Fewer water conflicts and increased profitability through catchment management

June 23, 2017 Malcolm Anderson

What mine owners need to consider when it comes to water use in addition to operational concerns.

At many mines, mine water management is primarily operational, concerned with having enough water for mining and mineral processing, and a strategy to safely, effectively and legally manage the mine’s wastewater.

Increasingly however, mine owners realize that they must consider the entire catchment when planning for mine water use, an approach that obliges the operator to address a much greater area of concern. The water issue that just got BIGGER now also gets more COMPLICATED since without an over-arching water use strategy, unforeseen issues can arise that increase costs and, when not managed correctly, cause damage to a company's ability to operate the mine.

Figure 1. A salt karst sinkhole in the Danakil Desert playa

According to Malcolm Anderson, technical director of groundwater with Stantec, it's about managing the water catchment appropriately and, “increasingly that involves taking a collaborative approach that solicits the inputs of multiple stakeholders.” Stakeholders include a wide range of governmental sectors and local communities depending on the mine’s proximity to a population centre. Stakeholders may also include individuals or non-governmental organizations (NGO’s) with an interest in the water, land or environment within the catchment area.

Faulty catchment management can be avoided by implementing the water management strategy over the life of mine and beyond. By consulting with all water stakeholders, and taking a long view, conflicts over water can be identified, discussed and ultimately managed. This concept is captured in the ICMM guidance published earlier this year.

“Catchment management is naturally comprised of the engineering and environmental aspects of water as well as the wider linkages and uses (e.g. agriculture, transportation, archaeology, and tourism and leisure interests). Also included are the temporal components such as socio-economic development, long term environmental mitigation and enhancement strategy and post mining plans,” notes Anderson.

In his talk, Anderson will discuss a potash mine being developed in Ethiopia that presents such opportunities for synergies. The mine is located in the Danakil Desert, one of the hottest, driest, most inhospitable places on Earth. Wildlife, vegetation, and amazingly for the very arid conditions, small fish, depend on the region’s unique ecosystem. While there are no population centres close by, community leaders have been consulted about mine development plans and water use.

Figure 2. Pumping test water scale deposits further down slope on the silt and clay playa

In Ethiopia, water resources and the allocation of water rights belong solely to the government, “So having a good relationship with the government is an important value that comes out of catchment management,” says Anderson. “In Ethiopia, the government was keen to develop the mine and at the same time, the mine was able to contribute in ways the government wasn't able to.” For instance the government carried out the initial water resources investigation, including drilling bore holes to identify water sources, whilst also building new roads, telephone and power infrastructure. That allowed the mining company to focus on mineral exploration. In the subsequent phases, water supply investigations focused on the reliability and resilience of alternative water supply options, which naturally was a key factor for the mine.

Storm run-off occurs in the catchment wadis only two or three times a year, and each event typically lasts less than 12 hours, so wildlife, the few local people, their flocks of sheep and goats, and most of the plants are dependent on the groundwater system. The regional groundwater flow, augmented by the storm-water infiltration, sustains spring flows and pond levels at a number of locations controlled by the geology and groundwater flow system. Because of the baseline surveys required for the catchment management process, these locations have been identified and the impacts on wildlife and vegetation from each mine development scenario, at each key location, have been systematically considered.

Along with drilling, the water investigation included satellite remote sensing, and geophysical surveys to determine the depth and quality of groundwater, and the construction and commencement of continuous monitoring of an extensive groundwater monitoring network. Maps of groundwater levels, temperature and water quality were prepared to determine the direction of water flows, and a conceptual model built to simulate the groundwater system in three dimensions. Anderson said this is where field expertise is the key to success.

Figure 3. Water scale deposits from a pumping test traversing an alluvial fan on the Danakil Rift Margin

“We had a blank slate and brought experience and skills to develop and implement an efficient program that proved a reliable water supply for the project,” said Anderson.

Anderson emphasized that determining the “deployable output” is a key part of ensuring mine water supply resilience, and also a good catchment management practice. This is the amount of water, of a certain quality, that can be pumped from the aquifer for the operation under worst case (usually during droughts), average and peak conditions. The deployable output is often conflated with the sustainable yield of an aquifer, but it is always lower, when catchment management principles are applied.

The other key advantage of the detailed investigations required to achieve good catchment management is the much greater insight into the identification of the optimum wellfield locations. This is especially true in the complex geological conditions in Dallol. For instance, the detailed catchment investigations helped avoid the costly mistake of installing wells in the wrong location: The wellfield briefly developed by mining operations in the 1960s would have progressively become saline over the life of the mine.

“Sizing that system based on how much water is available, and therefore scaling the (water supply dependent) mining plan, is critical. Catchment management is crucial for locating the system and getting these numbers right, and leads to substantial savings,” he concluded.

Content was originally published on Mining.com.

About the Author

Malcolm Anderson

Malcolm Anderson has 30 years of experience working on water resources projects in the UK, Africa, the Caribbean, and the Middle East. He has substantial experience working on mine water supply projects, water supply related risk assessments, very deep well design, and catchment management studies.

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