Water use and salinity dynamics in irrigated agriculture.

Abstract

Agricultural systems in the Nile Delta are under growing pressure from climate change. Freshwater supplies are declining, river flows are becoming less reliable, and salinity stress is intensifying. Egypt’s strong dependence on the Nile, combined with upstream withdrawals and limited storage, makes irrigation increasingly uncertain. To cope, farmers often use saline drainage water, but this raises serious risks for crop yields and long-term soil health. This study investigates how water availability, irrigation demand, and salinity stress interact at Buzoor Farm Complex in Sharkia Governorate, Egypt. Canal supply and reservoir capacity were calculated and compared with crop water requirements using the CROPWAT/CLIMWAT model. The Maas-Hoffman salinity framework was applied to estimate yield losses under different water quality and irrigation management conditions. Six representative crop rotations were assessed, and sweet melon was chosen as a case study because it is widely grown and highly sensitive to salt. Future climate scenarios for 2050 were tested, including higher temperatures, lower freshwater deliveries, greater salinity in drainage water, and more unreliable irrigation schedules. The results show that freshwater remains the key factor for sustaining yields. Across all crop rotations, current supply falls short by 18-44% over a three-year cycle. Farmers can make up part of this gap with drainage water, but doing so quickly raises soil salinity. For sensitive crops such as sweet melon, this can cause yield reductions of 70-100%, especially during the summer peak demand period. The analysis also shows that early crop stages are less affected, while mid- and late-season growth is highly vulnerable. Looking ahead, climate change is expected to make these stresses worse: higher temperatures increase crop water needs, reduced Nile flows limit supply, and drainage salinity further undermines production. The findings suggest that drainage water can only be used safely in small amounts and in combination with freshwater, ideally followed by deliberate leaching. Long-term resilience will require additional storage capacity, more reliable delivery schedules, and stronger management of salinity. For the wider Nile Delta, this means investing in infrastructure, improving water-use efficiency, and strengthening institutional coordination. Future research should extend salinity-yield modelling to other crops, and integrate economic and social aspects, to provide farmers and policymakers with practical tools for adaptation. Options such as drip irrigation, salt-tolerant crop varieties, and cooperative water-sharing schemes may help reduce vulnerability and protect food security in the region.