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Nhlaralumi River: Post 2012 Floods

Document by John Llewellyn for inclusion with the Ingwelala appeal that was recently submitted to DEDET objecting to the decision made regarding the repair of upstream dams (Referred to in the recent Chairman Message).

The purpose of this communication is to record observations made in recent times in the Nhlaralumi River which course follows a distance of about 12 kms northwards through the Ingwelala property. This river and its natural functioning in terms of flow rate and flow frequency is severely influenced by several large upstream impoundments. The dramatic Dando flood of 18 January 2012 caused the demise of these artificial impoundments where several of these dam walls failed, resulting in extensive damage to both the natural environment (riparian zone) and man-made infrastructures (dwellings, roadways and services) on the Ingwelala property.

My name is John Llewellyn. I have a tertiary education, a National Diploma in Nature Conservation from the Cape Technicon, graduating in 1989. I worked in formal nature conservation with the then Natal Parks Board that later became Ezemvelo KZN Wildlife between 1989 and 2006. My roles and responsibilities were Protected Area management, particularly terrestrial landscapes and ecosystems.  Since November 2006 I have been employed as the Reserve Manager of Ingwelala Share Block Limited, responsible for overseeing the general functioning of all aspects of this 3125 hectare proclaimed private nature reserve. One of the most important supervisory aspects is directing a dedicated conservation team consisting of ten permanent employees. This employment has the express objective of Ingwelala meeting with and complying with all the expectations detailed in the Master Management Plan of the Association of Private Nature Reserves, namely Timbavati Private Nature Reserve, Klaserie Private Nature Reserve, Balule Private Nature Reserve and Umbabat Private Nature Reserve. This Master Management Plan was approved by the Office of the MEC, the Mpumalanga Department of Economic Development, Environment and Tourism on 03 May 2011.

The Nhlaralumi River system should be perennial, but with the upstream impoundments it became ephemeral. The recent failure of the dam has effected a reversion to a perennial system and this is significant in many ways. Perennial systems provide an increased reliability of water and are thus more conducive to fauna and avifauna taking up residence (and not temporarily passing through).  The impact of any small residual pools in the drainage system on the surrounding grazing vegetation is reduced as grazers do not need to frequent these sites when water is more readily available along the entire water course. In other words there is no requirement for game to concentrate at artificial water points (or the few more persistent pools in the river) and impact negatively on available grazing.  Natural water dispersal along a perennial river results in natural game dispersal and a low grazing pressure, resulting in an overall better veld condition, lower erosion and lower management input requirements (such as burning).  The riparian vegetation is benefitted by the perennial nature of the river in that it is able to establish and maintain better growth vigour for longer periods with the increased availability of water – and this growth vigour aids improved basal cover and tree/shrub establishment that better protects the river banks from soil erosion and occasional flooding impact.

Stagnant pools, formed in times of low flow, are flushed more frequently with clean oxygen rich water, rejuvenating the natural migration patterns for fish and other aquatic species. It is well known that dams create significant barriers to the natural functioning of rivers and impact negatively on natural patterns of species migration.

The ecological flow requirement of any river system is well known, and the Department of Water Affairs (DWA) recognises this – and has under its general authorizations for small impoundments certain conditions that will allow the river to continue to flow. It is worth noting that none of the failed dams referred to here had any such pipes or structures. These dams thus had severe impacts on the ecological functioning of the Nhlaralumi River – all within a protected area. This is particularly important in this catchment as it is a water stressed catchment – again recognised by the DWA through the requirement to licence any dam greater than 10 000 cu metres compared to 50 000 cu metres in other areas).

One of the most obvious changes in the Nhlaralumi is that without the dams the water table is maintained at a higher level (closer to the bed surface). This means that the river surface flows easier, more frequently, whereas in the past the dams would capture most of the natural run off from moderate storms and rainfall, and the river downstream of the impoundments would only flow every four or five years once all the upstream impoundments were full. Only the eventual overflowing of dams created water flow downstream. In a natural cycle this is erratic and unpredictable, and vastly detrimental to the long term survival of large trees associated with healthy riparian areas, such as Appel-leaf (Lonchocarpus capassa), Tamboti (Spirostachys africana), Figs (Ficus spp.), Leadwoods (Combretum imberbe), Weeping Boer Bean (Schotia brachypetala) and Acacia spp. Their current growth vigour has noticeably improved.

Good growth vigour of grass swards and grassy banks are now apparent and this supports a healthier resident hippo population which are able to feed along the riparian zone creating hippo lawns, previously unknown on Ingwelala. There is a noticeable shift in the herbaceous and grass communities now providing for more plentiful palatable grass species, where previously the common species were forbs and grasses which were hardy and unpalatable. With the improved light penetration in the riparian zone and the rejuvenated trees there is a marked increase in broad leaf recruitment.

On any day you can find evidence of hippo everywhere, as many as nine individuals inhabiting Ingwelala, to the best of my knowledge a first, considering the previously water deprived river system.

Bird life has become much more prolific, especially those species associated with more permanent water bodies. Tangible examples are Spoonbills, Giant Kingfisher, Pied Kingfisher, Malachite Kingfisher, Brown-Hooded Kingfisher, Jacanas, Hammerkops, Egyptian Geese, Saddle-billed Storks, Plovers and Sandpipers. Fish Eagles are seen on a daily basis, breading and resident throughout the year. Previously the Fish Eagles would track short term fish migration in the wet years and as the pools dried up they would migrate away from Ingwelala. There appear to be a whole lot more bee eaters (more prevalent due to water bodies producing higher insect biomass).

Fish are able to migrate and the current biomass is sufficient to sustain the natural predation.

Hyenas, leopards and wild dogs also predate on fish when conditions are favourable.

The natural processes that have followed are remarkable in such a short space of time since the failing of the upstream dams in January 2012. Observing the changes in fauna and flora along the watercourse is note worthy, such as increased ranging by water dependant species buffalo and elephant. In understanding holistic management the impact of these large herbivores ranging on and utilizing the veld is considered very positive as their dunging and urine aids invaluable nutrient cycling.

A further tangible example of a proper functioning river is a nesting female crocodile at Old Farmhouse. This exhibits suitable habitat for a prehistoric creature that was surely prolific in our area once upon a time.

In closing the subsequent rains recorded in 2013 and 2014 floods were significant enough to cause flooding in the Nhlaralumi River system. Without the upstream impoundments the observation made was that there seemed little threat that the river system would not cope with the volume of flow, therefore reducing the threat of damage to infrastructure. This was born out in the very little damage caused by these flood events on Ingwelala – and no services or infrastructure was damaged. 


Pictures by Charlie Lynam