Novel Approach to Computing Critical and Normal Depth in Circular Channels

The critical depth and normal depth computation are essential for hydraulic engineers to understanding the characteristics of varied flow in open channels. These depths are fundamental to analyze the flow for irrigation, drainage, and sewer pipes. Several explicit solutions to calculate critical and normal depths in different shape open channels were discovered over time. Regardless of the complexity of using these explicit solutions, these formulas have a significant error percentage compared to the exact solution. Therefore, this research explicitly calculates the normal and critical depth in circular channels and finds simple, fast, and accurate equations. First, the dimensional analysis was used to propose an analytical equation for measuring the circular channels' critical and normal depths. Then, regression analysis has been carried for 2160 sets of discharge versus critical and normal depths data in a circular open channel. The results show that this study's proposed equation for measuring the circular channels' critical and normal depths overcomes the error percentage in previous studies. Furthermore, the proposed equation offers efficiency and precision compared with other previous solutions.

Potentials of Wood, Bamboo and Natural Fibre-Reinforced Composite Products as Substitute Materials for Fabricating Affordable Agricultural Equipment and Processing Machines in Africa

Modern agriculture depends heavily on technology. Land clearing, irrigation, drainage, crop storage and processing all require technological input. By modernising her agriculture, through wise application of science and technology, Africa can make significant headway in economic growth. However, an agricultural technology that is too sophisticated for a particular country/region is beyond its absorptive capacity. Hence, to achieve the objectives of agricultural mechanisation in Africa, it is imperative to take into account prevailing socio-economic conditions and the level of mechanisation necessary for optimal productivity. One major constraint to agricultural mechanisation in sub-Saharan Africa is the relatively high cost of imported metallic machine and equipment fabrication materials. Taking full advantage of substitute non-metallic materials may lower the cost of production and concomitantly empower rural fabricators with limited access to electricity and welding facilities to engage in local manufacturing of sundry agricultural machines and equipment. This Chapter presents illustrative examples of full and partial substitution of metallic with non-metallic materials in the fabrication of affordable machines and equipment for agricultural production, agro-processing, irrigation and drainage, crop drying and storage. Ways of addressing identified critical challenges of technology diffusion are also discussed.

The Effects, Distribution and Management Options for Major Banana Diseases in Tanzania

Emergences of Fusarium wilt, Bacterial wilt and Black Sigatoka diseases have caused banana yield loss of up 100% in Tanzania. Though there have been accumulated empirical data on yield decline due to diseases, lack of disease knowledge and selection of appropriate control methods has been a limiting factor in improving banana production. Therefore, this review focused on identifying different management options for major banana diseases, for purpose of providing reference and decision making tools to farmers, extension officers, researchers and decision makers. Using online resources, we identified several methods which are affordable, applicable and reliable for disease management in the country. These includes sanitation, intercropping, crop rotation, prevention, irrigation, drainage improvement, quarantine, use of silicon/calcium and awareness campaigns. Other method was biological control, which need further research on its applicability and impact on the environment. Moreover the use of resistant cultivars though being important, there is little achievement which have been made on breeding for resistance, because banana are polyploidy, parthenocarpic, have long generation time, loss of resistance and poor acceptability of new cultivars. We also found that, no single method is perfect for management of diseases; this is due to the fact that, in agricultural system, disease challenges rarely occur singly. So the approach to disease management should be pragmatic and geared towards integration of several appropriate methods. We hereby conclude that, researches should focus on identifying the best and feasible combination of control methods that can be used by Smallholder farmers.

Regional reclamation landscape technical systems: current status and rational use

The problems of the current state of possibilities of reconstruction and rational use of regional reclamation landscape technical systems have been considered. It has been noted that for studying the process of their formation and modern functioning GIS-method (GIS-packages SAS.Planet.Release and GoogleEarthPro) were used in addition to field landscape research. The meaning of the concept of “reclamation landscape technical system” as a structure in which interconnected hydraulic structures and water bodies that are necessary to ensure and maintain the optimal operation mode of the reclamation landscape complex has been clarified. The main types of reclamation such as hydraulic, cultural, chemical, agrotechnical and agroforestrytechnical have been partially discribed. The essence of the concept of “hydraulic reclamation” as a set of measures aimed at improving the water- air (waterlogging and dehydration) regime of soils has been considered more detailed. The expediency of resumption of reclamation measures in the territory of Ukraine has been confirmed, as 2/3 of its area is in conditions of unfavorable water regime. This study is focused on the analysis of drainage and humidification systems as the most effective in ensuring the regulation of excessive moisture or its deficit. It has been shown that the peak of reclamation works and construction of reclamation landscape technical systems was observed 1950–1965. The largest irrigation, drainage, polder and drainage-humidification systems in Ukraine have been discribed. It has been found that the decline of reclamation systems began in 1991 and was characterized by a reduction in the area of irrigated and drained lands and the deterioration of their ecological condition. Emphasis has been placed on the study of regional drainage and humidification systems and three stages of their development in Ukraine have been identified. Possible measures for the rational use of reclamation systems on the example of the Trubizh regional drainage and humidification landscape technical system have been proposed. It has been noted that the development of regional plans for the rational use of this system should be based on the analysis of the history of economic development of the Trubizh river basin and taking into account the specifics of the landscape structure of the canal-floodplain type. Reconstruction of the reclamation system has been recommended to conduct in two stages: the first one is based on the modernization of hydraulic structures and the main canal, the second one is based on the internal and landscape structure of the system. The feasibility of partial restructuring of the open network for closed drainage and the creation of temporary drainage channels has been confirmed, which will allow more rational use of resources of the Trubizh reclamation landscape technical system.

Mathematical Modelling of Surface-Groundwater Interactions under Varying Hydrological Conditions: Review of Past Works

Surface-groundwater interaction is a research area of significant importance for its central role in wastewater treatment, irrigation, drainage, flood control, erosion and sediment control. Mathematical models are often used for the estimation of surface-groundwater interactions under the variety of hydrological conditions. Due to cost effectiveness and ability to accommodate variations in aquifer parameters, mathematical models have gained immense importance in the past few decades. The objective of this review paper is to portray the contribution of the hydrologist towards the growing area of surface-ground water interaction from all over the world who proposed, analyzed, executed and validated the developed Mathematical models. To begin with, we briefly introduce the main mathematical equations that govern the flow of groundwater in unconfined and confined aquifer systems. The development of stream-aquifer models is presented in a chronological order to provide a clear understanding of the contributions of past works. The methodology used in the past work is adequately discussed without going into mathematical details. Furthermore, we also summarize recent developments concerning groundwater flow in presence of vertical streambed, partial penetration, stream-stage variations and multiple recharge/discharge basins.

The scientific activity of ICID to improve the irrigation in arid environments

<p>The International Commission on Irrigation and Drainage (ICID) was set up in 1950, with support from 11 countries as Founder Members, including Italy. Ital-ICID is the Italian National Committee of ICID founded in 1971, and is a scientific, technical, and professional not-for-profit organization working in the field of irrigation, drainage, land reclamation, and flood management, in accordance with the topics of the International Commission.</p><p>In this moment the environmental protection and the green economy are a very important goals, in this contest the ICID promotes and achieves equitable and sustainable development in agriculture water management. The actions of ICID are dedicated to improving the status of agricultural water management practices including rain-fed agriculture, supplemental irrigation, deficit irrigation and full irrigation, with a particular attention to the areas involved in extreme climate events, such as flood and droughts. ICID approach suggests cooperation rather than competition, and collaboration rather than individual actions to pave the way towards effective water management for securing the right of each and every individual to attain a fair share of water, food, energy, and stressed on the need to promote environment-friendly traditional wisdom.</p><p>ICID develops many annual and special publications promoting its activities, but “Irrigation and Drainage Journal” is the official international journal, and the flagship publication of ICID. It is a prestigious, peer-reviewed specialized publication that publishes papers on all scientific, technical, environmental and socio-economic issues associated with irrigation, drainage and flood management. The journal covers a wide range of subjects centering on dissemination of experience and new ideas in the quest for the sustainable use and protection of water and land to meet the World's increasing demand for food. Only in the last issues more than ten papers have been published concerning study on arid and semi-arid area, which involve the human intervention in the control of water for sustainable agricultural development.</p><p>For the future, ICID works towards enabling balance between agricultural and water policies, improving publicly operated irrigation schemes, advocating increased public and private investment in expansion of irrigated land, and modernizing existing infrastructure. The knowledge-based sharing of all aspects of agricultural water management, including collation of irrigation statistics, data and information exchange, sharing of successful management strategies, best practices, and local community involvement will be supported by ICID. It supports and encourages the multiple use of water, the use of non-conventional waters and the promotion of goods and services provided by irrigation systems, also supported by Information and Technology Communication tools. The cooperation mechanisms in ICID’s network are based on simple exchange of information through annual meetings, where practitioners, researchers and planners from all over the world share latest research and innovations. However, ICID also organizes triennial world irrigation and drainage congresses, world irrigation fora, regional conferences and workshops to address and discuss agricultural water management issues at global or regional level.</p>

Influence of tillage practice on major pathways of CH4 emission in rice paddy field

<p> Generally, during the paddy rice cultivation period, CH<sub>4</sub> produced in the soil is reported to be released to the atmosphere through three pathways: diffusion (<1%), bubbles (<10%), and via rice (> 90%). However, there are few studies have measured gas diffusion coefficient for soil below surface of the water, and there is no study has provided an accurate understanding of CH<sub>4</sub> dynamics in paddy fields. Furthermore, there are few studies that understanding the CH<sub>4</sub> dynamics in fertilizer-free and pesticide-free paddy fields, which is mainly controlled by inter-tillage practices. Therefore, this study aimed to clarify the effects of tillage and the number of inter-tillage and the presence or absence of fertilizer and pesticide on the CH<sub>4</sub> dynamics in rice paddy soil. This study compared three types of CH<sub>4</sub> flux, which were total CH<sub>4</sub> flux from rice paddy field measured by transparent chamber with plants, and soil derived CH<sub>4</sub> flux measured by dark chamber without plants, and gas diffusion flux calculated as a product of the gas diffusion coefficient and measured soil gas concentration gradient at the depths of 0-5 and 5-10cm. And they were compared with in the five rice cultivation periods (flooding, mid-drying, intermittent irrigation, drainage, and fallowing) and in the four treatment plots (conventional farming (CF), and fertilizer- and pesticide-free farming with zero-inter-tillage(T0), two-inter-tillage(T2), and five-inter-tillage (T5)). The CF was conducted according to the regional recommendation for tillage, fertilization and pest and weed control. The results showed that the peak of total CH<sub>4</sub> flux was observed in the mid-drying and intermittent irrigation periods in all treatments, and that the CH<sub>4 </sub>flux via rice plant accounted for 60-90% of the total CH<sub>4</sub> flux. The CF showed significantly highest CH<sub>4</sub> emission during the periods, and the increase of the number of inter-tillage tended to increase the CH<sub>4</sub> emission. In the drainage period, the CH<sub>4</sub> flux by bubbles in the CF and T5 accounted for more than 80% of the total CH<sub>4</sub> flux. In the fallowing period, the diffusion CH<sub>4</sub> flux at the depth of 5-10cm increased in all treatments, but the low total CH<sub>4 </sub>emission and increased CO<sub>2</sub> emission. This study revealed that incorporation of organic matter into soil in conventional rice farming tended to increase CH<sub>4</sub> emission. The main pathway of CH<sub>4</sub> emission from rice paddy field was via rice, and it was influenced by tillage significantly. The decomposition of organic matter from rice straw and weeds incorporated into soil was the source of the bubble of CH<sub>4</sub>. Furthermore, it seemed that the most of diffusively transferred CH<sub>4</sub> was easily oxidized to CO<sub>2</sub>.</p>