Improving discharge prediction for poorly gauged hydropower potential sites : a case study of Mabula Kapi site.
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Date
2023
Authors
Mukuka, Reynolds
Journal Title
Journal ISSN
Volume Title
Publisher
The University of Zambia
Abstract
Kafue Gorge Regional Training Centre (KGRTC) intends to carry out full feasibility
studies for the development of Mabula Kapi hydropower site located on Kaombe
River in Serenje District. KGRTC installed a hydrological gauging station at the site
in September 2019. However, the small hydropower potential site is considered to be
poorly gauged since it lacks adequate streamflow and/or rainfall data required for
hydropower planning and design. Mabula Kapi was initially investigated to
prefeasibility study level, using hydrological data from an adjacent catchment on
Lusiwasi River, which was considered to be hydrologically similar. The catchment
area-ratio method which was applied is a simple approximation because catchment
characteristics between donor and target catchments rarely match perfectly. For
Mabula Kapi site, the presence of a natural lake on the Lusiwasi donor catchment
raised uncertainties about similarities in the drainage network and therefore the
accuracy of transposing hydrological data. Additionally, anticipated future climate
changes raised uncertainties about the sustainability of the proposed hydropower
plant.
In this study, several discharge prediction methods were reviewed and rainfall-runoff
computer modelling was selected as the most suitable method for predicting discharge
for Mabula Kapi Catchment. The method was applied to accurately predict discharge
time series by creating a conceptual representation of relevant hydrological processes
for Mabula Kapi Catchment in a computer-based open-source model known as
PITMAN. The PITMAN model was largely selected due to limitations in local input
data availability and project budget. Satellite rainfall point data known as the Climate
Hazards Group InfraRed Precipitation with Station data (CHIRPS) was adopted as
one of the modeling inputs because of its good correlation with ground measured data.
A 30-year discharge time series was simulated for Mabula Kapi site using the
PITMAN model. The model was calibrated by matching simulated discharge and
observed discharge time series from the newly installed gauging station at Mabula
Kapi site. The derived time series were used to estimate the installed capacity (8.2
MW), annual energy yield (38 GWh) and design flood (120m3
/s). Runoff simulations
done in the model using future rainfall and temperature projections indicated that the
average annual energy for the power plant is likely to reduce by 11% from 2040 to
2059. It is recommended that the estimated energy reduction be taken into account
when conducting financial analysis for the project and that further climate tests be
done using other credible climatic projections which may be available.
Key words: CHIRPS, Hydropower, Modelling, Rainfall, Streamflow
Description
Thesis
Keywords
Hydropower. , Hydropower--Streamflow.