Riverbed levelling at Opa barrage now after monsoon

Ponda: As the river basin couldn’t be emptied due to tidal water in the Khandepar river near Opa barrage, the water resources department (WRD) has deferred levelling the river bed in front of the barrage to post monsoon. However, the WRD would complete the erection of the river bank erosion protection wall, said WRD executive engineer Mario Rebello.

A retaining wall is being constructed along the Khandepar river basin at the downstream side of the Opa barrage.

Rebello said they had prepared 1 cubic meter size square concrete blocks to place them where soil has been washed away at the river basin and deep ravines have been created.

It’s a natural phenomenon that soil is being washed away with the water current. Especially during monsoon, when the gates of the barrage are opened to release excess rain water, the water runs with a high current which can wash away river bed soil leading to development of the ravines, the senior officer said.

In such conditions, the concrete blocks are placed inside the ravines to level the river bed. “However, due to tidal water, the river basin couldn’t be emptied fully to place Geosynthetic membrane that maintain the concrete blocks stable. Each cube weigh around 1.5 tonne, Rebello said.

After finding that a major part of the Opa river was eroded near the barrage at the Opa Water Works, the WRD had taken up construction of a retaining wall to prevent further erosion.

The tender of the retaining wall and concrete blocks has been allotted to Unique Construction, Quepem, at a cost of Rs 5 crore.

The 8m high and around 40m wide barrage has six gates that can hold water up to 8m. “The WRD do not open first and last gates of the barrage during overflow in monsoon to avoid further erosion of the river bank,” Rebello said.