The second of our series on water sourcing Dave Walker, Technical Director, Mining & Minerals talks through the main factors that affect mines’ ability to access the appropriate quality and quantity of water.
Our planet is facing a real crisis in water resources. Climate change and population increases are changing the balance of supply and demand. Since 1950, the need for water has trebled and it will double again by 2050. It is water management that is emerging as the pre-eminent sustainability issue within the Global Mi
There are really two broad categories affecting the ability of a mining operation to access suitable water sources.
The first category is the absolute availability, which can be measured in either or both quantity and quality. In other words, this is the physical constraints brought about by climate or seasonality of rainfall, for example, or the access to aquifers or groundwater resources in sufficient volumes to satisfy demand. Appropriateness of water sources, usually quality related, is often linked to the question of availability. For example, salinity in arid environments, turbidity (suspended solids) or the presence of deleterious minerals, even in relative trace amounts making up the water chemistry may be an issue affecting mineral processing. Other quality issues include brownfields environments where water (geo) chemistry affects efficient mineral processing. This category of water availability or quality affecting projects or operations can be solved with a combination of technology and cost along with maximising water re-use and recycling. In extreme cases, the cost is prohibitive and may even prevent the project from being developed.
The second category is one driven by either legislative constraint, e.g. riparian rights, water use licensing and the like, or a competitive constraint on shared (often scarce) resources by environmental or social uses and rights. It is not uncommon for the challenges of the first category to drive or influence this second category. For example scarce or pressured resources will result in limited water abstraction permits and the higher the competitive aspects of quantity and quality issues, the tougher the conditions to be met. Competitive elements may include competing commercial practices, as well as communities and environmental drivers. An unfortunate consequence of competing industries comes down to politics, money and vested interests rather than altruistic concern for the environmental and social drivers.
SLR has been extensively involved in the development of water supplies for aggregate and other mines in dry climate environs, particularly in Southern California. In one instance, for a proposed 400 foot deep rock quarry pit, we helped develop a water supply and recharge management plans to satisfy California’s stringent sustainable water supply requirements. In order to partially offset the reduced aquifer supplies due to the demand from the quarry and materials crushing and screening operations, we developed an approach to increase natural recharge from local runoff by the construction of runoff collection and infiltration basins alongside and within the quarry pit. The team performed groundwater modelling to demonstrate that the remaining slight reduction in overall recharge to the aquifers would not in any way affect the yields from the local agricultural water supply wells.
Sometimes excess water is more a problem than a lack of to meet demands. This was the case in the western coalfields of NSW, Australia, where we were involved in dealing with the surplus water produced in underground mine operations. Offsite discharge of untreated water to streams was not an option, so water was dispersed using a sophisticated irrigation management scheme. This was achieved through a combination of a 500ML storage dam and irrigation scheme. The water was used to water perennial pastures, which was managed using land management and monitored beef cattle rotation techniques. This innovative approach solved water disposal need, while preserving the integrity of the agricultural lands and creating a unique salinity offset programme.