Impact of Climate Change on the Okavango River: The impact of the future discharge on the water supply of Okavango Basin - Beau Buijtenhuijs

Abstract

This study is about droughts in the Okavango Delta in Botswana. It investigates how low flows in the Okavango River is an indication to dry periods in the delta and how climate change may impact the frequency of these low flows and droughts. The Okavango Delta is a flood-pulsed wetland system and has rich wildlife and biodiversity. The wildlife and the communities that live around the delta are dependent on sufficient flooding during the seasonal floods. Historical dry periods in the Okavango Delta created problems for wildlife, for instance hippos getting stuck in mud pools that usually were full of water.

To research the effect of climate change on droughts in the Okavango Delta and low flows in the Okavango River, historical dry periods in the delta are connected to observed discharge data of the river and threshold values for the total annual volume that flows into the delta are determined. To project future droughts, the discharge of the Okavango River is modelled using the HBV model. Using the calibrated model, future discharge patterns are simulated based on the Shared Socio-economic Pathways SSP1-2.6, SSP2-4.5, SSP3-7.0 and SSP5-8.5. The used hydrological model, with the necessary ERA5 dataset and CMIP6 data for the SSP scenarios, are provided by the eWaterCycle platform.

The results show that if the CO2 emissions reach net-zero by 2050 (SSP1-2.6), the situation in the Okavango Delta is projected to improve in the period 2065-2099 when looking at the total number of hydrological droughts. The results also show that the number of hydrological droughts in the delta will about double when the CO2 emissions do not reach net-zero by the end of the century. These projections show that the frequency of problems in the delta, like hippo getting stuck in mud pools, will increase.