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30Apr

CLIMATE IMPACTS ON WATER RESOURCES

30 Apr, 2019 | Return|

Dr. Georges Vachaud is an Emeritus Senior Researcher at the French National Centre for Scientific Research, Paris CNRS with expertise in Geostatistics, Hydrogeology, and Hydrology. He was firstly responsible for team at the Institute of mechanics of Grenoble, then at the Laboratory of study in Hydrology and Environment, LTHE. He was also Chargé de mission at the Institute of Sciences of the Universe, and at the National Institute of Ecology and Environment at CNRS, Paris from 1997 to 2008. He served as Director of the Institute of the Environment, European University and Scientific Center, Grenoble and as Head of the “Water-Vietnam” Program MAE-CNRS-VAST, from 1998 to 2005. He is elected member of Academia Europaea (www.ae-info.org). Prof, Vachaud was at SQU recently to participate in the World Water Day 2018 celebrations.

Could you please say a few words about yourself?
The sustainable use of our water resources has always been a domain of strong interest for me. I graduated in Hydraulic Engineering. After completing my doctoral studies, I was recruited in the French Scientific Research Center (www.cnrs.fr) in which I progressively became in charge of research teams involved in water resources managements and environmental issues; I had also several responsibilities at the European level (President of the European Geophysical Society, now European Union of Geosciences), including at the scientific editorial level (editor in chief, Journal of Hydrology) .
My first implication was on the physics of transport processes in the groundwater_soil_plant_atmosphere continuum in connection with agricultural water use and contamination of groundwater by agricultural chemicals (nitrates, pesticides). Later I shifted on urban water use, particularly on the impact on untreated water residuals on the ecological status of rivers in large Asian mega poles (Taipei, Hanoi, HoChiMinh City). More recently my interest moved to climate change and water cycle, including the incidence of droughts and typhoons and the raise of sea water level.
Fresh water scarcity will be a very important challenge for economic and social development, in relation with development of urbanization and agriculture. Could you explain?
The amount of available fresh water is facing a dramatic issue: on one hand all studies related to climate change show that the quantity of rainfall may probably decrease whereas the demand will strongly increase in relation with population growth. At the world scale the water consumption is doubling every 30 years; for the Sultanate, the freshwater availability has dropped from 1300 m3 per capita in 1970 to 300 in 2010 due to population growth; furthermore 85% is consumed in the sector of agriculture with approximately 40% of losses .
How important is “water-food-energy and health nexus” paradigm in dealing with reducing the impact of climate change on the water cycle?
Alternative water resources must be developed to complement natural water resources as mitigation strategies. However we can no more consider the use of resource on the sole basis of physical mass balance (quantity available compared to needs). We must combine it with the possible impacts on health and food production, and with the sustainability of alternative methods, particularly the cost of treatment. The Sultanate has already a leading position with seawater desalinization processes, producing already 40% of the drinking water. An important development could be expected with the reuse of treated urban wastewater effluents, with a very high potential in agricultural irrigation, landscape irrigation and industry. But clearly the risk of microbiological and chemical contamination (particularly new emergent contaminants such as pharmaceutics, hormones, etc.), the cost of energy and the cost of distribution system could be limiting factors. One strong tendency at the European level is to redesign distribution infrastructures in order to have multiple waters quality for multiple purposes and multiple users.
What are the appropriate alternative technologies in agriculture and in fighting seawater intrusion? These are critical for Oman as well.
Besides an optimization of irrigation practices to limit the water losses due to misuse of sprinklers or channels, precision irrigation accounting for the variability of soil and crops could be a valuable alternative. Concerning seawater intrusion, a problem highly critical for the coastline of the Sultanate, the problem results probably of two different effects.
Firstly, in the present situation, an overexploitation of groundwater, yielding in a continuous decrease of the groundwater level and consequently to intrusion of seawater. The alternative irrigation with use of retreated urban water instead of pumped groundwater could be a solution. Another possibility is the creation of an underground non saline water barrier by well injection of residual water produced by treatment plants, but in relation with the available volume of treated water production this could probably be done be only at a local scale.
Secondly, on the long time and probably more critical, the raise of sea level resulting from the increase of temperature with climate change. Since 1990, the observed sea level increased regularly of about 4mm per year; 1/3 is due to thermal expansion of seawater, 2/3 to the melting of polar ice. Predictions resulting from models produced in the frame of the Intergovernmental Panel on Climate Change (IPCC) are very pessimistic if there is not a drastic change in emission rates of greenhouse gases, with a possible raise of 1m at the end of the century, resulting essentially form the accelerated melting of polar ice. No alternative technology could be foreseen, since the construction of a dike along the littoral is not imaginable. The only alternative would be the reduction, at the world scale, of gas emissions.

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