The potential of micro-hydropower generation in the Inkomati River Catchment in Mozambique.

Abstract

Hydropower is the leading source of renewable energy. It provides more than 97% of all electricity generated by renewable sources internationally. Small hydropower plants (SHPs) can be an alternative and a complement to large power generating plants, especially in the less developed world where the demand for electricity is growing rapidly. The socio-economic development in the Inkomati River Catchment has experienced slow growth in recent years. One of the major reasons identified is the lack of availability of electrical energy, which hinders agricultural production, job creation and economic growth, particularly in small rural communities. The installation of small hydropower plants in the Inkomati River Catchment which experiences variable flows has the potential to produce clean and cheap energy for boosting and sustaining economic growth in the region. Numerous hydrological studies conducted in the Inkomati River Catchment have focused on the mitigation of floods and droughts, while little attention has been given to the hydropower potential of the catchment. The objectives of this study were to: (i) derive and verify a simple methodology to estimate daily streamflow quantiles at gauged sites using flow duration curves (FDCs), (ii) to regionalise the FDCs in order to estimate daily streamflow quantiles at ungauged sites, and (iii) to demonstrate the use of the regionalised FDCs to estimate potential hydropower production at selected sites in the Inkomati River Catchment. To address these objectives, FDCs were computed using only reliable daily streamflow data gathered from twelve gauged stations across the Inkomati River Catchment. Since most of the gauged stations in the catchment are sparse, regionalisation was performed using morphoclimatic characteristics (drainage area, hypsometric fall, Mean Annual Precipitation (MAP) and river length) parameterized using a Geographic Information System (GIS). The methodology developed enables daily streamflow quantiles to be estimated at both gauged and ungauged sites. The verification of the accuracy of the regionalisation was done by calculating the root mean square error at two selected gauging stations, which were not used in the calibration procedure. The power equation was applied to determine the power potential at the Mac-Mac River and Ressano Garcia gauging stations, assuming a 50% and 70% overall plant efficiency (Є) of the turbine. The method estimates the flow and, given adequate head, the potential hydropower can be estimated, especially from small catchments (<100 km² drainage area).