Important wetlands in the Lesotho Highlands are in wretchedness
Gauteng is reckoning on the Lesotho Highlands Water Project (LHWP) for the bulk of its water, nevertheless researchers yelp there is a topic: wetlands mandatory to the legislation of the water that enters Lesotho’s dams are collapsing, and not sufficient is being performed to arrest their degradation.
“The degradation of montane and alpine wetlands in the Maloti-Drakensberg region of South Africa and Lesotho is likely one of the greatest threats to water security in water-scarce Southern Africa,” says South African soil science specialist Johan van Tol.
A see has well-known the disappearance of approximately 21 to 24% of wetlands in the Mohale and Katse dam catchments between 1995 and 2014.
Lesotho-essentially based thoroughly mostly ecologist Peter Chatanga says the wetlands show hide in the Lesotho Highlands are mostly palustrine wetlands, “meaning they are able to support vegetation”.
“These wetlands slow the flow of the water downstream, which helps to regulate soil erosion, which in turn helps to prevent sedimentation in the dams of the Lesotho Highlands Water Project. This is a huge contribution to the sustainability of the LHWP,” he says.
Complicated causes
There is monumental settlement that wetland loss and degradation performs a significant feature in dam sedimentation in Lesotho. However in accordance to Chatanga the causes of wetland degradation and loss “are many, complex, and interactive”.
He lists communal grazing as one.
“It’s a free-for-all in the river catchments of the Highlands. If you go up there with your animals, no one will ask you what you are doing. All land has a carrying capacity, and in the absence of regulation this will be exceeded and that is what is happening,” says Chatanga.
Improved accessibility to the Highlands is also a ingredient.
“In the past there was limited accessibility to a lot of the wetlands, but recently as a result of the LHWP there has been a lot of development including the building of good roads. This is good for the economy, but it increases the anthropogenic [man-made] pressures on those wetlands,” Chatanga says.
On a latest trip back and forth to the river valleys of the Malibamatso and Tshelenyana rivers (the predominant rivers feeding into Katse reservoir), GroundUp interviewed several herders who acknowledged they had pushed their animals up into the river valleys from the shoreline of the Katse Dam, a shuffle of four to 5 days. In the 2022/3 annual represent of the Lesotho Highlands Trend Authority (LHDA) , the displacement of herds by the inundation of the LHWP’s dams is cited as the predominant reason of wetlands degradation in the Lesotho Highlands.
Nowadays, many wetlands in the Lesotho Highlands are inhabited by a species of rodent called Sloggett’s ice rat (Myotomys sloggetti). In line with Chatanga, ice rats are a trademark of wetland degradation.
“They generally affect wetlands that are already somewhat degraded but once they get in they cause further degradation. They are burrowers, and when water floods the wetland it flows through those burrows, causing the top part to fall in, and the moment it falls, it forms a gulley,” says Chatanga.
In line with LHDA spokesperson Mpho Brown, “Ice rats are a secondary impact, and when the primary concern of livestock overgrazing is addressed, the ice rats situation should reverse”.
Problematic interventions
After failing to commission an Environmental Influence Evaluate forward of the construction of the Katse Dam, the LHDA took steps to handle environmental points in LHWP’s river valleys in the early 2000s, implementing a plan of soil conservation applications beneath a programme called Integrated Catchment Administration.
The impact of the interventions is much debated, nonetheless.
In line with Brown, the interventions are working.
“Wetlands and rangeland health condition assessments done under our in-house monitoring programs confirm improvement in terms of the indicators we monitor. There is tangible photographic and visual evidence of these which a site visit would be able to confirm,” he says.
Then another time, Phallang Lebesa, a vulnerable LHDA officer who worked on several wetlands’ restoration projects in the Lesotho highlands, says many of these bear since failed.
“The main objective is typically to block the erosion channel that is draining the wetland. In the past we mostly attempted to do this with gabion baskets and other structures, but if you visit those sites today you will see that the water has simply bypassed those barriers and created new channels, and in some cases the wire from the gabions has been removed by herders, who use it to reinforce the kraal walls at their cattle posts,” Lebesa says.
Chatanga says gabions were efficient in bettering the health of definite wetlands, nevertheless many interventions appear to were implemented without evaluation of the causes of complications.
For Van Tol, the absence of baseline examine on the that you would possibly per chance per chance per chance per chance also consider causes of wetland degradation is alarming, as is the absence of reviews quantifying the success of the interventions.
“There is a wealth of literature addressing the state of wetlands in the Maloti-Drakensberg but there are actually very few detailed baseline studies covering soils, vegetation, the extent and rate of degradation, and so forth. In the absence of baseline studies, it is unsurprising that interventions fail,” he says.
Van Tol is one of several researchers working on the Mount-aux-Sources Long Term Socio-Ecological Research platform, essentially based in 2022.
“Instead of sitting back and criticising the work that is being done currently, the aim is to do some of those missing baseline studies, so that appropriate interventions can be designed. These interventions should go beyond merely treating the symptoms and focus on improving the management of terrestrial land through better grazing practices and the restoration of both wetland and terrestrial soils,” he says.
How severe is the LHWP’s sedimentation topic?
The charge of sedimentation in Lesotho’s dams is a topic of some debate. The LHDA, in designate for the dams and catchments, would not frequently put up files on sedimentation stages.
The LHWP consists of two super dams called Katse and Mohale, a smaller reservoir called Muela and the Matsoku Weir, which transfers water from the Matsoku River into the Katse Dam by the exhaust of an eight-kilometre tunnel. A third super dam called Polihali is scheduled for completion in 2028.
Sediment surveys for Muela reservoir performed in 2003 and 2019 on behalf of the LHDA produced alarming findings. The first, performed proper six years after the completion of the dam, stumbled on that the dam was once 7% stout of sediment, a resolve that had risen to 12% by 2019.
“The rate of sedimentation in Muela is 0.5% a year,” says Brown, who confirmed that the sedimentation in the catchments of the LHWP is a recount.
Muela reservoir serves as a tailpond for the Muela underground hydroelectric vitality site that generates electrical energy to get the needs of Lesotho. The water it releases flows without lengthen into South Africa by the exhaust of a 38km tunnel.
Be part of free AllAfrica Newsletters
Catch the latest in African news delivered straight to your inbox
In a 2017 represent in the Lesotho Times, Reentseng Molapo, the LHDA manager in designate for asserting the infrastructure of the LHWP, warned that sedimentation in Muela Dam, because of soil degradation upstream, had the doable to shut down the total LHWP.
Sedimentation of Matsoku is so evolved that engineers bear needed to slash a channel thru the silt that has banked up in opposition to the weir, to allow water to float to the consumption works of the tunnel (viewable on Google Earth).
In line with Brown, an estimated 1.4% of Katse capacity has been lost to sediment since the dam was once flooded 28 years in the past, and the amount of sediment in Mohale dam is estimated at 0.8% – 1.3%. Polihali will probably lose 5% of its storage capacity in the first 50 years of its existence, and 10% within a hundred years, in accordance to a 2018 modelling see.
South African water specialist Ricard Holden says these numbers are “quite small”, and “sedimentation is not an immediate problem for the project’s end users.”
Erosion and sedimentation is an topic on the South African section of the LHWP, too, in particular alongside the Ash River, which carries water from Lesotho into South Africa, and in Sol Plaatjie Dam end to Bethlehem, where, in accordance to the Trans Caledon Tunnel Authority (TCTA), which takes care of the South African aspect of the LHWP, the silt delta has expanded very much.
In October, water flows thru the LHWP had been stopped at Katse to enable severe restore work to be performed. Water is scheduled to renew flowing in April 2025. In line with TCTA spokesperson Wanda Mkutshulwa, erosion scoping and repairs “along about 26 kilometres of the Ash River, fences, gates and gabions on the Caledon River”, is section of the work that will probably be performed for the duration of the six months stoppage of the LHWP.
