The Proposed Polavaram Project- Analysis of Water Availability vs. Water Use

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The Proposed Polavaram Project- Analysis of Water
Availability vs. Water Use

• Luna Bharati, B.K. Anand and Vladimir Smakhtin
• Hyderabad, August, 2007

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The Proposed Polavaram Project- Analysis of Water
Availability vs. Water Use

• Outline
• Study Objectives
• WEAP-Model Setup
• Defining spatial area
• Scenario development
• Defining water supply and demands
• Results from Scenario Analysis
• Conclusions

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The Proposed Polavaram Project- Analysis of Water
Availability vs. Water Use

• Objectives
• Quantify water availability/ water supply vs.
  water use/ water demand for
• Water use in the sub-watersheds (Mandals) falling
  under the Polavaram link command area.
• Areas outside of the command area that will be
  affected by the Polavaram project i.e. Author
  Cotton Barrage area, Left bank and the Prakasham
  Barrage area
• The water supply and water demand was assessed
  for
• 1) The current situation
• 2) After the Polavaram reservoir and link
  canal

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WEAP- Water Evaluation And Planning
systemStockholm Environment Institute U.S. Center

• Highlights
• Integrated water resources planning system that
  runs on a monthly time step
• Built-in models for Rainfall runoff and
  infiltration, evapotranspiration, crop
  requirements and yields, surface
  water/groundwater interaction, and instream water
  quality
• A database maintains water demand and supply
  information to drive mass balance model on a
  link-node architecture
• Embedded linear program solves allocation
  equations
• Minimal requirements runs under Windows
  98/2000/NT/XP on a Pentium computer with 256 MB
  RAM

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1. Model Setup-Determining Spatial Extent

• Drainage map extracted from SRTM.
  http//srtm.csi.cgiar.org/SELECTION/inputCoord.asp
  
• Sub-catchments delineated from 5th order stream
  outlets.
• Link command area was divided into 7
  sub-catchments

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1. Model Setup-Determining Spatial Extent

• The command area mandals were grouped into
  sub-catchments

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1. Model Setup-Determining Spatial Extent
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2. Scenario Formulation

• Scenario 1
• Reference Scenario with current water use under
  current supply and demand network. The water
  sources are groundwater and the river channel.
• Run under different crop rotation systems
• i) paddy-paddy ii) paddy- pulses (representing a
  low water intensity crop) iii) sugarcane
• Simulations with and without environmental flow
  requirements/demands
• Scenario 2
• With the Polavaram reservoir and Link canal
  water supply versus demand after the construction
  of the Polavaram project. The water source is the
  Polavaram reservoir and link canal, ground water
  and the river channel.
• Run under different crop rotation systems
• i) paddy-paddy ii) paddy- pulses (representing a
  low water intensity crop) iii) sugarcane
• Simulations with and without environmental flow
  requirements/demands

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3. Defining Supplies and Demands

• Water Supply
• Water source for the sub-catchments (RBC) are
  precipitation, surface water and groundwater.
• Water source for demands outside of the RBC are
  linked only to surface water
• In Scenario 1, Surface water is from the river
  flows
• In Scenario 2, Surface water is from the rivers,
  the Polavaram reservoir and link canal
• In Both Scenario 1 and 2, Ground water is
  represented by a node and the total availability
  and natural recharge was set based on
  Andrapradesh state government ground water reports

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3. Defining Supplies and Demands
Water Demand

• Agriculture
• Within the sub-catchments, the FAO method was
  used to calculate crop requirements
• Annual water demands from the government reports
  were used to set demands from the Prakasham
  Barrage, Author Cotton Barrage and Left bank
  demand
• Urban and Rural Domestic water use
• Mandal and District Level data
• NWDA feasability report
• Industry
• Calculated from district wise industrial output
• Livestock
• District Level data
• NWDA feasability report

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Environmental Flows Requirements

• The environmental water demands (environmental
  flows requirements) were estimated using the
  desktop method which is based on the use of a
  flow duration curve a cumulative distribution
  function of monthly flow time series (Smakhtin
  and Anputhas 2006).
• The environmental flows calculated for the lowest
  acceptable category D (largely modified rivers)
  were used in this analysis.

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Results Scenario 1(Current Water Use) Total
Unmet Demand

• Figure 1 shows monthly average (1991-2004) unmet
  demands from agriculture, domestic use, industry
  and livestock for the sub-watershed falling under
  the link command area for different cropping
  patterns and with inclusion of environmental
  flows. All cases include conjunctive surface and
  ground water use.
• The highest unmet demands are for the paddy-paddy
  with e-flows and lowest for paddy-pulses
• Unmet demands are in all months
• Figure 2. Scenario 1 monthly average (1991-2004)
  unmet demands based on water requirements from
  Author Cotton barrage and the Polavaram left bank
  canal area
• The unmet demands from the left bank and Arthur
  Cotton barrage are during the Rabi and dry
  seasons and are probably being met by groundwater

Figure 1 . Monthly average unmet demands for the
link command area
Figure 2. Monthly average unmet demands for
Arthur Cotton and left Bank
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Results Scenario 2 (Polavaram Project) Total
Unmet Demand

• Figure 3 shows monthly average (1991- 2005) unmet
  water demands under paddy- paddy crop rotation.
  Unmet demands in the link command area are
  minimal compared to those in Author Cotton area
  and left bank.
• Within the link command area, the water deficit
  situation improves from the current situation
  however, if environmental flows requirements are
  set, then there is a small deficit in the link
  command area under paddy- paddy cropping system
• Compared to the current situation, the pressure
  on water resources within the left and right bank
  command area reduces, however, there will be
  increased deficit in the Author cotton command
  area. This deficit is during the Rabi and summer
  seasons.

Figure3. monthly average (1991- 2005) unmet water
demands under paddy- paddy crop rotation
Figure 4. monthly average (1991- 2004) unmet
demand for the link command area
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Results Scenario 2 (Polavaram Project)
Million Cubic Meters

• Salient features from the government feasibility
  report was used to simulate the reservoir. The
  published monthly net evaporation was used to
  calculate evaporation losses.
• The reservoir reaches the inactive zone (3,381
  MCM) during every dry season which means that the
  water stored during each monsoon season will be
  utilized during the dry season of that same year.
  
• The reservoir storage capacity does not provide
  storage and ensure water for inter-annual
  variations.

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Results Environmental Flows Requirements
Figure 6. Class D flow requirements plotted
against measured flow from the gauging station at
Vijayawada.
Figure 7. Scenario 2 unmet environmental demand
for Godawari under paddy-paddy cropping pattern
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Conclusions

• The simulations suggest that the proposed
  Polavaram reservoir and link canal will reduce
  the pressure on water for the proposed command
  area of the reservoir. However, this will result
  in increased water deficits during Rabi and
  summer months in the lower Godawari Delta, which
  is being supplied through the Author Cotton
  barrage.
• Changing cropping patterns e.g. by planting paddy
  during the monsoon and a low water intensive crop
  such as pulses in the dry season in the link
  command area will decrease unmet demands for the
  lower Godawari Delta. However, this will not be
  enough to continue the present water use patterns
  in the Author Cotton command area.
• Similarly, the need to ensure environmental flows
  should also be considered in the context of
  seasonal variability, as it is mostly in the dry
  months that water allocation problems become
  critical. In the Godawari, it will not be
  possible to meet environmental flows requirements
  in June, just before the start of the monsoon if
  the onset of the rainy season is delayed.
• Meeting environmental flows requirements in the
  Krishna is a bigger problem than in the Godawari
  and the situation is not likely to improve even
  after the Polavaram project, as most of the water
  that is being transferred will be used for en
  route irrigation.
• This study suggests that water resources
  management in the region has to be done on a
  seasonal basis by taking monthly variability into
  consideration.

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Thank you...