Assessing development and climate variability impacts on water resources in the Zambezi River basin: Initial model calibration, uncertainty issues and performance

Abstract

Highlights Two hydrological models are established for 76 sub-basins covering the whole of the Zambezi River basin. While both models were successfully calibrated in most areas, there remain a number of uncertainties, mostly related to the available data. The poor simulations for the Shire sub-basins are associated with uncertainties in the observed flow data, as well as the dynamics of Lake Malawi. A further source of uncertainty is related to the interactions of some major tributary river systems with adjacent large wetland areas.

Assessing development and climate variability impacts on water resources in the Zambezi River basin. Simulating future scenarios of climate and development

“…Delta change is calculated using the mean and standard deviation for each RCM analyzing both annual totals and monthly distributions. The delta changes were then applied to the historical ET data used for the original model calibration ( Hughes et al, 2020 ) consistent with the hydrological model requirements. The final input to the hydrological model is a range of uncertainty (minimum and maximum values) in the annual potential evapotranspiration value for each warming level, while the seasonal distributions used for the scenarios remained the same as the historical data (the analysis of the RCM’s did not suggest significant changes in the seasonal distributions).…”

“…The initial calibration of the model ( Hughes et al, 2020 ) did not take into account all of the present day water uses, largely because the calibrations were based on historical observed stream flow data that may not reflect current levels of water use. There is very little information available to directly quantify water uses, and this is one of the typical data scarcity problems that is prevalent throughout southern Africa.…”

“…1 ). The rainy season is concentrated in the summer, 4–6 months between October and March, precipitation ranges from over 1 200 mm y −1 in some of the headwater areas of the Shire and Kafue sub-basins, to less than 700 mm y −1 in the more arid parts of Zimbabwe ( Hughes et al, 2020 ).

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“…The introduction to the first part of this study refers to the ultimate aim of hydrological models, which is to improve the decision-making capacity of water management authorities ( Hughes et al, 2020 ). One of the key issues for future water management is related to the likely impact of climate change on the natural water resources availability, as well as on the economic activities that rely and utlilise these resources ( Milly et al, 2008 ).…”

“…The companion of this study ( Hughes et al, 2020 ) described the hydrological models used to establish a basis for water resources assessments across the whole of the Zambezi River basin, outlined the model calibration approach and presented the results compared to the available observed stream flow data. The stated purpose of establishing the models is to establish an approach that allows for future water resources availability, under different scenarios of both development and climate change, to be assessed.…”