Water is one of the most critical inputs in Australian mining and industrial operations — and it is also one of the most vulnerable to loss. In the hot, arid regions where much of Australia’s mining activity is concentrated, evaporation from mining and industrial water storage is not just an operational inconvenience. It is a significant financial cost, a regulatory compliance challenge, and increasingly, a sustainability liability that boards and investors are scrutinising with growing attention.

Why Mining Operations Are Particularly Vulnerable

Mining operations typically maintain several types of water storage on or near site:

Process water dams — storing water used in ore processing, mineral separation, and dust suppression
Tailings storage facilities (TSFs) — holding the water-saturated slurry of waste material following ore processing
Clean water dams — storing potable and utility water for the site workforce and infrastructure
Stormwater retention basins — capturing and holding runoff from disturbed areas before treatment or reuse

All of these storage types are open to the atmosphere and exposed to the same evaporative forces that affect agricultural dams — but on a much larger scale and with significantly greater consequences when water runs short or quality targets are missed.

Many Australian mining regions — Western Australia’s Pilbara and Goldfields, South Australia’s outback, and Queensland’s Bowen and Surat Basins — experience annual potential evaporation in excess of 2,500 millimetres. For a tailings dam with a surface area of 50 hectares, that represents an annual evaporation volume exceeding 100 megalitres. At typical raw water procurement costs, that is a very large number — and it repeats every year.

The Financial Impact at Scale

For small farm dams, evaporation losses of a few megalitres per year are consequential but manageable. For large mining operations, the same physical process operates at an entirely different financial scale.

Consider a large open-pit mining operation in the Pilbara. Site water needs are measured in hundreds of megalitres per year. The licensed allocation from groundwater or surface water is fixed and costly. Any water that evaporates from open storage has to be replaced — either from licensed entitlements (with associated environmental and cost implications), from trucked supply (extremely expensive at remote locations), or from reducing other operational water uses.

A conservative estimate for large industrial water storage in hot Australian regions suggests that evaporation can account for 15 to 25 percent of total site water throughput annually — a fraction that, when expressed as an actual megalitre volume and multiplied by the true cost of water procurement, represents a material line item in site operating costs.

Evaporation and Tailings Water Chemistry

In mining operations, the concentration effect of evaporation takes on an additional dimension. Tailings water often contains dissolved heavy metals, process chemicals, and acid mine drainage components. As evaporation reduces water volume, these contaminants concentrate to higher levels — potentially exceeding threshold values set by environmental operating licences.

High concentrations of contaminants in tailings water can create compliance risks, trigger additional treatment obligations, and in extreme cases force operational slowdowns while water chemistry is brought back within limits. Reducing evaporation from tailings storage is therefore not just a water conservation measure — it is a direct risk management tool for maintaining environmental compliance and operating continuity.

Regulatory Drivers: Water Balance and Environmental Licence Conditions

Mining operations in Australia operate under increasingly strict water balance licence conditions. State environmental regulators — including the WA Environmental Protection Authority and NSW EPA — typically require mining operations to demonstrate that total water use, release, and storage remains within agreed parameters.

Evaporation is a key variable in water balance calculations. Where evaporation losses are high and uncontrolled, they make water balance predictions less reliable, increase the risk of water shortfalls during dry periods, and add uncertainty to annual environmental reporting. Implementing evaporation control measures improves the reliability and accuracy of water balance management — a benefit that has real value in maintaining positive regulatory relationships.

Evaporation Control Solutions for Industrial Scale

The solutions available for mining and industrial evaporation management are well-developed and proven at commercial scale.

Floating Geomembrane Covers

High-density polyethylene (HDPE) and reinforced geomembrane floating covers are the gold-standard solution for large water storage facilities. They can be manufactured and installed in custom configurations to fit any dam shape, and they achieve evaporation reduction rates of 80 to 95 percent. They also provide secondary containment benefits, preventing rainfall from entering tailings storage areas and reducing the volume of water requiring treatment.

Shade Ball Systems

For certain facility types — particularly clean water reservoirs — large volumes of black polyethylene shade balls can be deployed to cover the water surface, reducing solar input and wind interaction that drive evaporation. This approach has been deployed extensively in California and parts of Australia for drinking water reservoirs.

Evaporation Ponds with Controlled Surface Area

For some mining processes, managed evaporation ponds are deliberately used to reduce liquid waste volume. In these cases, the objective is controlled evaporation — and the goal is to manage the rate and ensure it stays within environmental parameters rather than suppressing it.

Dam Profile Optimisation

Where tailings dams are still in the design or early construction phase, optimising the dam profile to maximise storage depth relative to surface area reduces evaporation rates per unit volume stored. This is a design-phase intervention with long-term operational benefits, and it is the kind of technical input that the team at EvapCo — backed by Big Ditch’s extensive dam design and construction experience — can provide.

Sustainability Reporting and ESG Implications

Water stewardship is now a core component of ESG (Environmental, Social, and Governance) reporting for Australian mining companies. Institutional investors, major customers, and international partners increasingly require mining operations to demonstrate responsible water use — and that includes managing preventable water losses like evaporation.

Implementing formal evaporation control programs not only reduces operational costs and compliance risk, but it also provides quantifiable data points for sustainability reporting — demonstrating measurable water savings, reduced environmental footprint, and responsible resource stewardship to all stakeholder groups.

Summary

Evaporation is a major source of water loss for Australian mining and industrial operations, with annual losses at large sites potentially exceeding hundreds of megalitres. Beyond the direct financial cost of lost water, evaporation-driven concentration of tailings contaminants creates environmental compliance risks, and high evaporation rates complicate water balance management. Floating covers, shade ball systems, and optimised dam design are proven solutions that reduce losses, improve compliance reliability, and support ESG reporting targets.

Industrial-Scale Evaporation Management, Backed by 30 Years of Experience

EvapCo works with mining and industrial clients across Australia to design and implement evaporation control strategies tailored to operational scale, water chemistry, and environmental requirements. Supported by Big Ditch’s engineering capabilities, we deliver practical solutions that work in the field.

Contact EvapCo today to discuss your site’s water management challenges.

Frequently Asked Questions

How does evaporation affect water management in Australian mining operations?

Australian mining operations in arid and semi-arid locations can lose enormous volumes of process and site water to evaporation each year. Depending on dam size and location, losses can exceed hundreds of megalitres annually — water that must be replaced at significant cost. Evaporation also concentrates contaminants in tailings water, creating water quality and regulatory compliance challenges.

What are the best evaporation control solutions for large mining dams?

For large mining and industrial water storage facilities, the most effective evaporation control solutions include high-density polyethylene (HDPE) floating covers, shade ball systems for certain facility types, and geomembrane lining combined with partial floating cover systems. The optimal solution depends on the dam’s purpose, water chemistry, and operational access requirements.

Does reducing evaporation from mine site dams help with environmental compliance?

Yes. Reducing evaporation from tailings storage facilities and process water dams helps with environmental compliance by reducing contaminant concentration in stored water, limiting dust generation from exposed edges, helping maintain water balance within licensed thresholds, and reducing the risk of contaminated water overflow in heavy rainfall events.