Vladimir Smakhtin, Luna Bharati, Nilantha Gamage

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PLANNING WATER TRANSFERS IN KRISHA RIVER BASIN
TECHNICAL FEASIBILITY AND ENVIRONMENTAL IMPACTS

• Vladimir Smakhtin, Luna Bharati, Nilantha Gamage
• August, 2007

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APPROACH

• Analyse NWDA feasibility Reports identify and
  closely examine specific technical aspects of
  transfers using proposed links in and out of the
  Krishna Basin (IWMI benchmark basin)
• Detailed focus on Polavaram Vijayavada link
  using WEAP simulating scenarios of water use
  with and without the Project, with and without EF
  and with different crop rotations
• This ensures a combination of a larger-scale
  analysis (hydrological feasibility of transfers
  in general) with the specific analysis and
  scenario simulation using detailed data for 1
  link
• Examine environmental impacts of the project on
  Krishna Delta

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NRLP LINKS IN AND OUT OF KRISHNA
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NWDA METHOD USED TO JUSTIFY TRANSFERS

• Use annual data resolution. Add all known water
  abstractions back to available observed flows
  upstream of the link point to naturalize the
  flow
• Develop rainfall runoff relationships using
  naturalized flows and rainfall for the flow
  observation point
• Use this relationship to generate naturalized
  annual flow time series at the (ungauged) link
  point
• This TS is used to establish 50 and 75 assured
  (dependable) annual flows. 75 flow becomes the
  surface water available
• All projected water demands upstream of the point
  of potential transfer (e.g. for 2050) are then
  subtracted from the 75 dependable (assured) flow
  (yield). If the balance is positive it is a
  surplus basin and a candidate for transfer.
  Negative deficit basin. This completes
  justification for a transfer

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GAPS IN FEASIBILITY REPORTS

• Limited information is presented
• Data used are not described in full
• Methodology of hydrological justification of
  links could be improved
• Environmental aspects and impacts are very
  generally described and are primarily related to
  submergence of new land and resettlement of
  population
• No provision is made for ecological releases from
  either existing or planned reservoirs

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THE ISSUE OF DATA RESOLUTION AND ITS IMPACT ON
WATER AVAILABILITY ESTIMATES
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THE ISSUE OF DATA RESOLUTION AND ITS IMPACT ON
WATER AVAILABILITY ESTIMATES
Annual time step data
Monthly time step data
75 dependable flow (annual)
75 dependable flow (monthly)
75
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THE ISSUE OF DATA RESOLUTION AND ITS IMPACT ON
WATER AVAILABILITY ESTIMATES
Estimates of Surface Water Availability (MCM) at
50 and 75 dependability from annual (NWDA) and
monthly (IWMI) data resolution for selected link
points in and out of Krishna

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USE OF SPELL ANALYSIS AS A CRUDE ALTERNATIVE
An extract from the generated naturalized monthly
flow time series at Srisailam. Red line is the
planned transfer equivalent to flow volume of
4,783 MCM per month throughout the year. The
maximum annual spell (deficit) of around 40,000
MCM may be required to assure the above flow
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USE OF SPELL ANALYSIS AS A CRUDE ALTERNATIVE

• Set a feasible limit for maximum cumulative
  storage upstream of the site (e.g. 20 BCM for
  Srisalam- slightly higher than the already
  existing storage here)
• Do several runs with different flow thresholds
  until the maximum deficit in the Srisailam time
  series has dropped to the set maximum
• The corresponding threshold flow of X MCM per
  month (or converted to annual volume) becomes the
  estimate of water available for transfer.

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USE OF SPELL ANALYSIS AS A CRUDE
ALTERNATIVESrisalam Example
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USE OF SPELL ANALYSIS AS A CRUDE
ALTERNATIVEPolavaram Example
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ENVIRONMENTAL IMPACTS OF RESERVOIR CONSTRUCTION
ON KRISHNA DELTA
Reduced flow coupled with continuous storage
growth, which is now equal to 36 and 132 of the
natural and present day Krishna outlet mean
annual flow respectively.
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ENVIRONMENTAL IMPACTS OF RESERVOIR CONSTRUCTION
ON KRISHNA DELTA
The time series of sediment loads in Krishna at
Agraharam (upstream of most dams) and Vijayavada
(downstream of all dams). Most of the sediments
are trapped by dams
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ENVIRONMENTAL IMPACTS OF RESERVOIR CONSTRUCTION
ON KRISHNA DELTA
Three high resolution images (Landsat) of Krishna
Delta have been analysed - 1977, 1990 and
2000 Dynamics of six points (outlets of major
distributaries) have been examined in detail
(figure) Areas of deposition and erosion in the
entire delta have been calculated by comparing
1977 image (reference) and 2000 current
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ENVIRONMENTAL IMPACTS OF RESERVOIR CONSTRUCTION
ON KRISHNA DELTA
Total net land loss in the delta over 23 years is
1780 ha Rate of loss is 77 ha/year Erosion is
3 times more than deposition over the study
period Areas of erosion dominate coastline (red
in Figure) Most likely attributed to reduced
sediment delivery during this period
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CONCLUSIONS

• All NRLP transfers are justified based on the
  premise that natural annual flow volume which
  is exceeded 75 of the time (e.g.30 out of 40
  years) is available for water utilization. This
  ignores the variability within a year, which is
  extremely high in monsoon-driven Indian rivers.
  Result much more water may be perceived as
  available at a site of Transfer.
• All NRLP transfers are further justified based on
  the States maximum plans for irrigation (for
  2025 or 2050). This maximizes irrigation
  requirements and serves as THE driver for future
  water resources development.
• There is a needs for integrated water resources
  planning at the basin scale, when all links are
  modeled simultaneously. It applies to Krishna
  basin and to other basins earmarked for transfer.
• It is not possible to properly re-evaluate any
  plans without having the same starting conditions
  the same hydro data. Only very cautious
  statements can be made here.

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CONCLUSIONS, cont

• The alternative assessment of water available for
  transfer using spell analysis- is crude, but it
  suggests that the basins/sites which are thought
  of as surplus, may be effectively in deficit
  already
• The demands which are currently considered in
  feasibility reports include irrigation,
  hydropower, industry and domestic. Environmental
  demands must also be explicitly included at the
  planning stage. This will be a precautionary
  measure in the absence of other more detailed
  information at present.
• Past storage growth in the basin has led to
  retreat of the Krishna delta, where the rates of
  erosion exceed the rates of deposition. Even
  under existing storage delta will likely continue
  to shrink in the next decades. Environmental
  releases are necessary.
• Adding very limited environmental demand into the
  picture (in the range of 10-15 of the long-term
  annual flow) makes the transfer sites even more
  deficit and transfers even less feasible