Silt in Teesta triggers flood
The huge amount of silt deposited in the Teesta River and irrigation canals under Teesta irrigation project is creating hindrance to smooth flow of water, triggering recurrence of flood during the rainy season as the riverbed and the canal bed have risen as a consequence.
This situation has arisen as the silt trap situated near the Teesta Barrage has been nearly filled up as the Water Development Board (WDB) could not conduct proper dredging during the last two years. This will also create problems in irrigation of boro paddy fields in the dry season, as the water may not flow through the irrigation canals smoothly due to the raised beds, said AKM Shamsuzzoha, executive engineer, Dalia divisional office of WDB.
WDB sometimes diverts excess water of the Teesta through the irrigational canal network during flood to reduce water pressure in the river, he added.
WDB sources in Dalia division said the Teesta brings nine lakh tonnes of silt from upstream every year, and if the silt is not cleared by dredging of the silt trap, a large amount may be deposited on the river and irrigation canal beds, raising their heights.
The silt trap, an artificial deep-water body having an area of 54 acres and height of 47.56-metres above sea level, is located at the junction of the Teesta and the main irrigation canal at Dalia point in the district.
When river water carrying silt enters the main canal, it is diverted to the silt trap where the silt is trapped and the clear water flows through the canals to the desired places, sources said.
Md Rubayat Imtiaz, sub-divisional engineer of WDB in Dalia division, said “The silt trap in Dalia has risen by about 3.5 metres, making it unable to receive additional silt coming with upstream water, as sufficient dredging wasn't possible in the last two years due to fund constraint.”
“At least 4-5 lakh tonnes of silt need to be removed in the 2016-2017 fiscal year, otherwise the raised canal beds may obstruct smooth flow of water, which may hamper irrigation in the next boro season,” he added.
WDB officials said as river and irrigation canal beds have risen, onrush of water now overflows their banks, causing floods.
When this correspondent visited the silt trap, he found that the two WDB-owned dredgers, each having 530-horse power capacity, are lying almost idle as they are at least 20 years old. Both are presently capable of removing only 120 cubic metres of silt per hour.
Fuel consumption is also high as each dredger consumes 135 litres of diesel per hour, which would have been around 25 percent less if the dredgers were new.
AKM Shamsuzzoha said they had sent a letter to higher authorities requesting allocation of adequate fund in 2016-2017 fiscal year in order to carrying out full dredging in the silt trap for keeping the river bed and canal beds within the required depth.