Dredging for sand may give no remedy to silting reservoirs says officials

The major and medium irrigation projects in the State have lost up to 25 to 30 per cent of their gross water storage capacity. This is attributed mainly to the process of increasing silt accumulation in the reservoirs behind the dams

Hyderabad: The major and medium irrigation projects in the State have lost up to 25 to 30 per cent of their gross water storage capacity. This is attributed mainly to the process of increasing silt accumulation in the reservoirs behind the dams. As the problem is assuming serious proportion, moves are afoot for desilting projects in a big way calling global tenders.

However, this is viewed largely as an initiative driven by the lure of potential revenue that can be generated from sale of the sand extracted from the projects. The government has no policy of its own that is relevant to the condition of the State projects and soils.

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Erosion of soils is contributing substantially to the problem year after year. According to officials, the State must equip itself with a policy evolved by taking into consideration the factors pertinent to the basin concerned.

The State government is thinking more in the lines of the national framework laid down by the Ministry of Jal Sakti for sedimentation management. But its methods must be State-specific. The approach that may be scientifically suitable for Godavari basin may not be relevant to its Krishna basin project, felt officials.

Dredging of reservoirs would not yield sand alone that could be sold. It yields huge quantities of silt and clay and their disposal is a serious issue. The silt removed from the catchment of one reservoir may turn out to be a much bigger problem for another reservoir downstream unless it is addressed with a scientific approach.

The focus on revenue dimension alone may overshadow the environmental and community benefit aspects. Effective handling of the silt can be possible only by involving the industry that needs it as raw material, they added.

Three projects – Sriram Sagar, Nizam Sagar and the Kaddam Project – have been facing the serious siltation problem for years. The gross storage capacity of the Sriram Sagar had dropped from 112 tmc to 82 TMC. The State had lost over 26 per cent of the benefits from the project.

This is more because of the increased human activity in the upstream catchment. Unless the silt removed by dredging is properly disposed, it would have a bearing in the storage capacity of the downstream projects in next few years.

The gross storage capacity in Kaddam project, which is more than 50-years-old had come down by 50 per cent. The project can hold hardly 7.6 TMC of water now. The Nizam Sagar project which is over 100-years-old has an effective storage capacity of 17.80 TMC as against its designed storage capacity of 25.6 TMC.

The sedimentation problem was felt equally in Singur, Lower Manair and Mid Manair. It is high in Krishna basin projects including Nagarjuna Sagar and Jurala.

Of the 33 medium irrigation projects, the sedimentation experience was high in Palemvagu project and Musi. The State is planning to have a realistic assessment of the siltation by engaging agencies concerned.

The negative impact of the desilting exercise has to be borne in mind before jumping into action. There was considerable growth in the fish spawning grounds in the State during the last ten years because of the extra focus paid to the irrigation sector. Measures should be taken to ensure that they remain intact, stressed irrigation experts.