灌漑・排水システム工学

The development of irrigation and agricultural water management holds significant potential to improve productivity and reduce vulnerability to climactic volatility and land transformation in any country. Although Ethiopia has abundant rainfall and water resources, its agricultural system does not yet fully benefit from the technologies of water management and irrigation. Improved water management for agriculture has many potential benefits in efforts to reduce vulnerability and improve productivity. According to climate change assessments, less precipitation and higher temperatures can be expected in the country. Besides, an increment in drought studies shows high land degradation and nutrient depletion of agricultural land as well. Such climatic and land conditions require an effort to improve agricultural water management efficiency and to optimize irrigation technologies. There are currently available water-use and crop-growth simulation models, which can be combined with climate and land use scenarios in order to recommend, through many simulations, the most reliable irrigation management, as a result, agriculture will have to reduce either its relative water consumption per output by improving usage efficiency or its absolute water demand by decreasing agricultural production. More agricultural output per area and per drop of water used (crop yield and crop water productivity) means achieving more crops per drop. This review was, therefore, targeted at finding a better method for optimal irrigation water management that relies on accurate knowledge of plant water consumption, water flows, and soil moisture dynamics throughout the growing season. The decision-supporting tools should therefore capture the temporal and spatial variability of rainfall, soils, and crops. It is better to model the agricultural water management fully from field measurements or remote sensing using dynamic simulation models. In this paper, it is needed to review the Agro-hydrological model to investigate the agricultural water management. This agro-hydrological model is a good software package for crop water requirement computation as the inputs of the model are based on the real field conditions. As with any model, the reliability of the results depends on the reliability of the input data. The model can generate daily crop water needs (or irrigation requirements), which can assist the user in adjusting irrigation schedules based on weather conditions. On the other hand, with SWAP, an estimation can be made of the losses due to over irrigation.

The objective of the research is minimizing the seepage losses from irrigation canals while increasing the benefit from crop production in Eastern zone of Tigray Region Tabia Genfell, Kilite awulalo woreda korir Irrigation Scheme. During the design of canal the cropping pattern selected were pepper, cabbage, potato, tomato and onion for dry season and maize, wheat, teff, barley and pea for wet season. Realizing that the single crop cannot solve the food security and economic status of the farmers, this research was aimed to solve the problem by using the original cropping pattern along with optimization of canal cross-sections to minimize the shortage of discharge and maximize the net benefit. Accordingly, the linear programming (LP) model formulated, under different scenarios to obtain maximum benefit. The model developed under full design (assumption of no losses), existing condition (under measured seepage), under optimum discharge (minimum seepage) and lastly under optimum discharge and new proposed area and their result were compared to each other in terms of area allocation, maximum profit and saved discharge. The objective function of the model is maximization of net benefit and the constraints of the model were minimum area to be irrigated, maximum area under each secondary canal, constraints of seed and fertilizer cost and constraint of optimum discharge in canals. The result of maximum benefit scenario allocates the minimum required area for pepper, cabbage, potato and onion by allocating 62.5ha, which is maximum area for tomato crop. In terms of saving discharge, the existing condition and scenario IV first condition similar with value of 65% however despite of their saved water, the benefit of existing scenario (scenario II first crop pattern) less by 10% than scenario IV 1st crop pattern. The replacement of cabbage with spinach and potato with carrot in scenario IV second crop pattern save 75% of canal discharge but the net benefit reduced by 2,401,350.00 ETB from scenario IV first condition. In terms of saved discharge during optimization of canal cross-section 20%, 68%, 86%, and 69% amounts of discharge saved from Sc-1, Sc-2, Sc-3 and Sc-4 respectively when compared with existing condition.

The role of simulation models in understanding the processes in the soil-plant-atmosphere system has increased significantly in recent years. This is attributed to increased computing capabilities available today. Mathematical models, be it physically or empirically based, have the promising potential to explore solutions to water management problems. Evaluation of water management scenarios can be easily done, thus facilitating better recommendations for improved water use. Thus, in large-scale irrigated agriculture, there is potential benefit from improved rainwater and irrigation management, as well as upstream through reduced land degradation and associated soil erosion, which, when transported downstream, reduces the efficiency of irrigation schemes and best practices. The Kuraz Sugar Development irrigation project in the sub basin, which is one of the sub basins in Ethiopia, has suitable land for agriculture and livestock, and currently huge investment is found in irrigation projects, and of these, the dominant is state-owned irrigation, like the Kuraz Sugar Development irrigation project in the sub basin, which is planned to irrigate sugarcane on 175,000 hectares of land.

Water stress is a severe environmental constraint to plant productivity. Water stress induced loss in crop yield probably exceeds losses from all other causes, since both the severity and duration of the stress are critical. This Seminar describes the effects of water stress on the growth, phenology, water and nutrient relations, photosynthesis, assimilate partitioning, and respiration in plants, and the mechanism of Water stress resistance in plants on a morphological, physiological and molecular basis. Water stress reduces leaf size, stem extension and root proliferation, disturbs plant water relations and reduces water-use efficiency. Plants display a variety of physiological and biochemical responses at cellular and whole-organism levels towards prevailing drought stress, thus making it a complex phenomenon. CO₂ assimilation by leaves is reduced mainly by stomatal closure, membrane damage and disturbed activity of various enzymes, especially those of CO₂ fixation and adenosine triphosphate synthesis. The major mechanisms include curtailed water loss by increased diffusive resistance, enhanced water uptake with prolific and deep root systems and its efficient use, and smaller and succulent leaves to reduce the transpirational loss. Water stress effects can be managed by production of the most appropriate plant genotypes together with adjustment of agronomic practices (sowing time, plant density and soil management). Stress measurement is the quantification of the effects of environmental stresses on growth, productivity and survival of plants; Visual assessment of damages incurred Strain and measurement using different tools and protocols. Thermal sensing for plant water status, Leaf chlorophyll fluorescence, Measuring Plant Stress with an Infrared Thermometer and determination of water stress with spectral reflectance are among plant water stress measuring devices and techniques.

Coffee contributes more than 60% of the annual foreign currency and 30% of the government’s direct revenue and the livelihood of 25% of the Ethiopia’s population directly or indirectly depends on the whole value chain of coffee industry. Ethiopian coffee varieties are already well-known, and in high demand by the global market. The most limiting factors to coffee production in Ethiopia are climatic variability, soil moisture stress, poor agricultural practices, prevalence of pests and diseases. The study was conducted to evaluate the effect of in-situ rain water harvesting structures on soil moisture, growth parameters, yield and quality of coffee arabica on two locations at Mechara Agricultural research on-station and Sakina kebele in Daro Lebu district, West Hararghe zone, where moisture stress and low soil fertility are limiting factors. The in-situ rain water harvesting structures used as treatments were Half-moon (semicircular bund), Contour ridge, Negarim micro catchment and normal pit (farmers practice). The treatments were laid out in RCBD with three replications. The data on soil moisture content, growth parameters, yield and coffee bean quality were collected.

Statistical analysis software (R version 4.1.2) was used for data analysis to show mean separation for their significance difference at (P<0.05). Soil moisture content, Plant height, first primary branch, and canopy diameter has highly significance difference at (P<0.05) among the treatments at both site. From the in-situ water harvesting practices Semi-circular bund and Negarim micro catchment had shown the best soil moisture retention at (0-20) cm and (20-40) cm depth among others. The mean coffee quality parameters such as color, overall aromatic quality and Flavor are shown significant difference (P<0.05) among in-situ water harvesting structures by conserving soil moisture under coffee root zone. There is also coffee quality attribute difference between treatments which is the best option for both consumption and market. Among treatments semi-circular bund and Negarim micro catchment structures shown better performance in improving soil moisture stored within the root zone, reduces soil erosion and increase coffee growth, quality and yield of coffee Arabica in moisture stress areas of West Hararghe Zone and similar agro ecologies..