Assessment of the Agricultural Water Footprint of Major Crops in South India Under Changing Climatic Conditions

Background: South India, encompassing Tamil Nadu, Karnataka, Andhra Pradesh, Telangana, and Kerala, supports diverse, water-intensive agricultural systems that are increasingly vulnerable to climate variability. Intensifying thermal stress, shifting monsoon regimes, and growing groundwater depletion are altering the water balances of major crops, raising urgent questions about long-term agricultural sustainability and food security. The water footprint (WF) framework provides a comprehensive accounting tool for quantifying the freshwater consumption embedded in agricultural production, disaggregated into green (rainfall), blue (irrigation), and grey (pollution dilution) components. Objective: This systematic review synthesises evidence published between 2017 and 2026 on the agricultural WF of major South Indian crops - including rice, sugarcane, cotton, groundnut, maize, and sorghum - and examines how changing climatic conditions are projected to alter these values. Methods: Following PRISMA guidelines, a systematic search across Scopus, Web of Science, Google Scholar, FAO/IWMI repositories, and CMIP6 climate data portals yielded 56 studies for final synthesis. Results: Rice exhibits the highest total WF (1,750–2,230 m³ t⁻¹ across states), driven by its dominant Blue WF share (55–65%). Cotton's per-tonne WF (7,800–9,100 m³ t⁻¹) is the largest among field crops. Under RCP 8.5, irrigation WF for rice and cotton is projected to increase by 35–62% by 2080, driven by elevated evapotranspiration. Climate-smart interventions including drip irrigation, alternate wetting and drying (AWD), direct-seeded rice (DSR), and drought-tolerant varieties can reduce WF by 20–40% relative to conventional practice. Conclusion: WF reduction in South Indian agriculture requires an integrated strategy combining precision water management technologies, crop system diversification, and evidence-based national water governance reform.