Key Terms & Concepts — UPSC Mains
Water Stress Index
"A measure of the ratio between total water withdrawals and available renewable water resources in a region, indicating the degree of pressure on water supplies"
The Water Stress Index (also called the water exploitation index or water scarcity indicator) measures the ratio of total freshwater withdrawals (agricultural, industrial, and domestic) to total available renewable freshwater resources in a given area. A region is classified as water-stressed when annual withdrawals exceed 25% of available resources, and as water-scarce when they exceed 40%. The index was developed by Malin Falkenmark (1989) and has been adopted by the UN, World Resources Institute (WRI), and NITI Aayog for assessing water vulnerability.
NITI Aayog's Composite Water Management Index (CWMI) report warned that 21 Indian cities — including Delhi, Bengaluru, Chennai, and Hyderabad — would face Day Zero (complete water exhaustion) by 2030 if current trends continue. India houses 18% of the world's population but only 4% of freshwater resources. Water stress is tested under GS1 (Geography — water resources), GS3 (Environment — conservation), and GS2 (Governance — Jal Shakti, inter-state disputes).
- 1 Falkenmark Water Stress Indicator — below 1,700 cubic metres per capita per year is water-stressed; below 1,000 is water-scarce; below 500 is absolute scarcity
- 2 India's per capita water availability has declined from ~5,177 cubic metres (1951) to approximately 1,486 cubic metres (2021) — already below the water-stress threshold
- 3 WRI's Aqueduct Water Risk Atlas (2023) ranked India 13th among the world's most water-stressed countries
- 4 Agriculture accounts for approximately 80% of India's freshwater withdrawals, followed by domestic use (10%) and industry (10%)
- 5 NITI Aayog's CWMI ranks states on 28 indicators across 9 themes; Gujarat, Andhra Pradesh, and Madhya Pradesh were top performers; Jharkhand, Bihar, and Uttarakhand scored lowest
- 6 Groundwater overexploitation is a critical driver — India extracts about 25% of global groundwater, with 16% of assessment units classified as over-exploited by the Central Ground Water Board (CGWB)
- 7 Jal Jeevan Mission (launched 2019) aims to provide tap water connections to all rural households by 2024 — over 14.9 crore connections provided as of 2024
Chennai experienced its 'Day Zero' crisis in June 2019 when all four major reservoirs ran dry, forcing the city to rely entirely on water tankers and desalination. The city's water stress index exceeded 80%, meaning it was withdrawing far more water than its renewable supply could sustain.