‘Low temperatures signal less flooding’

One million cusecs of water might pass through barrages.

SUKKUR:

A super flood carrying 900,000 to one million cusecs of water will pass through all three barrages in Sindh, according to Met office readings of July 9.

The Meteorological office forecast says that there will be a 10% drop in rainfall and temperatures in Skardu. The decreasing temperatures will decrease the quantity of water which will in return make it easy for water to flow through barrages without causing any considerable damage to the dykes, said irrigation experts Abdul Aziz Soomro and Mandhal Shar.

According to Met office readings taken in Skardu on Saturday, with a temperature of 23.9 degrees Celsius, it was not warm enough for the ice to melt. Irrigation experts claim that temperatures can usually soar to 30 degrees. Since early July, the temperature in Skardu has not increased beyond 28 degrees. There will not be a considerable rise in river water levels till July 15. Reportedly, if rainfall in the catchment areas continues for another week then it might decrease the temperature in Skardu which will slow down the process of melting ice. “However, if the temperature rises above 30 degrees then the ice will melt and add volume to the river water level,” one expert said.

“We do expect a manageable amount of one million cusecs of water to flow in.” Also, the Guddu and Sukkur barrage structures mean that there is a slight difference between the upstream and downstream flows of water. “The pavements of the barrages are safe as they do not experience hydraulic jumps unlike those at Tarbela dam,” said an expert.

A hydraulic jump takes place when water is released from a barrage with tremendous force and usually at a height of six to eight feet. “Unlike at other barrages, water flows smoothly at Sukkur and Guddu without causing much damage to the pavements,” he said. “The structure of both barrages is capable of passing water up to 1.2 million cusecs.”

Measurements recorded at the Sindh barrages on Saturday showed a minimum rise in water levels. The upstream flow for Guddu barrage was 170,879 cusecs and downstream was 139,176 cusecs. While for Sukkur Barrage, the upstream was 128,230 cusecs and downstream was 79,340 cusecs. Kotri, measured at 43,370 cusecs upstream and 6,470 cusecs downstream.

Published in The Express Tribune, July 11^th, 2011.