Dam floods · Maharashtra

Maharashtra Upper Krishna Basin Flood 2019 Vadnere  Committee-2: A report with “difference”!

Guest Blog by Pradeep Purandare

SANDRP published my article entitled “Maharashtra Floods 2019: Don’t waste the crisis” on 26th May 2020.In that article I had explained the reasons behind my resignation from the Flood Study Committee. Exclusion of my chapter from the committee’s report was one of the reasons. Now, the said report is available in public domain & surprisingly enough, it includes my chapter; thanks to SANDRP!

In this note, I would like to draw the attention of all concerned towards the erroneous data, strange analysis & weird logic employed by the Vadnere Committee-2 in its report without discussing the serious issues in the committee meetings.

Key conclusion without support of logic or facts? The Vadnere Committee-2 report concludes (p 8, Vol. 1): “It can be seen that the contribution of free catchment, in the discharge observed in river Krishna, at Irwin Bridge at Sangli, was 49%… The discharge from free catchment, which was substantial and had no control.” This is used by the committee to suggest that dams did not contribute to flood disaster. However, it is shown below how factually wrong these figures are and hence, all their conclusions based on such wrong data are clearly baseless

Irwin bridge (Sangli), Rajaram weir (Kolhapur) & Rajapur weir (Maharashtra state border) are the River Gauging Stations (RGS) in Krishna basin where discharge measurement is done using Stage Discharge Curves (SDC).

Section of a map from Vadnere-2 report showing locations of Irwin Bridge, Ankali bridge, Kurundwad and Rajapur Weir

SDC is a graph / rating curve which shows the average discharge for a particular stage (water level) at a particular RGS for a given cross section. Rating curves are developed based on observed flow & surveys of the gauge site. The curve is the empirical relationship & can change over time. Extrapolating beyond the limits of the rating curve can lead to erroneous discharge values.

In view of above, it would be logical to verify following:

(1) Whether the SDCs at RGS at Irwin bridge, Ankali Bridge & Rajapur weir have been revised?

(2) Whether any extrapolation was done?

Stranger than Fiction The answer is stranger than the fiction! Read the observations (Annex-1) made by the Flood Study Committee during its field visit to flood affected area on 23 &24 Sept 2019.

The observations are self-explanatory and speak volumes. Forget revising SDC; the report says (p 34, Vol II): “It is observed that there is no river gauging station near the Irwin bridge.”

And “officials told that the SDC at Rajapur Weir is prepared with reference to the SDC available   at CWC site at Kurundwad” (p37 & 38, VolI) The point to be noted is Kurundawad is approximately 10 km u/s of Rajapur Weir.

Moreover, the report accepts that the river cross sections inputs for the model have not been updated since 2012 (P 341, Vol. 2): “For input of river cross sections in the model, survey was carried out in 2012, changes in the cross sections over the years have not been taken into consideration”.

Given the situation, the data generated at the so called RGS simply does not have any sanctity. The values are not the outcome of any scientific process to say the least!

Logically speaking, WRD & the report should have stated that in absence of reliable & accurate data no scientific conclusions can be drawn. But instead of that WRD & the report has ventured in carrying out the analysis of erroneous data. And this even contradicts one of the important findings. Let us see how committee has landed itself in a soup!

RTDSS facts contradict the Vadnere committee Real Time Decision Support System (RTDSS) for Krishna basin is dealt with in Section 4.4 of the Report of Flood Study Committee, titled: “Study Report by Water Resources Department, GoM: Real Time Decision Support System for Krishna Sub Basin”. The details of observed & simulated discharge & water levels at Irwin Bridge, Ankali Bridge & Kurundwad RGS sites are given in Tables 4.4.3, 4.4.5 & 4.4.7 in the said section. Based on this data it is claimed that “…….values are well within acceptable limit” [Table 4.4.9, Page 336 of RTDAS report, Vol 2] & hence, “All is well” about RTDSS. Let us see the “acceptable values”.

From above mentioned tables in the report, it is seen that the difference between observed and simulated water levels is quite significant. Its summary is given in Table-1 below

                                  Table – 1: RTDSS “with difference”!                                                     

Difference

(Meters)

Irwin

 Bridge

Ankali

 Bridge

Kurundwad

(CWC)

Average 1.1 1.8 1.8
Max 3.7 4.5 4.5
Min -1.7 -0.1 -0.1

Note: Difference is positive when Observed water level is higher than simulated water level and negative when observed water level is lower than simulated water level, as given in Table 4.4.3 (Irwin Bridge, see pp 335, Vol. II),  Table 4.4.5 (Ankali Bridge, see pp 337, Vol. II) and Table 4.4.7 (Kurundwad-CWC, see pp 339, Vol. II).

Similarly, the gist of observed & simulated runoff (in TMC or Thousand Million Cubic Feet) at above-mentioned G D Sites is presented here in Table–2.  These figures are for total runoff for the 20 day period of highest rainfall event from July 25 to Aug 13, 2019 as per the  Vadnere Committee–2 Report.

Table-2: Runoff contradictions

Runoff (TMC) Irwin

 Bridge

Ankali

 Bridge

Kurundwad

(CWC)

1.Total
(a)   Observed 188 218 325.5
(b)  Simulated 170 216 274.2
      (C)  Difference [(a) – (b)] 18 2 51.3
2.Total run off from free catchment (Simulated) 47 69 134.2
3 % Contribution from free catchment

(% wrt 1(a))

25 31.5 41.23
4 Contribution from free catchment

as reported in Table – 4.3.17, WRD

Report (4.3)

97.39

(49)

From Table-2, it is clear that

  • There is significant difference between observed & simulated runoff at Irwin Bridge (18 TMC) & Kurundwad (51.3 TMC)
  • Simulated free catchment Runoff is 47 TMC i.e.25% of total observed runoff at Irwin Bridge.
  • However, contribution from free catchment as reported on page 77 of Vadnere Committee – 2 Report, which is WRD Report (4.3) is 97.39 TMC i.e, 49% of total observed runoff.

It is claimed, time & again, by WRD officials, and uncritically reproduced by Vadnere Committee – 2 Report, that contribution of free catchment in the outflow was far greater than that of dam catchment. Above statistics given by them, however, contradicts their own argument! Contribution from free catchment is hardly 25%, their own report says.

Strangely, for Vadnere Committee–2 and WRD a difference of average 1 to 2 meters in water levels and 18 to 51 TMC in runoff is not a `significant difference’! In order to substantiate it’s claim that “…….values are well within acceptable limit” the committee has resorted to “Nonsense / Spurious Correlation” which reminds me the famous proverb “”Lies, damned lies, and statistics”.

As per the weird logic of the Committee the Observed & Simulated Data with such huge differences are correlated!

I earnestly request the distinguished members of the committee, especially those who are from the premium institutes like IIT, IITM, IMD, CWC, MRSAC & MWRRA to give their honest, studied opinion in this matter.

In Conclusion: It is clear from this brief note that the Vadnere committee -2 aAnalysis is full of contradiction, the simulations are without scientific rigor or sanctity and based on assumptions and extrapolations, they do not match with the observed values. More worryingly, the conclusions of the committee are contradicted by the details given by the WRD in the report itself. The attempt of the committee hence to show that the dams could not have played a significant role in flood moderation has no basis.

Pradeep Purandare is retired Asso Prof, WALMI, Aurangabad, Former Member  of Committees for (1) MMISF Act & Rules, (2) Marathwada Development Board, (3) Integratted State Water Plan & (4) Flood Study Committee. M 9822565232, pradeeppurandare@gmail.com He was also member of the Vadnere-2 Committee till he resigned in May 2020.

Annex-1:

Screenshot from the report of  Committee’s field visit on 23-24 Sept, 2019

(Source: Vol. 2 of Vadnere Committee – 2 Report)

Screenshot of the relevant parts of Vol 2 of Vadnere-2 report
Screenshot of a relevant section of the Vol 2 of Vadnere-2 report

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