Crop evapotranspiration in the Nile Delta under different irrigation methods
Hydrological Sciences Journal
Agriculture in Egypt, is receiving the biggest share of water amounting to nearly 85% of the available water resources. The policy of Egypt is to fill the gap in food production through vertical and horizontal expansion of the irrigated areas. Since about 97% of Egypt's water comes from outside Egypt, this requires very effective and serious action programs to increase water use efficiency. Indeed, the more water we save, the greater opportunity will be to expand the irrigated areas and
... d areas and increase food production, bringing the country towards food security. The overall objective of this research is to help the water policy planners to develop the appropriate methodology to determine crop coefficients and evapotranspiration in the irrigated agriculture, in order to develop suitable irrigation practices to optimize irrigation water use efficiency in sustainable irrigated agricultural cropping systems. This is the fundamental scope of the research where more emphasis was given to introduce SIMETAW as a new tool for better water management. The current research calibrated SIMETAW by using recent weather data sets of about 10 years at Zanklon location of the Nile Delta region. After the calibration procedure, the research examined SIMETAW as an efficient tool to evaluate the actual crop coefficient of two major field crops of wheat and maize. In this paper, how the simulation model determines ETaw as well as other model's out-puts under Nile Delta conditions will be discussed. Through the calibration process, SIMETAW shows high accuracy in simulating the initial weather parameters needed for calculating ETo and simulating ETo and ETc for a long time series. Also, it could be used efficiently to evaluate the actual and the projected Kc of field crops cultivated under different irrigation strategies, which lead to better irrigation planning. SIMETAW model is adopted simulation to be used under Nile Delta conditions for determining ETo and ETc using minimum weather data set. The model can estimate ETo from daily weather data using a modified version of the Penman-Monteith equation, or with temperature data only using the Hargreaves-Samani equation, with acceptable accuracy. SIMETAW could be used efficiently to estimate water balance and evaluate different irrigation strategies, which support irrigation planners for better improvement. Based on inputs, the SIMETAW application determines an efficient irrigation schedule for a particular crop and soil. This can be repeated for all crops and soil combinations within a particular zone of ETo. SIMETAW could be used efficiently to update the crop coefficients (Kc) and crop evapotranspiration (ETc) crops cultivated under different irrigation strategies. This updates of the ETc and Kc could be alternate option to adapt with the climate change. SIMETAW model could tremendously help Egyptian irrigation engineers with limited research funding to improve their knowledge of crop water requirements, whereas limited water supplies are problematic. More calibrations still required to assess the effect of the inter-annual climate variability (especially precipitation and wind speed) on the model simulation accuracy. Since the SIMETAW was calibrated only in the Nile Delta, calibration for the other regions such as Upper Egypt, new reclaimed lands and oasis is recommended.