Satellite-based drought analysis in the Zambezi River Basin: Was the 2019 drought the most extreme in several decades as locally perceived?

Petra Hulsman,Hubert H.G Savenije,Markus Hrachowitz

doi:10.1016/j.ejrh.2021.100789

Petra Hulsman, Hubert H.G Savenije + Show 1 more

Open Access

https://doi.org/10.1016/j.ejrh.2021.100789

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Abstract

Study regionThe study area is the river basin upstream of the Kariba dam located in the Zambezi River at the border of Zambia and Zimbabwe. Study focusDuring the dry season of 2019 in Sub-Saharan Africa, extremely low water levels occurred in the Zambezi. According to news media, locals perceived this drought as the worst in several decades. We analyzed the 2019 drought in the Zambezi River Basin upstream of the Kariba dam to determine whether it indeed was the longest, most intense, and severe drought, in terms of precipitation, total water storage and reservoir water level observations over recent decades. New hydrological insights for the regionData analysis indicates that the 2019 drought indeed had the lowest basin-averaged annual rainfall, most severe local rainfall deficit in the north of the basin, and lowest reservoir level since 1995. However, the rainfall deficit was more severe in 2002, both basin-wide and locally in the south of the basin. The total storage deficit was more severe in 2004, both basin-wide and locally in the central part of the basin. However, as the available storage data did not cover the entire deficit for 2019, its final duration and severity remain unknown. Therefore, it depends on the drought characteristic, hydrological variable, and location within the basin, whether the 2019 drought was indeed the most extreme over recent decades.

Highlights

During the dry season of 2019 in Sub-Saharan Africa, extremely low river water levels were observed
According to locals and the news media, this resulted in frequent power cuts of up to 18 h per day for at least 3 months starting in November 2020 (Carlowicz, 2019; Matiashe, 2019; Tshili, 2019). 250 km further upstream of the Kariba Reservoir, the Victoria Falls, which is known as one of the biggest waterfalls in the world, was reduced from a 1.7 km wide falls to multiple small waterfalls (Childs, 2019; Henson, 2019)
According to the precipitation-based drought index Standardized Precipitation Index (SPI), there have been multiple droughts in the Kariba Basin of which five droughts are characterized by SPImin < -1.5 (Table 2) and can be classified as “severe meteorological drought” according to the drought categories as defined by McKee et al (1993)

Summary

Introduction

During the dry season of 2019 in Sub-Saharan Africa, extremely low river water levels were observed. This was especially visible in the Zambezi River at Victoria Falls. Low water levels were observed in the reservoir upstream of the Kariba hydropower dam, which was down to 10% of usable water for hydro-power generation. The Zambezi River Basin is characterized by one distinct wet and one dry season. It exhibits high temporal and spatial variability in water availability and demand such that the dry season demand frequently exceeds water availability, resulting in water stressed areas

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