may affect
  groundwater dynamics and slow down groundwater
  salinization- At best return to pre 2000 period.

• 607 Mm3/yr for environmental flows?

In comparison Smakhtin and Anputhas (2007)
evaluates at 6.5 to 14.2 km3/yr the volume needed
to keep the Krishna basin in its current
moderately modified environmental Status

• No Direct impact on the Kolleru lake (canals may
  impede secondary stream flows in the Ramsar
  protected area)

Supply of water and/or Environmental Water
Allocation are needed but will not, alone, stop
environmental degradation. Need for Integrated
Coastal Management and Farm operation regulation
(Gowing et al. 2006)
Gowing, J.W. Tuong, T.P. Hoanh, C.T. (2006).
Land and Water Management in Coastal Zones
dealing with Agriculture-Aquaculture-Fishery
Conflicts In. Tuong, T.P. Hoanh, C.T. Gowing,
J.W. Hardy, B..(eds) (2006) Environment and
livelihoods in tropical coastal zones managing
agriculture-fishery-aquaculture conflicts. CABI,
Oxford. Smakhtin, V. Anputhas, M. (2007). An
assessment of environmental flow requirements of
Indian river basins. International Water
Management Institute Research report No. 107.
Colombo, Sri Lanka International Water
Management Institute.
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Will the Godavari diversions off-set the adverse
conditions?

• Can we expect
• More stable flows to Delta?
• Early releases to Delta?
• Godavari diversions a substitute or
  supplemental?
• Environmental flow?

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Thank You