Nurturing nature’s functional beauty:
Letšeng’s wetland and sponge projects
Mitigating the environmental impact from mining has always been a priority for Gem Diamonds. Towards the end of 2013, Letšeng initiated a wetland rehabilitation project, along the southern tributary of the Qaqa River.
Wetlands are lands saturated with water, either permanently or seasonally, and with distinct ecosystems. Wetlands provide many valuable services for humans and wildlife. They filter pollutants; reduce flooding and provide habitats for fish, wildlife, and indigenous plants.
Our wetland rehabilitation projects hold a three-fold purpose:
- to rehabilitate natural wetlands;
- to offset some of the negative environmental impact caused by mining; and
- to provide a natural source of water treatment.
The Qaga engineered wetland was constructed downstream of the Qaga waste rock dump. In addition to rehabilitating an area previously mined for alluvial diamonds, it is anticipated that the wetland, perhaps the highest man-made wetland in southern Africa, will improve water quality through natural biological and chemical filtering in the wetland biomass. Since 2013, the wetland has continued to develop naturally, allowing for indigenous vegetation to flourish. Through weekly volume control and water quality monitoring, there has been slow but steady progress with regards to wetland establishment and water quality improvement. We anticipate that results will improve as the wetland continues to establish itself over a longer period.
In 2015, Letšeng partnered with the Lesotho government on the sponge project, to protect and conserve the ’sponges’ or wetlands in the Khubelu catchment through the sustainable management of these wetlands.
The wetlands are crucial to the sustenance of the ecosystems and biodiversity in the catchment, which provides human beings with sources of livelihoods, sustain livestock and regulate water storage, quality, and flow. These benefits are not only important for the livelihoods of the local communities, but also for the growth of the economy of Lesotho. Conservation of the wetlands is expected to reverse the losses that are already experienced due to the degradation of the wetlands and ensure a sustainable flow of the services/benefits from the wetlands.
One major challenge facing this valuable natural resource, however, is that livestock overgrazing and trampling are affecting the rate of erosion of the wetlands. Overgrazing harms wetlands through soil compaction, removal of vegetation, and stream bank destabilisation. Wetlands offer some of the best forage for livestock as well as a water source and cover, so livestock tend to spend a disproportionately large time in wetlands.
Proper management of wetlands rests on effective rotational grazing that allows the wetlands to rest. The initial stages of this project, therefore, have involved educating local herdsman about sustainable grazing practices, ensuring that areas are grazed evenly, decreasing the risk of erosion. Following better grazing practices, the groundwater level is expected to increase, allowing the wetland to rehabilitate and sustain itself naturally.
Letšeng Diamond Mine, Bongani Ntloko working on the rehabilitation trials.
Letšeng Diamond Mine, artificial wetland project.
Investing for the future:
Managing nitrates at Letšeng
Protecting the environment in which we operate is an essential focus for Gem Diamonds. We recognise, however, that environmental impacts do occur. We endeavour to avoid these if at all possible and remediate when negative impacts do occur.
At Letšeng, ongoing water analysis over the years has indicated an increase in nitrates in our water due to mining explosives residue.
It is also important to note that all communities have potable water. Although water largely remains in a closed loop system, some water emanating from the site as a result of stormwater runoff is affected by nitrate. In 2014, in response to the upward trend in the nitrate levels, Letšeng commissioned a nitrate management study to find and implement solutions to the problem of nitrate-infused water leaving the lease area. The study was extensive and the solutions put in place have been far-reaching in combating this problem. An official nitrate task team, which works in collaboration with the Lesotho Government, was also established. The nitrate management project began with a nitrate audit conducted to improve blasting procedures and management, as well as reducing the levels of nitrates produced at the source.
Further studies were then conducted, including an investigation into the feasibility of a fertigation and bioremediation project and leach testing to better understand the scale of the issue.
In June 2015, a team from the University of the Free State conducted field testing at Letšeng to analyse the viability of the bioremediation project. Bioremediation is a strategy that uses naturally occurring organisms to break down pollutants such as nitrates into less toxic substances. Species in the bacterial genus Pseudomonas present high potential for bioremediation. During testing, the team discovered a dominance of Pseudomonas species in the water. Bioremediation proved viable for the removal of nitrates, sulphates and various other salts. Bioremediation and other management options are currently being explored to assess management options available to the operation.
In our ongoing efforts to pursue environmental best practice, in June 2015, Gem Diamonds sent representatives from both Letšeng and Gem Diamonds Limited to Canada to attend the 2015 Mine Closure Planning Conference and visit the local diamond mines. The trip was successful, and the team was able to gather vital information on nitrate management and rehabilitation planning which will
be implemented in the year ahead.
Dewatering and water management
The unique, underground nature of the Ghaghoo mine presents a number of challenges. One of the major issues the mine faces is the volume of groundwater discovered during underground tunnelling activities.
In early 2015, a study on the responsible management of the groundwater was finalised with several options presented, including the use of evaporation ponds, forced evaporation, constructed wetlands, water treatment for domestic consumption and use, water treatment for agricultural irrigation, game watering and finally, aquifer re-injection.
In determining the feasibility of these options, it was necessary to consider a number of factors such as financial viability, environmental care and sustainability, and efficiency. While water is a scarce commodity, the water obtained from underground is generally not suitable for use without significant treatment, which is extremely costly. Thus, consumption, either by humans or game, was not a viable solution. Treatment for agricultural irrigation was less extensive and therefore considerably cheaper, however, transporting the treated water would be expensive due to the remote location of the mine.
Minimising the environmental damage was also a major factor in our study. While game watering was reviewed as an option, the construction of a watering hole would severely alter the present desert-like environment and could have an effect on wildlife migratory patterns, as well as the natural ecological balance of the area of the Central Kalahari Game Reserve in which the mine is located. Wetland construction has the potential for natural water treatment, yet would again be an alteration of the natural environment. One option investigated was controlled evaporation of the water. However, the significant environmental impacts as well as infrastructural costs resulted in this option being disregarded.
After extensive consideration, aquifer re-injection was deemed to be a viable option. Re-injection of groundwater has several major advantages. First, manipulation of head gradients would allow us to have a measure of control over the hydrological flow, thus helping to manage the water on a long-term basis. Secondly, groundwater re-injection is environmentally sustainable and restorative, therefore providing an environmentally friendly aid in the aquifer’s natural decontamination process. And finally, the project presents a financially acceptable option. Operational costs are minimal, and initial infrastructural setup is comparatively feasible. Furthermore, we believe that aquifer re-injection is the most responsible course of action in an environment that experiences water scarcity.
The implementation and operation of the aquifer re-injection pilot project is planned for 2016, with further investigation and monitoring to take place before selecting a long-term management strategy.
Ghaghoo Diamond Mine,
Masego Odrile (Environmental Officer) conducting water quality monitoring.