ESTIMATION OF MONTHLY NATURAL FLOWS IN A HIGHLY DEVELOPED BASIN – the case study of Krishna
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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].

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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- [email protected]

[2] International Water Management Institute (IWMI), New Delhi.


ICID - IAH CPSP Study BASIN – the case study of Krishna

Application of CPSP Model to selected basins in India – Location of basins


Data availability
DATA AVAILABILITY BASIN – the case study of Krishna


Main Strengths or Advantages BASIN – the case study of Krishna

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”


Limitations of the approach BASIN – the case study of Krishna

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 BASIN – the case study of Krishna.

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 BASIN – the case study of Krishna?ØAllowed 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.


Ultimate utilization and limits of utilisation

BASIN – the case study of KrishnaUltimate 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)

ØHow 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 BASIN – the case study of Krishna LIMITS OF UTILISATIONKRISHNA BASIN, 2025. UTILISATION AT 75%DepedabilityDomestic and industrial use at the same levelStorage development at same level (Figures in billion cubic meters per year)


Conclusions

Conclusions BASIN – the case study of Krishna

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-WM:Better 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-EFRL&H: GW regime similar to WM2.. Irrigation benefits less than BaU-LD. Thus all new dam construction and water management efforts go towards EFR.


Conlusions contd

Conlusions (Contd BASIN – the case study of Krishna)

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

Issues for discussion BASIN – the case study of Krishna

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?


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