Understanding and modelling the effects of wetland on the hydrology and water resources of large African river basins

Abstract

Wetlands are important components of many large river systems. Some basin scale hydrological models do include explicit sub-models to deal with wetland impacts, but one of the key challenges is to estimate appropriate parameter values to represent the channel-wetland exchange processes. A combined modelling approach is applied in this study and involves the use of the detailed, daily time-step, LISFLOOD-FP hydraulic model to improve the understanding of channel-wetland exchange dynamics and to quantify the wetland parameters of a basin scale hydrological model. While there remain, many uncertainties associated with a lack of sufficient validation data, the LISFLOOD-FP results largely reflect the physical characteristics of the two floodplains (the Luangwa and Barotse in the Zambezi River basin). The LISFLOOD-FP results were also used to estimate the wetland parameters of the basin scale hydrological model with greater confidence and improved the downstream simulations results (albeit marginally). The results suggest that the influence of the floodplain on the monthly Luangwa flow regime is minimal, whereas the Barotse floodplain significantly attenuates the high flows and regulates the low flows of the Upper Zambezi River. The approach implemented in this study presents an important step towards the improvements of water resource assessments modelling for research and practical purposes in data-scarce river basins, however, further work is required to refine the model setup using additional field information related to exchange dynamics as well as high quality remote sensing data.