Hyderabad: The expert committee appointed to study the submergence aspects of the Polavaram dam has ruled that any reduction in the dam’s height or taking up alternatives like construction of barrages will not significantly reduce the submergence area.
The committee, headed by retired chief engineer M. Venkata Rao, has held that the dam height of Polavaram should not be altered.
“Taking into account the flow statistics of Godavari over the years, the benefits contemplated cannot be achieved without a minimum live storage at Polavaram of 75 tmc, full reservoir level of +150 ft, and minimum draw down level of +135 ft together with ground water extraction of the order of 70 tmc ft.”
The alternatives, suggested by retired chief engineers, T. Hanumantha Rao, M. Dharma Rao and S. Joga Rao, that included a series of barrages in place of Polavaram Dam provide only a very small fraction of the required live storage but at very great cost which would drastically curtail the benefits contemplated under the project.
Any reduction in the FRL (full reservoir level and the live storage) will curtail the benefits of the project including power, without resulting in any significant reduction in the submergence area and the ill effects of submersion.
The minimum draw down level cannot be kept lower than 135 ft keeping in view the obligatory provision for siltation in the reservoir and obligatory minimum level of the reservoir to be able to divert the required quantum of water from Godavari to Krishna and supply of water to Visakhapatnam as stipulated.
The committee was firmly of the view that maximum possible storage must be provided at Polavaram site, this being the terminal reservoir on the River Godavari.
It was also noted that reduction of FRL from +150 to +145 for instance, will severely reduce the benefits contemplated, without giving significant benefits in terms of reducing the submergence area.
FRL of 150 means submersion of 57,356 hectares and its reduction to 145 means a reduction in submergence of 5,915 hectares, only 10 per cent. Only four villages will be saved from submergence.
If the FRL is lowered to 145 ft, the live storage capacity will get reduced to 47 tmc from 75 tmc ft, corresponding to the original FRL of 150 ft. This, in turn will drastically get the ayacut reduced from 7. 20 lakh acre to 3.81 lakh acre.
Reduction of FRL to 135 ft will drastically reduce the benefits contemplated, making lifting from the reservoir inevitable without substantial reduction in the submergence area.
The proposal of Mr Hanumantha Rao has been quoted by several Telangana politicians and activists in their demands for reduction of the present dam design.
However, the committee after its research noted, “The proposal of T. Hanumantha Rao is to have a series of four barrages in place of one dam at Polavaram… After a study of the feasibility of this alternative proposal of barrages, it was found all the four barrage structures is only 16.38 tmc, which constitutes about 20 per cent of the live storage required under the Polavaram project. It is evident that with these barrages it is not possible to meet the demands as well as the benefits contemplated under Polavaram.”
