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Calculation of effective hydraulic parameters of concrete irrigation canals

Fatxulloyev Alisher, Rakhimov Qudratjon, Allayorov Davronjon, Samiev Luqmon, Otakhonov Makhsud

Journal of Water and Land Development

2023

no. 56

14--20

When taking water from pre-mountain rivers, for transferring of large amounts of river sediments, rich in mineral fertilizers, along with water to crop fields through irrigation networks requires high sediment transport capacity and deformation resistance from irrigation networks. The projecting and construction of irrigation canals with these features in the foothills requires concreting the canal. The high content of river sediments in the Sokh River (5 kg∙m-3) and the low efficiency of the Right Bank Irrigation Reservoir (10-15%) require high hydraulic efficiency of water intake canals from this system. The main challenge is to reduce costs in concreted canals and ultimately ensure technical superiority. In the research were used generally accepted research methods in hydraulics, in particular field research and consequently, mathematical analysis. Kokandsay, Kartan and Bachkir irrigation canals were accepted as the object of research, the canals were designed on the basis of the best hydraulic section, the canal side slope was taken as a variable parameter and the technical and economic efficiency was checked using computer software. As a result, it was found that the consumption of concrete raw material for 1 running meter can save 0.2-0.3 m3, depending on the adoption of the canal side slope, the acceptance of the slope of the canal wall at values 1-1.5 will increase up to sedimentation 10%.

On how defining and measuring a channel bed elevation impacts key quantities in sediment overloading with supercritical flow

Eslami Hasan, Yousefyani Hooshyar, Yavary Nia Mohsen, Radice Alessio

Acta Geophysica

2022

Vol. 70, no 5

2511--2528

The manuscript presents the results of an aggradation experiment performed in a laboratory channel with supercritical flow. The channel was fed with a stationary sediment load exceeding the transport capacity of the flow in the initial condition, thus inducing sediment aggradation and an increase of the bed slope. The experiment is part of a laboratory campaign mimicking sediment overloading in mountain rivers, a process that can determine increased hydraulic risk levels at key spots. A crucial issue in measuring sediment aggradation is the definition and determination of the bed elevation, this issue being quite relevant in experiments with a relatively large transport capacity, where a thick bed-load layer exists and hinders the possibility to determine with confidence a reference bed elevation. The determination of the bed elevation, in turn, impacts the quantification of a number of properties, including the initial sediment transport capacity of the flow, temporal scales of the aggradation process, water depth and Froude number. The manuscript presents a sensitivity analysis of the results to two extreme definitions for the bed elevation: the first one locates the bed at the upper edge of the bed-load layer, while the second one at the lower edge of the bed-load layer where the particles do not move. The presentation of the two alternatives is focused on the experimental methods they use, consistently with the intent of the special issue. Furthermore, it is demonstrated that the definition of the bed elevation also has a major impact on numerical models of the process. The experimental results have been reproduced numerically, demonstrating that the calibration parameters returning a best fit are also impacted significantly by how the bed is defined. The preferred definition for analyzing an experimental campaign is locating the bed below the bed-load layer.