The gap between demand and water supply in Chennai is set to increase to nearly 466 mld by 2030 and the imbalance would widen further in the next few decades, indicating need for effective and integrated interventions to curtail unmet demand, according to a study by Anna University and IIT-Madras.
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Using the Water Evaluation And Planning (WEAP) model, the study aimed at assessment of the present and future water availability and demand scenarios till 2050 and provide comprehensive and resilient water resources management strategies with different sources and rainfall patterns.
The model was run with rainfall scenarios like excess, normal and deficit to represent their potential impact on water resources and it indicated an upward trend in unmet demand, particularly under normal and deficit rainfall conditions over time, according to the study. Increasing population, rapid urbanisation, variability in rainfall patterns and limited resources exacerbated the water deficit.
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By 2030, the water demand in Chennai with an area of nearly 1,189 sq.km is likely to be around 2,365 million litres a day (mld) with a gap of 466 mld in water supply.
The study revealed the growing disparity between limited sources and ever-increasing demand. The city is projected to receive a supply of 1,988 mld by 2040 and 2,049 mld by 2050. The unmet demand is further expected to grow to nearly 717.5 mld by 2040 and a substantial 962 mld by 2050, said P.V.Razi Sadath, one of the researchers.
The study ‘WEAP Model-based evaluation of future scenarios and strategies for sustainable water management in the Chennai basin’ was published in the International Water Association’s Journal of Water Infrastructure, Ecosystems and Society. Ligy Philip, professor, Department of Civil Engineering, IIT Madras, coordinated the study, which included M.Rinisha Kartheeshwari in the team of researchers.
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L.Elango, the study’s author and visiting faculty at IIT-M, said the domestic water requirement was estimated at 135 litres per person per day and future water demand was projected using a linear trend method based on several factors, including population data. “We examined various interventions, like groundwater recharge, expansion of desalination plants, increasing reservoir and water treatment capacities and alternative storage options, like quarries and reclaimed water to enhance water availability,” Prof. Elango said.
The study showed that there was a notable decrease in gap between water supply and demand during deficit years too if combined interventions were implemented simultaneously. The unmet demand was projected to drop to 110 mld by 2030; 250 mld by 2040 and 454 mld by 2050.
“We need to adopt a multi-pronged approach for water resource management and prioritise groundwater recharge measures and use reclaimed water in order to reduce water deficit. Desalination may meet 40% of the needs. Reducing water use would also help decrease unmet demand,” Prof. Elango said.