HYDERABAD: Irrigation officials and experts from Punjab visited Kotri Barrage on Sunday in the wake of a reported dip upstream to see how to go about assessing nature of the dip and deal with upcoming flood season. They decided to start a bathymetric survey at the barrage to be conducted by International Sedimentation Research Institute (Isrip).

The experts were accompanying Sindh Irrigation Secretary Zarif Khero, who has called the Isrip team and also approached Chaudhry Ghulam Qadir, a retired chief engineer and former director of Punjab’s Nandipur Irrigation and Research Institute (IRI), for a model study.

Kotri Barrage chief engineer Haji Khan Jamali, Sindh Barrages Improvement Programme chief engineer Ghulam Mohiuddin Mughal, Barrage Management Unit chief engineer Sajid Bhutto, Development Region-I chief engineer Mansoor Memon, chief engineer Sohail Baloch and others were also present.

They discussed barrage regulation at length while examining drawings of the structure built in 1956.

Decide to start bathymetric survey, conduct model studies

They were given a presentation by the officials concerned.

The officials suggested that the bed configuration of the barrage up and down stream should be determined first which would reveal the size of the pit to see how barrage regulation should be ensured till this issue was fixed during upcoming floods.

Model studies to be undertaken

They decided to conduct model studies for the barrage for the purpose.

Mr Zarif told Dawn over phone that at this point of time upcoming flood season was the top priority. “We will see how to ensure a smooth flow of floodwaters downstream barrage and go about treating the problem post-flood season this year,” he said. He was of the view that the annual closure of barrage would provide an ideal opportunity to look at the problem closely at upstreat barrage.

“It was discussed that downstream flow of river should be centralised which will correct upstream approach flow of the river to prevent lateral/parallel flow upstream. This will avert eccentricity upstream approaching river flow,” said Mr Zarif.

“The pit at upstream barrage is said to be big and that’s why bathymetric survey is to begin, for which the Isrip team has been called from Nara canal where they have been working,” he said.

‘Pit bigger than normal this time’

The irrigation secretary said that it was understood that due to Indus river hydrology at upstream such pits had developed in the past at barrage but this time its size appeared bigger. He said model study would be prepared by July end so that the same could be presented to government along with cost. Besides, he added, river training works component would also be discussed in model study for proper barrage regulation in future.

The experts were informed that when Kotri barrage was built, its river training works were not prepared. The river hydrology at Kotri Barrage showed Indus river flows towards left guide bank and after hitting the divide wall, it turned to right guide bank when right side gates of the barrage were opened. An island has been created on the right side of river upstream.

Kotri Barrage chief engineer Haji Khan Jamali told Dawn over phone that bathymetric survey would clear everything about soil surface. “It will show whether soil surface under water is smooth or it has some craters or it is uneven,” he said.

According to him, this report is to be submitted to government by the experts’ team. Besides, he said, the barrage’s manual was to be updated since it was rehabilitated in 1998 by a British company.

Mr Jamali said that the company had prepared the standard operating procedure (SOP) that would be whether it was to be updated/amended as the barrage did not have river training works since day one. He said that 1948 model study had also anticipated that that river flows would move towards left guide bank.

“The [bathymetric] survey will reveal whether dumping of stone-covered actual part of deep channel or some crater is still left uncovered. This exercise will verify each and every thing to the satisfaction of everyone,” he said while mentioning that deep channel was created upstream the formal structure of Kotri barrage. “It will also verify health of the apron as well,” he said.

Annual closure

Kotri Barrage undergoes annual closure in mid-December. The officials wanted to ensure preparatory work including cost estimation. The Isrip team members would start their work from Monday. After cost estimation, the scheme would be submitted to Sindh government.

The experts also met Sindh Irrigation Minister Jam Khan Shoro and briefed him about their initial assessment and work methodology.

According to Mr Shoro, since it is purely a technical matter, he could just understand that the pit is feared to have developed at barrage upstream for which the experts are going to prepare model studies. He said that he was informed that the pit had developed due to scouring by water upstream.

The minister said that experts would create coffer dam to go about the work. “Expenditures won’t be an issue because it is an important matter; it doesn’t matter whether an elected or caretaker government is there [in November]. The proposed works have to be carried out,” he said.

Published in Dawn, July 10th, 2023