Assessment of hydraulic performance of the Eastern National Water Carrier, Namibia: Flumes three to four
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Date
2019
Authors
Mutelo, Mukendoyi A.
Journal Title
Journal ISSN
Volume Title
Publisher
University of Namibia
Abstract
In response to drought impacts, water augmentation by developing more boreholes in the Grootfontein-Otavi karst area and increase the use of the Eastern National Water Carrier (ENWC) was prioritised. Hence, plans to increase water transportation should be based a sound understanding of the hydraulic behaviour of the ENWC. Thus, this study sought to utilise the HECRAS model for the primary objective of assessing the hydraulic performance of the section between flumes 3 and 4 i.e. evaluating the hydraulic behaviour of the ENWC and determining its maximum water transportation capacity using HEC-RAS as well as perform a rough estimate of
leakage and evaporation losses. The results show that the mean Manning's roughness coefficients n = 0.099, 0.124, 0.028 and 0.038 were respectively found in Canal! and 2, and Siphon land 2. An assessment of observed and the predicted water depth exhibited a very good agreement, that yielded an R2 = 0.997. The estimated maximum capacity of the canal system between flumes 3
and 4 was found to be discharge Q = 0.3 m3/s while the flows accommodated in different sections of the canal ranged from Q = 0.3 to 1 m3 /s. A variation of the roughness coefficients did not seem to noticeably alter the estimated maximum capacity or influence the water levels of the normal flow regimes. With respect to leakage losses, the majority of canal sections i.e. Canal 1, Siphon 1 and Siphon 2, bad leakage losses of the order of20% or more of mean discharge in those respective sections. Therefore, it can be deducted that the hydraulic state of the aqueduct is undesirable when compared to the roughness condition n = 0. 015 of concrete-lined aqueducts. Hence robust strategies for operation and maintenance of the aqueduct are required.
Description
A thesis submitted in fulfillment of the requirements for the Degree of Master of Science (Civil Engineering)
Keywords
Hydraulic performance assessment, water supply sustainability, Manning's roughness coefficient, Leakage loss