Estimated Water Requirements for the Conventional 

Flotation of Copper Ores

By Donald I. Bleiwas

Open-File Report 2012–1089

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia: 2012

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Suggested citation:

Bleiwas, D.I., 2012, Estimated water requirements for the conventional flotation of copper ores: U.S. Geological 

Survey Open-File Report 2012–1089, 13 p., available only at http://pubs.usgs.gov/of/2012/1089/. 

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copyright owners to reproduce any copyrighted material contained within this report.

Front cover: A photograph of the tailings storage facility for the Sierrita copper porphyry mine in Arizona. 

The facility is about 4.5 kilometers across at its widest point. Photograph courtesy of Freeport-McMoRan 

Copper & Gold Inc.
iii

Contents

Introduction.................................................................................................................................................................... 1

General Description of Ore Processing in a Conventional Copper Flotation Plant ........................................................ 2

Estimated Requirements for Process Water.................................................................................................................. 3

Makeup Water Requirement for Conventional Copper Flotation.................................................................................... 3

The Tailings Storage Facility.......................................................................................................................................... 4

Entrainment of Water in the Tailings Storage Facility .................................................................................................... 4

Evaporation of Water From the Tailings Storage Facility............................................................................................... 4

Seepage From the Tailings Storage Facility .................................................................................................................. 5

Water Contained in the Final Copper Concentrate ........................................................................................................ 5

Model of a Water Balance for a Conventional Flotation Copper Circuit Facility ............................................................. 5

Summary ....................................................................................................................................................................... 6

References Cited........................................................................................................................................................... 6

Figures

1. Simplified flow of water through a conventional flotation plant and unlined tailings storage waste facility 

illustrating water losses, reclamation of process water, and addition of makeup water................................... 10

2. Ball mills (A) and cyclones (B) in the mill house at the Sierrita beneficiation plant in Arizona......................... 10

3. Banks of rougher cells in the flotation circuit of the Sierrita copper porphyry mine, Arizona........................... 11

4. Photograph of the tailings storage facility for the Sierrita copper porphyry mine in Arizona............................ 11

Tables

1. Engineering and operational parameters for a conventional copper flotation circuit with 

a 50,000-metric ton-per-day ore feed capacity ............................................................................................... 12

2. Total water requirements, water losses, and makeup water for a conventional copper flotation 

circuit with a 50,000-metric-ton-per-day ore feed capacity located in a semiarid environment ....................... 13
iv

Conversion Factors

SI to Inch/Pound

Multiply By To obtain

Length

kilometer (km) 0.6214 mile (mi)

Volume

liter (L) 0.2642 gallon (gal)

cubic meter (m3) 264.2 gallon (gal) 

Mass

metric ton 1.102 ton, short (2,000 lb)

metric ton per day 1.102 ton per day (t/d) 
1

Estimated Water Requirements for the Conventional 

Flotation of Copper Ores

By Donald I. Bleiwas

Introduction

This report provides a perspective on the amount of water used by a conventional copper 

flotation plant, including the makeup water required to compensate for water losses. Much of the global 

supply of copper originates from mines that also produce byproduct molybdenum, but for simplicity, a 

single copper concentrate has been modeled for this study. In 2011, approximately 13 million metric 

tons (Mt), or about 80 percent of the world’s primary copper supply, originated from concentrate 

produced by flotation (International Copper Study Group, 2012). In 2011, about 60 percent of primary 

copper produced in the United States originated from flotation (Daniel E. Edelstein, Copper Commodity 

Specialist, U.S. Geological Survey, written commun., March 20, 2012).

Copper sulfide ores must be concentrated before they can be economically transported to a

smelter. Froth flotation is part of a copper beneficiation process in which finely ground ore is placed in 

aerated tanks that contain a water-based solution from which a copper-sulfide-rich froth is recovered 

through the use of a combination of physical and chemical interactions. The remaining non-ore minerals 

(tailings) are disposed of (Herbst and Pate, 1999; Rosenqvist, 2004). Flotation circuits are custom 

designed to accommodate the chemical and physical nature of the ore, the climate where the plant is 

located, and the intended production capacity; nonetheless, the great majority of circuits have common 

methods of processing the ore, which include (1) ore-size reduction; (2) the use of a water-based 

solution with recirculation; (3) the production of one or more concentrates; and (4) the production of 

tailings. The tailings is the finely ground waste product (which generally represents more than 98

percent of the original copper ore) suspended in a water-based slurry that is emplaced in a tailings 

storage facility (TSF).

Water is required for many activities at a mine-mill site, including ore production and 

beneficiation, dust and fire suppression, drinking and sanitation, and minesite reclamation. Assessing 

the availability of a sufficient and reliable supply of water for an operation to function effectively is 

essential, especially in areas where water may be difficult or expensive to acquire because of an 

unfavorable climate [arid and (or) high evaporation rate]; competition with other end uses, such as by 

agriculture, industry, or municipalities; and (or) compliance with regulatory requirements.

The availability of water is a long-term concern for most mine planners, especially for most lowgrade copper mines that usually have a lifespan that exceeds two decades. The water required to operate 

a flotation plant may outweigh all of the other uses of water at a mine site, and the need to maintain a 

water balance is critical for the plant to operate efficiently. Process water may be irretrievably lost or not 

immediately available for reuse in the beneficiation plant because it has been used in the production of 

backfill slurry from tailings to provide underground mine support; because it has been entrapped in the 

tailings, evaporated from the TSF, or leaked from pipes and (or) the TSF; and because it has been 

retained as moisture in the concentrate. Water retained in the interstices of the tailings and the 
2

evaporation of water from the surface of the TSF are the two most significant contributors to water loss 

at a conventional flotation circuit facility.

When the amount of water reclaimed from the TSF is insufficient to meet the plant’s 

requirements, the lost water must be replaced from sources of “fresh water,” which include lakes, 

reservoirs, rivers, and wells; precipitation and runoff collected in the TSF may also be sources of 

makeup water. The amount of makeup water needed can be very significant, especially in arid regions 

where the availability of water is problematic. The need to conserve water, especially in arid regions and 

areas where there is competition for limited water resources, motivates plant managers to minimize 

water use whenever possible.

General Description of Ore Processing in a Conventional Copper Flotation Plant

Figure 1 is a generalized diagram of a conventional copper flotation plant from the point where 

ore first enters the circuit to the production of concentrate and tailings. To prepare ore for the flotation 

process, run-of-mine ore, which may contain from about 2 to 5 percent water, by weight, when mined, is 

delivered to the crusher(s) to be reduced in size. At this stage, much of the moisture with the ore may be 

lost to evaporation and drainage because of climatic conditions, residence time in stockpiles, and the 

heat generated in the crusher. At most operations, water is sprayed into a crusher and onto conveyor 

belts to suppress dust in the plant, but this usage represents only a small fraction of the plant’s total 

water usage. The crushed ore is transferred to a semiautogenous (SAG) mill or ball mill where the ore is 

further reduced in size. Water is added to the ball mill, in which a slurry that usually contains from 

about 20 to 55 percent solids is produced (Singh, 2010; International Mining, 2011) (see fig. 2). The 

mill operates in a closed circuit with screens that size the ore and cyclones that sort the ore by size and 

density. The underflow from the cyclones is sent back to the mill to be reduced further in size, generally 

from 75 to 200 microns, with further regrinding in some cases to improve the liberation of desirable 

components of the ore from unwanted waste (Huss, 2009; International Mining, 2011; Cameron Wolf, 

Senior Process Engineer, Tetra Tech MMI, written commun., March 21, 2012). The overflow (in the 

form of water-based slurry) is transported to the flotation circuit where the copper sulfide ore minerals 

are concentrated and separated from the nonmineralized material by a series of rougher (see fig. 3) and 

cleaner flotation cells, which produce successively higher grade concentrates. This flotation slurry, also 

referred to as pulp, contains from 25 to 40 percent solids. After the series of concentration steps, the 

final copper concentrate is sent to thickeners and pressure filters where the moisture content is reduced 

from about 40 percent to about 8 to 10 percent, by weight (Singh, 2010). The water removed from the 

concentrate is usually reused in the circuit. At this point, the concentrate, which contains from 25 to 

35 percent copper, is ready to be shipped to a smelter.

The tailings produced from the flotation process are most often transported by pipeline to the 

TSF as slurry that contains roughly 40 to 60 percent solids (see fig. 4). The higher solids content is 

achieved when the slurry is thickened or clarified to recover water for recycling back to the plant. By 

doing so, the operation reduces the cost of pumping reclaimed water from the TSF and lessens the loss 

of water that occurs in the TSF. Tailings are discharged into the TSF by several methods, including 

subaerial slurry, subaqueous slurry, and less commonly, dry deposition. Tailings that contain a high 

sulfidic content (pyrite) may be deposited in the TSF subaqueously to prevent oxidation of wastes 

(Wardell Armstrong International Ltd., 2007).

Water is reclaimed from the tailings impoundment for reuse in the process after the solids 

contained in the slurry are allowed to decant. Makeup water is added to most beneficiation plants to 

compensate primarily for the loss of water entrained in tailings and evaporation. Makeup water is also 

required when mill tailing slurry is thickened to about 70 to 80 percent solids and used as hydraulic and 
3

(or) paste backfill for ground support in underground mines (Grice, 1998). Most of the water contained 

in the backfill is not available for reuse.

Estimated Requirements for Process Water

It was estimated, based on discussions with industry specialists and the examination of 

numerous site-specific reports for operating and proposed operations and other published literature, that 

the amount of water required to process copper sulfide ore through a conventional crush-grind-flotationconcentrate circuit ranges from roughly 1.5 metric tons (t) to about 3.5 t of water to process 1 t of ore 

[Wels and Robertson, 2003, 2004; Misra and others, 2005; Wills and Napier-Munn, 2006; Chilean 

Copper Commission, 2008; Gault Group, Inc., 2008; Mongolyn Alt (MAK) Group, 2008; MWH, 2008;

SRK Consulting, 2009; Tetra Tech, 2009; Keane and others, 2010; Singh, 2010; Gunson and others, 

2012; Cameron Wolf, Senior Process Engineer, Tetra Tech MMI, written commun., March 21, 2012]. In 

the southwestern United States, approximately 2.5 to 3 t of water are required to process 1 t of copper 

porphyry ore that contains roughly 0.5 percent copper (Gault Group, Inc., 2008; Vargas, 2008; Mining 

Engineering, 2010; Singh, 2010). The highest ratio of water to ore feed discovered in the literature was 

KHGM Polska Miedzs S.A.’s Lubin Mine in Poland, which uses about 4 to 5 t of water to process 1 t of 

copper ore (KGHM Polska Miedzs S.A., 2011). The chemical and physical nature of the ore are the 

primary determinants of water requirements and include such factors as the size and shape of the 

mineral grains; the distribution and density of the mineral assemblage (including the ore grade); the 

settling rate; the clay content; and the hydrophobic characteristics of the ore, including its behavior in a 

water-based solution containing a mix of chemicals.

Makeup Water Requirement for Conventional Copper Flotation

Makeup water is defined in this report as the amount of water required to compensate for water 

losses from the process of flotation and losses that occur in the tailings storage facility (TSF). Losses at 

the grinding and flotation portion of the facility are relatively minor. They include evaporation from 

flotation cells, water used in thickeners, and water contained in the concentrate. Water from leaks, spills, 

and overspray in a beneficiation plant is generally recovered from sumps and reused.

The most significant factors that contribute to makeup water requirements result from the loss of 

water in the TSF caused by evaporation and water retained in tailings. Makeup water requirements 

range from roughly 10 percent (where dry-paste tailings are produced because water is scarce and 

conservation is a high priority) to 100 percent in cases where water is abundant, mostly from 

precipitation and runoff into impoundments and reservoirs, or where it is not possible to recirculate 

water from tailing impoundments (U.S. Bureau of Mines, 1993; U.S. Environmental Protection Agency,

Office of Solid Waste, 1994; Chilean Copper Commission, 2008). Based on the reviews of literature 

and discussions with industry specialists, it is estimated that for most operations makeup water accounts 

for 10 to 50 percent of the plant’s total water requirement [U.S. Environmental Protection Agency, 

Office of Solid Waste, 1994; Yukon Zinc Corporation Ltd., 2007; Chilean Copper Commission, 2008;

Vargas, 2008; Mongolyn Alt (MAK) Group, 2008; SRK Consulting, 2009; Tetra Tech, 2009; Keane 

and others, 2010; Singh, 2010; Gunson and others, 2012; Cameron Wolf, Senior Process Engineer, 

Tetra Tech MMI, written commun., March 21, 2012]. There are also unusual cases, such as at the Fort 

Knox operation in Alaska, where the availability of makeup water from the TSF is affected by the 

freezing of the tailings pond (Gillespie and others, 2004).
4

The Tailings Storage Facility

The tailings storage facility (TSF) is an important source of makeup water for processing ore in 

the flotation facility and is also the major contributor to water loss. Most TSFs associated with flotation 

have four major components: (1) dams and (or) embankments that contain the tailings; (2) a beach, over 

which the slurry traverses; (3) a pond overlying saturated tailings; and (4) a dry beach of accumulated 

tailings that may be occasionally rewetted by slurry. The water losses in the TSF result from (1) 

entrainment of water in the tailings; (2) active beach evaporation; (3) rewetting; (4) pond evaporation; 

and (5) seepage [Wels and Robertson, 2004; Mongolyn Alt (MAK) Group, 2008; Keane and others, 

2010; Gunson and others, 2012; Cameron Wolf, Senior Process Engineer, Tetra Tech MMI, written 

commun., March 21, 2012]. Wels and Robertson (2003) estimated water losses from tailings 

impoundments of three large copper operations in Chile that produced from 66,500 metric tons per day 

(t/d) to 161,000 t/d of tailings in a slurry of about 53 percent solids. They estimated that the percentage 

of water recovered from the TSF for reuse ranged from a low of 20 percent for the Chuquicamata 

facility located in the Atacama Desert in Chile to a high of nearly 58 percent for the TSW used for the 

tailings generated from the Candelaria operation located in the central region of Chile. Nearly all the 

losses were attributable to evaporation and entrainment of water. The losses at these two sites represent 

32 percent and 20 percent, respectively, of the flotation facilities’ total water requirement based on the 

assumption that 2 t of water are required to process 1 t of ore and the stated makeup water requirements. 

Approximately 70 to 80 percent of the water contained in the tailings slurry discharged to the Morenci 

and Sierrita, Arizona, TSFs is not recovered because of evaporation, entrainment in tailings, and 

seepage, which leaves about 25 percent of the water available for reuse (University of Arizona, Water 

Resources Research Center, 2002; Gault Group, Inc., 2008; MWH, 2008). Figure 1 shows the major 

sources of water loss from the circuit and the TSF. A detailed list of the components that pertain to the 

availability of water for reuse in a TSF is presented by Goñi (2011).

Entrainment of Water in the Tailings Storage Facility

Water entrained in the TSF may range from 30 percent to more than 50 percent of the water 

contained in the slurry [Wels and Robertson, 2003, 2004; Mongolyn Alt (MAK) Group, 2008; Siepka, 

2009; Keane and others, 2010; Wardrop Engineering Inc., 2010; Gunson and others, 2012; Singh, 2010;

Cameron Wolf, Senior Process Engineer, Tetra Tech MMI, written commun., March 21, 2012]. The

range is mostly a function of grain size, mineralogy, permeability, and thickness of the accumulation of 

tailings. In general, less water is retained in thicker tailing deposits because of overlying pressure and in 

those that contain heavy minerals, such as magnetite, because of the material’s greater density. Through 

compression, the two factors result in displacement of the water from the tailings. An estimated 

52 percent of the water placed in the Tranque de Talabre—a TSF for the Chuquicamata porphyry copper 

mine, which is located in Chile’s Atacama Desert—is retained in tailings and is therefore unavailable 

for reuse (Wels and Robertson, 2003). Entrainment of water at the Mission Complex copper porphyry 

operation near Tucson, Ariz., was estimated to be nearly 30 percent of the water discharged to the TSF 

(Singh, 2010) and is probably representative of other TSFs in the southwestern United States that 

receive slurried tailings generated from porphyry copper ores.

Evaporation of Water From the Tailings Storage Facility

Evaporation is primarily a function of the geometry of the impoundments, especially its areal 

extent and water depth, and climatic factors, which include the combined effects of solar radiation, air 
5

temperature, humidity, precipitation, wind duration, fetch, and intensity (Wels and Robertson, 2003, 

2004; Singh, 2010; Goñi, 2011; Gunson and others, 2012). The amount of evaporation of water from the 

TSF may range from about 5 percent to more than 60 percent of the total water loss for the entire 

flotation-tailings storage impoundment facility and may exceed 15 percent of total plant requirements

[Wels and Robertson, 2003, 2004; Reid and Derek, 2004; Reid, 2005; Mongolyn Alt (MAK) Group, 

2008; BHP Billiton, 2009; Keane and others, 2010; Singh, 2010; Wardrop Engineering Inc., 2010; 

SNC-Lavalin Group Inc., 2011; Gunson and others, 2012; Cameron Wolf, Senior Process Engineer, 

Tetra Tech MMI, written commun., March 21, 2012]. An estimated 28 percent of the water placed in the 

Tranque de Talabre at the Chuquicamata porphyry copper mine is lost to evaporation and is therefore 

unavailable for reuse (Wels and Robertson, 2003). The combination of high altitude, low humidity, clear 

skies, and high temperature results in the loss to evaporation of approximately 30 percent of the water 

contained in the tailings slurry placed in Arizona’s Mission Complex’s TSF and more than 40 percent of 

the water in tailings slurry discharged to the TSF for the Sierrita Mine, which is also located in Arizona 

(Gault Group, Inc., 2008; MWH, 2008).

Seepage From the Tailings Storage Facility

Additional losses may also result from seepage from embankments that border the tailings 

holding area or dam and possibly from percolation to the subsoil or groundwater underlying the tailings 

impoundment because liner systems are not always used. Collection systems bordering the tailings 

impoundment are designed to recover the water and minimize losses (Tailings.info, 2012). Water lost 

through seepage is relatively minor at lined impoundments and those constructed on clays or other 

materials with low water conductivity but can be significant if the underlying material is permeable. In 

general, water loss attributable to seepage for most TSFs is small relative to losses from entrainment and 

evaporation because of the low permeability values of the fine-grained tailings (Wels and Robertson, 

2003). Data that pertain to losses through seepage from TSFs are limited, but such losses probably 

account for less than 10 percent of the makeup water requirements and less than 5 percent of total water 

requirements for most operations.

Water Contained in the Final Copper Concentrate

Copper concentrate is shipped from the plant with a moisture content of approximately 8 to 

10 percent, by weight. For most properties that employ conventional flotation, this represents less than 

2 percent of the total water loss at the facility (Siepka, 2009; Singh, 2010; Gunson and others, 2012). 

The relatively low moisture content is achieved through the use of thickeners and pressure filters.

Model of a Water Balance for a Conventional Flotation Copper Circuit Facility

A simplistic model was developed for a conventional flotation plant and TSF located in a 

semiarid region to provide a perspective on the amount of water that is required to (1) process the ore 

and (2) compensate for losses for water contained in the concentrate, the TSF, and other losses. The 

largest difference between this model and one developed for a more temperate region is that it is based 

on somewhat higher evaporative losses. The loss of water attributed to evaporation in an arid region, 

such as the southwest region of the United States and the high-desert regions of Chile, would be 

appreciably higher. The factors used in the calculations and estimates of water requirements and losses 

are shown in tables 1 and 2. Based on the broad assumptions described in tables 1 and 2, it was 

calculated (using figures rounded to two significant digits) that a conventional copper flotation facility 

that processes 17.5 Mt of ore per year containing 0.50 percent copper would produce about 290,000 t of 
6

concentrate containing 27 percent copper and would require about 44 Mt of process water based on a 

circuit designed to process copper porphyry ore that uses 2.5 t of water per metric ton of ore. Of this 

amount, about 17 Mt of water would be sent to the TSF as a slurry consisting of 50 percent solids. 

Approximately 11 Mt of water, or nearly 60 percent of the water sent to the TSF, would be lost to 

entrainment in the tailings and evaporation and seepage from the TSF, which leaves about 6 Mt for 

reclaim water (supernatant) for the plant. For simplicity, it was assumed that there were no additions of 

water to the TSF from precipitation or runoff. About 200,000 t, or less than 1 percent of the total annual 

amount of water required at the modeled facility, is lost as moisture contained in the shipped 

concentrate and as the result of evaporation in various parts of the plant facility. To compensate for 

these losses, the balance of the plant’s water requirement (about 11 Mt of water) would need to be 

acquired from sources other than the TSF. If the modeled flotation plant were to operate at the 

parameters described in tables 1 and 2 for a period of 20 years, approximately 340 Mt of water would be 

required to compensate for moisture contained in concentrate and losses that occur in the plant and the 

TSF. About 35 percent of the required amount of water would be available from the TSF, and 

65 percent would need to be acquired from other sources.

Summary

This brief study of the water requirements to process copper sulfide ores by conventional 

flotation circuits illustrates that the requirement for makeup water is a significant factor for the 

successful operation of a plant. The two leading factors in the loss of process water are its entrainment 

in the interstices of the tailings deposited in the TSF and evaporation of water from the TSF. The 

availability of a reliable supply of makeup water for the concentration plant and water required for other 

components of the mining operation, such as dust control, is a major concern to companies when they 

contend with factors that affect the demand for water beyond the requirements of the mine and mill. 

These factors may include competition with other industrial or municipal demands, high net evaporation 

rates, absence of infrastructure, limited water resources, regulations, and social pressures. These types of 

concerns could be relevant for several decades, considering the relatively long lifespan of most mines 

that process ore from low-grade copper porphyry deposits.

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Figure 1. Simplified flow of water through a conventional flotation plant and unlined tailings storage facility 

illustrating water losses (labeled in italics), reclamation of process water, and addition of makeup water. In addition 

to the sources of water loss noted, minor amounts are also lost by evaporation and overspray in the plant.

B 

A 

Figure 2. Ball mills (A) and cyclones (B) in the mill house at the Sierrita beneficiation plant in Arizona.

Photograph courtesy of Freeport-McMoRan Copper & Gold Inc.; used with permission.
11

Figure 3. Banks of rougher cells in the flotation circuit of the Sierrita copper porphyry mine, Arizona. Photograph 

courtesy of Freeport-McMoRan Copper & Gold Inc.; used with permission. 

Figure 4. Photograph of the tailings storage facility for the Sierrita copper porphyry mine in Arizona. Note the 

slurry pipeline in the foreground and where it traverses the tailings as indicated by the white arrow. The sun’s

reflection can be seen on the tailings pond in the right-middle portion of the photograph. Photograph courtesy of 

Freeport-McMoRan Copper & Gold Inc.; used with permission. 
12

Table 1. Engineering and operational parameters for a conventional copper flotation circuit with a 50,000-metric 

ton-per-day ore feed capacity.

[Mt, million metric tons; t, metric ton; TSF, tailings storage facility]

Engineering and operational parameters for a modeled copper porphyry 

deposit using conventional flotation Value

Daily plant capacity 50,000 t

Operating days per year 350

Annual plant ore capacity 17.5 Mt

Copper ore feed grade 0.50 percent

Copper recovery 90 percent

Metric tons of concentrate per year 292,000

Final copper concentrate grade 27 percent

Final concentrate moisture content 10 percent

Tailings deposited in the TSF per year 17.2 Mt

Solids contained in tailings slurry (percent solids) 50 percent
13

Table 2. Total water requirements, water losses, and makeup water for a conventional copper flotation circuit with a 50,000-metric-ton-per-day ore feed 

capacity located in a semiarid environment.

[Mt, million metric tons; N/A, not applicable; t/t, metric ton of water per metric ton of ore; TSF, tailings storage facility]

Type of water use or water loss

Estimated total annual water 

requirements (includes process water, 

water to TSF, water losses, and makeup 

water)1

Estimated percentage of total 

annual water requirement

Estimated annual 

water losses 

(percent)

Total annual process plant water requirement. 44 Mt2 N/A N/A

Flotation circuit process water requirement (includes grinding). 2.5 t/t ore N/A N/A

Water contained in copper concentrate. 0.03 Mt Less than 0.5 Less than 1

Water contained in tailings slurry and deposited in the TSF.3 17 Mt 39 63

Water entrained in the TSF. 6.9 Mt 16 40

Water deposited in TSF attributed to evaporative losses. 3.4 Mt 8 20

Water deposited in TSF attributed to seepage losses. 0.52 Mt 1 3

Water losses attributed to dust control, evaporative losses from plant 

flotation cells, and thickeners.

0.17 Mt Less than 0.5 Less than 1

Water reclaimed from the TSF pond for process water (reclaimed water is 

included as a component of makeup water).

6.4 Mt 15 37

Water acquired from other sources for process water (“fresh” water is a 

component of makeup water).4

11 Mt 25 N/A

Total annual makeup water requirement.5 17 Mt 40 N/A

1

Calculations are rounded to two significant figures and may not add because of rounding.

2

One metric ton of water is equivalent to 1,000 liters or 1 cubic meter.

3

The balance of the process water, 27 Mt, is recirculated and recovered from thickeners and filters. 

4

Also referred to as “fresh” water. Sources may include natural bodies of water, wells, and reservoirs and captured runoff and precipitation into the TSF. Captured runoff 

and precipitation into the TSF are not included in the model.

5

Reclaimed water from the TSF, plus water from other sources.