Water stewardship

We actively minimise freshwater use by recycling and reusing water on site, recovering run-off water, managing the impact and flow of stormwater and economising our water consumption. Our stormwater management system is designed to catch and redirect stormwater drainage into our freshwater dam, and we continually explore additional catchment and freshwater supply opportunities for our operation and PACs.

We ensure responsible consumption with respect for the natural resources we need. Our operations rely on a continuous supply of water. We are mindful of our valuable relationship with our PACs, especially regarding access to sufficient potable water. We know we cannot secure water resources for our mine without ensuring that the water requirements of our PACs are met, and our Group water management policy considers the needs of all stakeholders. Various operational departments have implemented initiatives to reduce process water consumption, secure adequate water reserves to operate during potential future drought conditions, and ensure stable access to water for PACs.

Our Letšeng operation is located in the Maluti Mountains of Lesotho and our social licence to operate depends on regular engagement with government and local communities, as well as financial and practical support to address challenges with sustainable solutions. One of the UN SDGs Gem Diamonds has adopted is SDG 6 – Clean Water and Sanitation. Access to safe water and sanitation is a basic human right, and Letšeng has been working with stakeholders to improve access to water and sanitation for our communities.

Since 2010, we have provided 10 schools and five villages with access to safe potable water and dignified sanitation facilities through our corporate social investment (CSI) programme. These facilities have not only improved the health and hygiene of students at the schools and for inhabitants of the villages, but also the health of the water-related ecosystems that previously became polluted with E coli.

In addition to the water and sanitation provision projects in our PACs, Letšeng initiated a wetland rehabilitation and establishment programme to restore these critical ecosystems to fully functioning status. Wetlands are lands saturated with water, either permanently or seasonally, with distinct ecosystems that provide valuable services for humans and wildlife – filtering pollutants, reducing flooding and providing habitats for fish, wildlife and indigenous plants.

Our wetland rehabilitation projects serve a three-fold purpose, to:

  • rehabilitate natural wetlands;
  • offset environmental impacts; and
  • provide a natural source of water treatment.

The Qaqa engineered wetland was constructed downstream of the Qaqa 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 indigenous vegetation to flourish. Through weekly water quality monitoring, there has been steady progress regarding 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 Government of the Kingdom of Lesotho on the “sponge project” to protect and conserve the “sponges” or wetlands in the Khubelu catchment through sustainable management. The wetlands are crucial to the sustenance of ecosystems and biodiversity in the catchment, providing livelihoods for humans, sustaining livestock and regulating water storage, quality and flow. These benefits are important for the livelihoods of local communities and the growth of the economy of Lesotho. Conservation of the wetlands is expected to reverse the losses already experienced due to degradation and ensure a sustainable flow of services and benefits from the wetlands. We have published several case studies demonstrating our investment in innovative technology to manage water stewardship and mature our processes and technologies.

Monitoring and measuring

Letšeng Diamonds monitors the water quality in the Patiseng and Maloraneng streams and the Khubelu River monthly. We collect water samples from several points in these watercourses and at varying distances downstream from the Letšeng mine. The samples we collect are subject to independent laboratory testing.

We developed a comprehensive water monitoring protocol, collecting water samples monthly, quarterly and biannually from selected sites throughout the mining lease area, and from control sites in rivers unaffected by mining activities. The water is analysed for various chemicals, including nitrates, sulphates and metals. Additionally, river health is monitored by measuring the biological status of diatoms and South African Scoring System Version 5 samples.

The mine’s performance on water quality is reported to stakeholders as mandated by the Record of Decisions issued by the Lesotho Department of Environment.

Letšeng appointed GroundTruth, an independent water, wetlands and environmental engineering firm, to develop a Biannual Water Quality Monitoring Report to support our SEMP commitments. GroundTruth collects water samples according to scientific methodology and sends these to a South African National Accreditation System and ISO 17025-accredited water laboratory in South Africa for chemical, microbiological and environmental analysis.

The Biannual Water Quality Monitoring Report informs our Annual Environmental Performance Report submitted to the Department of Environment.

Water quality

Elevated nitrate levels are often associated with mining activities, but can also be also attributed to the application of fertilisers, human and animal waste, and other sources. As nitrates are produced by the decay of plants and animal and human waste, nitrate pollution of water typically occurs wherever intensive land use activities take place. Nitrate-nitrogen concentrations exceeding 20mg/ℓ are a common occurrence in groundwater. Nitrates may also be naturally present as a result of soil nitrification processes, from the mineralisation and mobilisation of nitrate from natural soil or host rock lithologies.

Water quality assessments at Letšeng confirmed that, before mining activities commenced, the natural levels of nitrate in the surface water around the mine were approximately 15mg/ℓ. The World Health Organization published guidelines on the concentration of nitrates that are considered detrimental to health, and found there are no adverse health effects where drinking water consistently contains nitrates at concentrations below 50mg/ℓ. Ongoing water analysis over the years has indicated an increase in nitrates in our water, mainly due to mining explosives residue. In 2014, in response to the increase in nitrate levels, Letšeng commissioned an extensive nitrate management study to find and implement solutions to prevent nitrate-infused water leaving the lease area. The established solutions have been far-reaching and effective. We also constituted an official nitrate task team, working in collaboration with the relevant government departments in Lesotho. The operation has implemented the following solutions to conserve water quality:

  • Commissioned a wetland construction and rehabilitation programme.
  • Refined and amended blasting practices and procedures to limit the volume of nitrates from explosives released into the environment.
  • Partnered with water conservation experts to trial the feasibility of fertigation and bioremediation as treatment methods, and conducted leach testing to better understand the management options.

During 2021, we successfully completed the bioremediation pilot project at Letšeng to treat water with potentially higher volumes of nitrates leaching from the waste rock dumps, and a modular bioremediation project is scheduled for commissioning in Q3 2023. The bioremediation project will treat water seeping from the mine waste rock dumps, and the treated water will be discharged from the plant into a newly constructed wetland before leaving the mine lease area.

We prioritise the needs of our stakeholders in our approach to water management, and our water strategy is based on international best practice. Letšeng has a comprehensive water monitoring and stewardship plan, including external and independent assessment of water quality inside and outside our mine lease area. We also consider the water quality results of other stakeholders in the region – the Lesotho Highlands Development Authority being a key stakeholder as the custodian of the Katse and Muela freshwater dams. Run-off from the mine found its way to two rivers near the mine, Matsuku and Khubelu. These rivers are major waterways in Lesotho and form part of the Lesotho Highlands Water Provision Scheme. Historical testing results indicate that mine activities have not impacted the water quality in either of the rivers. The most recent environmental and water quality report from the Lesotho Highlands Development Authority indicates that nitrate levels in the dams are consistently below 1mg/ℓ, and they have confirmed that the water in the dams is of a good quality.

Our water quality testing protocol includes monitoring biological parameters, notably E.coli and total coliforms. E.coli bacteria normally live in the intestines of healthy people and animals. When E.coli is found in surface water, the water has been contaminated with faeces from humans or animals. High levels of E.coli and coliforms are especially common in rural subsistence farming communities with livestock, such as our communities. It should be noted that elevated levels of nitrate do not cause gastrointestinal issues.

Independent water quality assessments, conducted through an accredited laboratory, have consistently found elevated levels of E coli and total coliforms in the Maloraneng Village (20km from the Letšeng mine), Patising village and Lithakong village (23km from Letšeng) surface water sources. The E coli contamination is mainly due to livestock fouling the surface water sources around the villages.

Most types of E coli are harmless or cause brief bouts of diarrhoea. However, a few strains can cause severe stomach cramps, bloody diarrhoea, vomiting and bacterial dermatitis. Healthy adults usually recover from E coli infection within a week. Young children and older adults have a greater risk of developing a life-threatening form of kidney failure.

Letšeng is proud of our history of corporate social responsibility and partnerships with communities to ensure shared benefit. Our on-site clinic provides emergency and primary health care for community members, and the considerable number of bacterial gastroenteritis cases treated through our clinic resulted in a decision to assist communities with the provision of potable drinking water, which we have done since 2014. The provision of safe drinking water resulted in a significant decrease in gastroenteritis cases in the communities.


Bioremediation is a process that utilises naturally occurring micro-organisms in the soil to break down chemical compounds found in water (for example, nitrates) and convert them to harmless gases found in the atmosphere (for example, nitrogen). It is more cost-effective and less labour and energy-intensive than traditional technologies such as reverse osmosis.

Our pilot bioremediation plant has been operational at Letšeng since the beginning of 2017. Initial water quality samples indicate that 95% to 99% of nitrates have been removed from treated water during this process.

Based on this success, in 2021, Letšeng commissioned the design of a bioremediation project to treat water seeping from the mine waste rock dumps into the RTZ catchment dam. The aim is to discharge treated water from the plant into a newly constructed wetland, ensuring that natural sequestration takes place and any particulates settle out of the water. This passive treatment process ensures that biodiversity and water quality are protected.

The location and construction of the bioremediation project have presented challenges relating mainly to access to power and long lead times from global supply chains for necessary equipment. We have reviewed the implementation of this project and prioritised the construction of a 300 000 litre per day plant, which we plan to commission in Q3 2023. In prioritising the implementation of this project, we approved a modular design and workstreams and hold bi-weekly bioremediation cadence meetings to ensure the project remains on track. In the meantime, we relocated our pilot bioremediation plant and a second similar-sized bioremediation plant to the bottom of the waste dump area in the RTZ valley. We are currently treating approximately 40 000 litres of water a day.

We are investigating the opportunity to use renewable energy for the bioremediation plant(s), and have identified a site for sufficient renewable energy-powered capacity to power the baseload needed.