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You searched for subject:(conveyance loss). Showing records 1 – 3 of 3 total matches.

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Addis Ababa University

1. Adam, Tefera. Hydraulic and Hydrologic Factors on Conveyance Efficiency: Case of Fantale and Tibila Irrigation Schemes .

Degree: 2013, Addis Ababa University

In planning and designing an irrigation system, a major problem is to decide what efficiency to apply in the calculations. Since basic knowledge on this subject is lacking, it is common practice that this efficiency is either assumed or derived from existing irrigation systems. Obviously, the efficiency thus obtained is unlikely to suit the conditions of the project area in its future state. Most irrigation projects in Ethiopia are found to work below their expectation. One of the main reason behind is the difference in the conveyance & application efficiency envisioned (designed) and the actual values obtained in the projects design life. For irrigation projects having extensive length of main canal and secondary canals, the effect of conveyance efficiency is far more important than the application efficiency in deciding the project future performance. To evaluate the effect of conveyance efficiency, variation from the designed value, two irrigation schemes, Fantale and Tibila constructed in 2003 and 2008 respectively were used as case study. The designed value was taken from the respective design reports and the existing conveyance efficiency is obtained by measuring discharge, depth of flow, wetted perimeter, wetted area and bed slope of the canal at different locations. The conveyance efficiency given at the design stage was 95% for both schemes which was directly taken from FAO recommendations. However, the values obtained during the study were 34.4% and 89% respectively for Fantale and Tibila schemes. Such a decrease in conveyance efficiency is found to be due to hydraulic and hydrologic factors. The factor is hydraulic in a sense that the conveyance characters (roughness coefficient, hydraulic radius and bed slope) used in the designed stage has no longer exists in the current situation of the schemes. The factor is hydrologic in a sense that the variation in hydraulic radius from the designed values has resulted in increase in the water depth which intern increases the top width of the water surface which further resulted in increasing in seepage and evaporation losses. Thus a designed conveyance efficiency taken directly from standard books has effect on the overall performance of an irrigation project. Conveyance efficiency selected should be based on construction material, method and quality, managerial activities, technological and other factors affecting conveyance efficiency. Advisors/Committee Members: Mebruk M. (Dr) (advisor).

Subjects/Keywords: Conveyance efficiency; Evaporation loss; Fantale & Tibila irrigation schemes

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Adam, T. (2013). Hydraulic and Hydrologic Factors on Conveyance Efficiency: Case of Fantale and Tibila Irrigation Schemes . (Thesis). Addis Ababa University. Retrieved from http://etd.aau.edu.et/dspace/handle/123456789/4100

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16th Edition):

Adam, Tefera. “Hydraulic and Hydrologic Factors on Conveyance Efficiency: Case of Fantale and Tibila Irrigation Schemes .” 2013. Thesis, Addis Ababa University. Accessed December 05, 2020. http://etd.aau.edu.et/dspace/handle/123456789/4100.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7th Edition):

Adam, Tefera. “Hydraulic and Hydrologic Factors on Conveyance Efficiency: Case of Fantale and Tibila Irrigation Schemes .” 2013. Web. 05 Dec 2020.

Vancouver:

Adam T. Hydraulic and Hydrologic Factors on Conveyance Efficiency: Case of Fantale and Tibila Irrigation Schemes . [Internet] [Thesis]. Addis Ababa University; 2013. [cited 2020 Dec 05]. Available from: http://etd.aau.edu.et/dspace/handle/123456789/4100.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Adam T. Hydraulic and Hydrologic Factors on Conveyance Efficiency: Case of Fantale and Tibila Irrigation Schemes . [Thesis]. Addis Ababa University; 2013. Available from: http://etd.aau.edu.et/dspace/handle/123456789/4100

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation


Universiteit Utrecht

2. Thonon, Ivo. Deposition of sediment and associated heavy metals on floodplains.

Degree: 2006, Universiteit Utrecht

In recent years, floodplains have become widely acknowledged as important natural sinks for sediments and associated substances like nutrients, PAHs, PCBs and heavy metals. The character of floodplains will change in the near future because of landscaping measures (excavation of secondary channels, lowering floodplains and removing minor embankments) and the rehabilitation of floodplain forests. In addition, climate and upstream land-use change will change the discharge frequency distribution and the suspended sediment concentrations. These three groups of changes affect the patterns and processes of sediment and associated heavy-metal deposition on floodplains. We studied the key factors behind the process of floodplain deposition, the present deposition patterns and how the patterns and processes will change due to the environmental changes. We firstly measured patterns, amounts and characteristics of floodplain deposition during inundations of several floodplains along the River Rhine branches in The Netherlands. The results of these measurements showed the strong influence of inundation hydrodynamics, river works and floodplain morphology on the deposition patterns. Next, we measured settling velocities of suspended matter during these inundations using a LISST-ST (a laser particle sizer and settling tube), which delivered an effective settling velocity of 0.000067 m/s. We subsequently used this settling velocity in a floodplain deposition model (MoCSED) that uses the ‘Method of Characteristics’ to simulate transport and deposition of sediment on floodplains. Since the model results were promising, we used the model to calculate scenarios for two selected floodplains experiencing floodplain rehabilitation in the near future. In one of them, a floodplain lake will be excavated, while in the other a secondary channel will be constructed. In addition, we studied the effect of set-aside practices in the Rhine basin and more frequent peak discharges due to climate change on the deposition of sediment and associated heavy metals. We conclude from this work that the conveyance loss of sediment on the Waal River floodplains will rise under climate change scenarios but will decrease when set-aside is included. The combination of climate change, set-aside and floodplain rehabilitation will result in the highest increase in conveyance losses (now 5 % for metals and 7 % for sediment). The sediment (now 1.5 kg/m2 per year for Waal River floodplains and 2.3 kg/m2 per year for IJssel River floodplains) and metal deposition rates will not change under that combination. This shows that when assessing effects of environmental changes on floodplain deposition both conveyance losses and deposition rates should be studied.

Subjects/Keywords: Aardwetenschappen; floodplain; sediment deposition rate; sedimentation; River Rhine; heavy metal; modelling; Method of Characteristics; settling velocity; conveyance loss; climate change

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Thonon, I. (2006). Deposition of sediment and associated heavy metals on floodplains. (Doctoral Dissertation). Universiteit Utrecht. Retrieved from http://dspace.library.uu.nl:8080/handle/1874/8133

Chicago Manual of Style (16th Edition):

Thonon, Ivo. “Deposition of sediment and associated heavy metals on floodplains.” 2006. Doctoral Dissertation, Universiteit Utrecht. Accessed December 05, 2020. http://dspace.library.uu.nl:8080/handle/1874/8133.

MLA Handbook (7th Edition):

Thonon, Ivo. “Deposition of sediment and associated heavy metals on floodplains.” 2006. Web. 05 Dec 2020.

Vancouver:

Thonon I. Deposition of sediment and associated heavy metals on floodplains. [Internet] [Doctoral dissertation]. Universiteit Utrecht; 2006. [cited 2020 Dec 05]. Available from: http://dspace.library.uu.nl:8080/handle/1874/8133.

Council of Science Editors:

Thonon I. Deposition of sediment and associated heavy metals on floodplains. [Doctoral Dissertation]. Universiteit Utrecht; 2006. Available from: http://dspace.library.uu.nl:8080/handle/1874/8133

3. Thonon, Ivo. Deposition of sediment and associated heavy metals on floodplains.

Degree: 2006, University Utrecht

In recent years, floodplains have become widely acknowledged as important natural sinks for sediments and associated substances like nutrients, PAHs, PCBs and heavy metals. The character of floodplains will change in the near future because of landscaping measures (excavation of secondary channels, lowering floodplains and removing minor embankments) and the rehabilitation of floodplain forests. In addition, climate and upstream land-use change will change the discharge frequency distribution and the suspended sediment concentrations. These three groups of changes affect the patterns and processes of sediment and associated heavy-metal deposition on floodplains. We studied the key factors behind the process of floodplain deposition, the present deposition patterns and how the patterns and processes will change due to the environmental changes. We firstly measured patterns, amounts and characteristics of floodplain deposition during inundations of several floodplains along the River Rhine branches in The Netherlands. The results of these measurements showed the strong influence of inundation hydrodynamics, river works and floodplain morphology on the deposition patterns. Next, we measured settling velocities of suspended matter during these inundations using a LISST-ST (a laser particle sizer and settling tube), which delivered an effective settling velocity of 0.000067 m/s. We subsequently used this settling velocity in a floodplain deposition model (MoCSED) that uses the ‘Method of Characteristics’ to simulate transport and deposition of sediment on floodplains. Since the model results were promising, we used the model to calculate scenarios for two selected floodplains experiencing floodplain rehabilitation in the near future. In one of them, a floodplain lake will be excavated, while in the other a secondary channel will be constructed. In addition, we studied the effect of set-aside practices in the Rhine basin and more frequent peak discharges due to climate change on the deposition of sediment and associated heavy metals. We conclude from this work that the conveyance loss of sediment on the Waal River floodplains will rise under climate change scenarios but will decrease when set-aside is included. The combination of climate change, set-aside and floodplain rehabilitation will result in the highest increase in conveyance losses (now 5 % for metals and 7 % for sediment). The sediment (now 1.5 kg/m2 per year for Waal River floodplains and 2.3 kg/m2 per year for IJssel River floodplains) and metal deposition rates will not change under that combination. This shows that when assessing effects of environmental changes on floodplain deposition both conveyance losses and deposition rates should be studied.

Subjects/Keywords: floodplain; sediment deposition rate; sedimentation; River Rhine; heavy metal; modelling; Method of Characteristics; settling velocity; conveyance loss; climate change

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Thonon, I. (2006). Deposition of sediment and associated heavy metals on floodplains. (Doctoral Dissertation). University Utrecht. Retrieved from https://dspace.library.uu.nl/handle/1874/8133 ; URN:NBN:NL:UI:10-1874-8133 ; urn:isbn:90-6809-377-0 ; URN:NBN:NL:UI:10-1874-8133 ; https://dspace.library.uu.nl/handle/1874/8133

Chicago Manual of Style (16th Edition):

Thonon, Ivo. “Deposition of sediment and associated heavy metals on floodplains.” 2006. Doctoral Dissertation, University Utrecht. Accessed December 05, 2020. https://dspace.library.uu.nl/handle/1874/8133 ; URN:NBN:NL:UI:10-1874-8133 ; urn:isbn:90-6809-377-0 ; URN:NBN:NL:UI:10-1874-8133 ; https://dspace.library.uu.nl/handle/1874/8133.

MLA Handbook (7th Edition):

Thonon, Ivo. “Deposition of sediment and associated heavy metals on floodplains.” 2006. Web. 05 Dec 2020.

Vancouver:

Thonon I. Deposition of sediment and associated heavy metals on floodplains. [Internet] [Doctoral dissertation]. University Utrecht; 2006. [cited 2020 Dec 05]. Available from: https://dspace.library.uu.nl/handle/1874/8133 ; URN:NBN:NL:UI:10-1874-8133 ; urn:isbn:90-6809-377-0 ; URN:NBN:NL:UI:10-1874-8133 ; https://dspace.library.uu.nl/handle/1874/8133.

Council of Science Editors:

Thonon I. Deposition of sediment and associated heavy metals on floodplains. [Doctoral Dissertation]. University Utrecht; 2006. Available from: https://dspace.library.uu.nl/handle/1874/8133 ; URN:NBN:NL:UI:10-1874-8133 ; urn:isbn:90-6809-377-0 ; URN:NBN:NL:UI:10-1874-8133 ; https://dspace.library.uu.nl/handle/1874/8133

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