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  , B K Anand .
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ESTIMATION OF MONTHLY NATURAL FLOWS IN A HIGHLY DEVELOPED BASIN – the case study of Krishna
BUILDING FUTURE WATER ASSESMENTS SCENARIOS FROM MONTHLY NATURAL FLOWS IN A HIGHLY DEVELOPED BASIN – the case study of Krishna
- Anil D Mohile, B K Anand
 Consultant, Water Resources, New Delhi. Formerly Chairman Central Water Commission and Ex-offico, Secretary to Governement of India. Email- [email protected]
 International Water Management Institute (IWMI), New Delhi.
ICID - IAH CPSP Study
Application of CPSP Model to selected basins in India – Location of basins
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”
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?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”
In strict hydrologic sense, there is no Utilisation!
Is utilization to be measured as “Withdrawal” or as
Utilisation, as withdrawal depends on:
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 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)
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.
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?Ø Can the irrigated areas be underestimated in Governmental figures?Ø Can we use the “Limits of Utilisation” approach?