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It is alleged that as on today actual river flow data of about 58 years is available which is adequate and that this data shows that 75% dependable flow of river is about 22.5 MAF. In this behalf, it may be noted that the matter of hydrology was considered on several different occasions and is duly finalised with no scope for further deliberations.
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Government of India appointed a Committee in September, 1964 headed by Dr. A.M. Khosla for drawing up a master plan for the optimum and integrated use of Narmada water resources. The committee submitted its report concluding the availability of 28.92 MAP with 75% dependability.
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The Central Water and Power Commission in July-August, 1966 submitted a report stating that 75% dependable flow of the river at Navagam be taken as 27 MAP.
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Narmada Water Disputes Tribunal (NWDT) framed the issue relating to hydrology. That before the tribunal the 4 states after considering the observed flow data from 1948 to 1965 and the hindcast data from 1891 to 1948 reached an agreement on 12th July, 1974 thereby the availability of waters was taken as 28 MAP with 75% dependability. This agreement was reached between the 4 states after considering in detail, various conclusions for determining availability, which included taking into account, the observed flow data and hindcast data as stated above.
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The Central Water Commission in April, 1993 (which is the highest Technical body of the Government of India) observed that in view of the peculiar characteristics of the Narmada river and the coefficient of variation of annual flows of Narmada basin being larger, the data length required for assessing the utilisable flows is to be over 130 years. The CWC reaffirmed the justification by the tribunal in its award of using of 27-28 MAP as basis for water planning. Any data for a lesser period, is considered inadequate for assessing utilisable annulal flows within + 5% Error band since the coefficient of variation of Annual flow in case of Narmada basin is around 0.35 (As aqainst less than 0.2)
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The matter relating to hydrology was also referred to the International Consultant namely M/s. H.R. Wallingford which concluded the availability at 27 MAP at 75% dependability.
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The Narmada Valley Development Authority conducted studies which indicated that the hydro-meteorological cycle for Narmada basin at Garudeshwar to be 79 years and working on this period the 75% dependable yield was worked out in the range of 27.64 to 27.892 MAP.
All above shows that hydrology of the project is reviewed by experts several times and it is concluded that what NWDT has considered still holds good.
