DATA AVAILABILITY - International Water Management Institute

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Feb 21, 2014 (3 years and 3 months ago)

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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 Mohile
[
1
]
, B K Anand
[
2
]







[1]

Consultant, Water Resources, New Delhi. Formerly Chairman
Central Water Commission and Ex
-
offico, Secretary to Governement
of India. Email
-

anildmohile@yahoo.co.in



[2]

International Water Management Institute (IWMI), New Delhi.



ICID
-

IAH CPSP Study

Application of CPSP Model to selected basins in India


Location of basins

DATA AVAILABILITY

Monthly observed flows, at
terminal site
Good
Water development
information
Good
Monthly irrigated area and
crop information
Not so
good
Monthly reservoir levels and
storages
Good
Main Strengths or Advantages




Could work in monthly time steps, not annual




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”


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.


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.




How we tackled this problem
?





Allowed large evapotranspiration through
anthropogenic swamps. This reduced the returns.




Looked into, and reduced reservoir capacities
due to likely sedimentation




Slightly increased irrigated area estimates
from Governmental sources.






Allowed large evapotranspiration through anthropogenic swamps. This reduced
the returns.




Looked into, and redused reservoir capacities due to likely sedimentation




Slightly increased irrigated area estimates from Governmental sources.



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:




Availability




Limits imposed on the use (EFR, legal,etc)




How you use ( Avoiding wasteful ET, efficiencies,etc.)

We prefer to establish the different limits under each scenario
.
This is illustrated in our results.




RESULTS ABOUT

LIMITS OF UTILISATION

KRISHNA BASIN, 2025. UTILISATION AT
75%Depedability

Domestic and industrial use at the same level

Storage development at same level

(Figures in billion cubic meters per year)





Scenario


BaU
-
HD


HD
-
WM

HD
-
WM2

WM
-
EFRL

WM
-
EFRL
&H


Max Possible
Withdrawal


65.5

69.9

74.1

51.0

48.4

Max Possible
Withdrawal


50.0

48.5

48.1.2

39.2

37.5

Max possible useful
consumption


27.5

34.1

31.8

26.4

25.0

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
-
WM
2
:
GW regime considerably improved.

HD
-
WM
:
Better GW regime. Improvement in irrigated area,
as compared to wm
2
, is small.

HD
-
WM
-
EFRL
:
GW regime similar to WM
2
. For maintaining
low flows considerable irrigation has to be given up. All

water management efforts go towards EFR low
maintenance.

HD
-
WM
-
EFRL&H
:
GW regime similar to WM
2
.. Irrigation
benefits less than BaU
-
LD.

Thus all new dam construction
and water management efforts go towards EFR.


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...




Issues for discussion








Can we obtain more data about irrigated
areas?




Can the irrigated areas be
underestimated in Governmental figures?




Can we use the “Limits of
Utilisation” approach?