A study of the likely changes in the hydrology of Okavango river due to upstream developments

Abstract

Drinking water supply in Botswana is mainly based on groundwater abstractions which are mostly done in Northern part of the country which includes the Okavango River Catchments. Hydrological modeling of Okavango River Catchment is essential to help in understanding of the hydrology of the watershed and for its water management. The Water Evaluation and Planning (WEAP) model system is used to set up an integrated hydrological model for Okavango River Catchment. This report documents the application of a monthly rainfall-runoff model for the Okavango River Basin. Stream flow is mainly generated in Angola where the Cuito and Cubango rivers arise. They then join and cross the Namibia/Angola border, flowing into the Okavango wetland in Botswana. The Model gives the results of hydrographs showing how the downstream Region of the Okavango River Basin is likely to behave as the Upstream Region implements its proposed developments. It shows that both the Low and Medium development scenarios can be implemented without any harm to the river and the environment within the river catchment. The low development scenarios is the development implemented in 2015, medium scenario is developments implemented in 2022 whilst High development scenario is implemented in 2032. The High Development Scenario shows that the implementation of the developments may results in very low flows downstream that may even leave some parts of the Okavango Delta with very low flows or even dry when exposed to prolonged low flows. This may also have serious impacts on ecology and tourism in Botswana, and even change the cause of the famous Okavango River. The overall conclusion is that the model, in spite of the limited data access, adequately represents the hydrological response of the basin and that it can be used to assess the impact of future development scenarios.