With heavy dependence on the Yeleru canal to meet industrial and domestic water needs, the annual maintenance of the canal is not adhered to resulting in its yield falling.
The open, contour canal running 153 km has an efficiency of 55 per cent owing to seepage, evaporation and pilferage i.e., if 100 cusecs water is released at the source only 55 cusecs reaches the end point.
Annual maintenance of the canal was last taken up in 2011.
Regular, systematic maintenance work closing it for 60 to 70 days is in the long-term interest of the canal. Because it is not done, efficiency fell from 55 to 40 per cent over the years, says retired Superintendent Engineer (Irrigation) U. Narayana Raju.
Maintenance of contour canals in which depth is not uniform is critical and highly technical, he says. In such canals, the depth runs from 20 feet to 30 feet and gets silted with mud falling from the bunds and along with water flow also silt accumulates. When there is rain due to cyclones, the precipitation will be heavy. By its very design, annual maintenance is crucial for contour canals, says Mr. Raju.
Another important factor is de-weeding. The quantity received depends on velocity too and if weeds are not removed they will impact on the flow. In a similar manner, when the canal depth is low and silt accumulates even if water is released it does not flow well, he says.
Since GVMC has to meet the water needs of the city that has top priority it can even take up annual maintenance in November and December. He recalled that maintenance taken up during his tenure in November, 2003 increased the yield from 45 to 58 per cent.
But it could not be done to cater to the needs of the industry, which is very crucial.
The alternative is for the Visakhapatnam Steel Plant and NTPC to increase their storage capacity and fill them up in November and December.
More importantly, eight identified storage reservoirs, including six new ones, should be readied to get the fullest advantage and stock 12 tmcft of flood water once the Polavaram Main Canal under which 23.4 tmcft of water is allocated to the city under Bachawat Award is ready, Mr. Raju says.
Lining of the canal -- either with used refractory bricks or fly ash of NTPC -- will also improve efficiency by 20 per cent, he says.
