Wednesday , 24 October 2018

Why Goa needs desalination plants

Nandkumar M. Kamat

An unprecedented water supply crisis is developing. The environment department needs to immediately begin work to identify 20 hectares plots one each in north and south Goa and call for global tenders to build two ultramodern mega desalination plants. A provision of `1000 crores need to be made in the budget estimates, 2019-20 for two plants costing `500 crores each with capacity of 100 million liters per day (MLD) enough to augment and supply water to one million people.

The 15th finance commission soon to visit Goa would be receptive to such onetime assistance since Goa is an eco fragile state vulnerable to impact of sea level rise. This would tremendously boost ecology and economy and would permanently provide eco hydrological insurance for the state.

Monsoon has failed in Goa. I had already written about this scenario in this column on July 8– “the real worry is the reduction of rainfall in catchment area of Mandovi and Zuari basins which drain 70 per cent of area. Is climate change already desertifying Goa’s water banks, the Western Ghats? Why doesn’t it rain like in the past (4500-6000 millimetres) in the foothills of Western Ghats? The general trend along 1600 kilometres north to south, Songadh, Gujarat to Agasthyamalai Hills to the south as far as the Ariankavu pass, is alarming. The IISc, Bengaluru used statistical methods and modelled trend of rainfall time-series data of 100 years using the Auto-Regressive Integrated Moving Average (ARIMA). They discovered a decreasing trend in the rainfall pattern discernible over forest, agricultural and grassland areas from 2013 in northern, central and southern western ghats.”

The almost dry July, August and September months proved me correct. With just a week left for official end of this year’s south west monsoon, we can see an impending soil moisture stress and water supply crisis and a booming water supply tanker culture like Maharashtra. Cyclonic circulations in Bay of Bengal during November sometimes bring heavy post monsoon rains to Goa but already the deficit is huge in terms of local lentic, lotic and fragile groundwater resources.

The inflated claims of government of adequate fresh water and treated water sources are only notional and in reality, very little of the turbid water is useful. Not rigorously subjected to detail chemical and heavy metal analysis the manganese toxicity from Selaulim water supply is a grave public health concern. On 21 January this year sensing failure of monsoon I sent an appeal by email to CM, Goa, Parrikar which mentioned – “Time and technology is now becoming favorable for state of Goa to think of establishing high volume affordable onshore or offshore coastal desalination plants, at least by 2020-21 one each in North and South Goa in view of non-reliability of our committed water works which would continue to face several problems of getting adequate quantity of sufficient quality raw water.”

The clay colloids every year are clogging the filters in Opa treatment plant. Selaulim water is contaminated with manganese ions which can cause a rise in Parkinsonian syndrome. In Chennai desalinated water costs 6 paise a litre, `60 for 1000 litres against `15 for a litre of bottled water. So why are we spending so much money on water storage, treatment, distribution and supply?

The panel of experts of which I was a member under Rtd CE Maharashtra Desukar had prepared during 1999-2000 the master plan for utilisation of water resources of Mahadayi/Mandovi upto AD 2050. We found that Goa is a water deficit state because on paper purely notionally we have 8570 MCM (million cubic meters) freshwater available but at 21 per cent practical utilisation only 1760 MCM can be used whereas needs may exceed 2570 MCM.

The POE therefore gave a thought 17 years ago to desalination technology as an option and made these recommendations in the report “Recycling of water for reuse, use of regenerated waters, use of saline water for irrigating salt resistant crops and even installation of desalination plants for conversion of sea water to fresh water could be some possible future alternative technologies. However, for large scale adoption of the sophisticated technologies one must wait for further technological progress. All such schemes involving higher technologies such as desalination, it is felt, could be of supplemental nature and may need to be considered after available conventional water resources are exploited to the maximum extent.”

Mentioning clearly that this is the right time to think on desalination plants I had urged him to provide token funds in the budget of STE department for FY 2018-9 under the new subhead “exploring techno-economic feasibility of desalination plants”. I had advised the CM to also consult BARC and NIOT on desalination technologies for Goa.

To those who travel all over Goa and are familiar with the normal hydrography, physiography and green vegetation the coming dry season, cracked soils and onset of desertification would be shocking scenes. Factor in the record heat in October and from February to May resulting in rapid evaporation from all reservoirs and then one can see what a deficit monsoon can cause. Goa has no future without timely commissioning of modern desalination plants. If the work begins now then people would not have to worry about failure of the monsoon in coming years.

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