Chennai: With fastest growing population and ever increasing demand for water, the gap between supply and demand of water in the Chennai city would be doubled by 2030 if no additional water resources are created, according to a new study.
“The water demand is increasing by 20 MLD of water every year from 2016. But, the supply cannot increase beyond 800 MLD due to the absence of additional sources of water,” the study said.
At present, the demand of the city is about 830 MLD of water and the supply is about 630 MLD. The gap is 200 MLD and it would likely to increase to 400 MLD in the year 2030 in the present scenario.
Currently, the city’s water supply is largely met from four reservoirs (51 per cent), Veeranam lake (19 per cent), desalination plants (17 per cent) and Krishna river (11 per cent). The wells contribute to one per cent of the water supply.
“In the year 2030, the maximum value of demand coverage is obtained as 83 per cent for the month of October and minimum 55% for months of February and March,” Professor L.El-ango, head, Department of Geology, Anna University and co-author of the research paper said.
Using Water Evaluation and Planning Model, the study was conducted to predict the gap in water supply and demand in Chennai until 2050.
The objective of the study published in Groundwater for Sustainable Development is to predict the outcomes of various steps to enhance the availability of water in the Chennai city.
The researchers also forecast outcomes of various scenarios including with additional reservoir, desalination plant and reuse of wastewater in the research paper published in Groundwater for Sustainable Development journal recently.
“Along with approved new desalination plant and additional reservoir near Chennai city, the reuse of wastewater from Adyar and Cooum rivers could meet the water requirement up to 2050,” Professor Elango said.
Chennai Metropolitan Water Supply and Sewerage Board (CMWSSB) planned to meet the additional water requirements in future from new desalination plants and a new reservoir at the northwest of Chennai besides seeking additional water from Krishna river.
The scenarios such as the new desalination plants and reservoirs were considered from the year 2020 since they are expected to be operational by that time. The average monthly rainfall calculated from the past thirty year data was used from the year 2016-2030.
A fifth reservoir is being established by joining two lakes in Kannakotai and Thervoykandigai to store water from Krishna river apart from its own catchment area. The storage capacity of the new reservoir will be 1 TMC and Krishna river.
“It is found that average annual variation in coverage of demand for the year 2020 has fallen to 10 per cent. The fluctuation increases to 20 per cent for the year 2030 but it is still much more stable as the minimum coverage is 80 per cent in contrary to 55 per cent of the normal scenario,” the study said.
The proposed desalination plant will initially have a treatment capacity of 200 MLD. The annual fluctuation in the gap of water supply and demand will come down to 25 per cent if the plant comes operational.
But reusing the wastewater seems to provide a long-lasting solution to solve the issue of water availability.
“Chennai’s dependency on rainfall is uncertain, but the Adyar and Cooum rivers promise a regular source of water is treated and reused. It would also lead to a huge amount of environmental benefits along with catering city’s water demand,” Professor Elango explained.
“Assuming 60 per cent of the sewage is treated and used for various suitable purposes such as cleaning, washing and toilet flushing about 486 MLD of water can be reused,” he added.
If all the three options in a place the water availability will be more than the requirement at least up to the year 2050.
“Beyond this period, it is necessary to look for new option to increase the water availability and meet the growing demand for water due to rapid urbanization,” researchers concluded.
