After several dry years, there has been a flood in the Krishna River. In what is being cited as rare, the river was in spate twice within 30 days. But all flood moderation and dam safety protocols seem to have been violated or ignored.
While Almatti is the first major dam on the Krishna River, it is the Srisailam Dam, which receives water from the Tungabhadra Tributary, sees the biggest of floods. In 2009 (October 3) the reservoir which has a capacity to hold a maximum of 350 tmcft received an inflow of 25.5 lakh cusecs and 14.8 lakh cusecs was discharged from a height of 250 feet.
The dam was subjected to maximum stresses during the flood for the first time after its commissioning. The dam tilted towards downstream by 4 mm on the day (October 3). The tilt reached a maximum of 8.8 mm on October 8, 2009 and it later returned to its normal position.
Each square metre of the dam was subjected to a pressure of 170 tonnes, 27 tonnes in excess of the permitted 143 tonnes. These are the kind of forces that play and extra caution is needed to control them.
Though the flood witnessed at the reservoir this year was of a much lower magnitude, irrigation department engineers lament that protocols have been ignored. The marked reduction in coordination after bifurcation could be a reason for the lapses. With the Krishna River acting as a border between the two Telugu States, two major reservoirs -- Srisailam and Nagarjuna Sagar -- are common to both States with Telangana (TS) on one side and Andhra Pradesh (AP) on the other.
While AP was given full operational control over Srisailam, TS was given control over Nagarjuna Sagar (NSP) as some form of temporary natural justice until more permanent mechanisms are developed.
Earlier, Srisailam was used primarily for power generation and NSP for storage. After bifurcation each State has its own priority. Besides the changes in priorities both States want to make the best use of the flood waters. AP wants to divert as much as possible to Rayalaseema and TS wants to use it for power generation.
In these changing priorities the importance of flood moderation and gate operation protocols seems to have taken a backseat.
New guidelines
The Central Water Commission (CWC) has also come up with new guidelines in 2018. For reasons unknown, irrigation engineers were to ignore all protocols set by the CWC, says a retired irrigation engineer who requested anonymity.
The operation of gates was gave scant regard to safety of dam structure, gate components and to dissipation of energy being released into the channel or river, he said.
The total failure in ‘inflow forecasting’ was another reason for the fumbling in following of protocols. The damage to the dam, gates and other structures that play a role in flood management should be evaluated as soon as the flood recedes at project, says the engineer.