The Central Water Commission (CWC) in a study titled ‘Assessment of India’s Water Resources 2024’ has estimated India’s average annual water availability at 2,115.95 billion cubic meters (BCM) between 1985 and 2023.
What is CWC’s water availability figure based on?
In its study, CWC evaluated annual net-flow based on average annual water availability using rainfall, evapotranspiration, land use, land cover, and soil datasets as key inputs. Water availability has been assessed in all river basins of the country except the three western tributaries of the Indus (Indus, Jhelum and Chenab).
How is water availability distributed across geographical areas?
According to the CWC report, Brahmaputra (592.32 BCM), Ganga (581.75 BCM), and Godavari (129.17 BCM) were the top three basins with water availability across the country, while Sabarmati (9.87 BCM), Pennar (10.42 BCM) and Mahi (13.03 BCM) ) were the bottom three basins in terms of water availability.
What were the results of previous evaluations?
The 2,115.95 BCM figure is higher than the previous estimate made in 2019, which calculated water availability at 1,999.2 BCM from 1985 to 2015.
Before 2019, about half a dozen water availability assessments were done using different methods. All these had water availability of less than 2,000 BCM, compared to the earliest estimate of 1,443.2 BCM in 1901-03.
Why is the current water availability figure higher than the previous assessment?
This is mainly due to methodological factors. First, the new assessment takes into account Bhutan’s contribution to the Brahmaputra, which was not included in the 2019 assessment. Second, Nepal’s contribution to the Ganges was only partially taken into account in the 2019 assessment, but the present study fully incorporates it. .
According to the CWC, “The current study includes all transboundary waters entering India in the Brahmaputra Basin, the Ganges Basin and the Indus Basin (Eastern Rivers).”
Why is such an assessment important?
Assessment of water availability is important for the sustainable management of water resources that face challenges from factors such as urbanization, industrialization and climate change.
It is also a prerequisite for calculating per capita water availability, which is one of the indicators used to measure water scarcity. According to the most common method of calculating water scarcity, known as the Falconmark Indicator or Water Stress Index, a country is considered to be under “water stress” if its per capita water availability is less than 1,700 cubic meters. Availability of less than 1,000 cubic meters of water per capita makes the country “lack of water“, while availability of water less than 500 cubic meters per person means “absolute water scarcity”.
According to the Ministry of Water Power, the average annual per capita water availability for 2021 was 1,486 cubic meters based on the annual water availability of 1,999.2 BCM assessed in CWC’s 2019 study. Taking into account the latest estimates, this number would be higher (1,513 cubic meters using a projected 2024 population of 1.398 billion) but still less than 1,700 cubic meters.
Can all available water be used?
However, CWC’s numbers do not refer to usable water. For example, in 2019, average water resource availability was assessed at 1999.2 BCM, but usable surface water resources were estimated at only 690 BCM.
According to the CWC, the ratio of usable surface water resources to average water resources capacity is very high in small basins except west flowing river basins from Tapi to Tadri and Tadri to Kanyakumari, Sabarmati and Mahi. According to CWC, the ratio of usable surface water resources to average water resource potential is found to be minimum in Brahmaputra sub-basin.
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