SHILLONG, April 20 - Meghalaya Power Minister James Sangma informed the Assembly that the Umiam reservoir faces no threat from siltation, at least for the next 100 years, as per a study conducted in 2004.
He was replying to a question asked by Independent legislator, Syntar Klas Sunn who wanted to know if the high siltation in Umiam Lake is adversely affecting the power generation of the dam.
Sangma informed the House recently that the Umiam reservoir has a catchment area of 221.5 sq km and water spread of 10.148 sq. km at full reservoir level. The storage reservoir is used for feeding the existing five power stations located in the Umtru basin downstream.
The river Umiam was impounded by constructing a concrete dam of about 69 metre height in 1965 during construction of the 4x9 Mega Watt (MW) Umiam Stage-l Project.
At present, the Umiam Lake is the “mother reservoir for power generation of the entire State of Meghalaya,” and preserving the live storage of the Umiam reservoir is of utmost importance to Meghalaya Power Generation Corporation Limited (MePGCL), the Power Minister stated.
However, the increasing urbanisation of Shillong and its neighbouring areas has substantially increased the silt load in the two main tributaries of river Umiam, namely, Wah Umkhrah and Umshyrpi, both of which flow through the heart of Shillong.
The Power Minister said, studies were conducted by WAPCOS in 1990 and Tojo Vikas International Pvt Ltd., New Delhi in 2004 for silt assessment.
The studies conducted by WAPCOS were mainly limited to hydrographic surveys for silt assessment with relation to the original bed profiles. The study by WAPCOS indicated an average rate of siltation of 26.1 Hectare Metre per 100 sq km per year.
However, the siltation studies carried out by Tojo Vikas (India) Pvt Ltd., New Delhi, were much more elaborate and involved both hydrographic and topographic studies of Umiam reservoir by using state-of-the-art high- tech instruments like Global Positioning System, Digital Echo Sounder, Analogue Echo Sounder, etc.
The live storage of the reservoir as on 2004 has reduced by 4.64 per cent and the dead storage has reduced by 36.33 per cent. “Accordingly, when Umiam reservoir would be 100 years old, the loss in live storage would be 15 per cent and the loss in dead storage 73 per cent,” Sangma informed the House.
As per the study, dredging of Umiam reservoir to eliminate the silt deposits and enhance the storage capacity does not appear to be an attractive proposition. As per the Report, the dredging is proposed for 2.17 Million Cubic Metre which is only 1.53 per cent of the live storage capacity of the reservoir.
“The cost of dredging even for this insignificant volume of 1.53 per cent of live storage will involve a cost of about Rs 41 crore at the rate of Rs 189/- per cubic metre, which is not economically viable,” Sangma said.
To another question asked by Sunn, whether there is any proposal to harness wind energy of the State, the Power Minister answered in the affirmative.
He said, a Pilot Project on Wind Energy was sanctioned by the Government during 2011-12 for an amount of Rs 700 lakh to be implemented by Meghalaya Energy Corporation Limited but it could not be implemented as there was no response to the tender issued despite the tender being extended thrice.
He also informed the House that Wind Mapping is being undertaken by Meghalaya New and Renewable Energy Development Agency with the support of National Institute of Wind Energy, Chennai to assess the wind potential at different locations of the State by installing Wind Monitoring Stations at 50 metre height.
Based on the assessment Umshnong village in Jaintia Hills was chosen for further conduct of studies to harness wind energy. Moreover, 63 sites have been identified in the State by National Institute of Wind Energy, Chennai which has the potential for harnessing wind energy, the Minister informed.