Assessment of water levels and the effects of climatic factors and catchment dynamics in a shallow subtropical reservoir, Manjirenji Dam, Zimbabwe

Abstract

Natural water level fluctuations have associated effects on water quality and resident aquatic communities, although their impacts are magnified if the dams have other non-seasonal designated multiple uses. Research demonstrates that excessive water level fluctuations impair ecosystem functioning, ultimately leading to shifts between clear-water and turbid states in shallow lakes. However, these data lack for Manjirenji Dam in Zimbabwe, thus hampering efforts towards effective freshwater resources management in the shallow reservoir. This study analyzed water levels and their fluctuations, and assessed the effects of climatic factors and catchment dynamics using a combination of historical and remote sensed data for the shallow Manjirenji Dam in Zimbabwe. Time series and multiple regression analysis were used to determine water level trends, and the influence of catchment and climatic components in Manjirenji Dam. Lake levels have increased since construction, though their non-significant seasonal variation in the Manjirenji Dam reflects the overlapping effects of catchment and climatic variables. Despite the inferred high stability and resilience, the high fluctuation widths expose the dam to hydrodynamic and climate shocks which have major ecological and conservation implications. A climate change based integrated water resources management approach is necessary for sustainable water resources utilisation in the Manjirenji Dam.