Estimated water Footprint for cotton under three climatic regions in Egypt

Background: Irrigation for agricultural purposes accounts for roughly 70% of global water intake. The concept of the water footprint (WF) serves as a crucial indicator of freshwater use, playing a significant role in tackling the climate crisis and preventing nitrate pollution in water resources. As a decision-making tool, WF supports crop selection based on water intake and productivity, aiming to optimize agricultural water use sustainably. This study investigates the relationship between climate variability and the water footprint of cotton cultivation in Egypt. Three climatic zones Nile Delta, Middle Egypt, and Upper Egypt were selected to represent distinct microclimates. Climate data from 2020 to 2024 were used to estimate reference evapotranspiration (ETo) and evaluate cotton crop water use (CWU), in conjunction with data on cultivated area and yield. Results: The water footprint of cotton, including lint and seeds, was calculated for the three regions, considering blue and grey water components. Green water was excluded due to Egypt’s negligible rainfall. The average WF for cotton production in Egypt was 3905 m³/ton, with lint accounting for approximately 10,041 m³/ton and seed for 6342 m³/ton. These values illustrate the strong influence of microclimatic conditions and nitrogen application on water demands and WF across regions. Water use efficiency (WUE) and nitrogen use efficiency (NUE) were also analyzed. The average WUE for cotton was 0.28 kg/m³, while NUE was 14.9 kg N/kg yield. Conclusions: The study demonstrates that regional climatic differences significantly affect the water and nitrogen footprint of cotton production. The findings offer a useful methodological approach to support decision-making in water resource management, helping policymakers and stakeholders enhance the sustainability and efficiency of water use in cotton-growing regions in Egypt.