According to a detailed study on Kerala flood carried out by the Central Water Commission (CWC), the state’s major dams, on the eve of torrential rains, barring Idukki, were all already full to capacity. Thus making it impossible to contain cumulative runoff totalling more than 200 per cent of the storage capacity of all the small and big reservoirs in the state.
As stated in the detailed report submitted by the CWC to the water resources ministry last week, Kerala received 12 billion cubic meters (BCM) of water in three days of exceptional rain lasting from 15th to 17th August. This is almost more than double the capacity (5.8 BCM) of all the reservoirs in the state.
In view of the state’s experience and several affirmations made the report recommended revisiting the ‘rule curves’- strategic water levels for planning operations of a dam and all reservoirs. The report said that the dams neither added to the flood nor did it help to reduce the flow. Though standard operating procedures were followed incessant rains in June-July and exceptional rains in August left the state defenceless, the report said.
CWC director (hydrology) N N Rai said, “The dams did not release anything extra of what they received. The authorities had released water in a controlled manner. The commission has come to the conclusion after computing and analysing step by step inflow and outflow of water during the entire season”. He also shared that the report would recommend “revisiting rule curves of all reservoirs” in view of shrinking of their water carrying capacity over the years.
The CWC besides listing extreme weather conditions have also referred to other reasons including encroachment of floodplains and other activities in the catchment area behind the disastrous outcome of such intense rainfall.
The CWC is, however, an advisory commission only. All the dams are maintained by the state government with the help of experts in the management bodies, taking into account periodic alerts sent by different central agencies.