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Media Release: KNP Breaches Dam to Prevent Poison Spreading

01 August 2007

A key dam in the Southern area of the Kruger National Park (KNP), the Nhlanganzwane Dam will be breached this week in order to rid it of an algal poison that has claimed the lives of a number of animals over the past two years.

“We didn’t take the decision to breach the dam lightly, but our primary concern is to stop the spread and effect of this deadly algal poison,” said the KNP’s Head of Conservation Services Dr Freek Venter.

KNP rangers first picked up the problem during autumn and early winter of 2005, when carcasses were found in the region. As they were already several days old, the cause of death could not be determined

When a fresh carcass was discovered, a full range of tests were conducted and it was found that the animal had Microcystis poisoning. During that time, the water level of this and other dams in the area were also unusually low and a high number of hippos (100) also inhabited the dam.

These large hippo densities probably resulted in higher levels of urinary and faecal eutrophication which, in turn, resulted in an abnormally high level of the algae Microcystis spp. A total of 54 carcasses were detected during the 2005 outbreak and these included white rhinos, lions, cheetahs and zebras.

Various options were considered at the time but nature found its own solution. The areas around the dam were overgrazed and a veld fire in the area meant that the hippo population dispersed to the Sabie and Crocodile Rivers and the algal reduced significantly which resulted in mortalities decreasing to zero after July 2005.

Roughly two years later, June 2007, mortalities were again discovered in the area of the Nhlanganzwane Dam, these included white rhinos, zebras and wildebeest and again a high population of hippos, plus the algae Microcystis spp have been noted in this and other dams in the area.

“These discoveries meant that KNP management were faced with various options, which included fencing off the dam which isn’t practical because of the large amount of elephants in the area and removing the hippo, which is also not practical because past experience shows that the hippo return soon afterwards, thus we took the decision to breach the dam,” Dr Venter concluded.

Construction machines will be on site until Monday August 6, 2007.

The closure of the dam also ties in with the KNP’s policy of closing artificial water points in order to return the area to its purest natural state.

Nhlanganzwane Dam is situated in the extreme South Eastern area of the KNP to the South of Lower Sabie Rest Camp and to the North East of Crocodile Bridge Rest Camp and Entrance Gate.

Issued by:

Raymond Travers, Media Relations Practitioner, Kruger National Park. Contact: Tel: 013 735 4116, cell: 082 908 2677 or email:


William Mabasa, HOD: Public Relations and Communications, Kruger National Park. Contact: Tel: 013 735 4363, cell: 082 807 3919 or email:

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