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Vladimir Smakhtin, Luna Bharati, Nilantha Gamage

August, 2007

PLANNING WATER TRANSFERS IN KRISHA RIVER BASIN:

TECHNICAL FEASIBILITY AND ENVIRONMENTAL IMPACTS

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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

0

2000

4000

6000

8000

10000

0 50 100 150 200 250 300 350

Days since 1 March 1990

Dis

cha

rge

, m3

/s

Daily Monthly Yearly

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THE ISSUE OF DATA RESOLUTION AND ITS IMPACT ON WATER AVAILABILITY ESTIMATES

1.00

10.00

100.00

1000.00

10000.00

1 5 10 20 30 40 50 60 70 80 90 95 99

%Time Flow is exceeded ("DEPENDABILITY")

Flo

w,

m3/

s

Monthly Annual

Annual time step data

Monthly time step data

75%

75% dependable flow (annual)

75% dependable flow (monthly)

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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

Donor /Receptor point

Dependability 50% Dependability 75%

Annual data Monthly annualized

Annual data Monthly annualized

Krishna – Alamatti 24041 958 21405 326

Krishna- Srisalam 66428 8626 57398 1684

Godavari- Inchampalli 76185 10546 66193 4497

Godavari – Polavaram

96549 12155 80170 5132

Krishna Vijayavada Not available 11808 Not available 1964

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USE OF SPELL ANALYSIS AS A CRUDE ALTERNATIVE

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5000

10000

15000

20000

25000

30000

0 12 24 36 48 60 72 84 96 108 120 132 144 156 168 180 192 204 216 228 240 252 264 276 288 300

Months since July 1901

Mon

thly

Flo

w V

olum

e, M

CM

Flow threshold

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

NWDA IWMI Surface Water Availability 57398 32400 Surface water import (+) - Surface water export (-) 7848 7848 Regeneration (+) Domestic use 2624 Industrial use 3748 Irrigation use 2773 Sub-total 9145 9145 9145 Overall availability 58695 33697 Surface water requirement for (-) Irrigation use 43559 43559 Domestic use 3278 3278 Industrial use 4687 4687 Hydropower 1154 1154 Environmental use N/a 5300 Sub-total 52678 (-) 52678 (-) 57978 Surface water balance (+) 6017 (-) 24281

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USE OF SPELL ANALYSIS AS A CRUDE ALTERNATIVEPolavaram Example

NWDA IWMI Surface water availability 80170 36000 Surface water import(+) 3888 3888 Surface water export (-) 13318 13318 Regeneration from (+) Domestic use 1512 Industrial use 2402 Irrigation use 3138 Sub-total 7052 7052 7052 Overall availability 77792 33622 Surface water requirement for (-) Irrigation use 47541 47541 Domestic use 1890 1890 Industrial use 3002 3002 Hydropower (evaporation losses) 6380 6380 Consumptive use from Polavaram 3808 3808 Environmental use N/a 8200 Sub-total 62621 (-)62621 (-) 70821 Surface water balance (+) 15171 (-) 37199

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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