Only 14 pages are availabe for public view
Evapotranspiration (ET) is a vital variable for water resources planning and supply-demand management. Effective agricultural water management and improving crop water productivity (CWP), especially in arid regions is critically depend on the improved estimation of water demand and the on-time water supply. Implementing the 2030 Middle East and North Africa (MENA) agenda for sustainable development requires evidently a transformational change in managing the natural resources including water, land, and energy. Egypt is one of the arid Near East and North Africa countries (NENA) that needs to strategically analyze and well-planning its water resources allocation. This planning should consider the assessment of sustainable conjunctive use of surface and groundwater resources when applicable and recharge rates, develop, and implement effective conservation practices to ensure alignment with the goals of setting the suitable limits of water consumption, making the best utilization of each DROP of water to enhance CWP for different cropping systems under different soil and crop management practices.
Mechanized raised-bed technology has been recently identified as an effective means of increasing productivity and saving irrigation water, however, ET dynamics and crop response to irrigation and ET still need further assessment for different crops under raised bed technology. One of the objectives of this research is to quantify and analyze the absolute water saving which represented by water consumptive use of new spring high yielding bread wheat cultivars under raised bed technology and traditional farmer practice and investigate the feasibility of both production systems in Egypt. In this study wheat crop evapotranspiration (ETa) was measured using two energy balance flux towers installed in two wheat fields. One field was cultivated using raised bed in middle Egypt at Sids Research Station and the other field was cultivated in the traditional planting method in Nile Delta at Sakha Research Station for comparative analyses.
Climatic zone had significant impact on ETo and ETa. Cumulative grass-reference evapotranspiration (ETo) was 434 mm and 557 mm at Sakha (flatbed) and Sids (raised bed) sites, respectively. Cumulative actual evapotranspiration (ETa) was 321 mm and 375 mm at Sakha and Sids sites, respectively. In terms of yield response to water use, the CWP was 12% higher with the raised bed production system (1.99 kg/m^3) as compared with the traditional flatbed practice (1.77 kg/m^3).
Determination of the actual crop evapotranspiration using sophisticated micro-metrological method and measure the energy fluxes at high frequency shed the light on the importance of raised bed adaptation and scaling up in Egypt not only in decreasing applied irrigated water but also in reducing crop evapotranspiration while increasing grain yield.
The comparative analysis of irrigation schedule based on the traditional method (ETc_FAO-56) and energy balance flux tower data (ETa_EB) showed an overestimation of (ETc_FAO-56) in Sakha and Sids sites. The cumulative crop evapotranspiration (ETa_EB) was 375.4 mm and the cumulative crop (ETc_FAO-56) was 556.9 mm at Sids station. On the other hand, the results also showed the same trend at Sakha station. The cumulative crop (ETa_EB) was 321.4 mm and the cumulative crop (ETc_FAO-56) was 430.67 mm and that advocates the importance of measuring actual evapotranspiration using energy balance flux towers for irrigation schedule in terms of saving irrigation water.
Eddy covariance as an energy balance method for measuring actual evapotranspiration ETa still in a limited use in Egypt due to its complexity. The cost and level of carefulness required to ensure accurate measurements make it difficult to use. Therefore, the third and last objective was studied aiming to identify and quantify actual evapotranspiration using integrated satellite data for sustainable water management in dry areas. The results showed reliable data retrieved from the new model compared to measured data from energy balance, the cumulative (ETa_EB) was 375.4 mm and (ETa_RS) was 411.7 mm in Sids station, while (ETa_EB) was 321.4 mm and (ETa_RS) was 328.6 mm in Sakha station, respectively.
This study addressed the impact of different management practice on crop evapotranspiration and crop coefficient under different climatic zones simultaneously is extremely rare, which is identified as very important topics for effective wheat water management and with significant knowledge, information, and data gap. To bridge this knowledge gap on locally available crop coefficients for wheat under different management practice.
Finally, with great importance, estimating water demand by measure water use and decide how much water is needed throughout the growing season, in addition to wheat crop mapping enables the decision-makers to carry out regional planning of water supply, assessment water accounting across each governorate and plan for future needs of water on the country level.