Lack of river management a key reason for floods in Krishna: Expert
The immediate cause for the latest floods was a lower pressure built up over the Bay of Bengal, besides a land-based cyclone, which drew moisture from both Arabian Sea and Bay of Bengal: IMD
The devastating floods in Krishna and Godavari River basins that wreaked havoc in several parts of Andhra Pradesh and Telangana in the past week, leading to death of 75 people and displacement of more than 59,000 people in both the states, is unusual in the terms of short spurt of extreme rainfall.
The immediate cause for the latest floods, according to the Indian Meteorological Department, was a lower pressure built up over the Bay of Bengal, besides a land-based cyclone, which drew moisture from both the Arabian Sea and Bay of Bengal. The combination of these factors led to very heavy rains in both the Telugu states, starting from the night of August 30 and continuing till September 3.
“Over 27 per cent of the state’s annual rainfall occurred in just 48 hours, causing severe flooding in many areas and Vijayawada, particularly, bore the brunt of the deluge with 290 mm of rainfall in a single day on the night of August 31 and September 1, which was the highest rainfall in the last 30 years,” said Andhra Pradesh Disaster Management Authority managing director Ronanki Kurmanath.
During this period, several parts of Telangana received the highest rainfall ranging from 438 mm in Mahabubabad to 435 mm in Warangal, 425 mm in Suryapet and 422 mm in Khammam.
Cause of floods
Experts attributed the flooding in several parts of the state to extreme rainfall but held massive construction on the river flood plains in both Krishna and Godavari basins as a contributing factor. The two flood plains fall receive 84% of rainfall during monsoon, starting from June to September, thereby increasing probability of floods during the rainy season.
Compared to Godavari, which witnesses floods almost every year, Krishna river is less prone to floods. According to the official data, the Krishna river, the second largest eastward draining interstate river basin, witnessed as many as 17 floods in the last 100 years.
According to Veeramalla Prakash, chairman of Indian Peninsular River Basin Council (IPRBC), the major cause of floods to the Krishna river are torrential rains in the upper catchment area in Maharashtra and Karnataka, although cyclone and deep depression-induced rains have been one of the major common causes of floods.
“One of the main reasons for floods in Krishna river is lack of proper river management by the riparian states. Maharashtra and Karnataka impound Krishna water in their dams to the brim before releasing to the downstream. This is causing floods in their respective states due to backwaters of these dams. For example, Sangli city and its surroundings suffer from floods whenever water is impounded in Almatti dam by Karnataka,” Prakash said.
However, the flooding has aggravated in recent decades due to climate change induced extreme rainfall in upstream of the river, forcing the two states to open the gates of the dams and release water to the downstream, resulting in floods in Andhra Pradesh.
The worst flood the state had witnessed in Krishna river before 2024 was in the first week of October 2009. Due to heavy rainfall in Karnataka, the gates of Almatti and Narayanpur dams on Krishna river and Tungabhadra dam on Tungabhadra river were lifted affecting many districts along the river course.
Kurnool town was submerged in the backwaters of the Srisailam dam due to unprecedented inflows then. The Srisailam dam, which was designed to withstand a maximum flood flow of 19 lakh cusecs, received 25.4 lakh cusecs of water for eight hours on October 2, 2009. At the Nagarjunasagar dam, too, more than 11 lakh cusecs of waters and by the time the flood reached Prakasam barrage, it was around 10.94 lakh cusecs.
“Had the water been released by Karnataka periodically to the downstream, there would not have been such a huge flood to the river and destruction in Andhra Pradesh,” Prakash said.
Like 2009, the latest flood in Krishna river that ravaged Vijayawada and its surroundings was also because of impounding of water in the dams upstream. “All the dams in Maharashtra and Karnataka were filled to the brim in July itself. So, was the case with Srisailam and Nagarjunasagar,” said Prakash.
The damage to one of the gates of Tungabhadra dam added to the misery, as more water to the extent of 32 tmc (thousand million cubic feet) joined the Krishna river in Andhra Pradesh. So, when there were heavy rains upstream in the last week of August, the already swelling Krishna river received more inflows and the irrigation authorities had to open all the gates of major dams, leading to flooding, official said.
According to state irrigation minister Nimmala Ramanaidu, the discharge at Prakasam barrage on Krishna river at Vijayawada reached up to 11.43 cusecs on September 1, which was the highest since the barrage was built in 1852-56. “This resulted in submergence of colonies along the river course in Vijayawada and the villages in Krishna district downstream,” Ramanaidu said.
But more than Krishna river, it was the unprecedented floods to its tributary Munneru, which ravaged Telangana’s Khammam town, and Budameru, an independent river, passing through northern side of Vijayawada that caused extensive damage to the lives and properties in several colonies.
The Munneru river, typically a dry tributary, swelled unexpectedly, causing a flash flood in just one hour between 10 am and 11 am on September 1. With no prior warning or announcement from the authorities, the flood devastated Khammam, for the first time in the last 70 years, disaster management officials said.
“The flash floods to Munneru was because of a sudden surge in the Akeru forest stream upstream about four kilometres away. It came like a Tsunami to the people of Khammam, who built their colonies along the river course,” said R Satyanarayana, a resident of Khammam.
Similar was the case with Budameru river, which created havoc in the colonies of Vijayawada, that are submerged even after a week. Originating from the hills of Mylavaram, Budameru traverses 176 kilometres before it empties into the Kolleru Lake. Several streams join it on the way. At Velagaleru near Vijayawada, a barrage with 11 locks impounds water if the flow is sluggish.
The last time Budameru received floods was in 2005, when it received an inflow of more than 75,000 cusecs which submerged many areas in Vijayawada.
Following a hue and cry, the then government constructed the Budameru diversion channel (BDC) in 2006-07, which meant for diverting the Budameru flood into the 37,500-cusec-capacity Polavaram Right Canal which finally empties into the Krishna.
In the last 17 years, there has not been much flood in Budameru river. During this period, Vijayawada expanded rapidly and several new colonies like New Rajarajeswaripet, Nandamuri Nagar, Nunna, Payakapuram, Singh Nagar, Devi Nagar and others came up, making the Budameru shrink into a narrow drain. Even the bunds along the river were destroyed and encroached upon by the greedy realtors.
“The river no more exists and its flood plains have been taken over by all types of construction. The canal was primarily built to divert river water to Polavaram canal after 2005 floods and 11 gates were built on the river to prevent it from entering the city. This created a false hope,” said independent weather man, Pradeep John.
This hope dashed on September 1, when heavy rainfall in the upper catchment of Budameru resulted in an inflow of 50,000 cusecs of water into the river. The water could not be diverted from Budameru into Krishna river through a diversion channel as the Krishna river was already in spate with 11 lakh cusecs. Hence, the massive flooding
So, it created a rebound effect as 50,000 cusecs of water flowed back into Budameru with tremendous speed. The authorities were forced to open 11 locks at Velagaleru to let the water into the river. Had it not been done, water would have submerged Narla Tata Rao Thermal Power Station.
So, it entered Vijayawada city and flooded the colonies which came up on the flood plains of Budameru. Even after a week, the colonies are still in water.
As mentioned above, compared to Krishna basin, Godavari basin is more prone to floods, because it flows through huge forest areas which has several tributaries like Manjira, Pranahita, Sabari, Indravati and Kinnerasani, which get huge floods during the rainy season, which join the Godavari river at different locations.
“Most of these tributaries pass through the forest area and flow at a faster pace, causing flash floods to the Godavari river. Added to this, they bring a lot of silt along with them, because of which there will be a heavy submergence of areas in the flood plains of the river. Even moderate rainfall in the upstream of the river leads to massive floods,” said Prof D Narasimha Reddy, independent climate expert and former visiting faculty of University of Hyderabad.
According to Veeramalla Prakash, the floods to Godavari river in Telangana and Andhra Pradesh begin only after Kaleshwaram. “The Maharashtra government constructed a series of dams and barrages, and a number of small lift irrigation schemes on the river course. That led to the disturbance in the natural river course, depriving the water to downstream projects in Telangana like Kadem project, Sri Ram Sagar Project (SRSP) and Sripada Yellampalli project,” Prakash said.
In order to meet the irrigation requirements of Telangana, the previous BRS government took up the construction of lift irrigation project of Kaleshwaram at the confluence of Pranahita with Godavari river, which has three barrages, which would be filled up by lifting water from the river and from there to different parts of northern Telangana.
“What is causing floods to the river leading to submergence of human habitations and agriculture fields is the greed to impound more water to the brim. When there are heavy rains on the upstream, the irrigation authorities are forced to lift the gates of these barrages to release water to the downstream, resulting in heavy floods,” Prof Narasimha Reddy said.
Historically, the highest flood level recorded in Godavari at Bhadrachalam was 75.60 feet in 1986, with a discharge of 27 lakh cusecs. In 2022, the flood level reached 71.30 feet, with a discharge of 21.78 cusecs.
The heavy flows in Godavari river at Telangana’s Bhadrachalam reach Polavaram dam, which is still under construction in West Godavari and from there to Dowleswaram barrage near Rajahmundry. In 2022, more than 23 lakh cusecs of water was released from this barrage, inundating several island villages in Konaseema region enroute to Bay of Bengal.
“Submergence of thousands of acres of crops, destruction of houses and evacuation of lakhs of people to the relief camps has been a regular phenomenon in this region every year,” Reddy said.
Water conservationists like Bhiksham Gujja have expressed apprehensions that once the Polavaram dam is completed, its backwaters might submerge many parts of Bhadrachalam, which is already getting flooded whenever the water level increases in the Godavari river.
Another prominent water expert and former professor of IIT Bombay B V Subba Rao, who was also a former member of Lakes, Reservoirs and Water Domain of Bureau of Indian Standards said the main reason for frequent floods to might rivers like Godavari and Krishna, besides their tributaries and other rivulets was the disturbances in the river courses, affecting their natural flow.
“If expanding agriculture in the flood plains of rivers is the reason for floods in the rural areas, fast growing urbanisation leading to encroachments is the reason for flooding in urban areas,” he said.
Rao said the river flood pattern has been undergoing drastic changes in the last 20 years and the river basins have experienced unscientific and unsustainable land use. “However, no scientific studies have been conducted in this direction,” he said.