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G.K. Nair

A view of the Mallappally bridge across the Manimala river. Indiscriminate sand mining has exposed the foundations of the bridge.

KOCHI, Feb. 9

SAND mining from almost all the rivers in Kerala goes on unabated despite the restrictions and controls imposed by the State Government.

It has not only deepened the river beds to below the sea level but threatens the existence of several road bridges across these rivers, according to Mr N.K. Sukumaran Nair, Vice-President of the Aluva-based Kerala River Protection Council.

"It is the violation of the law passed by the Kerala Legislature unanimously on December 6, 2001," he told Business Line.

He alleged that the controls envisaged in the law are not being enforced.

As a result of the fall in the riverbed level to below the sea level, the water available in 20-30 km stretch of several rivers from their confluences to upward has become saline.

Besides, the water level in the wells on the embankments has fallen sharply since the monsoon season has ended.

Another concern is that the indiscriminate mining has bared the bases of the pillars of the bridges to the extent that the well foundation that are supposed to remain under the riverbed are now exposed by three metres, Mr Nair said.

The worst affected rivers in the State are Manimala, Pampa, Achenkovil and Kallada, in Pathanamthitta district, Periyar and Bharatapuzha.

The stream discharge data of Central Water Commission (CWC) stations in the Manimala, Pampa, Achenkovil and Kallada river basins have been analysed to get an idea about the natural replenishment of these rivers.

It is estimated that about 65,899 MT - equivalent to 8,237 truckloads - per year of sand is being transported downstream of the respective gauging stations as suspension.

The daily dividend worked out on the basis of 200 working days in a year comes to only 41 truckloads per day (tlpd).

"If one is very particular about sustainable mining, only 41 tlpd of sand can be mined from the river stretch downstream of the CWC stations," official reports said.

At the same time, the existing quantity of sand being mined from the river stretches downstream of gauging stations amounts to 851 tlpd.

"When the extraction rate exceeds the replenishment rate, significant and potentially irreversible changes occur in the hydraulic conditions and channel stability."

On the other hand, these rivers provide drinking water to lakhs of people in the respective basins.

"Unfortunately, these rivers are on the verge of severe deterioration due to indiscriminate quarrying of sand for constructions. The riverbanks, at many locations, are being cut deeply for developing new sand mining locations," a CWC official said.

"Slumping of river banks, marked changes in riverbed configuration, mining of sand from prohibited areas close to engineering structures and over-deepening of river channels are some of the problems that need immediate attention."

It is estimated that the riverbed has been lowered about 1.2 m in Manimala in 1990-2000, 1.23 m in Pampa (1985-2000), 1.3 m in Achenkovil (1980-1995) and 2.23 m in Kallada (1980-2000).

Apart from instream mining, mining of sand from land areas such as paddy fields and floodplains is also practised in many panchayats.

The layers of sand inter-bedded within floodplain areas have been exploited as an alternative to river sand.

The floodplain mining also damages the environmental setting of the area.

"It is because the sandy layers intervened within the floodplain deposits have direct baring on the local hydrological regime and ground water movement," the official said.

"Removal of sediments and creation of deep pits by way of mining sand will result in lowering of water table to deeper levels."

Later, the dug wells of such locations have also to be deepened in tune with the lowering of water table.

Water logging, collapse of wells adjacent to mining sites, marked changes in the scenic beauty and geomorphology, reduction in agricultural land, etc., are some of the problems that follow floodplain mining.

Further, there are several reports of pit capturing and even change of the natural course of rivers in areas subjected to intense floodplain mining, the officials added.

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