Monthly Drought Bulletin August 2021

SAWS Drought Bulletin

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1. Overview

Rainfall received during August was above-normal in large parts of the Free State and North-West and over the northeastern parts of the Northern Cape, western-half of the Limpopo Province as well as in parts of KwaZulu-Natal and the Western Cape. The remainder of the country experienced somewhat dry conditions in isolated areas.

During the 3-month period from June 2021 to August 2021, above-normal rainfall was mainly received in North-West and over the northeastern parts of the Northern Cape as well as in isolated areas of the Free State, KwaZulu-Natal and the Western Cape. The remainder of the country experienced somewhat dry to moderately dry conditions in isolated areas.

During the 6-month period from March 2021 to August 2021, moderately dry to severely dry, with extremely dry conditions in small isolated areas, were experienced in parts of the Free State, North- West, the Limpopo Province and the Eastern and Northern Cape, Free. The remainder of the country experienced somewhat dry conditions in isolated areas.

The 12- and 24-month SPI maps give an indication of areas where prolonged droughts exist, in other words, where below-normal rainfall occurred over a period of one year or longer. On the 12- month SPI map, extremely dry conditions continues to dominate the southwestern parts of the Eastern Cape. On the 24-month SPI map, extremely dry conditions are still noticeable in small parts of the Eastern and Northern Cape. This situation indicated that substantial rainfall is necessary to alleviate the dry conditions in these regions.

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SAWS Drought Bulletin

______2. Rainfall assessment (1- and 3-monthly maps)

Figure 1: Assessment of rainfall maps for 1-month (August 2021; top) and for 3-month (June to August 2021; bottom)

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SAWS Drought Bulletin

______3. Indications of Drought

3.1. Standardized Precipitation Index (SPI)

Figure 2: Short to medium term SPI Maps for 1-month (August 2021; top), 3-month (June 2021 to August 2021; middle) and 6-month (March 2021 to August 2021; bottom)

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SAWS Drought Bulletin

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Figure 3: Long term 12-month SPI map (September 2020 to August 2021; top) and 24-month SPI map (September 2019 to August 2021; bottom)

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SAWS Drought Bulletin

______3.2 Vegetation Condition Index (VCI) and Temperature Condition Index (TCI) The use of VCI and TCI help to monitor the severity of drought by comparing the current vegetation state with same period the previous year. Low and high values indicate bad and good vegetation state conditions respectively.

Figure 4 show the state of vegetation in South Africa. The Northern Cape, the Free State, the eastern parts of the North West, as well as the western parts of the Eastern Cape and Gauteng are experiencing stressed vegetation conditions compared to the same period the previous year. The rest of the country is showing improved vegetation conditions compared to the same period the previous year.

Figure 4: VCI (left) and TCI (right) in the week of the 13th of September 2021

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SAWS Drought Bulletin

______4. Drought stricken regions

4.1 SPI and SPEI

Based on the SPI maps shown in Figure 3, dry conditions persist in the south-western parts of the Eastern Cape and south-eastern parts of the Northern Cape. To further investigate the severity of the drought we use the SPEI alongside SPI. The SPEI consider both the precipitation and potential evapotranspiration in determining drought. Unlike the SPI, SPEI captures the impact of increased temperatures on water demand. Figure 5 presents the SPI and SPEI at Willowmore at both 12 and 24 months. Willowmore, representative of the western parts of the Eastern Cape, continues to experience extremely dry conditions despite recent rainfall. Figure 6 presents SPI time series at 12 and 24 months over Williston. From the SPI time series it is notable that the area of Williston continue to experience.

Figure 5: Time series plots for Willowmore weather station for 12- and 24-month SPI (top) and SPEI (bottom).

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SAWS Drought Bulletin

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Figure 6: Time series plots for Williston weather station for 12- and 24-month SPI

5. Dam levels The table below show the average dam level per province for the week of the 13th September 2021 compared to the same period the previous year. All the provinces are showing improved dam levels, with an exception of the Gauteng province which have dropped by 4.8% compared to the same period last year. Table: Provincial Dam levels in the week of the 13th September 2021 and for the same period in 2020 (Source: DWS).

Same time Last 13 August 2021 Province Year Update (% Full) (% Full) Eastern Cape 50 50.2 Free State 76.3 91 Gauteng 98.3 93.5 KwaZulu-Natal 56.2 67 Limpopo 62.3 80.7 Mpumalanga 67.6 79.1 Northern Cape 94.8 95 North West 64.7 76.2 Western Cape 76.4 82.1

End of document

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