- This monsoon season Kerala suffered from one of the most severe floods in its history — comparable to the floods of 1924. In August 2018, the state witnessed severe rainfall that affected nearly the whole state and resulted in the death of nearly 500 humans and thousands of animals.
- Dams are often blamed for worsening floods, but not this time, as an analysis by the Central Water Commission held that dams neither worsened the floods nor reduced their intensity.
- The CWC analysis also called for the creation of a dynamic ‘flood cushion’ by reviewing the rule curves of all the reservoirs in Kerala. Activists assert that the report misses key points and is protecting dam operators from any blame.
Dams are often blamed for worsening the impact of floods. But this time, when Kerala witnessed one of the worst floods in its history, dams are not in the line of fire. India’s Central Water Commission (CWC), in its latest report on the devastating Kerala floods, has held that “dams in Kerala neither added to the flood nor helped in reduction of the flood” while squarely holding the heavy rainfall responsible for the disaster.
However, the report called for inspection of Poringalkuthu dam in Kerala and reviewing its spillway capacity. The report also sought a review of the “rule curves of all the reservoirs in Kerala” for creating “flood cushion” for moderating floods.
According to the historical records, Kerala had witnessed one of its most severe floods in 1924 and the CWC report noted that the rainfall of August 15-17, 2018 in Kerala was “almost of the same order as that of rainfall which occurred during July 16-18, 1924.”
“The storm of August 15-17, 2018 resulted in heavy flooding in Periyar, Pamba, Chalakudi and Bharatpuzha sub-basins of Kerala. The rainfall during August 15-17, 2018 was almost comparable to the historical July 16-18, 1924 rainfall of Kerala, particularly in Periyar, Pamba, Chalakudi and Bharatpuzha sub-basins,” the CWC report noted.
It said that Kerala experienced an “abnormally high rainfall from June 1, 2018, to August 19, 2018” resulting in severe flooding in 13 out of 14 districts in the state.
Dams no role to play in augmenting flood impact in Kerala, says CWC
According to the CWC analysis, “As per IMD (India Meteorological Department) data, Kerala received 2,346.6 millimetres of rainfall from June 1, 2018, to August 19, 2018, in contrast to an expected 1649.5 mm of rainfall. This rainfall was about 42 percent above the normal.
During August 1, 2018, to August 19, 2018, total rainfall occurred in Kerala was about 758.6 mm against the normal of 287.6 mm, which was 164 percent above normal.”
The analysis explained that out of 758.6 mm rainfall from August 1-19, about 414 mm rainfall occurred in just three days — August 15-17, which led to severe flooding.
“Due to severe rainfall from August 15-17, 2018, the gates of about 35 dams were also opened due to the extremely large inflow of water in the reservoirs. During August 2018, the reservoirs were either at FRL (full reservoir level) or only a few feet below the FRL. From the analysis it has been found that the dams in Kerala neither added to the flood nor helped in reduction of flood, as most of the dams were already at FRL or very close to FRL on August 14, 2018, due to more than normal rainfall in the months of June to July 2018,” the report emphasised.
The CWC report even noted “had the reservoir been a few feet below FRL, the flooding conditions would not have changed much, as the severe storm continued for three days and even for four days at majority of the places, and in any case it would have been necessary to release from the reservoirs after first day of the extreme rainfall.”
“The release from reservoirs had only a minor role in flood augmentation as released volume from the reservoirs were almost similar to inflow volumes,” it added.
A senior official of the CWC said dams didn’t play any role. “If such high level of rainfall happens again in Kerala, similar kind of flooding will happen. Dams neither worsened the floods nor prevented it,” the official told Mongabay-India.
James Wilson, who is a special officer in the interstate water advisory committee of the Kerala government, said “CWC is right about the statement about the role of the dams in the present intensity of floods”.
“Of course, our dams’ flood negotiation capacity is limited to negotiate very small return periods because we were forced to made a trade off during their construction. In Kerala all dams are possible only in high ranges where we limited submergence considering the optimum utilisation and economic considerations even in 60s and 70s,” explained Wilson.
He stated that Kerala’s reservoirs can hardly store 6.6 percent of average annual run-off for the lean season use.
“Now due to the changed scenario of dry spells between the monsoons, we are forced to part a portion of this water for irrigation and drinking water for dry spells in monsoon. So, even if we keep 20 percent in our larger reservoirs ie, with capacity of 200 MCM or above, and such of intense floods occur, that space will be filled up in 5-6 hours and we will be forced to release the rest of the inflow. Thus, the dams in Kerala are good enough to negotiate a maximum of 1 in 100 year — or if go conservative, a maximum of 1 in 50 year flood,” he added.
However, the CWC stressed that it is “essential to review the rule curves of all the reservoirs in Kerala” and they “need to be meticulously drawn particularly for the reservoirs having the live storage capacity of more than 200 MCM, in order to create some dynamic flood cushion for moderating the floods of lower return periods particularly in the early period of monsoon.”
However, Wilson stated that “none of our rivers are perennial like Himalayan rivers” and emphasised that “even a 20 percent flood cushion will create huge stress in the water availability for lean period.”
“Either increasing the storage capacity by raising height of reservoirs or building new reservoirs result in submergence of vast lands of forest in Western Ghats. So it’s a nuanced decision making. There are many structural issues we face in our river systems like low river banks in deltas, shrunken backwater lakes and small outlets to sea. How sustainably we can address these limitations require detailed deliberations from different domain experts,” he added.
Report ignores some key issues
“The CWC report is firstly not looking at some key issues related to dams,” said Himanshu Thakkar, coordinator of the South Asia Network on Dams, Rivers and People (SANDRP), a network of organisations and individuals working on issues related to the water sector, specifically associated to large dams.
“Did Kerala dams follow rule curve? Did Kerala dams do everything to reduce the water releases during floods? What more Kerala dams have done? Did Kerala dams have any flood forecasting, emergency action plans, assessment of downstream channel’s carrying capacity, inundation maps, alerting the vulnerable people in advance?” questioned Thakkar.
“Without answering these questions, to conclude that Kerala dams did not contribute to floods can only be seen as ideological assertion to save the dams and dam operators from any blame. To now say that Kerala dams need updated rule curve, without asking if the rule curve were followed, shows inconsistency and worse,” he added.
Thakkar further questioned that “if none of the storage available in Kerala could have helped, is the conclusion, how is more of them going to help?”
“In fact all the worst affected basins, as listed in CWC report, involved dams and their mismanagement. It is clear that CWC report is not a scientific report but is essentially an ideological document to save the dams and dam operators from any blame,” Thakkar said.
According to data from India’s ministry of home affairs, a total of 1375 human lives were lost and over 400 were injured this monsoon season due to floods across eight states. Of the eight states, the damage in Kerala is the most prominent as it recorded loss of 498 human lives so far (till September 13) and injuries to at least 140 persons, the death of 46,867 animals and 17.2 million poultry.
The floods affected over 5.4 million people. It also fully damaged 1,952 houses and partially damaged 21,964 houses. The floods also affected a total of 57,000 hectares of crop area, uprooting of 4,920 trees, damage to 3,652.5 kilometres of district roads, 2590.49 km of panchayat road, 106.1 km of state highways and damage to over 5400 electric poles.
Banner Image: August 2018 floods were one of the worst floods to hit Kerala in nearly a century. Photo by Praveenp/Wikimedia Commons.