Simulation modelling for integration of hydropower, irrigation water and water supply potentials of Lweya Basin, Malawi

ABSTRACT

The Nkhata Bay district in Northern Malawi faces rapid population growth, thus rising water demands for services such as agriculture production, water supply and electricity. Lweya River basin covers about two-thirds of the district and is the main water source for gravity-fed irrigation, water supply schemes, and a potential of gravity hydropower generation. However, there is no framework to support the decisions on water uses in the basin without adversely affecting downstream uses. Therefore, this study used simulation modelling to integrate the development and management of the surface water resources projects in a sustainable manner in the basin. The Soil and Water Assessment Tool (SWAT) model calibration results gave NS = 0.71 and R² = 0.76, and NS = 0.80 and R² = 0.86 on a daily and monthly basis, respectively. The model was used for integration where the simulated flow enabled estimation of Flow Duration Curve indices at short records and ungauged project sites, which were compared with potential water demands of 0.73, 8.61 and 20.52 m³/s for water supply, irrigation and hydropower, respectively. The integration of potentials used priorities set in Malawi's Water Resources Management Policy and Strategy (1994). Between the options, the best scenario was hydropower development located upstream of other uses on the main Lweya River.

KEYWORDS:

• Hydropower
• integration
• irrigation
• Lweya basin
• SWAT model
• water supply

Acknowledgement

Sincere gratitude is extended to the Government of Malawi for providing a study scholarship to the first author for the Master of Science in Water Resources Engineering. Also, the publication of this research was facilitated by a writing grant from the Office of the Deputy Vice Chancellor – Research of the University of Dar es Salaam, Tanzania.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by Government of Malawi and The Office of the Deputy Vice Chancellor - Research of the University of Dar es Salaam, Tanzania: [grant number CoET-WRE19001].