As of mid-June 2024, oceanic and atmospheric indicators in the central-eastern Pacific Ocean align with neutral El Niño Southern Oscillation (ENSO) conditions, while diminishing El Niño conditions remain in the western Pacific. Predictions from various climate models suggest that the ENSO-neutral conditions will persist for the remainder of the Southern Hemisphere winter season. In addition, all climate model forecasts show potential La Niña conditions from the spring season. An important observation is that sea surface temperatures in the Southern Hemisphere have been cooling since December 2023. However, there remains great uncertainty regarding the onset, as well as the probability of La Nina conditions amongst the different models. For example, the NOAA CPC models show a 75% chance for La Niña conditions to persist during the August to October period, while the IRI shows 45% likelihood for La Nina conditions during this period (Figure 1). These differences are due to the relatively low skill of seasonal forecast models during this time of the year. Therefore, these probabilities should be used with caution.

Figure 1: ENSO Probabilities based on CPC and IRI models.

Due to the relatively good rainfall received in uMngeni-uThukela Water’s area of operation during the rainfall season, most UUW-operated dams have remained in relatively high storage levels during May and June 2024. For example, the storage trajectories of the Mgeni System are shown in Figure 2 below.

Figure 2: Historical storage trajectories for the Mgeni System.

Due to the high storage levels observed in most UUW-operated dams, the risk of non-supply remains relatively low for UUW’s customers in the short to medium-term. However, it is important for water users to implement demand-side water resources management strategies such as reusing water for non-potable purposes and fixing household leaks. uMngeni-uThukela Water will continue to monitor the ENSO signal and an update will be issued at the onset of the spring season.

 

According to model assessments by the International Research Institute for Climate and Society, the El Niño Southern Oscillation (ENSO) signal remains in an El Niño state for the April-May-June (AMJ) period. Therefore, an El Niño advisory remains as oceanic and atmospheric indicators in the central-eastern Pacific Ocean continue to align with the diminishing El Niño event. The multi-model based forecasts suggest that neutral conditions will prevail from late autumn into winter, with a high likelihood for La Niña conditions to develop towards the end of winter.

Figure 1: Mid-April ENSO Forecast by IRI.

uMngeni-uThukela Water’s area of operation received relatively normal to above-average rainfall during April 2024. As a result, all dams managed by uMngeni-uThukela Water remained in relatively high storage levels during April and were at full supply capacity on 01^st May 2024. Only the Ludeke, Hazelmere, iMvutshane and Pongolapoort Dams were below full supply capacity as these are managed at relatively low storage levels for safety reasons.

Table 1: Dam levels as % of full supply capacity in UUW and some DWS-managed dams on 1^st May 2024, compared to the previous two years.

Site Name	Dam Level (% of full supply capacity)
	01 May 2024	01 May 2023	01 May 2022
Mearns Dam	108	103	117
Spring Grove Dam	101	99	101
Midmar Dam	100	97	101
Henley Dam	105	105	107
Albert Falls Dam	101	99	102
Nagle Dam	100	95	102
Inanda Dam	101	101	103
Home Farm Dam	101	100	113
Nungwane Dam	101	101	102
Umzinto Dam	100	99	100
E.J. Smith Dam	100	98	100
Mhlabatshane Dam	101	100	101
Ludeke Dam	46	65	100
Hazelmere Dam	84	56	53
iMvutshane Dam	61	62	90
Goedertrouw Dam	98	100	99
Pongolapoort Dam	87	84	89
Olifantskop Dam	104	102	110
Spioenkop Dam	100	99	100
Wagendrift Dam	101	100	102
Woodstock Dam	100	95	101

The high storage levels indicate that there is no risk of non-supply for UUW’s customers in the short-term. However, the beginning of May is a critical period for water resources planning in UUW’s area of operation, as it marks the onset of the dry season. Therefore, it is important for water users to conserve water during this period. uMngeni-uThukela Water will continue to monitor the ENSO signal, as well as developments in SA’s neighbouring countries, i.e. Malawi, Zimbabwe and Zambia, who are currently experiencing an El Niño-induced drought. The next update will be issued at the end of May 2024.

Based on oceanic and atmospheric conditions in the central-eastern Pacific Ocean, an El Niño advisory remains. According to the mid-March model assessments by the International Research Institute for Climate and Society, the El Niño Southern Oscillation (ENSO) signal remains in an El Niño state for the March-April-May (MAM) period. There is a high likelihood for neutral conditions to develop in autumn, while the long-term assessments suggest a potential return of a La Niña cycle later in the year.

The ongoing El Niño event has reached its peak and is currently diminishing. However, its effects are currently being experienced in various parts of the world. For example, South Africa’s neighboring countries, i.e. Malawi, Zambia and Zimbabwe are currently experiencing an El Niño-induced drought and have each declared a state of national disaster due to its impacts on livelihood, e.g. electricity supply (hydro-power). Therefore, it is essential for South Africa to remain alert as an El Niño advisory remains.

Figure 1: Mid-March ENSO Forecast by IRI.

Similar to February 2024, most of South Africa, as well as uMngeni-uThukela Water’s area of operation, received below-average rainfall during March 2024. However, most dams managed by uMngeni-uThukela Water remained in relatively high storage levels, with the levels of major dams such as Midmar, Albert Falls, Inanda and Goedertrouw Dams currently at 96%, 100%, 101% and 99% of full supply capacity, respectively.

Figure 2: March 2024 rainfall as a percentage of the long-term average (Source: South African Weather Service)

Although relatively below-average rainfall was received during March 2024, there is no risk of non-supply to UUW’s customers in the short term. However, prolonged periods of below-average rainfall (as suggested by the South African Weather Service) may increase the risk of non-supply through low storage levels. Furthermore, developments from SA’s neighbouring countries (i.e. Zambia, Zimbabwe and Malawi) warrant the need to remain alert and closely monitor climatic conditions and dam levels.

Table 1: A three month comparison of water levels as % of full supply capacity in UUW and some DWS-managed dams.

Site Name	Dam Level (% of full supply capacity)
	01 February 2024	01 March 2024	01 April 2024
Mearns Dam	106	103	108
Spring Grove Dam	95	99	101
Midmar Dam	100	100	96
Henley Dam	105	107	105
Albert Falls Dam	101	101	100
Nagle Dam	101	100	86
Inanda Dam	102	102	101
Home Farm Dam	104	103	101
Nungwane Dam	102	101	101
Umzinto Dam	100	100	100
E.J. Smith Dam	100	100	100
Mhlabatshane Dam	101	101	101
Ludeke Dam	68	46	49
Hazelmere Dam	83	83	84
iMvutshane Dam	87	60	56
Goedertrouw Dam	100	99	99
Pongolapoort Dam	81	81	84
Olifantskop Dam	106	104	106
Spioenkop Dam	101	100	100
Wagendrift Dam	101	101	101
Woodstock Dam	91	96	100

uMngeni-uThukela Water (UUW) encourages its customers, and water users in general, to practice and promote water resources conservation measures. UUW publishes home-based water conservation tips on a weekly basis through the company’s social media platforms and encourages the public to share more tips that promote water use efficiency at household level. uMngeni-uThukela Water will issue an update at the end of April 2024.

Hey there, water users! uMngeni-uThukela Water (UUW) would like to share the latest update on the ongoing El Niño cycle. Model assessments indicate that the El Niño event has reached its peak, with ENSO currently in a moderate-strong El Niño state. UUW will continue to monitor the development of ENSO as an El Niño advisory remains. Remember to use water sparingly.

Most sites in uMngeni-uThukela’s area of operation saw below-average rainfall in February, with some receiving as little as 50% of normal rainfall, e.g. Mearns Weir and Inanda Dam. We are closely monitoring rainfall, dam levels and the ENSO signal as we approach the end of summer.

Even though February brought below-average rainfall, our dams are on relatively high storage levels, ensuring no immediate risk of non-supply for our customers. However, forecasts are calling for below-average rainfall and above-average temperatures for the next three months in South Africa.

To tackle potential challenges head-on, let’s all do our part in practicing efficient water usage. Keep an eye out for the conservation tips provided by UUW weekly. Stay tuned for more insights. Together, let’s ensure sustainable water management.