Land Use and Land Cover Re-Patterning as a Method for Streamflow Regime Modification in Lilongwe River Catchment in Malawi

Abstract

Land use and land cover changes (LULCCs) have been increasingly shown to exacerbate water-related problems such as floods and droughts worldwide. Malawi has not been spared such issues despite the reported opportunities for ameliorating the same through land use or cover (LUC) re-patterning. Using Lilongwe River Catchment as a case in point, this study set out to assess LUC re-patterning as a method for modifying streamflow regimes in Malawi. The study assessed the period from 2020 to 2049 and it was conducted by initially identifying the current land cover pattern in Lilongwe River Catchment using remote sensing techniques such as atmospheric correction and image classification. The streamflow regime resulting from this land cover pattern was then determined using a hydrological model known as the Soil Water Assessment Tool (SWAT), and climate modelling techniques. Practical land use patterns for the catchment were then determined using the Dynamic Conversion of Land Use and its Effects (Dyna-CLUE) model. An ideal streamflow regime was then later defined based on information obtained from a systematic review of literature, existing legal instruments and institutional frameworks governing land use planning in Malawi. The effect of each land use scenario (n = 6) on the Lilongwe River flow regime was then examined to determine which scenario yielded ideal streamflow requirements for the catchment under different climatic conditions (n = 3). Calibration and validation of the SWAT model yielded satisfactory values of Nash-Sutcliffe Efficiency (NSE) and Coefficient of Determination (R2) of 0.65 and 0.64 for the calibration period, and 0.62 and 0.62 for the validation period respectively. Results of the study demonstrated that all identified land use scenarios improved the river’s streamflow regime, though not enough to meet the minimum 2049 projected demand of 5 m3/s. The best combination of land use and climate scenario yielded potentially helpful positive changes of up to +4% (0.5 m3/s) in dry season flow and +3% (0.8 m3/s) in wet season flow. It was thus concluded that LUC re-patterning may not be the best tool for modifying streamflow regimes in Lilongwe river catchment. Some evidence suggests repetition of this study in other catchments in Malawi may however show variations against the current conclusion since hydro-climatic conditions vary across the country. Further assessments on the same are thus strongly recommended.