Ever since the last week of July, the India Meteorological Department has been giving heavy rainfall warnings in Maharashtra. Low pressure systems building up in the Arabian Sea and Bay of Bengal were to cause very heavy rain along the western coastal zone and adjoining areas. They were also to teach us one more lesson on floods, and how we could prepare for such a situation. Preparedness depends heavily on scientific tools and data, and also relies on experience, insight and wisdom. It also needs the right people, and service of experienced people.
The present situation could have been mitigated, if not averted, to some extent. The catchment areas of the Malaprabha and Ghataprabha rivers of the Krishna basin in Karnataka recorded heavy to very heavy rain since August 4 and 5. Cumulative outflow from the Almatti Dam is 280.944 tmcft, as against live storage of 80.62 tmcft as on August 9, 2019, with live storage at 68% of the total storage.
The heavy release of water is a measure to avert or manage the situation arising from the huge and sudden release of water from Maharashtra dams. Normally, a thing which is not measured properly cannot be managed properly.
This is especially true of rainfall and runoff; risk and vulnerability map the village cadastral-scale in rural areas, and ward-level in urban areas. An adequate number of monitoring stations for rainfall and runoff needs to be ensured. In spite of experiencing frequent weather-related disasters, a serious attempt to improvise monitoring and casting medium and long-range forecasting needs serious consideration.
The Doppler Weather Radars, if they existed, could have certainly provided useful inputs, and is now casting short-term forecasting of flood causing weather systems. In the prevailing situation, preparedness measures have been taken by releasing water from the Almatti sooner, as water was released from dams in Maharashtra. However, the scope for better preparedness in reservoir management exists in the present scenario.The present live storage in Almatti is 68 per cent of its total live storage. Much of the excess water provenance is in Maharashtra. The present system of water resources development is designed for 50 per cent probability of rainfall spectrum. In extreme events, rainfall is not considered for utilization.
In the background of an increase in extreme events — both severe consecutive droughts and heavy short duration floods — there is a need to redefine the assessment, development and management of water resources. The Krishna basin in Karnataka has experienced floods in three out of 19 years since 2000. So, the probability is around approximately 16%. It means the opportunities of utilising excess water, comes in a gap of three years, every two decades. Are we prepared to utilise such window of opportunities with a probability of 16%? If the answer is yes for the above, then are we should be prepared to maintain the system so that it is up-and-ready when the opportunity presents itself. A backward look tells us of many such floods and droughts in the past. What is excess to one, could be the life source to another, for instance --the community in the lower riparian areas. The ecosystem does need floods now and then, but a balance needs to be arrived at, if we need to think of utilising excess water. Our hydrological regime has undergone a big transformation and that calls for a new understanding.
V S PRAKASH
Founder and Former Special Director, KSNDMC