Abstract:The Terai region in Nepal has water resources with very low head and medium to high discharge conditions. Hence, the people of the Terai region are not being able to utilize the water resources available near them due to the limitation of technology. This study is intended to serve the purpose of further research of ultra-low head gravitational water vortex turbines useful for power generation in the Terai region.Gravitational water vortex turbine is an ultra-low head turbine which can operate in as low head as 0.7m with similar yield as conventional hydroelectric turbines characterized with positive environmental yield. This study has been carried out in two phases. In the first phase, two different turbines are to designed and fabricated and the performance characteristics of the new turbine are to be compared with that of the installed turbine. The second phase includes the design and fabrication of the conical basin. Experimental tests will be carried out and the performance of the system with the use of a conical basin will compared with that of the system using the cylindrical basin. A site testing also has been carried out to ensure the performance of system.

River bed and floodplain sediments are a direct reflection of river channel processes. This paper examines sediment transfer processes at river junctions, using as a case study the River Kas, a tributary of the River Mula, Godavari basin, Maharashtra, India. The study uses four cross-sections, two from upstream tributaries, one in the main confluence zone, and one downstream. Sediment samples are collected from each cross-section and adjacent banks. To understand the tributary impact on the main channel, variations in sand, silt and clay percentages and variations in the shape of sediment particles were recorded. Data suggest that the percentage of silt and clay increased away from the active channel towards banks along a cross-section, except for the mid-channel bar and the downstream segment of the confluence. The `a axis' and `c axis' lengths of particles increased for the samples on the confluence compared to upstream and downstream samples. Sediment characteristics between tributary and the main stream reflect both downstream distance from sediment source and the characteristics of the respective transport processes. The distribution of fine material at the tributary mouth suggests that there have been instances in the past where the mainstream flow has dominated the confluence and has led to slack water deposits on the tributary mouth. Construction of a weir for local flow regulation also affects the pattern and character of sediments. In this large, seasonal river, confluence sedimentology is a joint product of flow variation, confluence morphology and the additional effects of human activity. The study thus provides insights into confluence dynamics and characteristics which may not be revealed in the more intensively researched temperate confluences of smaller scale.

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