DATA AVAILABILITY

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ESTIMATION OF MONTHLY NATURAL FLOWS IN A HIGHLY
DEVELOPED BASIN the case study of Krishna And
BUILDING FUTURE WATER ASSESMENTS SCENARIOS FROM
MONTHLY NATURAL FLOWS IN A HIGHLY DEVELOPED BASIN
the case study of Krishna - Anil D Mohile1,
B K Anand2  

1 Consultant, Water Resources, New Delhi.
Formerly Chairman Central Water Commission and
Ex-offico, Secretary to Governement of India.
Email- anildmohile_at_yahoo.co.in  2
International Water Management Institute (IWMI),
New Delhi.
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ICID - IAH CPSP Study
Application of CPSP Model to selected basins in
India Location of basins
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DATA AVAILABILITY
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Main Strengths or Advantages Ø       Could work
in monthly time steps, not annual Ø       Instead
of a single value, or average pattern, could
establish a 15 yr. Time series of natural
flows 1. This could highlight the negative flow
problem, required relook at data, and improved
credibility of the natural
flow series. 2. Encompassed annual flow
variability, as required in studying the over
the year storages Could
establish a computational process, which included
water balances and accounts We could, thus study
the effects of both the developmental and
environmental actions on residual flows. Through
this process, we could establish the limits of
utilization
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Limitations of the approach Did not model the
whole land phase of the hydrologic cycle.
Modelled the cycle only regarding anthropogenic
changes. Did not model sub-basins. Used a lumped
approach however averaged irrigation
requirements from distributed ET0 and effective
rainfall.
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Illustration of negative natural flow
computation. Observed flow
200 Add for
withdrawals and reservoir evaporation
1600 Subtract
estimated returns
600 Add, exports minus imports
200 Subtract reservoirs depletion
1500 Estimate of natural flow
Minus 100 This is not
possible. Some data is inaccurate.
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How we tackled this problem?Ø       Allowed
large evapotranspiration through anthropogenic
swamps. This reduced the returns.Ø       Looked
into, and reduced reservoir capacities due to
likely sedimentationØ       Slightly increased
irrigated area estimates from Governmental
sources.

• Ø       Allowed large evapotranspiration through
  anthropogenic swamps. This reduced the
  returns.Ø       Looked into, and redused
  reservoir capacities due to likely
  sedimentationØ       Slightly increased
  irrigated area estimates from Governmental
  sources.

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Ultimate utilization and Limits of
Utilisation

• In strict hydrologic sense, there is no
  Utilisation!
• Is utilization to be measured as Withdrawal or
  as
• Consumption
• Utilisation, as withdrawal depends on
• Ø       Availability
• Ø       Limits imposed on the use (EFR,
  legal,etc)
• Ø       How you use ( Avoiding wasteful ET,
  efficiencies,etc.)
• We prefer to establish the different limits under
  each scenario. This is illustrated in our
  results.
•  

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RESULTS ABOUT LIMITS OF UTILISATIONKRISHNA
BASIN, 2025. UTILISATION AT
75DepedabilityDomestic and industrial use at
the same levelStorage development at same level
(Figures
in billion cubic meters per year)
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Conclusions

• BaU-LD GW regime almost unacceptable. Large
  fall in Gw table expected.
• Bau-HD GW regime only slightly improved.
  Increase in irrigated area.
• HD-WM2 GW regime considerably improved.
• HD-WMBetter GW regime. Improvement in irrigated
  area, as compared to wm2, is small.
• HD-WM-EFRL GW regime similar to WM2. For
  maintaining low flows considerable irrigation has
  to be given up. All water management efforts go
  towards EFR low maintenance.
• HD-WM-EFRLH GW regime similar to WM2..
  Irrigation benefits less than BaU-LD. Thus all
  new dam construction and water management efforts
  go towards EFR.

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Conlusions (Contd)

• 1.        Development in basins like Krishna
  would essentially require additional storages.
• 2.        The BaU, as a strategy, would work a
  limited extent. However, the ground water regime
  would get severely affected. Water level
  reduction would occur throughout.
• 3.        Water management improvement through
  anti water logging measures, drainage
  improvements and reuse of saved water, appears to
  be the best option..
• 4.        Distribution efficiency improvements
  would give further benefits,but, their quantum
  does not appear to be very large.
• 5.        A large price for monitoring EFR would
  have to be paid in terms of giving up benefits in
  other uses. This clearly is an issue to be
  decided through trade-offs, considering societal
  preferences...
•  

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Issues for discussion       

• Can we obtain more data about irrigated
  areas?Ø       Can the irrigated areas be
  underestimated in Governmental figures?Ø      
  Can we use the Limits of Utilisation approach?