The north-east monsoon has been bountiful in the State but there is a wide difference in storage levels of irrigation reservoirs and hydel reservoirs.
On Monday, important irrigation reservoirs had, on an average, storage of over 90 per cent of their total capacity, whereas in the hydel reservoirs it was hardly 60 per cent.
While major irrigation reservoirs are maintained by the Water Resources Department (WRD)/ Public Works Department, the hydel reservoirs are run by the Tamil Nadu Generation and Distribution Corporation (TANGEDCO). For the purpose of this study, seven reservoirs, coming under the control of the WRD, and 18 of the TANGEDCO were taken into account.
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For the period ending December 8, the State recorded 47 per cent excess rainfall — 57 cm rainfall against the normal 39 cm. Twenty eight out of 32 districts registered excess rainfall while the remaining four — Chennai, Kancheepuram, Tiruvallur and Nagapattinam — fell in the category of “normal rainfall.”
As regards storage position, the primary reason for the low average of the hydel reservoirs is poor rainfall in their catchment. Even among the hydel reservoirs, only the Pykara and Kundah groups of reservoirs have less storage compared to others. This is surprising as the Nilgiris district where they are located recorded excess rainfall of 66 per cent.
Of the hydel reservoirs, those in the basins of Parambikulam-Aliyar (Kadamaparai and Upper Aliyar alone), Periyar-Vaigai (Suruliyar alone) and Kodayar have an average storage in the range of 94 to 100 per cent. Only the storage of the Pykara and Kundah reservoirs is barely around 50 per cent.
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In respect of irrigation reservoirs, the lowest is 84 per cent [Mullaperiyar] and the highest, 100 per cent [Mettur]. Parambikulam, Thunakkadavu and [Tamil Nadu] Sholayar have been covered under the category of irrigation reservoirs.
As for the storage of hydel reservoirs [expressed in terms of million units], the figure was 1,570 MU on Monday.
So far, hydro generation achieved was 3,523 MU while it was around 4,100 MU for the corresponding period of the previous year. During April 2009-March 2010, the total generation was 5,640 MU, around eight per cent of the overall availability of electricity of the State. Nearly two-thirds of the total hydro generation was recorded during July-December 2009.
A senior official of the TANGEDCO explains that though the share of hydro power is less than 10 per cent of the overall power availability, the hydel stations come extremely handy to authorities in times of sudden failure of coal-based thermal power stations or steep fall in production of wind energy.
In the last two years, conscious efforts are being made to optimise the generation of hydro power and reduce the average cost of production through more systematic planning and execution in the management of the stations. As of now, the cost has come down to 24-25 paise per unit from 54 paise earlier.