The multi-crore Polavaram project in Andhra Pradesh is currently embroiled in legal issues. But now, the project is being contested on technical issues as well. A study carried out by the International Water Management Institute (iwmi), an international non-profit research and development organization, has questioned the fundamental basis on which the project was designed.
It was designed on the estimation that since the Godavari river has surplus water, it will be transferred to the water-deficit Krishna basin. The iwmi report has found that the Godavari does not have enough water to spare. A feasibility report by the National Water Development Agency (nwda) on the other hand says Godavari is water surplus.It calculated the surface water availability at Polavaram--the downstream-most dam on the Godavari (there are three dams)--to be 80,170 million cubic metres (mcm), considering 75 per cent assured flow (water available for 75 per cent of time in a year). nwda officials calculated the figure using annual average rainfall data. iwmi calculated surface water availability to be 36,000 mcm using monthly data. After deducting all water allocations, as designed by nwda, there is a deficit of 37,199 mcm (see table Godavari Surplus or not?).
"The problem with the annual average is it does not consider variability of flow within a year, which is very high in monsoon-driven rivers," says Vladimir Smakhtin, a hydrologist with iwmi, in his report. The catchment area gets around 70 per cent of rainfall just between June and September.
nwda officials disagree. "Estimates based on annual average and monthly average will certainly vary. Since rainfall is not uniform throughout the year, it is better to take annual average. Our methodology is used for all inter-basin water transfer and is peer reviewed and approved by technical experts," says N K Bhandari, chief engineer with nwda.
Smakhtin says the nwda method of calculation also overlooks the allocation of water to keep the river ecosystem alive. The water used for such purposes is called environmental water, which is an equally important component of use, besides other uses such as irrigation, domestic and industrial projects. "The present planning of inter-basin water transfer is based on future irrigation requirement and ignores environmental water demand, which is important to maintain the ecology of the basin," says Parikshit Gautam, director, Freshwater and Wetland Conservation Programme, wwf- India. iwmi estimates that 8,200 mcm of water flow is required to keep the river fit for fisheries and wildlife. This itself is a conservative figure as this flow cannot make the river fit for human consumption by checking human and industrial waste.
Besides, says Smakhtin, "Even if the project continues, the water will be consumed en-route because of numerous uses. The objective of filling up Krishna basin will remain unfulfilled."