Abstract:
Metolong dam is located 30 km east of Maseru town, with the dam retaining wall built inside the
Phuthiatsana River. The purpose of the dam is to supply portable water to Maseru, Roma
Mazenod, Morija and Teyateyaneng. The Instream Flow Requirement (IFR) given post
Metolong dam construction and meant to sustain life downstream of the dam was used to
estimate how much hydropower can be generated from IFR. Even though the study is aimed at
assessing the hydropower generation potential of the dam, it did not address the sedimentation
rate occurring inside the dam per year and how much storage capacity is lost due to
sedimentation. Microsoft excel spreadsheet is used to estimate how much electricity can be
generated from IFR and to examine how the water temperature affects the electricity projections.
The results show that the dam has the capacity to produce 65kW from In-stream flow
requirement (IFR) in April, as a month with the highest IFR and 7 kW in September, as a month
with the lowest IFR. These power production figures are studied together with the water
temperature in three scenarios to observe the effects of water temperature on power production.
The outcome is that they seem to have no significant effect. The power production is based on
when a Radial flow PAT (Pump As Turbine) of 0.6 efficiency and generator of 0.955 efficiency
are attached at IFR release point. The dam head ranges between 23 m – 44 m for IFR, with water
releases of 0.01 m3/s – 0.3 m3/s. This power can be used for distributed generation or net
metering by the Water and Sewage Company (WASCO). The financing of the project is not
expected to exceed $50 000 given the condition of the already installed penstock at the recovery
period of less than 4 years factoring in fluctuations of power brought by those of IFR for
environmental purposes downstream of Metolong dam.
