CHENNAI : Predictably, the groundwater table throughout the State has improved remarkably, following the bountiful northeast monsoon. Still, "pockets of black spots" have witnessed fall in the groundwater level.

For instance, Vellore district in the north recorded nearly 70 cm, almost double the normal rainfall for the northeast monsoon.

However, six out of 22 groundwater observatory wells of the Central Groundwater Board saw a fall in the groundwater level when the present levels (January 2006) were compared with the decadal mean water levels of January 1996-January 2005.

Similarly, in Thanjavur district in the central belt, five wells out of 23 saw the groundwater level going down, when compared with the decadal levels. This district too received the benefit of successful northeast monsoon (75 per cent more than the normal 54 cm).

Tirunelveli district in the south too had its share of wells whose levels had fallen, compared to the decadal levels.

Five out of 31 wells came under this category. During the northeast monsoon, this district recorded 55 cm rain, about 30 per cent higher than the normal.

The negative fluctuation or the fall indicates greater groundwater exploitation over and above the recharge.

These form part of the findings of a survey of groundwater monitoring wells carried out by the Board last month.

One of the reasons is the presence of more number of energised agricultural pumpsets in these areas.

Experts say that the free power supply scheme for agricultural connections is a cause for indiscriminate use of electricity and water.

According to the data available with the Tamil Nadu Electricity Board, Vellore district accounts for about 1.2 lakh pumpsets, Thanjavur 50,000 and Tirunelveli 70,000.

Positive side

Notwithstanding the "pockets of black spots," 86 per cent of the total number of the wells analysed had shown rise in the groundwater levels. Improvement in the water level in the range of 0 to 2 metres was noticed in 46 per cent of the wells. Twenty three per cent of the wells reflected rise in the range of 2-4 metres and 17 per cent, more than four metres.

Chennai, Dharmapuri, Villupuram, Erode, Karur, Namakkal, Perambalur, Sivaganga, and Theni reported that in none of their wells, the groundwater levels went down. Coimbatore, Pudukottai, Salem, Tiruvannamalai and Virudhunagar were among the districts in which about 90 per cent of their wells had witnessed rise in groundwater levels.

What is to be noted here is that the 2005 northeast monsoon was unprecedented with the departure of actual rainfall from the normal being 79 per cent (on real time basis).

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