U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2006–5171

Prepared in cooperation with the Albuquerque Bernalillo County Water Utility Authority

Potential Chemical Effects of Changes in the Source of

Water Supply for the Albuquerque Bernalillo County

Water Utility Authority

Potential Chemical Effects of Changes 

in the Source of Water Supply for the 

Albuquerque Bernalillo County Water

Utility Authority

By Laura M. Bexfield and Scott K. Anderholm

Prepared in cooperation with the Albuquerque Bernalillo County Water

Utility Authority

Scientific Investigations Report 2006–5171

U.S. Department of the Interior

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

DIRK KEMPTHORNE, Secretary

U.S. Geological Survey

Mark D. Myers, Director

U.S. Geological Survey, Reston, Virginia: 2008

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endorsement by the U.S. Government.

Although this report is in the public domain, permission must be secured from the individual 

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

Suggested citation:

Bexfield, L.M., and Anderholm, S.K., 2008, Potential chemical effects of changes in the source of water supply for 

the Albuquerque Bernalillo County Water Utility Authority: U.S. Geological Survey Scientific Investigations Report 

2006−5171, 48 p.
iii

Contents

Abstract...........................................................................................................................................................1

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

Purpose and Scope ..............................................................................................................................3

Previous Investigations........................................................................................................................3

Current and Future Water-Supply Strategies for the Albuquerque Bernalillo County

Water Utility Authority ............................................................................................................4

Acknowledgments................................................................................................................................4

Methods...........................................................................................................................................................4

Collection and Analysis of Samples of Mineral Precipitates ........................................................5

Selection of Water Samples for Chemical Modeling......................................................................5

Ground Water...............................................................................................................................5

Surface Water..............................................................................................................................6

Modeling Methods................................................................................................................................6

Software........................................................................................................................................6

Parameters Included in Geochemical Modeling....................................................................6

Range of Physical and Chemical Conditions Modeled..........................................................8

Range of Mixing Ratios Modeled............................................................................................10

Evaluation of Modeling Results...............................................................................................10

Calculation of Corrosion Indices......................................................................................................12

Mineral Precipitates in the Current Distribution System ......................................................................12

Laboratory Results..............................................................................................................................12

Mineral Composition .................................................................................................................17

Chemical Composition ..............................................................................................................17

Modeling Results ................................................................................................................................17

Corrosion Indices................................................................................................................................22

Chemical Modeling of Surface Water and Ground-Water/Surface-Water Mixtures ......................24

Surface Water.....................................................................................................................................24

Ground-Water/Surface-Water Mixtures ........................................................................................27

Potential Chemical Effects of Changes in the Source of Water Supply on the

Distribution System........................................................................................................................37

Summary........................................................................................................................................................37

References Cited..........................................................................................................................................38

Appendix........................................................................................................................................................41

Figures

1. Albuquerque Bernalillo County Water Utility Authority well fields and selected

features associated with the new water distribution system and with collection

of surface-water and mineral precipitate samples ................................................................2

2. Flow chart of chemical modeling tasks ....................................................................................9
iv

Tables

1. Representative ground-water samples used in chemical modeling ...................................7

2. Representative surface-water samples from the Rio Grande at Albuquerque

used in chemical modeling .........................................................................................................7

3. Minerals having at least one calculated saturation index greater than 0.1 .....................11

4. Mineral composition of mineral-precipitate samples ..........................................................13

5. Chemical composition of mineral-precipitate samples........................................................14

6. Saturation indices for selected minerals, as calculated by PHREEQC for selected 

ground-water compositions......................................................................................................18

7. Corrosion indices calculated for selected ground-water compositions,

surface-water compositions, and ground-water/surface-water mixtures.......................23

8. Saturation indices for selected minerals, as calculated by PHREEQC for selected

surface-water compositions.....................................................................................................25

9. Saturation indices for selected minerals, as calculated by PHREEQC for selected 

ground-water/surface-water mixtures ...................................................................................28

Conversion Factors, Abbreviations, and Datum

Multiply By To obtain

inch (in.) 2.54 centimeter (cm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

square foot (ft2) 929.0 square centimeter (cm2)

square inch (in2) 6.452 square centimeter (cm2)

gallon (gal) 0.003785 cubic meter (m3) 

million gallons (Mgal) 3,785 cubic meter (m3)

cubic inch (in3) 16.39 cubic centimeter (cm3) 

cubic foot (ft3) 0.02832 cubic meter (m3) 

acre-foot (acre-ft) 1,233 cubic meter (m3)

gallon per minute (gal/min) 0.06309 liter per second (L/s)

million gallons per day (Mgal/d) 0.04381 cubic meter per second (m3/s)

pound, (lb) 0.4536 kilogram (kg) 

atmosphere, standard (atm) 101.3 kilopascal (kPa)

pound per cubic foot (lb/ft3) 0.01602 gram per cubic centimeter (g/cm3)

Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows:

°F=(1.8×°C)+32

Vertical coordinate information is referenced to the National Geodetic Vertical Datum of 1929 (NGVD 29).

Horizontal coordinate information is referenced to the North American Datum of 1927 (NAD 27).

Altitude, as used in this report, refers to distance above the vertical datum.

Specific conductance is given in microsiemens per centimeter at 25 degrees Celsius (μS/cm at 25 °C).

Concentrations of chemical constituents in water are given either in milligrams per liter (mg/L) or 

micrograms per liter (μg/L).
Abstract

Chemical modeling was used by the U.S. Geological 

Survey, in cooperation with the Albuquerque Bernalillo County 

Water Utility Authority (henceforth, Authority), to gain insight 

into the potential chemical effects that could occur in the 

Authority’s water distribution system as a result of changing 

the source of water used for municipal and industrial supply 

from ground water to surface water, or to some mixture of the 

two sources. From historical data, representative samples of 

ground-water and surface-water chemistry were selected for 

modeling under a range of environmental conditions anticipated 

to be present in the distribution system. Mineral phases calculated to have the potential to precipitate from ground water 

were compared with the compositions of precipitate samples 

collected from the current water distribution system and with 

mineral phases calculated to have the potential to precipitate 

from surface water and ground-water/surface-water mixtures.

Several minerals that were calculated to have the 

potential to precipitate from ground water in the current 

distribution system were identified in precipitate samples from 

pipes, reservoirs, and water heaters. These minerals were the 

calcium carbonates aragonite and calcite, and the iron oxides/

hydroxides goethite, hematite, and lepidocrocite. Several other 

minerals that were indicated by modeling to have the potential 

to precipitate were not found in precipitate samples. For most 

of these minerals, either the kinetics of formation were known 

to be unfavorable under conditions present in the distribution 

system or the minerals typically are not formed through direct 

precipitation from aqueous solutions.

The minerals with potential to precipitate as simulated 

for surface-water samples and ground-water/surface-water 

mixtures were quite similar to the minerals with potential 

to precipitate from ground-water samples. Based on the 

modeling results along with kinetic considerations, minerals 

that appear most likely to either dissolve or newly precipitate 

when surface water or ground-water/surface-water mixtures 

are delivered through the Authority’s current distribution 

system are carbonates (particularly aragonite and calcite). 

Other types of minerals having the potential to dissolve or 

newly precipitate under conditions present throughout most of 

the distribution system include a form of silica, an aluminum 

hyroxide (gibbsite or diaspore), or the Fe-containing mineral 

Fe3(OH)8. Dissolution of most of these minerals (except perhaps the Fe-containing minerals) is not likely to substantially 

affect trace-element concentrations or aesthetic characteristics 

of delivered water, except perhaps hardness. Precipitation 

of these minerals would probably be of concern only if the 

quantities of material involved were large enough to clog pipes 

or fixtures. The mineral Fe3(OH)8 was not found in the current 

distribution system. Some Fe-containing minerals that were 

identified in the distribution system were associated with relatively high contents of selected elements, including As, Cr, Cu, 

Mn, Pb, and Zn. However, these Fe-containing minerals were 

not identified as minerals likely to dissolve when the source 

of water was changed from ground water to surface water or a 

ground-water/surface-water mixture.

Based on the modeled potential for calcite precipitation 

and additional calculations of corrosion indices ground water, 

surface water, and ground-water/surface-water mixtures are 

not likely to differ greatly in corrosion potential. In particular, surface water and ground-water/surface-water mixtures 

do not appear likely to dissolve large quantities of existing 

calcite and expose metal surfaces in the distribution system to 

substantially increased corrosion. Instead, modeling calculations indicate that somewhat larger masses of material would 

tend to precipitate from surface water or ground-water/surfacewater mixtures compared to ground water alone.

Introduction

The Albuquerque Bernalillo County Water Utility Authority 

(henceforth, Authority), which supplies water to residents and 

businesses in the Albuquerque metropolitian area of central New 

Mexico (fig. 1), currently (2005) is in the process of implementing a major change in its approach to municipal and industrial 

water supply. Historically, ground water has been the sole source 

of water delivered to the Authority’s customers. However, large 

declines in ground-water levels across the metropolitan area 

have raised concerns about sustainability of the continued use 

of ground water to meet all water demand by customers of the 

Potential Chemical Effects of Changes in the Source of 

Water Supply for the Albuquerque Bernalillo County

Water Utility Authority

By Laura M. Bexfield and Scott K. Anderholm
NEW MEXICO

Middle Rio

Grande Basin

Area of

figure 1

0 2 4 6 MILES

0 2 4 6 KILOMETERS

Base compiled from U.S. Geological Survey digital data, 1:100,000,

1977, 1978, and City of Albuquerque digital data, 1:2,400, 1994

EXPLANATION

Lomas

Line delineating wells included in the same field

Well field name

Pipeline for surface-water delivery

Municipal-supply well

Reservoir receiving treated surface water

Reservoir where mineral-precipitate

samples were collected

Site of surface-water sample collection

Charles

Wells

Volcano

Cliffs

Zamora

College

West

Mesa

Leavitt

Atrisco

Rio Grande at

Albuquerque

Gonzales Duranes

Griegos

Coronado

Webster Walker

Ponderosa

Thomas

Leyendecker

Vol

Andia

Love

Lomas

Ridgecrest

Burton

Yale

San

Jose Miles

Santa

Barbara

Water

Treatment

Plant

DIVERSION

DAM

25

40

25

CIBOLA

NATIONAL

FOREST

CIBOLA

NATIONAL

FOREST

SANDIA

INDIAN

RESERVATION

KIRTLAND AIR FORCE BASE

ALBUQUERQUE

CNF

35°00’

35°05’

35°10’

106°45’ 106°40’ 106°35’ 106°30'

Arroyo De Las Calabacillas

Leyendecker

Reservoir

Volcano Cliffs

Reservoir

College

Reservoir

Don

Reservoir

Gutierrez

Reservoir

Ponderosa

Reservoir

Charles Wells Reservoir

Coronado

Reservoir

Burton

Reservoir

Yale

Reservoir

Tijeras Arroyo

Rio

Grande

40

Figure 1. Albuquerque Bernalillo County Water Utility Authority well fields and selected features associated with the new water 

distribution system and with collection of surface-water and mineral precipitate samples.

2 Potential Chemical Effects of Changes in the Source of Water Supply
Authority (Anderson and Woosley, 2005). Potential regional-scale 

problems of concern include increased cost and decreased quality 

of ground water delivered to area residents, reduced surfacewater availability as a result of induced infiltration of water 

from the Rio Grande into the aquifer system, and land-surface 

subsidence. The Authority (previously the City of Albuquerque) 

has, therefore, adopted a water-supply strategy that (in addition to 

conservation and water-recycling projects) calls for transition in 

2008 from complete reliance on ground water to primary reliance 

on surface water, supplemented by ground water (Albuquerque 

Bernalillo County Water Utility Authority, 2006). Similar shifts 

in water source have been implemented previously by other communities of the southwestern United States, including Tucson, 

Arizona (Price and Jefferson, 1996; Swanson and others, 1998). 

The Authority owns rights to native Rio Grande water, in addition to water that is diverted across the Continental Divide from 

streams in the Colorado River Basin to the Rio Grande Basin by 

the San Juan-Chama Transmountain Diversion Project. Under the 

Authority’s new water-supply strategy, San Juan-Chama water 

diverted from the Rio Grande will supply most municipal and 

industrial water demand, except during times of high demand 

or drought, when ground-water withdrawals will supplement 

surface-water supplies.

Subsequent to the transition in the primary source of 

water supply in 2008, the Authority plans to continue delivering water mostly through the existing infrastructure. The 

existing infrastructure has previously carried only ground 

water, in some cases for as long as about 50 years. Under 

the new water-supply strategy, water delivered through any 

particular section of the infrastructure at any particular time 

could consist of all surface water, all ground water, or a 

mixture of ground water and surface water. The chemistry of 

surface water being delivered will vary through time, as will 

the ratio of ground water to surface water in water mixtures. 

Because San Juan-Chama water from the Rio Grande can 

differ in chemical characteristics from ground water in the 

Albuquerque area, delivery of surface water or mixtures of 

ground water and surface water through the existing infrastructure could potentially result in chemical changes within 

the distribution system that negatively impact the quality 

of water delivered to customers or the efficiency of water 

transport. Negative impacts could include dissolution of 

precipitates that have previously been deposited by ground 

water, resulting in changes to the quality or aesthetic characteristics of water delivered to customers. Alternatively, 

new solid phases could precipitate in the distribution system, 

possibly reducing efficiency of water transport. The U.S. 

Geological Survey (USGS), in cooperation with the Albuquerque Bernalillo County Water Utility Authority, investigated the potential chemical effects in the distribution system 

of variability in the source of water used for municipal and 

industrial supply. This investigation could provide important 

knowledge in preventing or alleviating problems that could 

be faced by the Authority, as well as other water providers 

and communities along the Rio Grande that are considering 

similar changes in water supply.

Purpose and Scope

The purpose of this report is to illustrate the potential 

chemical effects of the change in the source of municipal and 

industrial supply for the Authority from exclusively ground 

water to primarily surface water, supplemented by ground water. 

In particular, information is presented on mineral precipitates 

demonstrated by laboratory analysis to be present in the Authority’s distribution system, in addition to precipitates that chemical 

modeling with the geochemical software package PHREEQC 

indicates could be present. The potential (as indicated by chemical modeling) for surface water alone, or mixtures of ground 

water and surface water, to dissolve existing precipitates is discussed. Also, the potential for various mixtures of ground water 

and surface water to form new precipitates in the distribution 

system is examined.

Previous Investigations

Chemical data for ground water and surface water in the 

Albuquerque area are available from a variety of databases 

and published studies. For chemistry of ground water from 

the Authority’s municipal-supply wells in particular, the 

Authority maintains an extensive database of field measurements, major-, minor-, and trace-element chemistry, and other 

selected constituents from samples collected by the Authority’s staff on typically a biannual basis from each well. In 

Bexfield and others (1999), this database is described in detail, 

and summary statistics for most constituents are presented by 

well. Chemical data for water from the Authority’s municipalsupply wells also have been presented in several investigations 

of overall ground-water chemistry in the Albuquerque area, 

including those by Anderholm (1988), Logan (1990), Bexfield 

and Anderholm (2002), and Plummer and others (2004). A 

study of arsenic in ground water of the Albuquerque area also 

included analysis of ground-water chemistry from the Authority’s wells, in addition to analysis of solid precipitates from the 

Authority’s reservoirs (Mark Stanton, U.S. Geological Survey, 

written commun., 2004).

Previous studies by the USGS have included analysis 

of surface-water chemistry from various sites along the Rio 

Grande near Albuquerque. Data on field measurements, 

major-, minor-, and trace-element chemistry, and other constituents are available from the USGS National Water Information 

Systems (NWIS) database. Detailed chemical data for sites 

near Albuquerque also have been published in Kelly and Taylor (1996), Wilcox (1997), and Plummer and others (2004).

Potential chemical effects of mixing surface water and 

ground water during proposed artificial recharge efforts in 

the Albuquerque area were modeled by Whitworth (1996). 

In particular, subsurface injection and surface infiltration of 

Rio Grande water were simulated with geochemical models. 

Results suggested that either method of artificial recharge 

was likely to be successful, although surface infiltration 

showed the higher potential to result in substantial quantities 

of mineral precipitation.

Introduction 3
Studies of methods to minimize corrosion in the 

Tucson, Arizona water distribution system subsequent to 

the transition from ground water to surface water as the 

primary source of municipal supply were conducted by 

Price and Jefferson (1996) and Swanson and others (1998). 

Both studies determined that maintenance of pH above certain levels was critical to reducing disturbance of existing 

precipitates and, consequently, to minimizing associated 

corrosion.

Current and Future Water-Supply Strategies for 

the Albuquerque Bernalillo County Water Utility 

Authority

Currently (2005), the Authority obtains its municipalsupply water from about 95 wells, which are grouped into 25 

well fields (fig. 1). In general, ground water from each well 

within a field is pumped into a common reservoir. Prior to entering the reservoir, the water is treated with sodium hypochlorite 

for disinfection and, for wells located east of the Rio Grande, 

the water is fluoridated (City of Albuquerque, 2004). Water 

is moved by pump stations from reservoirs at lower altitudes 

to reservoirs at higher altitudes (including higher-altitude 

reservoirs that are not associated with an individual well field) 

along main trunk lines that run generally east-west through 

Albuquerque. Therefore, water in most of the Authority’s 

reservoirs is a mixture of ground water from more than one well 

field. From the reservoirs, water enters distribution lines through 

19 individual entry points, resulting in 19 distribution zones 

across the city. Within each individual distribution zone, water is 

of the same quality (City of Albuquerque, 2004).

Starting in 2008, the Authority plans to begin diverting 

San Juan-Chama water from the Rio Grande for delivery to 

customers. The water will be diverted from the river using 

an inflatable diversion dam located near the north end of 

Albuquerque, and will be delivered to a water treatment plant 

(fig. 1). Design plans for the water treatment plant (CH2M 

Hill, 2003a and b) indicate that the stages of water treatment will include: presettling; ferric chloride and sulfuric 

acid addition for coagulation; settling/clarification; ozone 

and hydrogen peroxide addition and biological filtration 

(to provide disinfection, control taste and odor, and biodegrade organic compounds); sodium hypochlorite addition 

for secondary disinfection, fluorosilicic acid addition for 

increased fluoride; and lime addition for pH control (CH2M 

Hill, 2003a and b). Finished water will be pumped from storage at the plant to the existing distribution system through 

new large-diameter pipelines that deliver water to existing 

reservoirs (fig. 1).

The Authority anticipates that water levels in the Rio 

Grande will occasionally be too low (particularly during times of drought) for diversion of surface water to be 

practical. At these times, ground water will be the primary 

or sole source of water delivered to customers. In addition, 

during times of high demand or relatively low surface-water 

supply, surface water from the Rio Grande will be mixed 

with ground water to meet demand. The waters will be 

mixed in existing reservoirs, and then delivered through the 

system.

Acknowledgments

The authors thank the several individuals with the 

Albuquerque Bernalillo County Water Utility Authority who provided great assistance to this investigation. In 

particular, John Stomp with the Water Resources Division 

provided important information about the current and future 

water-supply strategies for the Authority. Barbara Gastian, 

Water Quality Manager, provided access to data used in 

this report and supplied information about the current and 

future water distribution system. Bill Lindberg, formerly 

with the Water Systems Division (later with the Wastewater 

Utility Division Water Quality Laboratory), also provided 

information about operation of the Authority’s distribution system, and shared samples of precipitates from the 

Authority’s reservoirs for laboratory analysis. Rick Duran 

with the Water Systems Division assisted with collection of 

precipitate samples from pipes. Greg Gates of CH2M Hill 

and Joe Chwirka, formerly of CH2M Hill, consultant to the 

Albuquerque Bernalillo County Water Utility Authority, 

provided information about expected treatment processes 

to be applied to future surface-water supplies. David Price, 

Chief Engineer for the Authority, conducted a helpful 

review of a draft of the report.

Several other individuals within the USGS also made 

substantial contributions to this investigation. Mark Stanton 

kindly shared chemical data for solid samples previously collected from Authority reservoirs, and provided solid samples 

for analysis of mineralogy. Blair Jones generously conducted 

analysis of mineralogy for all samples. David Parkhurst provided helpful advice about the chemical modeling of surfacewater treatment processes. Stephanie Moore (formerly of 

the USGS) conducted selection of surface-water samples for 

chemical modeling. In addition, Jeff Langman of the USGS 

and Brad Goodell, a private citizen, provided assistance in 

obtaining precipitate samples.

Methods

This investigation of potential chemical effects of 

shifts between ground-water and surface-water sources of 

municipal and industrial supply for the Authority included 

collection of samples of mineral precipitates from the 

Authority’s distribution system, analysis of these samples 

for chemical and mineralogical composition, selection of 

existing chemical analyses of ground water and surface 

water for chemical modeling, and design and implementation of modeling approaches. The methods used to accomplish each of these major tasks of the investigation are 

described in this section.

4 Potential Chemical Effects of Changes in the Source of Water Supply
Collection and Analysis of Samples of Mineral 

Precipitates

Precipitates from ground water within the Authority’s 

distribution system were collected and analyzed for mineralogical composition to determine whether they would be likely 

to dissolve in the presence of surface water or ground-water/

surface-water mixtures. Precipitate samples also were analyzed to determine chemical composition and, therefore, the 

chemical constituents that would be likely to enter distribution water as a result of dissolution.

Samples of precipitates were collected from various parts of the Authority’s distribution system to obtain 

information about the mineralogical and chemical compositions formed under a range of environmental conditions 

(in particular, temperatures and pressures). Samples from 

the Authority’s distribution lines were obtained from two 

locations in the southeastern and south-central parts of 

Albuquerque. The availability of sample-collection sites 

from distribution lines was limited to areas where pipes were 

being repaired or replaced by the Authority. Samples were 

obtained from both iron and steel pipes of about 4 to 6 inches 

in diameter by dislodging material attached to the interior of 

the pipe wall. (Files of the Albuquerque Bernalillo County 

Water Utility Authority indicate that about 4 percent of the 

length of pipe in the distribution system is composed of steel/

galvanized steel, about 46 percent is cast iron/ductile iron, 

about 29 percent is polyvinyl chloride, and about 22 percent 

is cement/concrete (Shawn Hardeman, University of New 

Mexico, written commun., 2006). Numbers do not add up 

to 100 percent because of rounding.) One sample of mineral 

precipitate was collected from the interior of a discarded 

residential water heater that had been used for about 10 years 

in the east-central part of Albuquerque. Samples from three 

of the Authority’s storage reservoirs (Gutierrez, Ponderosa, 

and Yale in fig. 1) were obtained for this investigation from 

Mark Stanton of the USGS and Bill Lindberg of the Authority. The samples had been collected during the 1990s from 

the walls or floors of reservoirs that had been drained for 

maintenance.

With the exception of samples from Ponderosa Reservoir, all precipitate samples were divided in two, placed 

without further processing in plastic bags, and shipped for 

laboratory analysis of mineral and chemical composition. 

For the purposes of a previous investigation, one of the 

four samples from Ponderosa Reservoir had been sieved 

to collect and analyze only the fraction with a particle size 

of 2 millimeters or less, and one had been sieved to collect 

and analyze only the fraction with a particle size greater 

than 2 millimeters. All four Ponderosa Reservoir samples 

had previously been analyzed for chemical composition by 

the USGS in Denver, Colorado using inductively coupled 

plasma-mass spectrometry (ICPMS) (Mark Stanton, USGS, 

written commun., 2003). Chemical analysis of three newly 

collected samples was conducted through the USGS 

National Water-Quality Laboratory in Denver, Colorado, 

also using ICPMS (Arbogast, 1996). Mineralogical analysis of all precipitate samples was conducted by Blair Jones 

at a USGS laboratory in Reston, Virginia using X-ray diffraction (Jenkins, 2000).

Selection of Water Samples for Chemical 

Modeling

As described in the “Previous Investigations” section, 

chemical data are available for numerous ground-water and 

surface-water samples collected in the Albuquerque area. For 

the chemical modeling conducted for this investigation, a 

subset of all available data was selected that would be manageable for analysis while providing adequate representation of 

the range in chemistry of waters that would be used as sources 

of municipal and industrial supply for the Authority. Selection 

of appropriate subsets of ground-water data and surface-water 

data required slightly different approaches.

Ground Water

Ground-water-chemistry data examined for selection of a representative subset for modeling were limited 

to data collected for the Authority’s municipal-supply 

wells. Because of the numerous data available for each 

well, individual representative samples needed to be 

chosen for further consideration. Because the measured 

ground-water chemistry from an individual supply well 

varies through time, selection of individual representative 

samples required knowledge of the “typical” chemistry for 

each well. Bexfield and others (1999) presented statistics 

indicative of the “typical” chemistry of the Authority’s 

municipal-supply wells (formerly of the City of Albuquerque) sampled from 1988 through 1997 as part of a City of 

Albuquerque program. Few municipal-supply wells have 

been added to or removed from the distribution system 

since 1997. The dataset evaluated by Bexfield and others 

(1999) was, therefore, used as the primary source of 

ground-water-chemistry data for this investigation.

For each well in the Bexfield and others (1999) dataset, the median values of selected parameters were compared to the measured values of those parameters in each 

individual sample. Parameters that were included represented oxidation/reduction conditions and major-, minor-, 

and trace-element chemistry. Some parameters were not 

included in this evaluation because they duplicated information provided by other parameters (for example, calcium 

as Ca in comparison to calcium as CaCO3) or were rarely 

detected in samples. The ground-water samples chosen to 

represent individual wells were those that included a full 

set of the desired parameters for which the sum of the differences of the parameter values from their median values 

was smallest, unless any individual parameter had an 

exceptionally large deviation from its median or the overall 

electrical charge did not balance to within 10 percent.

Methods 5
Once representative ground-water samples were 

selected for each of the more than 90 municipal-supply 

wells operated by the Authority (table 1), the samples were 

evaluated for similarity and differences in general chemical 

composition. The purpose of this evaluation was to select 

a subset of samples that would adequately represent the 

variability in the chemistry of ground water used by the 

Authority for municipal and industrial supply. Bexfield and 

Anderholm (2002) used chemical data from the Authority’s municipal-supply wells to delineate five “water-quality 

regions” across the Albuquerque area. Ground-water 

chemistry was determined to differ substantially among 

these regions, whereas chemistry within an individual region 

was relatively homogeneous. Starting with these previously 

observed patterns in ground-water chemistry, 10 wells were 

ultimately chosen for chemical modeling as a part of this 

study (table 1).

Surface Water

Because the USGS NWIS database contains chemical data for multiple sampling sites along the Rio Grande 

extending back in time for more than 30 years, this database was selected as the primary source of surface-waterchemistry data for this investigation. The two sampling 

sites in the database that are closest to the Authority’s 

planned diversion point for San Juan-Chama water from 

the Rio Grande and that have chemical data from multiple years are the Rio Grande at San Felipe (about 20 

miles north of the diversion dam) and the Rio Grande at 

Albuquerque (about 8 miles south of the diversion dam; 

fig. 1). Data from the site at San Felipe was determined not 

to be suitable for chemical modeling as source water for 

the Authority’s municipal and industrial supply because 

inflow from the Jemez River, which has distinctly different surface-water chemistry from the Rio Grande (Plummer and others, 2004), is often sufficient to substantially 

alter the chemical characteristics of Rio Grande water 

between San Felipe and Albuquerque. Data from the site 

at Albuquerque was determined to be representative of the 

chemistry of river water that will be used by the Authority 

because data from Plummer and others (2004) indicate that 

inflows to the Rio Grande between these two points typically do not substantially alter the chemical characteristics 

of the river water.

Analyses for all of the major elements were available in the NWIS database for about 40 samples collected 

from the Rio Grande at Albuquerque between 1971 and 

1995 (table 2). These samples were collected during all 

seasons of the year and for discharge ranging from about 

20 to 7,170 cubic feet per second. A total of eight samples 

from various seasons and flow conditions were chosen for 

chemical modeling (table 2). The samples were selected to 

be representative of the observed range in chemical composition at the site.

Modeling Methods

Chemical modeling of the effects of changing water 

source on the Authority’s distribution system required decisions about the modeling software to use, the chemical 

parameters to include, the range of environmental conditions 

and water treatments to model, the ground-water/surface-water 

mixing ratios to use, and the model output to retain and interpret. These modeling issues are discussed in this section.

Software

The public-domain software package PHREEQC 2.8 

(Parkhurst and Appelo, 1999) was selected to conduct the 

chemical modeling for this investigation. PHREEQC is 

designed to perform various low-temperature aqueous geochemical calculations, including speciation and saturationindex (SI) calculations. The minteq.dat database that is 

distributed with the PHREEQC software was used for all 

calculations because this database contains thermodynamic 

data for some elements of interest for this study that are not 

included in other databases distributed with the software. Like 

other geochemical equilibrium models, PHREEQC has some 

limitations worth noting. In particular, the databases must 

necessarily be compiled from various literature sources, so 

that there is the possibility that aqueous models defined by the 

database files are not consistent with the original experimental 

data. Regardless of this issue, geochemical modeling software 

is very useful in identifying which minerals have the potential 

to dissolve in or precipitate from solution given specified 

conditions. For the purposes of this study, therefore, the 

PHREEQC software was appropriate. Input to the PHREEQC 

software for the calculations conducted as part of this study is 

provided in the Appendix.

Parameters Included in Geochemical Modeling

The geochemical models designed for this study included 

about 20 of the numerous chemical and physical parameters 

that were available for the 10 ground-water samples and 8 

surface-water samples selected for the modeling effort (tables 

1 and 2). These 20 parameters were selected to provide all 

of the information necessary in calculation of SIs for minerals known to be present in the Authority’s water distribution 

system (as discussed in the section “Mineral Precipitates in the 

Current Distribution System”) and any other minerals thought 

to have the potential to precipitate from waters of the area, 

given their general chemistry. Some of the available chemical parameters (particularly certain trace metals) were not 

included in the geochemical modeling because the database 

did not include the data necessary for calculation of SIs for 

minerals that included those particular elements. In addition, 

such minerals were thought to be unlikely to precipitate from 

area waters; even if they did precipitate, the resulting quantities would be very small.

6 Potential Chemical Effects of Changes in the Source of Water Supply
Table 1. Representative ground-water samples used in chemical modeling.

[μS/cm, microsiemens per centimeter at 25 degrees Celsius; deg. C, degrees Celsius; mV, millivolts; mg/L, milligrams per liter; μg/L, micrograms per liter. Values in bold are essubstituted for less-than values. Values in italics are estimated concentrations substituted for missing values]

Albuquerque Bernalilo 

County Water Utility 

Authority well field 

and well number 

(fig. 1)

Specific 

conductance (μS/

cm)

pH, field 

(standard 

units)

Water 

temperature 

(deg. C)

Eh, field 

(mV)

Calcium 

(mg/L as 

Ca)

Magnesium 

(mg/L as 

Mg)

Sodium 

(mg/L as 

Na)

Potassium 

(mg/L 

as K)

Alkalinity (mg/L 

as HCO3)

Sulfate 

(mg/L as 

SO4)

Chloride 

(mg/L 

as Cl)

Fluoride 

(mg/L 

as F)

Silica 

(mg/L as 

SiO2)

Nitrate 

(mg/L 

as N)

Aluminum 

(μg/L 

as Al)

Arsenic 

(μg/L as 

As)

Copper 

(μg/L 

as Cu)

Charles 2 327 7.64 19.0 176 41.1 3.9 23.3 1.6 135 35.7 11.3 0.58 31.4 0.44 3.0 2.0 0.5 Duranes 6 514 7.48 19.0 131 51.6 12.1 42.5 9.5 205 96.0 14.1 0.46 69.6 0.05 3.0 4.0 0.5 

Leavitt 2 508 8.85 23.8 185 4.4 0.5 102.4 1.2 179 65.0 18.2 1.44 29.1 1.28 3.0 33.0 0.5 Love 5 338 7.73 22.7 161 37.9 3.0 26.9 2.8 133 19.4 24.3 0.60 28.1 0.32 3.0 2.0 0.5 Miles 1 440 7.76 25.7 138 33.6 7.4 40.1 7.4 130 43.6 37.8 0.74 67.2 0.22 3.0 21.0 0.5 Ridgecrest 1 406 7.35 22.5 204 49.4 7.6 28.7 2.1 182 55.4 11.5 0.58 28.2 0.87 3.0 2.0 0.5 Thomas 6 522 7.45 23.3 67 61.0 4.7 40.8 3.0 157 31.3 62.4 0.51 35.2 0.18 3.0 6.0 0.5 Vol Andia 3 394 7.91 18.0 180 47.1 5.7 18.3 2.7 123 50.4 19.6 0.48 36.7 0.72 3.0 8.0 0.5 

Walker 2 632 7.75 28.7 109 39.5 5.6 77.3 4.8 174 37.2 87.4 1.19 41.5 0.05 3.0 36.0 0.5 Zamora 1 417 7.88 24.3 206 20.2 3.4 58.0 6.4 158 54.6 9.3 0.72 70.1 0.86 3.0 14.0 0.5 

Table 2. Representative surface-water samples from the Rio Grande at Albuquerque used in chemical modeling.

[cfs, cubic feet per second; μS/cm, microsiemens per centimeter at 25 degrees Celsius; deg. C, degrees Celsius; mg/L, milligrams per liter; μg/L, micrograms per liter; —, no daconcentrations substituted for less-than values. Values in italics are estimated concentrations substituted for missing values]

Date of sample collection Discharge (cfs)

Specific 

conductance (μS/

cm)

pH, field 

(standard 

units)

Water 

temperature 

(deg. C)

Dissolved 

oxygen 

(mg/L)

Calcium 

(mg/L as 

Ca)

Magnesium 

(mg/L as 

Mg)

Sodium 

(mg/L 

as Na)

Potas-sium (mg/L 

as K)

Alkalinity 

(mg/L as 

HCO3)

Sulfate 

(mg/L 

as SO4)

Chloride 

(mg/L 

as Cl)

Fluoride 

(mg/L 

as F)

Silica 

(mg/L as 

SiO2)

Nitrate 

(mg/L 

as N)

Aluminum 

(μg/L as 

Al)

Arsenic 

(μg/L 

as As)

08/16/1971 214 690 7.70 25.5 — 70.0 9.0 60.0 5.9 163 150.0 37.0 0.70 28.0 — 5.0 3.0 05/03/1982 3,350 290 8.30 15.0 — 37.0 6.7 16.0 2.9 110 68.0 5.6 0.40 17.0 — 5.0 2.0 

07/15/1986 2,750 260 7.80 10.5 7.6 28.0 4.9 17.0 3.1 99 45.0 4.5 0.20 17.0 — 5.0 3.0 11/07/1986 2,030 350 8.05 9.0 — 42.0 7.0 27.0 3.4 135 59.0 12.0 0.40 21.0 — 5.0 3.0 02/03/1987 2,810 325 7.90 5.0 11.5 39.0 6.9 23.0 2.8 134 61.0 14.0 0.40 21.0 — 5.0 3.0 05/11/1988 1,800 390 8.70 20.5 7.9 41.0 8.5 32.0 2.6 143 76.0 13.0 0.50 18.0 — 5.0 3.0 

11/07/1988 414 470 8.46 16.0 8.3 53.0 9.7 33.0 3.8 183 73.0 13.0 0.40 22.0 — 5.0 4.0 08/22/1995 881 372 7.81 24.0 7.0 37.0 8.3 24.0 3.2 141 57.0 7.6 0.40 19.0 — 20.0 3.0 
Not every sample selected for geochemical modeling 

included a quantified value for each of the parameters listed 

in tables 1 and 2. For several ground-water samples and 

one surface-water sample, at least one of the metals was not 

detected by the laboratory and was reported as being less 

than a specified value. When this occurred, the non-detection 

was substituted with a quantified value selected from historical data obtained from a laboratory with lower detection 

limits, such as from Plummer and others (2004), for the same 

or nearby sampling sites. Most ground- and surface-water 

samples also were missing data entirely for at least one trace 

element. Substitution values again were assigned based on 

historical data for the same or similar sites; substitution 

values were generally the historical median. These substitution values should be sufficiently accurate for the primary 

purpose of the geochemical modeling in this study, which is 

to establish the general tendency for selected minerals to dissolve in or precipitate from solution.

Some individual samples also were missing a reliable 

indicator of the degree to which the water was oxygenated. For the surface-water samples, any samples without 

a dissolved-oxygen concentration were assumed to be near 

or at saturation, which appears to be reasonable based on 

historical dissolved-oxygen concentrations for the Rio 

Grande at Albuquerque. For the ground-water samples, the 

available Eh values were all positive, which is a qualitative indication that the samples were all at least slightly 

aerobic. However, the samples for Duranes 6 and Walker 

2 had nitrate concentrations less than the detection level 

of 0.05 milligrams per liter (mg/L) as nitrate, and previous geochemical studies in the area (Plummer and others, 

2004) have indicated that such small nitrate concentrations typically are associated with small dissolved-oxygen 

concentrations (less than 0.5 mg/L). Therefore, historical 

dissolved-oxygen data from Plummer and others (2004) for 

either the same wells or nearby wells were used to assign 

the general degree of oxygenation that would be assumed 

for the starting ground-water compositions during geochemical modeling.

Range of Physical and Chemical Conditions 

Modeled

Water delivered to the Authority’s customers will be subjected to a variety of physical and chemical conditions during 

transport through the new distribution system. Surface water in 

particular will undergo treatment that will include the addition 

of compounds to induce settling, alter pH, and otherwise 

adjust water chemistry as described in the section “Current 

and Future Water-Supply Strategies for the Albuquerque 

Bernalillo County Water Utility Authority.” Even subsequent 

to treatment, surface and ground water will be exposed to 

variations in water temperature, atmospheric-gas pressure, and 

oxidation/reduction conditions. PHREEQC simulations were 

designed to account for the various conditions that could affect 

water chemistry (fig. 2).

PHREEQC was used to model the surface-water treatment processes described by CH2M Hill (2003a and b) and 

their effects on the eight surface-water samples of table 2 

as closely as possible (fig. 2). The processes were modeled to use average anticipated chemical doses applied in 

the order that follows, which reflects the order outlined in 

CH2M Hill (2003a and b). The addition of a fixed quantity 

of 30 mg/L of ferric chloride to the original surface-water 

composition was simulated, along with addition of sufficient sulfuric acid to reduce the pH of the water to 6 (for 

enhanced coagulation). Because no organic matter had 

been included in the surface-water compositions used in 

initial modeling, the water composition was modified to 

include a quantity of organic matter (0.6 mg/L) equivalent to quantities typically detected in samples from the 

Rio Grande. Next, the simulation included the addition of 

1.5 mg/L of ozone (an oxidizer of organic compounds), 

0.2 mg/L of hydrogen peroxide, and sufficient oxygen to 

increase the dissolved-oxygen concentration of the water 

to near the 24 mg/L expected in the treatment plant design 

plans as a result of the ozonation process. Reduction of 

the dissolved-oxygen concentration back to about 10 mg/L 

also was simulated, along with removal of about 75 percent of the carbon dioxide content of the water through 

stripping, to match specifications in CH2M Hill (2003a). 

Finally, addition of 4 mg/L of sodium hypochlorite, 1 mg/L 

of fluorosilicic acid, and sufficient hydrated lime to bring 

the pH of the water to 8.0 were simulated. The resulting 

solution compositions were saved for analysis, as were 

additional compositions having simulated water temperatures of 2 and 50 degrees Celcius (oC) to simulate transport 

through parts of the water distribution system that could be 

exposed to cold outdoor temperatures or to heating such as 

occurs in a residential water heater (fig. 2).

For ground water, the chlorination and fluoridation 

processes applied prior to distribution were not simulated 

in PHREEQC because the effects of these treatments alone 

were judged to have negligible effect on ground-water 

chemistry in terms of parameters that were important to the 

geochemical modeling of this study. However, in addition 

to the native ground-water compositions, PHREEQC was 

used to model other compositions reflecting the environmental conditions ground water was likely to be exposed 

to during distribution. In particular, compositions having 

simulated water temperatures of 2 and 50oC were saved for 

analysis (fig. 2). Also, compositions equilibrated with a 

log partial pressure of carbon dioxide (log pCO2) equal to 

-3.5 and a log partial pressure of oxygen (log pO2) equal 

to -0.67 were simulated to reflect complete equilibration 

with atmospheric conditions. Also, compositions with a 

log pCO2 of -3.0 and a log pO2 of -5.0 (values generally 

between the partial pressures found in starting waters and 

partial pressures in the atmosphere) were simulated to 

reflect partial equilibration with atmospheric conditions, as 

might occur in a storage tank and downstream distribution 

areas.

8 Potential Chemical Effects of Changes in the Source of Water Supply
Representative

ground-water

(GW) samples

Representative

surface-water

(SW) samples

• Adjust temperature between

2 and 50 degrees Celsius

• Adjust log pCO2 between

original and –3.5 atmospheres

• Adjust log pO2 between

original and –0.67 atmospheres

Following proposed plan of

treatment:

• Add ferric chloride

• Add sulfuric acid

• Add ozone and hydrogen

peroxide

• Adjust CO2

 and O2

• Add sodium hypochlorite

• Add fluorosilicic acid

• Add hydrated lime

Subsequently adjust temperature

(2 to 50 degrees Celsius)

Observe range

of saturation

indices

Observe range

of saturation

indices

Dissolve

Precipitate

Compare

Adjust temperature and

atmospheric gases to

expected conditions

upon mixing in reservoirs

Adjust temperature and

atmospheric gases to

expected conditions

upon mixing in reservoirs

Mix, using

GW:SW ratios

of 1:9 and 9:1

Observe range

of saturation

indices

Compare

Adjust temperature to

2 or 50 degrees Celsius

Observe range

of saturation

indices

Compare

Dissolve

Precipitate

Dissolve

Precipitate

Dissolve

Precipitate

Figure 2. Flow chart of chemical modeling tasks.

Methods 9
Range of Mixing Ratios Modeled

In addition to separate ground-water and surface-water 

solutions, solutions resulting from the mixture of the two 

water sources were modeled in PHREEQC. Each treated 

surface-water composition was mixed individually with each 

of the ground-water compositions that had been simulated to 

represent partial equilibration with atmospheric conditions. 

The solutions were mixed in ratios of 9 to 1 and 1 to 9 (fig. 

2) to cover a wide range of potential mixing scenarios and 

resulting chemical compositions. The compositions of all 

resulting ground-water/surface-water mixtures were saved 

for evaluation, including mixtures that were cooled to 2oC 

and heated to 50oC.

Evaluation of Modeling Results

For each individual ground-water or surface-water 

composition simulated prior to the modeling of ground-water/

surface-water mixtures, the SIs calculated by PHREEQC 

were saved for all minerals. The SI for a mineral is defined 

as the log of the result of dividing the ion-activity product 

for the mineral-water reaction by the thermodynamic equilibrium constant of the mineral. If the resulting SI is positive, 

the solution is supersaturated with respect to that mineral 

and the mineral would have the potential to precipitate. If the 

resulting SI is negative, the solution is undersaturated with 

respect to that mineral and the mineral would tend to dissolve, assuming that the mineral was present and in contact 

with the solution. An SI that is about 0 ± 0.1 indicates little 

or no potential for a mineral to either dissolve or precipitate. 

Because PHREEQC generated SIs for a very large number of 

minerals, the SIs for only selected minerals were retained for 

further analysis. Table 3 lists these minerals, which each had 

an SI greater than 0.1 for at least one of the simulated groundwater or surface-water compositions.

The SIs for the minerals shown in table 3 were compared 

among pairs of simulated compositions of ground-water, 

surface-water, and (or) ground-water/surface-water mixtures 

that could potentially be present in the same part of the distribution system during different times. For example, SIs were 

compared between the treated surface-water compositions 

and the ground-water compositions that had been simulated to 

represent partial equilibration with atmospheric conditions (as 

might be present throughout much of the distribution system). This comparison was conducted to determine whether 

any minerals with SIs greater than 0.1 for the ground-water 

compositions had SIs less than -0.1 for the surface-water 

compositions, or vice versa. A mineral with an SI greater 

than 0.1 for the ground-water composition would have the 

potential to have precipitated out of solution and to be present in the current distribution system. If the same mineral 

had an SI less than -0.1 for any of the treated surface-water 

compositions, that mineral would tend to be dissolved when 

the source of water flowing through the distribution system 

changed from ground water to surface water. Depending on 

the mineral composition and the quantity dissolved, the surface water subsequently delivered to customers could potentially have degraded quality or aesthetic characteristics. There 

would be a similar concern for minerals having an SI greater 

than 0.1 for surface water and an SI less than -0.1 for ground 

water during times when a long period of surface-water 

delivery was followed by a period of ground-water delivery. 

The same would be true for switches between the delivery of 

either ground water or surface water and any ground-water/

surface-water mixture.

Analysis of the SI results from the geochemical modeling conducted during this study focused on the minerals with 

reaction kinetics favorable to the formation of substantial 

quantities of precipitate under temperatures and pressures 

expected to be present in the distribution system. Some of 

the minerals listed in table 3 commonly have been found to 

precipitate from natural waters and, therefore, would have a 

reasonable likelihood of forming within the Authority’s distribution system when their SIs exceeded 0.1. These minerals 

include:

•	 a form of calcium carbonate (aragonite or calcite); and

•	 a form of iron oxide or hydroxide (ferrihydrite, 

goethite, hematite, lepidocrocite, maghemite).

In general, these minerals are made up of elements that 

are present within the ground-water and (or) surface-water 

compositions being studied (tables 1 and 2) at a concentration that could allow for substantial quantities of precipitate 

to form.

Several other types of minerals in table 3 are considered unlikely to precipitate in substantial quantities from 

water within the Authority’s distribution system because of 

known kinetic limitations, because there is little geologic 

evidence that the minerals commonly form at low temperature and pressure, and (or) because at least one element 

making up the minerals has very small dissolved concentrations in the waters being studied. These include igneous 

and metamorphic minerals of the amphibole group (tremolite), the feldspar group (albite/analbite, microcline, and 

sanidine), the mica group (muscovite), the pyroxene group 

(diopside), the serpentine group (chrysotile), and the zeolite 

group (analcime and laumontite/leonhardite), most of which 

form at high temperatures and (or) pressures (Kraus and 

others, 1951; Klein and Hurlbut, 1985; Judson and Kauffman, 1990). Clay minerals (halloysite, kaolinite, montmorillonite, nontronite, pyrophyllite, sepiolite, and talc), 

which are secondary minerals that typically form through 

weathering of primary aluminosilicate minerals (Klein 

and Hurlbut, 1985; Langmuir, 1997), also are considered 

unlikely to precipitate from water within the Authority’s 

distribution system. Although some clay minerals capable 

of forming in low-temperature environments could potentially form within the Authority’s distribution system where 

the appropriate primary minerals were present, the rates of 

reaction would be very slow (Langmuir, 1997).

10 Potential Chemical Effects of Changes in the Source of Water Supply
Table 3. Minerals having at least one calculated saturation index 

greater than 0.1.

[Minerals in bold were the focus of this study because they were considered 

most likely to form under conditions present in the Albuquerque Bernalillo 

County Water Utility Authority distribution system.]

Mineral name Chemical formula

albite NaAlSi3O8

analbite NaAlSi3O8

analcime NaAlSi2O6:H2O

aragonite CaCO3

birnessite MnO2

bixbyite Mn2O3

Ca-nontronite Fe2Al0.33Si3.67O10(OH)2Ca0.165

calcite CaCO3

chalcedony SiO2

chrysotile Mg3Si2O5(OH)4

cristobalite SiO2

cupric ferrite CuFe2O4

cuprous ferrite CuFeO2

diaspore AlOOH

diopside CaMgSi2O6

dolomite CaMg(CO3)

2

Fe(OH)2.7Cl0.3 Fe(OH)2.7Cl0.3

Fe3(OH)8 Fe3(OH)8

ferrihydrite Fe(OH)3

goethite FeOOH

halloysite Al2Si2O5(OH)4

hausmannite Mn3O4

hematite Fe2O3

huntite CaMg3(CO3)

4

jarosite-K KFe3(SO4)2(OH)6

K-nontronite Fe2Al0.33Si3.67O10(OH)2K0.33

kaolinite Al2Si2O5(OH)4

laumontite CaAl2Si4O12:4H2O

leonhardite Ca2Al4Si8O24:7H2O

lepidocrocite FeOOH

maghemite Fe2O3

magnesite MgCO3

magnetite Fe3O4

manganite MnOOH

Mg-ferrite MgFe2O4

Mg-nontronite Fe2Al0.33Si3.67O10(OH)2Mg0.165

microcline KAlSi3O8

montmorillonite Mg0.485Fe0.22Al1.71Si3.81O10(OH)2

muscovite KAl3Si3O10(OH)2

Na-nontronite Fe2Al0.33Si3.67O10(OH)2Na0.33

nsutite MnO2

pyrolusite MnO2

pyrophyllite Al2Si4O10(OH)2

quartz SiO2

sanidine KAlSi3O8

sepiolite Mg2Si3O7.5OH:3H2O

talc Mg3Si4O10(OH)2

tremolite Ca2Mg5Si8O22(OH)2

willemite Zn2SiO4

ZnSiO3 ZnSiO3

The kinetics of some minerals listed in table 3 are not 

well known, which complicates efforts to determine whether 

the minerals would be likely to form in the Authority’s distribution system when their SI exceeded 0.1. One example is 

diaspore, which is typically a product of diagenesis or hydrothermal alteration (Deer and others, 1962). Even if diaspore 

could form under conditions in the distribution system, 

concentrations of Al also are probably too small to allow 

formation of substantial quantities. As indicated in table 3, 

three silica minerals (chalcedony, cristobalite, and quartz) had 

a calculated SI greater than 0.1 for at least one of the modeled 

ground-water or surface-water solutions. Chalcedony is a 

cryptocrystalline variety of quartz that can precipitate from 

aqueous solution at low temperatures. Xu and others (1998) 

indicate that chalcedony is the most likely silica mineral to 

precipitate when a solution is undersaturated with respect to 

amorphous silica but oversaturated with respect to quartz. 

However, chalcedony generally is found as a pseudomorph, 

lining or filling cavities in rocks (Klein and Hurlbut, 1985), 

and may or may not form under conditions present within 

the Authority’s distribution system. Cristobalite is not likely 

to form within the Authority’s distribution system because it 

crystallizes at high temperatures (Klein and Hurlbut, 1985). 

Whitworth (1996) indicates that pure quartz does not typically 

precipitate at short time scales (residence times of water in the 

Authority’s distribution system probably are on the order of 

hours to days), and that α-quartz usually forms as amorphous 

silica (Whitworth, 1996). However, none of the modeled solutions had an SI greater than 0.1 for amorphous silica, indicating that it may not be likely to form.

Table 3 shows that three magnesium or cacium-magnesium 

carbonates (dolomites, huntite, and magnesite) have at least one 

SI greater than 0.1. However, dolomite does not easily precipitate from most natural waters at low temperatures (Deer and 

others, 1962; Langmuir, 1997). Large deposits of dolomite are 

thought to be secondary in origin, resulting from replacement of 

some calcium in limestone with magnesium (Klein and Hurlbut, 

1985). Huntite forms in low-temperature environments, but is 

thought to typically occur as an alteration product of existing 

carbonates (Deer and others, 1962; Dollase and Reeder, 1986). 

Magnesite tends to precipitate at elevated temperatures and (or) 

pressures, and most commonly occurs as an alteration product 

of magnesium-rich igneous and metamorphic rocks (Deer and 

others, 1962). Therefore, calcite and aragonite are the carbonate minerals most likely to precipitate from water within the 

Authority’s distribution system.

The reaction kinetics are not well known for formation of some Fe, Mn, Cu, and Zn minerals listed in table 3. 

For most of the water compositions being studied (tables 1 

and 2), concentrations of Mn, Cu, and Zn are very small. 

Therefore, even if conditions within the Authority’s distribution system were kinetically favorable for the formation of 

minerals containing these elements, only small quantities of 

these minerals would be expected to form. Minerals containing Fe would be more likely to form in substantial quantities, 

particularly given the planned addition of ferric chloride 

Methods 11
during surface-water treatment. Of the Fe minerals in table 3, 

ferrihydrite, goethite, hematite, lepidocrocite, and maghemite 

appear most likely to precipitate from natural waters at low 

temperatures (Deer and others, 1962; Pough, 1998).

Calculation of Corrosion Indices

To further evaluate the potential of the various groundwater and surface-water compositions to dissolve (rather than 

precipitate) solid phases with subsequent adverse effects on 

water quality or possible damage to distribution lines, corrosion indices were calculated and compared among water 

compositions. Most of these indices focus on stability of calcite. Calcite formation helps to protect pipes from corrosion, 

even though the formation of large quantities of calcite can 

reduce the area of pipe available to conduct water. Dissolution 

of existing calcite could expose metal pipes to greater corrosion, in addition to possibly affecting the quality or aesthetic 

characteristics—taste, odor, and appearance—of water delivered to customers (depending on elemental composition of 

any material associated with the calcite precipitate). Potential 

effects of water compositions on lead and copper corrosion in 

particular were not examined.

For this study, the Langelier, Ryznar, and Larson-Skold 

corrosion indices were calculated. The Langelier and Rynar 

equations used for this study included corrections for temperature and dissolved-solids concentration. The Langelier 

Saturation Index (LSI) is defined as the difference between 

the actual pH of the water and the hypothetical pH the water 

would have if it was in equilibrium with calcite. The index is 

calculated as:

LSI = pHf – pHs;

pHs = [9.3 + (log10(DS) – 1 / 10) + (-13.12 

x log10(T + 273) + 34.55)] - 

[(log10(Ca2+) – 0.4) + log10(alk)],

where pHf is the field pH, pHs is the hypothetical pH for 

equilibrium with calcite, DS is the dissolved-solids concentration in mg/L, T is the water temperature in oC, Ca2+ is 

calcium in mg/L as calcium bicarbonate, and alk is alkalinity in mg/L as calcium carbonate (Kingston Technical 

Software, 2004). A positive LSI value indicates that calcium 

carbonate scale is likely to form in pipes, whereas a negative 

value indicates that calcium carbonate is likely to dissolve, 

exposing pipes to potential corrosion in the presence of 

oxygen. The Ryznar Stability Index (RSI) is a modification 

of the LSI based on field studies. The RSI = 2(pHs) – pHf; in 

general, a value less than 6 indicates that calcium carbonate 

scale is likely to form and a value greater than 8 indicates 

that the water is fairly corrosive (Kingston Technical Software, 2004). The Larson-Skold Index (LKI) also is based on 

field studies and measures whether the chloride and sulfate 

content of water might interfere with scale formation. The 

LKI = (Cl- + SO4

2-) / (HCO3-

 + CO3

2-), where the constituents shown are chloride, sulfate, bicarbonate, and carbonate, 

respectively, all with units of equivalents per million. An LKI 

below about 0.8 indicates that chloride and sulfate probably 

will not interfere with scale formation, whereas values above 

0.8 indicate the potential for chloride and sulfate to reduce 

scale formation and enhance corrosion (Kingston Technical 

Software, 2004).

Mineral Precipitates in the Current 

Distribution System

As described in the section, “Collection and Analysis of 

Samples of Mineral Precipitates,” samples of mineral precipitates were collected from various parts of the Authority’s 

distribution system and analyzed for mineralogical and chemical compositions. The laboratory results can be compared to 

results expected based on the SIs calculated using PHREEQC 

and can be used to determine the chemical constituents that 

would be likely to enter distribution water if mineral dissolution was to occur.

Laboratory Results

A total of 10 samples of mineral precipitate from three reservoirs, two pipes, and one residential water heater were analyzed 

for mineralogical compositions. Chemical data were obtained for 

a total of 13 samples, mostly from reservoirs. Similar minerals 

were found in most samples, whereas the overall chemical compositions were somewhat variable (tables 4 and 5).

12 Potential Chemical Effects of Changes in the Source of Water Supply
Table 4. Mineral composition of mineral-precipitate samples.

Sample description Minerals identified

Whole sample collected from a residential water heater near the 

intersection of Monroe and Candelaria NE 

calcite, aragonite, goethite, total clay

Whole sample collected from a 4-inch diameter pipe near the 

intersection of Hazeldine and Barelas SW

magnesite, goethite, and quartz trace

Whole sample collected from Yale Reservoir (fig. 1) hematite, goethite, and total clay trace

Whole sample collected from Gutierrez Reservoir (fig. 1) calcite, traces of quartz and feldspars, and total clay trace

Whole sample collected from a 4-inch diameter coupling near 

the intersection of Cagua and Bell SE

rhodochrosite, goethite, total clay trace, and weak possibility of 

gypsum and zeolite-hornblende

Whole sample collected from a reducer near the intersection of 

Hazeldine and Barelas SW

lepidocrocite-goethite and gibbsite

Sample of particles greater than 2 millimeters in size, obtained 

from the collector line at Ponderosa Reservoir (fig. 1)

amorphous iron oxyhydroxide (?) and calcite as determined by 

reaction of sample to dilute hydrochloric acid

Sample of particles less than 2 millimeters in size, obtained from 

the collector line inflow at Ponderosa Reservoir (fig. 1)

quartz, plagioclase, calcite, potassium feldspar trace, amorphous 

iron, and clay traces

Whole sample collected from Ponderosa Reservoir overflow 

(fig. 1)

quartz, potassium feldspar, plagioclase, calcite, amorphous iron, 

and clay traces

Whole sample collected from the floor of Ponderosa Reservoir 

at the overflow (fig. 1)

quartz, potassium feldspar, plagioclase, calcite, amorphous iron, 

and clay traces

Mineral Precipitates in the Current Distribution System 13
Table 5. Chemical composition of mineral-precipitate samples. [Data for Ponderosa Reservoir samples provided by Mark Stanton, USGS, written commun., 2003; ppm, parts per million] Sample description Calcium (percent) Magnesium (percent) Sodium (percent) Potassium (percent) Phosphorus (percent) Aluminum (percent) Iron (percent) Titanium (percent) Arsenic (ppm) Antimony (ppm) Barium (ppm) 

Whole sample collected from Yale Reser- voir (fig. 1) 0.34 0.005 0.005 0.008 0.072 0.024 46 <0.005 150 0.4 56 Whole sample collected from Gutierrez Reservoir (fig. 1) 41 0.91 0.032 0.007 0.007 0.016 0.27 <0.005 7.3 <0.1 770 

Whole sample collected from a 4-inch diameter coupling near the intersection of Cagua and Bell SE 0.32 0.073 0.026 0.06 0.013 0.16 44 0.008 96 5.7 51 Sample of particles greater than 2 millime- ters in size, obtained from the collector line at Ponderosa Reservoir (fig. 1) 2.9 0.26 1.4 1.70 0.04 3.9 22 0.12 170 1.0 900 Sample of particles less than 2 millimeters in size, obtained from the collector line inflow at Ponderosa Reservoir (fig. 1) 1.6 0.13 1.2 1.30 0.032 3.2 34 0.11 190 2.8 610 Whole sample collected from Ponderosa Reservoir (fig. 1), between the collector line overflow and silt ring 3.0 0.42 1.1 1.90 0.066 4.1 13 0.25 250 5.4 1,300 Whole sample collected from the center of 

Ponderosa Reservoir (fig. 1)

2.4 0.35 0.042 0.19 0.059 0.92 12 0.029 120 0.3 5,100 

Whole sample collected from the center of 

Ponderosa Reservoir (fig. 1)

4.6 0.44 0.039 0.21 0.10 1.1 9.4 0.069 680 1.5 2,200 

Whole sample collected from the Ponderosa 

Reservoir overflow (fig. 1)

1.6 0.28 0.044 0.16 0.05 0.87 6.4 0.069 230 0.8 510 

Whole sample collected from the overflowfloor of Ponderosa Reservoir (fig. 1) 10 0.50 0.052 0.18 0.058 1.2 8.6 0.054 540 2.1 2,200 Whole sample collected from the floor of 

Ponderosa Reservoir at the overflow (fig. 1)

2.9 0.40 0.048 0.26 0.064 1.2 7.5 0.092 210 0.9 590 

Whole sample collected from the floor of 

Ponderosa Reservoir (fig. 1)

20 0.62 0.026 0.09 0.027 0.51 5.8 0.038 53 0.3 460 

Whole sample collected from the floor of 

Ponderosa Reservoir (fig. 1)

38 0.72 0.021 0.033 0.015 0.23 0.8 0.018 28 0.1 600 
Table 5. Chemical composition of mineral-precipitate samples.—Continued

Sample description Cerium (ppm) Chromium (ppm) Cobalt (ppm) Copper (ppm) Europium (ppm) Gallium (ppm) Gold (ppm) Holmium (ppm) Lanthanum (ppm) Lead (ppm) Lithium (ppm) Manganes

(ppm) 

Whole sample collected from Yale Reservoir (fig. 1) 1.4 44 <2 7.4 <1 <1 <1 <1 <1 <1 <1 60 Whole sample collected from Gutierrez 

Reservoir (fig. 1)

<1 1.1 14 11 <1 <1 <1 <1 <1 10 2 180 

Whole sample collected from a 4-inch 

diameter coupling near the intersection of Cagua and Bell SE

1.4 94 410 310 <1 21 <1 <1 <1 7.3 1.4 1,100 

Sample of particles greater than 2 millimeters in size, obtained from the collector 

line at Ponderosa Reservoir (fig. 1)

30 16 11 370 <1 10 <1 <1 17 70 10 1,200 

Sample of particles less than 2 millimeters 

in size, obtained from the collector line inflow at Ponderosa Reservoir (fig. 1)

34 56 24 350 <1 11 <1 <1 17 52 10 2,900 

Whole sample collected from Ponderosa 

Reservoir (fig. 1), between the collector line overflow and silt ring

49 62 32 2,600 <1 12 <1 <1 26 350 17 13,000 

Whole sample collected from the center of 

Ponderosa Reservoir (fig. 1)

34 110 32 5,400 <1 5 <1 1.7 24 370 8 50,000 

Whole sample collected from the center of 

Ponderosa Reservoir (fig. 1)

42 160 36 4,200 <1 5 <1 1.1 24 600 12 47,000 

Whole sample collected from the Ponderosa Reservoir overflow (fig. 1) 36 58 15 2,000 <1 4 <1 <1 20 230 9 5,300 Whole sample collected from the overflow 

floor of Ponderosa Reservoir (fig. 1)

25 110 42 3,600 <1 5 <1 <1 14 310 13 49,000 

Whole sample collected from the floor of 

Ponderosa Reservoir at the overflow(fig. 1)

45 54 25 2,000 <1 6 <1 <1 24 270 12 8,600 

Whole sample collected from the floor of 

Ponderosa Reservoir (fig. 1)

14 6 30 490 <1 2 <1 <1 7.6 210 8 1,000 

Whole sample collected from the floor of 

Ponderosa Reservoir (fig. 1)

6.8 4 6 140 <1 1 <1 <1 3.7 42 6 900 
Table 5. Chemical composition of mineral-precipitate samples.—Continued Sample description Nickel (ppm) Niobium (ppm) Scandium (ppm) Silver (ppm) Strontium (ppm) Tantalum (ppm) Thallium (ppm) Thorium (ppm) Tin (ppm) Uranium (ppm) Vanadium (ppm) 

Whole sample collected from Yale Reser- voir (fig. 1) <1 <4 <2 <0.1 14 <1 <1 <1 <1 19 130 Whole sample collected from Gutierrez Reservoir (fig. 1) 1.3 <4 <2 <0.1 1,600 <1 <1 <1 1.9 3.6 <2 Whole sample collected from a 4-inch diameter coupling near the intersection of Cagua and Bell SE 150 <4 <2 <0.1 23 <1 <1 <1 7.6 20 79 Sample of particles greater than 2 millime- ters in size, obtained from the collector line at Ponderosa Reservoir (fig. 1) 22 5 2 <0.1 320 <1 1 4.5 14 11 77 Sample of particles less than 2 millimeters in size, obtained from the collector line inflow at Ponderosa Reservoir (fig. 1) 55 8 <2 0.2 160 <1 <1 3.3 25 6.6 41 Whole sample collected from Ponderosa Reservoir (fig. 1), between the collector line overflow and silt ring 50 8 5 0.3 310 <1 1.4 5.6 330 6 70 Whole sample collected from the center of 

Ponderosa Reservoir (fig. 1)

63 <4 3 0.1 420 <1 2.9 2.6 53 16 21 

Whole sample collected from the center of 

Ponderosa Reservoir (fig. 1)

43 <4 3 0.3 320 <1 1.2 4.4 320 8.5 85 

Whole sample collected from the Ponderosa Reservoir overflow (fig. 1) 25 <4 3 0.1 100 <1 <1 3.6 140 5.5 48 Whole sample collected from the overflow 

floor of Ponderosa Reservoir (fig. 1)

59 4 3 0.3 550 <1 1.6 2.1 420 6 87 

Whole sample collected from the floor 

of Ponderosa Reservoir at the overflow (fig. 1)

30 <4 4 0.2 170 <1 1.1 5 160 6.8 56 

Whole sample collected from the floor of 

Ponderosa Reservoir (fig. 1)

59 <4 <2 <0.1 800 <1 <1 1.6 51 8.6 23 

Whole sample collected from the floor of 

Ponderosa Reservoir (fig. 1)

13 <4 <2 <0.1 1,600 <1 <1 <1 16 4.9 11 
Mineral Precipitates in the Current Distribution System 17

Mineral Composition

Analysis with X-ray diffraction determined that some 

minerals were common to several of the 10 samples submitted 

for analysis (table 4). In particular, calcite was identified in 

Gutierrez Reservoir, the residential water heater, and all four 

samples from the Ponderosa Reservoir. Goethite was identified 

in Yale Reservoir, the residential water heater, and the three 

pipe samples (in one of the pipe samples, it was recorded as 

lepidocrocite-goethite). Iron found in the Ponderosa Reservoir 

was in the form of amorphous iron and possible amorphous 

iron oxyhydroxides. Other minerals that were detected in 

one sample each were aragonite, hematite, rhodochrosite 

(MnCO3), and gibbsite; one sample also had a weak possibility 

of gypsum (CaSO4) and zeolite-hornblende.

Quartz, plagioclase feldspar, potassium feldspar, and 

a trace quantity of clay were reported for several samples. 

These minerals were typically found together in the reservoir 

samples. Because of their locations within the reservoirs 

combined with kinetic considerations (see “Evaluation of 

Modeling Results” section), it appears likely that most of these 

minerals are associated with sand and clay particles that were 

suspended in water during pumping and subsequently settled 

out once the water reached the reservoirs.

Use of X-ray diffraction for identification of minerals has 

some limitations. The technique can identify minerals in crystalline form, but is not able to identify amorphous minerals. In 

particular, the presence of amorphous SiO2 or amorphous Mn 

oxides and oxyhydroxides will not be detected by X-ray diffraction. Also, minerals present at small weight fractions (less 

than about 5 percent) may not be apparent (Jenkins, 2000).

Chemical Composition

Chemical compositions for all 13 samples analyzed 

by ICPMS are listed in table 5. Four samples (3 from Ponderosa Reservoir and 1 from Gutierrez Reservoir) are more 

than 10 percent calcium, likely indicating a large portion of 

calcite. Six samples (4 from Ponderosa Reservoir, 1 from Yale 

Reservoir, and 1 from a pipe) are more than 10 percent iron. 

All samples except the one from Yale Reservoir contain Mn, 

Cu, and (or) Zn exceeding 1,000 parts per million (ppm). No 

minerals containing Cu or Zn were identified during X-ray 

analysis, perhaps because such minerals were present only in 

small weight fractions, or because these two metals are sorbed 

onto other materials, including clays and Fe oxides or oxyhydroxides. Three other heavy metals—Cr, Pb, and Sn—and 

As exceed 100 parts per million in some samples. Samples 

that are highest in percent Ca are lowest in As content, which 

probably indicates that As does not tend to co-precipitate with 

calcite, and is more likely to co-precipitate with or be sorbed 

by Fe-containing minerals. The contents of Ba and Sr, two 

alkali earth metals, also exceeded 100 parts per million in 

several mineral samples. For individual precipitate samples, 

Si and (or) O (which were not included in analysis) probably 

make up most of the mass that is not accounted for by the elements listed in table 5.

Water that had a tendency to dissolve the solid phases 

found in the Authority’s current distribution system could be 

adversely affected in terms of quality or aesthetic characteristics if substantial dissolution occurred. Dissolution of calcite 

could increase water hardness. Dissolution of solid phases 

having high contents of Fe or other metals (whether because 

of sorption or incorporation into the mineral structure) could 

affect the color and taste of water, in addition to the quality of 

the water relative to U.S. Environmental Protection Agency 

(USEPA) drinking-water standards. Of the elements listed in 

the previous paragraph as being found in substantial quantities in the mineral precipitates sampled, As, Ba, Cr, Cu, and 

Pb have enforceable, health-based USEPA drinking-water 

standards (USEPA, 2006). For the metals Fe, Mn, and Zn, the 

USEPA has established non-enforceable guidelines related 

to water taste, odor, and color. Any increases that occurred in 

trace-element concentrations as a result of mineral dissolution 

would likely vary throughout the Authority’s distribution system, depending on factors that included the composition of the 

minerals present in a particular part of the system, the degree 

to which the water was already saturated with respect to those 

minerals, the volume of water in contact with the minerals, 

and the contact time between the minerals and the water. The 

concentration of a particular metal in the water prior to contact 

with minerals in the distribution system also would be a determining factor in whether mineral dissolution could cause the 

water to approach or exceed a drinking-water standard for that 

metal. In addition to mineral dissolution, desorption of trace 

elements from solid phases could potentially increase traceelement concentrations in delivered water. Again, the starting 

trace-element concentrations of the water, the volume of water 

in contact with the minerals, and the contact time between the 

minerals and the water would be determining factors in the 

magnitude of any concentration increases that might occur as 

a result of desorption. Modeling of adsorption and desorption 

processes within the Authority’s distribution system was not 

conducted for this study.

Modeling Results

Geochemical modeling using 10 ground-water compositions representative of water currently delivered through the 

Authority’s distribution system indicated that the SIs of multiple minerals were greater than 0.1. Of the minerals listed in 

table 3, the only one without an SI greater than 0.1 for any 

ground-water composition was Fe3(OH)8. As described in the 

section “Analysis of Modeling Results,” some of the minerals in table 3 could reasonably be expected to precipitate 

in the distribution system, whereas others probably would 

not because of kinetic considerations. For the ground-water 

compositions, table 6 shows the SIs of minerals from table 3 

having reaction kinetics considered favorable to their precipitation under conditions present in the Authority’s distribution system, in addition to selected minerals having kinetics 

that are not well known. The SIs for some minerals varied 

depending on the modeled temperature and atmospheric-gas 

pressures. Higher temperatures resulted in smaller SIs for 
Table 6. Saturation indices for selected minerals, as calculated by PHREEQC for selected ground-water compositions. [deg. C, degrees Celsius; pCO2, partial pressure of carbon dioxide; pO2, partial pressure of oxygen; atm, atmospheres] Sample source (from table 1) Simulated temperature (deg. C) Simulated log pCO2 (atm) Simulated log pO2 (atm) pH aragonite birnessite calcite chalcedony cupric ferrite cuprous ferrite diaspore 

Charles 2 unaltered unaltered unaltered 7.64 -0.27 -12.54 -0.13 0.11 11.00 11.34 1.49 Duranes 6 unaltered unaltered unaltered 7.48 -0.21 -12.75 -0.07 0.45 11.34 11.59 1.56 Leavitt 2 unaltered unaltered unaltered 8.85 0.07 -8.04 0.21 -0.02 10.34 9.72 0.34 Love 5 unaltered unaltered unaltered 7.73 -0.16 -12.41 -0.02 0.01 11.88 11.57 1.40 Miles 1 unaltered unaltered unaltered 7.76 -0.17 -12.51 -0.04 0.36 12.29 11.65 1.29 Ridgecrest 1 unaltered unaltered unaltered 7.35 -0.33 -13.95 -0.19 0.02 9.55 10.67 1.65 Thomas 6 unaltered unaltered unaltered 7.45 -0.19 -12.65 -0.05 0.11 11.65 11.64 1.59 Vol Andia 3 unaltered unaltered unaltered 7.91 -0.02 -11.40 0.12 0.18 10.57 10.94 1.35 Walker 2 unaltered unaltered unaltered 7.75 0.03 -11.50 0.17 0.11 12.66 11.71 1.18 Zamora 1 unaltered unaltered unaltered 7.88 -0.21 -11.94 -0.07 0.39 11.14 11.01 1.23 Charles 2 23.0 -3.50 -0.67 8.59 0.69 6.47 0.83 0.04 11.41 2.35 0.63 Duranes 6 23.0 -3.50 -0.67 8.74 1.03 6.82 1.17 0.38 12.12 2.70 0.48 Leavitt 2 23.0 -3.50 -0.67 8.72 -0.06 6.37 0.08 0.00 10.48 1.88 0.51 Love 5 23.0 -3.50 -0.67 8.58 0.66 6.48 0.80 -0.01 11.73 2.51 0.64 Miles 1 23.0 -3.50 -0.67 8.57 0.56 6.48 0.69 0.37 11.83 2.56 0.65 Ridgecrest 1 23.0 -3.50 -0.67 8.70 0.97 6.38 1.11 -0.01 10.50 1.89 0.52 Thomas 6 23.0 -3.50 -0.67 8.64 0.94 7.39 1.08 0.09 12.15 2.72 0.58 Vol Andia 3 23.0 -3.50 -0.67 8.55 0.66 6.49 0.80 0.11 10.73 2.01 0.67 Walker 2 23.0 -3.50 -0.67 8.68 0.83 7.65 0.97 0.16 11.79 2.54 0.53 Zamora 1 23.0 -3.50 -0.67 8.66 0.50 6.42 0.64 0.39 10.57 1.93 0.57 Charles 2 unaltered -3.00 -5.00 8.08 0.16 5.13 0.30 0.10 11.47 3.24 1.22 Duranes 6 unaltered -3.00 -5.00 8.25 0.54 5.89 0.68 0.45 12.31 3.66 1.09 Leavitt 2 unaltered -3.00 -5.00 8.24 -0.48 4.31 -0.35 0.01 11.10 3.29 0.92 Love 5 unaltered -3.00 -5.00 8.11 0.21 4.32 0.34 0.01 12.13 3.75 1.09 Miles 1 unaltered -3.00 -5.00 8.11 0.17 3.62 0.31 0.35 12.49 4.08 0.97 Ridgecrest 1 unaltered -3.00 -5.00 8.23 0.53 4.58 0.67 0.01 10.98 3.17 0.99 Thomas 6 unaltered -3.00 -5.00 8.17 0.51 5.23 0.65 0.10 12.66 4.05 1.01 Vol Andia 3 unaltered -3.00 -5.00 8.03 0.10 5.26 0.24 0.18 10.64 2.78 1.27 Walker 2 unaltered -3.00 -5.00 8.25 0.51 4.46 0.65 0.11 12.82 4.39 0.70 Zamora 1 unaltered -3.00 -5.00 8.19 0.09 4.10 0.23 0.39 11.19 3.36 0.95 
Table 6. Saturation indices for selected minerals, as calculated by PHREEQC for selected ground-water compositions.—Continued

Sample source 

(from table 1)

Simulated 

temperature 

(deg. C)

Simulated 

log pCO2

(atm)

Simulated 

log pO2 (atm) pH aragonite birnessite calcite chalcedony

cupric 

ferrite

cuprous 

ferrite diaspore 

Charles 2 2.0 -3.00 -5.00 7.90 -0.29 9.07 -0.12 0.32 9.69 1.45 0.65 Duranes 6 2.0 -3.00 -5.00 8.08 0.11 9.84 0.27 0.67 10.63 1.92 0.65 Leavitt 2 2.0 -3.00 -5.00 8.03 -1.03 9.30 -0.86 0.29 8.96 1.08 0.65 Love 5 2.0 -3.00 -5.00 7.90 -0.32 9.07 -0.15 0.27 10.00 1.60 0.65 Miles 1 2.0 -3.00 -5.00 7.89 -0.42 9.02 -0.25 0.65 10.08 1.64 0.65 Ridgecrest 1 2.0 -3.00 -5.00 8.03 0.02 9.30 0.19 0.27 8.96 1.08 0.65 Thomas 6 2.0 -3.00 -5.00 7.96 -0.02 10.12 0.15 0.37 10.51 1.86 0.65 Vol Andia 3 2.0 -3.00 -5.00 7.86 -0.32 8.98 -0.15 0.39 8.95 1.07 0.65 Walker 2 2.0 -3.00 -5.00 8.01 -0.12 10.50 0.05 0.44 10.23 1.72 0.65 Zamora 1 2.0 -3.00 -5.00 7.97 -0.47 9.20 -0.30 0.67 8.96 1.09 0.65 Charles 2 50.0 -3.00 -5.00 8.23 0.69 -1.25 0.85 -0.25 14.15 5.98 -0.19 Duranes 6 50.0 -3.00 -5.00 8.38 1.02 -0.53 1.18 0.08 14.96 6.38 -0.35 Leavitt 2 50.0 -3.00 -5.00 8.36 -0.05 -1.02 0.11 -0.29 13.29 5.55 -0.33 Love 5 50.0 -3.00 -5.00 8.22 0.66 -1.25 0.82 -0.30 14.47 6.14 -0.18 Miles 1 50.0 -3.00 -5.00 8.21 0.55 -1.30 0.72 0.08 14.56 6.19 -0.17 Ridgecrest 1 50.0 -3.00 -5.00 8.34 0.96 -1.06 1.12 -0.31 13.31 5.56 -0.30 Thomas 6 50.0 -3.00 -5.00 8.27 0.93 -0.23 1.09 -0.20 14.93 6.37 -0.24 Vol Andia 3 50.0 -3.00 -5.00 8.18 0.66 -1.35 0.82 -0.18 13.45 5.63 -0.15 Walker 2 50.0 -3.00 -5.00 8.32 0.83 0.16 0.99 -0.14 14.60 6.21 -0.29 Zamora 1 50.0 -3.00 -5.00 8.30 0.50 -1.13 0.66 0.09 13.36 5.59 -0.26 
Table 6. Saturation indices for selected minerals, as calculated by PHREEQC for selected ground-water compositions.—Continued Sample source (from table 1) Simulated temperature (deg. C) Simulated log pCO2 (atm) Simulated log pO2 (atm) goethite hematite huntite lepido- crocite maghemite manganite Mg-ferrite 

Charles 2 unaltered unaltered unaltered 5.32 15.62 -7.13 4.67 5.69 -5.85 5.65 Duranes 6 unaltered unaltered unaltered 5.57 16.11 -5.70 4.91 6.19 -5.90 6.27 Leavitt 2 unaltered unaltered unaltered 4.84 14.69 -5.33 4.02 4.39 -2.56 6.63 Love 5 unaltered unaltered unaltered 5.70 16.40 -6.77 4.91 6.18 -5.81 6.84 Miles 1 unaltered unaltered unaltered 5.87 16.76 -5.36 4.98 6.31 -5.94 7.89 Ridgecrest 1 unaltered unaltered unaltered 4.67 14.34 -6.56 3.89 4.14 -6.97 4.37 Thomas 6 unaltered unaltered unaltered 5.67 16.33 -6.87 4.85 6.07 -5.77 6.43 Vol Andia 3 unaltered unaltered unaltered 5.07 15.12 -5.83 4.46 5.27 -4.98 5.75 Walker 2 unaltered unaltered unaltered 6.05 17.12 -4.98 5.05 6.45 -4.92 8.36 Zamora 1 unaltered unaltered unaltered 5.30 15.61 -5.92 4.46 5.27 -5.49 6.52 Charles 2 23.0 -3.50 -0.67 5.39 15.79 -3.09 4.59 5.55 4.02 8.07 Duranes 6 23.0 -3.50 -0.67 5.75 16.50 -0.53 4.95 6.25 4.38 9.51 Leavitt 2 23.0 -3.50 -0.67 4.93 14.85 -5.87 4.13 4.61 3.92 6.45 Love 5 23.0 -3.50 -0.67 5.55 16.10 -3.47 4.75 5.86 4.03 8.27 Miles 1 23.0 -3.50 -0.67 5.60 16.20 -2.53 4.80 5.96 4.03 8.72 Ridgecrest 1 23.0 -3.50 -0.67 4.94 14.87 -1.35 4.14 4.63 3.94 7.64 Thomas 6 23.0 -3.50 -0.67 5.76 16.53 -2.36 4.96 6.29 4.94 8.97 Vol Andia 3 23.0 -3.50 -0.67 5.05 15.11 -2.90 4.26 4.87 4.04 7.46 Walker 2 23.0 -3.50 -0.67 5.59 16.17 -1.99 4.79 5.93 5.20 8.77 Zamora 1 23.0 -3.50 -0.67 4.97 14.95 -3.11 4.18 4.71 3.97 7.28 Charles 2 unaltered -3.00 -5.00 5.50 15.97 -5.39 4.84 6.04 3.43 6.88 Duranes 6 unaltered -3.00 -5.00 5.92 16.82 -2.70 5.27 6.89 4.19 8.50 Leavitt 2 unaltered -3.00 -5.00 5.25 15.51 -7.56 4.43 5.21 3.01 6.25 Love 5 unaltered -3.00 -5.00 5.78 16.56 -5.30 4.99 6.34 2.93 7.75 Miles 1 unaltered -3.00 -5.00 5.93 16.87 -3.99 5.03 6.42 2.48 8.70 Ridgecrest 1 unaltered -3.00 -5.00 5.21 15.42 -3.12 4.43 5.22 3.17 7.21 Thomas 6 unaltered -3.00 -5.00 6.04 17.08 -4.06 5.23 6.81 3.89 8.61 Vol Andia 3 unaltered -3.00 -5.00 5.10 15.17 -5.35 4.48 5.32 3.47 6.04 Walker 2 unaltered -3.00 -5.00 6.06 17.14 -3.06 5.06 6.47 3.56 9.37 Zamora 1 unaltered -3.00 -5.00 5.29 15.59 -4.72 4.45 5.25 2.84 7.12 
Table 6. Saturation indices for selected minerals, as calculated by PHREEQC for selected ground-water compositions.—Continued

Sample source 

(from table 1)

Simulated 

temperature 

(deg. C)

Simulated 

log pCO2

(atm)

Simulated 

log pO2 (atm) goethite hematite huntite

lepidocrocite maghemite manganite Mg-ferrite 

Charles 2 2.0 -3.00 -5.00 4.83 14.56 -8.06 4.85 6.06 5.82 3.47 Duranes 6 2.0 -3.00 -5.00 5.30 15.49 -5.32 5.32 6.99 6.59 5.19 Leavitt 2 2.0 -3.00 -5.00 4.46 13.82 -10.84 4.48 5.32 6.04 2.06 Love 5 2.0 -3.00 -5.00 4.99 14.87 -8.46 5.01 6.37 5.82 3.66 Miles 1 2.0 -3.00 -5.00 5.03 14.95 -7.50 5.04 6.44 5.77 4.09 Ridgecrest 1 2.0 -3.00 -5.00 4.46 13.82 -6.21 4.48 5.32 6.05 3.25 Thomas 6 2.0 -3.00 -5.00 5.24 15.38 -7.26 5.26 6.88 6.87 4.47 Vol Andia 3 2.0 -3.00 -5.00 4.46 13.81 -7.89 4.48 5.31 5.73 2.79 Walker 2 2.0 -3.00 -5.00 5.10 15.09 -6.89 5.12 6.59 7.25 4.34 Zamora 1 2.0 -3.00 -5.00 4.47 13.83 -8.06 4.48 5.33 5.95 2.80 Charles 2 50.0 -3.00 -5.00 6.49 18.10 -2.31 4.80 5.96 -0.56 11.86 Duranes 6 50.0 -3.00 -5.00 6.89 18.90 0.22 5.20 6.76 0.16 13.39 Leavitt 2 50.0 -3.00 -5.00 6.06 17.24 -5.06 4.37 5.10 -0.32 10.32 Love 5 50.0 -3.00 -5.00 6.65 18.42 -2.69 4.96 6.27 -0.55 12.06 Miles 1 50.0 -3.00 -5.00 6.70 18.51 -1.76 5.00 6.36 -0.61 12.49 Ridgecrest 1 50.0 -3.00 -5.00 6.07 17.26 -0.59 4.38 5.12 -0.36 11.50 Thomas 6 50.0 -3.00 -5.00 6.88 18.88 -1.62 5.19 6.73 0.47 12.78 Vol Andia 3 50.0 -3.00 -5.00 6.14 17.39 -2.14 4.45 5.25 -0.65 11.22 Walker 2 50.0 -3.00 -5.00 6.72 18.55 -1.23 5.02 6.40 0.86 12.62 Zamora 1 50.0 -3.00 -5.00 6.10 17.31 -2.33 4.40 5.16 -0.43 11.12 
22 Potential Chemical Effects of Changes in the Source of Water Supply

most Mn oxides/hydroxides and some silicates and larger SIs 

for most carbonates. The mineral huntite tended to have positive SIs only when the simulated water temperature was 50oC. 

Ground-water compositions simulated with less oxygenation 

generally resulted in smaller, and in some cases negative, SIs 

for Mn oxides/hydroxides.

Of the minerals shown in table 6, several were positively 

identified in x-ray diffraction analysis of mineral precipitates 

from the Authority’s distribution system. These were aragonite, 

calcite, goethite, hematite, and lepidocrocite. Also identified 

through examination of the precipitates were amorphous 

forms of Fe or Fe oxyhydroxides, which can form more readily than some Fe minerals with distinct crystalline structure. 

The lack of detection of some minerals listed in table 6 is not 

surprising—particularly, minerals with SIs greater than 0.1 for 

only a limited number of ground-water compositions at high 

temperatures and amorphous forms of Mn that typically are 

not detected by x-ray diffraction. The lack of detection of other 

minerals containing Mn or Cu could be explained by quantities 

of these minerals being very small or by their formation not 

being kinetically favored. Comparison between the modeled 

SIs and the minerals identified in the distribution system is 

helpful in demonstrating that many of these minerals are not of 

substantial concern for changes in the source of water delivered 

through the distribution system, despite having SIs greater 

than 0.1 in the model simulations. Formation of most of the 

minerals that have SIs greater than 0.1 but were not identified 

by x-ray diffraction probably is not kinetically favorable under 

conditions present within the distribution system.

Rhodochrosite (MnCO3) and gibbsite were positively 

identified among samples from the Authority’s distribution system, despite having SIs less than -0.1 for all modeled 

ground-water compositions. Rhodochrosite generally forms in 

high temperature metasomatic deposits and hydrothermal veins 

(Deer and others, 1962); therefore, its presence may be the 

result of transportation into the Authority’s distribution system 

from an outside source. Gibbsite typically occurs as an alteration product of aluminosilicate minerals or as a low-temperature 

hydrothermal mineral, although it has been prepared artificially 

by autoprecipitation from aqueous solutions at temperatures as 

low as 30oC (Deer and others, 1962). Therefore, it cannot be 

determined whether the gibbsite was transported into the system 

from an outside source, formed in situ by alteration of other 

minerals, or precipitated as a more kinetically favorable form 

of Al hydroxide than diaspore (which had positive SIs for all 

ground-water compositions except those with at 50oC).

The PHREEQC models did not include simulation of the 

co-precipitation of elements such as As and Zn with—or their 

sorption onto—precipitating minerals. Therefore, the chemical 

compositions determined during laboratory analysis of mineral 

precipitates from the Authority’s distribution system may 

include larger quantities of these elements than were simulated 

during modeling.

PHREEQC can be used to estimate the likely quantity 

of solid phases that could precipitate from or be dissolved by 

a simulated solution. For each mineral listed in table 6, the 

maximum quantity that could potentially precipitate or dissolve 

per kilogram (kg) of water was estimated for all the groundwater compositions that had been simulated to represent partial 

equilibration with atmospheric conditions (without a temperature 

change). This was done by designing individual simulations for 

each mineral that allowed that mineral to come to equilibrium 

with its solution. The simulations indicated that most minerals 

could potentially form about 1x10-3 to 2x10-2 mg of precipitate 

per kg of water. These quantities apply to all of the minerals 

containing heavy metals in their structures. Calcite, aragonite, 

and chalcedony could potentially form as much as about 1 to 60 

mg of precipitate per kg of water. Calcite showed the potential 

to form the largest quantities of precipitate, ranging from about 

10 to 60 mg with a median of about 20 mg per kg of water; only 

one ground-water composition showed the potential to dissolve 

calcite. Given 20 mg of precipitate per kg of water at about 

23oC, calcite could form up to about 6 cubic feet of precipitate 

per filling of a 6-million-gallon-capacity reservoir, covering a 

floor 150 feet in diameter to a depth of about 0.0045 inches. At 

about 50 mg of precipitate per kg of water heated to 50oC, calcite 

could form up to about 0.22 cubic inches of precipitate per filling 

of a 50-gallon-capacity water heater, covering a floor 1.5 feet 

in diameter to a depth of about 0.0008 inches. The estimated 

quantities of precipitate for these ground-water compositions 

can be compared with the estimated quantities for surface-water 

compositions to determine whether those quantities might 

change substantially when the source of water delivered through 

the distribution system changes.

Corrosion Indices

Corrosion indices were calculated for the ground-water 

compositions resulting when samples from table 1 were simulated to have a log pCO2

 of -3.0 and a log pO2 of -5.0 (representing partial equilibration with atmospheric conditions). The LSIs 

(table 7) for the ground-water compositions vary from -0.6 to 

0.5, with only the value for water pumped from Leavitt 2 being 

less than 0. These values are consistent with PHREEQC simulations of the same ground-water compositions (table 6), which 

show calcite being above saturation for all compositions except 

the one derived from Leavitt 2 water. Based on the calculated 

LSIs and the simulated calcite SIs, ground water delivered 

through the Authority’s current distribution system would tend 

to precipitate a protective coating of calcite and, therefore, is 

typically non-corrosive. LKIs for the ground-water compositions 

range from 0.4 to 1.1, which is consistent with the LSIs, indicating that the ground-water samples are typically non-corrosive. 

RSIs range from 7.2 to 9.4; two ground-water compositions have 

values greater than 8.0, indicating moderate corrosion potential. 

These corrosion indices can be compared with the ones calculated for surface water to determine whether there might be a 

substantial change in corrosivity when the source of water delivered through the Authority’s distribution system changes. Higher 

corrosivity would generally be associated with a higher tendency 

for mineral dissolution and oxidation of metals to adversely 

affect the quality and aesthetic characteristics of delivered water.
Mineral Precipitates in the Current Distribution System 23

Table 7. Corrosion indices calculated for selected ground-water compositions, surface-water compositions, and ground-water/

surface-water mixtures.

[For ground water, calculations are for compositions modeled to represent partial equilibration with atmospheric conditions. For surface water, calculations are for compositions modeled to have undergone treatment at the water treatment plant. For ground-water/surface-water mixtures, calculations are for 

mixtures of these compositions in the ratios shown. Calcite SI, calcite saturation index calculated with PHREEQC; LSI, Langelier Saturation Index; LKI, 

Larson-Skold Index; RSI, Ryznar Stability Index]

Sample source (from tables 1 and 2) Calcite SI LSI LKI RSI

Charles 2 0.30 0.1 0.4 7.9

Duranes 6 0.68 0.5 0.6 7.3

Leavitt 2 -0.35 -0.6 0.6 9.4

Love 5 0.34 0.1 0.5 7.8

Miles 1 0.31 0.1 0.9 7.9

Ridgecrest 1 0.67 0.5 0.4 7.3

Thomas 6 0.65 0.5 0.9 7.2

Vol Andia 3 0.24 0.0 0.7 8.0

Walker 2 0.65 0.5 1.1 7.3

Zamora 1 0.23 0.0 0.5 8.2

Rio Grande at Albuquerque 8/16/1971 0.30 0.2 3.5 7.6

Rio Grande at Albuquerque 5/3/1982 -0.20 -0.3 2.5 8.7

Rio Grande at Albuquerque 7/15/1986 -0.36 -0.5 2.1 9.1

Rio Grande at Albuquerque 11/7/1986 -0.13 -0.3 2.2 8.6

Rio Grande at Albuquerque 2/3/1987 -0.21 -0.4 2.2 8.8

Rio Grande at Albuquerque 5/11/1988 -0.01 -0.1 2.6 8.3

Rio Grande at Albuquerque 11/7/1988 0.14 -0.0 2.2 8.0

Rio Grande at Albuquerque 8/22/1995 0.05 -0.1 2.1 8.1

Mixture of Charles 2 with Rio Grande at Albuquerque 8/16/1971, ratio 1:9 0.30 0.2 3.1 7.6

Mixture of Charles 2 with Rio Grande at Albuquerque 5/3/1982, ratio 1:9 -0.13 -0.3 2.1 8.6

Mixture of Charles 2 with Rio Grande at Albuquerque 7/15/1986, ratio 1:9 -0.28 -0.5 1.8 8.9

Mixture of Charles 2 with Rio Grande at Albuquerque 11/7/1986, ratio 1:9 -0.08 -0.3 1.9 8.6

Mixture of Charles 2 with Rio Grande at Albuquerque 2/3/1987, ratio 1:9 -0.15 -0.4 1.9 8.7

Mixture of Charles 2 with Rio Grande at Albuquerque 5/11/1988, ratio 1:9 0.03 -0.1 2.3 8.2

Mixture of Charles 2 with Rio Grande at Albuquerque 11/7/1988, ratio 1:9 0.16 -0.0 2.0 8.0

Mixture of Charles 2 with Rio Grande at Albuquerque 8/22/1995, ratio 1:9 0.08 -0.1 1.9 8.1

Mixture of Charles 2 with Rio Grande at Albuquerque 8/16/1971, ratio 9:1 0.30 0.1 0.7 7.9

Mixture of Charles 2 with Rio Grande at Albuquerque 5/3/1982, ratio 9:1 0.25 0.0 0.6 8.0

Mixture of Charles 2 with Rio Grande at Albuquerque 7/15/1986, ratio 9:1 0.24 0.0 0.5 8.0

Mixture of Charles 2 with Rio Grande at Albuquerque 11/7/1986, ratio 9:1 0.26 0.0 0.6 8.0

Mixture of Charles 2 with Rio Grande at Albuquerque 2/3/1987, ratio 9:1 0.25 0.0 0.6 8.0

Mixture of Charles 2 with Rio Grande at Albuquerque 5/11/1988, ratio 9:1 0.27 0.1 0.6 8.0

Mixture of Charles 2 with Rio Grande at Albuquerque 11/7/1988, ratio 9:1 0.28 0.1 0.6 7.9

Mixture of Charles 2 with Rio Grande at Albuquerque 8/22/1995, ratio 9:1 0.27 0.1 0.6 7.9

Mixture of Duranes 6 with Rio Grande at Albuquerque 8/16/1971, ratio 1:9 0.35 0.2 2.9 7.5

Mixture of Duranes 6 with Rio Grande at Albuquerque 5/3/1982, ratio 1:9 -0.07 -0.2 2.0 8.5

Mixture of Duranes 6 with Rio Grande at Albuquerque 7/15/1986, ratio 1:9 -0.21 -0.4 1.7 8.8

Mixture of Duranes 6 with Rio Grande at Albuquerque 11/7/1986, ratio 1:9 -0.03 -0.2 1.8 8.5

Mixture of Duranes 6 with Rio Grande at Albuquerque 2/3/1987, ratio 1:9 -0.10 -0.3 1.8 8.7

Mixture of Duranes 6 with Rio Grande at Albuquerque 5/11/1988, ratio 1:9 0.08 -0.1 2.2 8.1

Mixture of Duranes 6 with Rio Grande at Albuquerque 11/7/1988, ratio 1:9 0.20 0.0 1.9 7.9

Mixture of Duranes 6 with Rio Grande at Albuquerque 8/22/1995, ratio 1:9 0.13 -0.0 1.8 8.0
24 Potential Chemical Effects of Changes in the Source of Water Supply

Table 7. Corrosion indices calculated for selected ground-water compositions, surface-water compositions, and ground-water/

surface-water mixtures.—Continued

Sample source (from tables 1 and 2) Calcite SI LSI LKI RSI

Mixture of Duranes 6 with Rio Grande at Albuquerque 8/16/1971, ratio 9:1 0.64 0.4 0.8 7.3

Mixture of Duranes 6 with Rio Grande at Albuquerque 5/3/1982, ratio 9:1 0.61 0.4 0.7 7.4

Mixture of Duranes 6 with Rio Grande at Albuquerque 7/15/1986, ratio 9:1 0.60 0.4 0.7 7.4

Mixture of Duranes 6 with Rio Grande at Albuquerque 11/7/1986, ratio 9:1 0.61 0.4 0.7 7.4

Mixture of Duranes 6 with Rio Grande at Albuquerque 2/3/1987, ratio 9:1 0.61 0.4 0.7 7.4

Mixture of Duranes 6 with Rio Grande at Albuquerque 5/11/1988, ratio 9:1 0.62 0.4 0.7 7.4

Mixture of Duranes 6 with Rio Grande at Albuquerque 11/7/1988, ratio 9:1 0.62 0.4 0.7 7.4

Mixture of Duranes 6 with Rio Grande at Albuquerque 8/22/1995, ratio 9:1 0.62 0.4 0.7 7.4

Mixture of Leavitt 2 with Rio Grande at Albuquerque 8/16/1971, ratio 1:9 0.31 0.2 2.9 7.5

Mixture of Leavitt 2 with Rio Grande at Albuquerque 5/3/1982, ratio 1:9 -0.13 -0.2 2.0 8.5

Mixture of Leavitt 2 with Rio Grande at Albuquerque 7/15/1986, ratio 1:9 -0.28 -0.4 1.7 8.8

Mixture of Leavitt 2 with Rio Grande at Albuquerque 11/7/1986, ratio 1:9 -0.08 -0.2 1.8 8.5

Mixture of Leavitt 2 with Rio Grande at Albuquerque 2/3/1987, ratio 1:9 -0.15 -0.3 1.8 8.7

Mixture of Leavitt 2 with Rio Grande at Albuquerque 5/11/1988, ratio 1:9 0.03 -0.1 2.2 8.1

Mixture of Leavitt 2 with Rio Grande at Albuquerque 11/7/1988, ratio 1:9 0.16 0.0 1.9 7.9

Mixture of Leavitt 2 with Rio Grande at Albuquerque 8/22/1995, ratio 1:9 0.08 -0.0 1.8 8.0

Mixture of Leavitt 2 with Rio Grande at Albuquerque 8/16/1971, ratio 9:1 0.01 -0.2 0.8 8.6

Mixture of Leavitt 2 with Rio Grande at Albuquerque 5/3/1982, ratio 9:1 -0.14 -0.3 0.7 8.9

Mixture of Leavitt 2 with Rio Grande at Albuquerque 7/15/1986, ratio 9:1 -0.19 -0.4 0.7 9.0

Mixture of Leavitt 2 with Rio Grande at Albuquerque 11/7/1986, ratio 9:1 -0.12 -0.3 0.7 8.8

Mixture of Leavitt 2 with Rio Grande at Albuquerque 2/3/1987, ratio 9:1 -0.14 -0.3 0.7 8.9

Mixture of Leavitt 2 with Rio Grande at Albuquerque 5/11/1988, ratio 9:1 -0.11 -0.3 0.7 8.8

Mixture of Leavitt 2 with Rio Grande at Albuquerque 11/7/1988, ratio 9:1 -0.06 -0.3 0.7 8.7

Mixture of Leavitt 2 with Rio Grande at Albuquerque 8/22/1995, ratio 9:1 -0.12 -0.3 0.7 8.8

Chemical Modeling of Surface Water 

and Ground-Water/Surface-Water 

Mixtures

As described in the section “Analysis of Modeling 

Results,” chemical modeling was conducted for both surfacewater compositions and ground-water/surface-water mixtures to 

determine the SIs of selected solid phases relative to the SIs of 

the same minerals for the ground-water compositions. Surfacewater compositions used for mixing and for direct comparisons 

with ground-water compositions were the compositions that 

resulted from the simulation of surface-water treatment as 

described in the section “Range of Physical and Chemical Conditions Modeled.”

Surface Water

Similar to the modeling results for ground water, the modeling results for surface water indicated that nearly all of the 

minerals of table 3 had an SI greater than 0.1 for at least one 

of the simulated surface-water compositions. The exceptions 

were analbite, analcime, diopside, huntite, magnesite, sepiolite, 

and willemite. The mineral Fe3(OH)8 had an SI greater than 0.1 

for several surface-water compositions, but no ground-water 

compositions. For the surface-water compositions, the SIs 

of selected minerals from table 3 with favorable or uncertain 

reaction kinetics for formation are shown in table 8.

For some of the solid phases listed in table 8, several 

ground-water compositions have SIs greater than 0.1 and only 

about half or fewer of the simulated surface-water compositions have SIs greater than 0.1. These minerals are aragonite, 

calcite, and chalcedony. Because the SIs of these minerals are 

positive for several ground-water compositions but negative 

for several surface-water compositions, there is a reasonable 

likelihood that a switch to delivery of surface water will result 

in dissolution of these minerals where they have already been 

deposited in the distribution system by ground water. However, 

of these minerals, only aragonite and calcite have actually 

been identified in samples of mineral precipitate from the 

Authority’s distribution system. Laboratory analysis indicated 

that the metal content of mineral samples with a high portion of 

calcite tended to be relatively low, with the notable exception 

of relatively high Zn content. Therefore, the dissolution of 

these minerals would probably result primarily in an increase 

in water hardness and perhaps in the Zn concentration of 

delivered water. Despite having no positive SIs for the
Table 8. Saturation indices for selected minerals, as calculated by PHREEQC for selected surface-water compositions.[All results are for surface-water samples simulated to have undergone treatment at the proposed treatment plant. deg. C, degrees Celsius]

Sample source (from table 2)

Simulated 

temperature 

(deg. C) pH aragonite birnessite calcite chalcedony

cupric 

ferrite

cuprous 

ferrite diaspor

Rio Grande at Albuquerque 8/16/1971 unaltered 8.00 0.16 6.15 0.30 -0.01 19.05 6.53 1.29 Rio Grande at Albuquerque 5/3/1982 unaltered 8.00 -0.34 8.71 -0.20 -0.10 18.06 5.52 1.51 Rio Grande at Albuquerque 7/15/1986 unaltered 8.00 -0.51 9.86 -0.36 -0.04 17.60 5.06 1.38 Rio Grande at Albuquerque 11/7/1986 unaltered 8.00 -0.29 10.22 -0.13 0.07 17.43 4.89 1.30 Rio Grande at Albuquerque 2/3/1987 unaltered 8.00 -0.37 11.26 -0.21 0.12 17.00 4.46 1.07 Rio Grande at Albuquerque 5/11/1988 unaltered 8.00 -0.15 7.36 -0.01 -0.14 18.59 6.06 1.47 Rio Grande at Albuquerque 11/7/1988 unaltered 8.00 0.00 8.44 0.14 0.00 18.43 5.90 1.51 Rio Grande at Albuquerque 8/22/1995 unaltered 8.00 -0.09 6.72 0.05 -0.16 18.93 6.40 1.96 Rio Grande at Albuquerque 8/16/1971 2.0 8.02 -0.18 12.08 -0.01 0.28 16.66 4.11 0.87 Rio Grande at Albuquerque 5/3/1982 2.0 8.00 -0.55 12.09 -0.38 0.07 16.68 4.13 0.87 Rio Grande at Albuquerque 7/15/1986 2.0 8.00 -0.65 12.10 -0.48 0.07 16.69 4.14 0.87 Rio Grande at Albuquerque 11/7/1986 2.0 8.00 -0.40 12.07 -0.23 0.16 16.67 4.13 0.87 Rio Grande at Albuquerque 2/3/1987 2.0 8.00 -0.42 12.07 -0.25 0.16 16.67 4.13 0.87 Rio Grande at Albuquerque 5/11/1988 2.0 8.01 -0.43 12.09 -0.26 0.09 16.67 4.12 0.87 Rio Grande at Albuquerque 11/7/1988 2.0 8.01 -0.22 12.07 -0.05 0.18 16.96 4.41 0.87 Rio Grande at Albuquerque 8/22/1995 2.0 8.01 -0.42 12.29 -0.25 0.12 16.67 4.12 1.48 Rio Grande at Albuquerque 8/16/1971 50.0 7.93 0.40 0.77 0.56 -0.28 21.16 8.66 0.32 Rio Grande at Albuquerque 5/3/1982 50.0 7.94 0.08 0.84 0.24 -0.49 21.20 8.70 0.31 Rio Grande at Albuquerque 7/15/1986 50.0 7.95 -0.01 0.85 0.15 -0.49 21.21 8.71 0.31 Rio Grande at Albuquerque 11/7/1986 50.0 7.93 0.21 0.81 0.38 -0.40 21.18 8.69 0.32 Rio Grande at Albuquerque 2/3/1987 50.0 7.93 0.20 0.81 0.36 -0.40 21.18 8.69 0.32 Rio Grande at Albuquerque 5/11/1988 50.0 7.94 0.18 0.82 0.35 -0.46 21.18 8.69 0.31 Rio Grande at Albuquerque 11/7/1988 50.0 7.92 0.37 0.78 0.54 -0.38 21.45 8.96 0.33 Rio Grande at Albuquerque 8/22/1995 50.0 7.94 0.19 1.01 0.36 -0.44 21.18 8.68 0.91 
Table 8. Saturation indices for selected minerals, as calculated by PHREEQC for selected surface-water compositions.—Continued Sample source (from table 2) Simulated temperature (deg. C) ferrihydrite goethite hematite huntite lepido- crocite maghemite manganite Mg-fe

Rio Grande at Albuquerque 8/16/1971 unaltered 4.49 8.90 22.81 -4.95 8.01 12.38 3.86 14.4Rio Grande at Albuquerque 5/3/1982 unaltered 4.50 8.52 22.00 -7.06 8.02 12.39 5.53 12.5

Rio Grande at Albuquerque 7/15/1986 unaltered 4.50 8.35 21.64 -8.08 8.02 12.40 6.28 11.6Rio Grande at Albuquerque 11/7/1986 unaltered 4.50 8.29 21.50 -7.24 8.02 12.39 6.50 11.5Rio Grande at Albuquerque 2/3/1987 unaltered 4.50 8.13 21.16 -7.73 8.02 12.39 7.17 10.7Rio Grande at Albuquerque 5/11/1988 unaltered 4.50 8.73 22.44 -5.87 8.02 12.39 4.65 13.6Rio Grande at Albuquerque 11/7/1988 unaltered 4.50 8.56 22.08 -5.62 8.02 12.39 5.35 12.8Rio Grande at Albuquerque 8/22/1995 unaltered 4.50 8.85 22.71 -5.44 8.02 12.39 4.31 14.2Rio Grande at Albuquerque 8/16/1971 2.0 4.49 8.00 20.88 -7.45 8.01 12.38 7.69 10.3Rio Grande at Albuquerque 5/3/1982 2.0 4.50 8.00 20.90 -8.60 8.02 12.40 7.70 10.2Rio Grande at Albuquerque 7/15/1986 2.0 4.50 8.01 20.90 -9.12 8.02 12.40 7.71 10.Rio Grande at Albuquerque 11/7/1986 2.0 4.50 8.00 20.90 -8.10 8.02 12.39 7.69 10.2Rio Grande at Albuquerque 2/3/1987 2.0 4.50 8.00 20.90 -8.11 8.02 12.39 7.69 10.2Rio Grande at Albuquerque 5/11/1988 2.0 4.50 8.00 20.89 -7.96 8.02 12.39 7.69 10.3Rio Grande at Albuquerque 11/7/1988 2.0 4.50 8.00 20.89 -7.24 8.02 12.39 7.68 10.3Rio Grande at Albuquerque 8/22/1995 2.0 4.50 8.00 20.90 -7.86 8.02 12.39 7.89 10.3Rio Grande at Albuquerque 8/16/1971 50.0 4.49 9.70 24.52 -3.32 8.01 12.38 0.35 17.9Rio Grande at Albuquerque 5/3/1982 50.0 4.50 9.71 24.54 -4.27 8.02 12.39 0.42 17.9Rio Grande at Albuquerque 7/15/1986 50.0 4.50 9.71 24.54 -4.76 8.02 12.40 0.44 17.8Rio Grande at Albuquerque 11/7/1986 50.0 4.50 9.71 24.53 -3.82 8.02 12.39 0.40 17.9Rio Grande at Albuquerque 2/3/1987 50.0 4.50 9.71 24.53 -3.82 8.02 12.39 0.41 17.9Rio Grande at Albuquerque 5/11/1988 50.0 4.50 9.71 24.53 -3.68 8.02 12.39 0.40 18.0Rio Grande at Albuquerque 11/7/1988 50.0 4.49 9.71 24.53 -3.04 8.01 12.38 0.37 18.0Rio Grande at Albuquerque 8/22/1995 50.0 4.50 9.71 24.53 -3.58 8.02 12.39 0.59 18.0
ground-water compositions, rhodochrosite and gibbsite 

were identified among mineral-precipitate samples from the 

Authority’s current distribution system. Negative SIs for these 

same minerals for the surface-water compositions indicate 

that surface water would tend to dissolve these minerals, 

where present.

The one mineral from table 8 that has positive SIs for most 

surface-water compositions but negative SIs for most groundwater compositions is Fe3

(OH)8. If formation of this mineral is 

kinetically favorable, it could precipitate during delivery of surface water through the Authority’s distribution system and subsequently dissolve when the primary source of water reverted 

to ground water during periods of high demand or drought. The 

resulting release of Fe into solution could adversely affect water 

color and taste. The modeling also indicates that at temperatures such as those found in residential water heaters some Mn 

oxides including birnessite and nsutite would tend to precipitate from surface water but tend to be dissolved by ground 

water. A change in water source from surface water to ground 

water could therefore result in the release of Mn into solution, 

potentially affecting the aesthetic characteristics of the water. 

Modeling indicates that ground-water compositions also could 

potentially dissolve Mn oxides even at lower temperatures if the 

less-oxygenated water from some wells did not become well 

enough equilibrated with atmospheric conditions to cause the 

SIs of the Mn oxides to be greater than 0 ± 0.1.

As was done for the ground-water compositions, 

PHREEQC was used to estimate the likely quantity of mineral 

that would precipitate from or be dissolved by the simulated 

surface-water compositions. For each mineral listed in table 

6, the maximum quantity that could potentially precipitate or 

dissolve per kilogram (kg) of water was estimated for all the 

surface-water compositions that had been simulated to undergo 

treatment at the treatment plant. Similar to the results for ground 

water, the simulations indicated that several minerals could 

potentially form about 5x10-3 to 1x10-2 mg of precipitate per 

kg of water. These were mostly the minerals containing Al, 

Cu, Mn, or Zn. Simulations involving calcite, aragonite, and 

chalcedony indicated that they could potentially form as much 

as about 1 to 10 mg of precipitate per kg of water for compositions with positive SIs, or dissolve as much as about 1 to 10 mg 

of mineral per kg of water for compositions with negative SIs. 

In contrast to ground water, most of the Fe-containing minerals 

showed the potential to form about the same magnitude of precipitate as calcite and aragonite, or about 3 orders of magnitude 

more Fe-containing precipitate than would form from ground 

water. The Fe-containing minerals could potentially form about 

15 to 25 mg of precipitate per kg of water. Chemical modeling 

indicated that the relatively large potential quantity of Fe precipitates is a result of the addition of ferric chloride for coagulation 

during surface-water treatment. If such a large increase in the 

quantity of Fe-containing precipitates forming in the distribution system did occur during surface-water delivery, the ability 

of the distribution system to convey water could potentially be 

reduced over time in some areas by a reduction in the effective 

cross-sectional areas of the conveyance pipes. However, even 

at about 30 mg of precipitate per kg of water, hematite would 

form no more than 5 cubic feet of precipitate per filling of a 

6-million-gallon-capacity reservoir, covering a floor 150 feet in 

diameter to a depth of about 0.0037 inches.

Surface-water compositions simulated to have undergone 

treatment at the water-treatment plant were used to calculate 

corrosion indices for comparison with those calculated for 

ground water (table 7). Dissolved-solids concentrations used 

in the calculation of the LSIs and RSIs for the surface-water 

compositions were estimated using the results of the PHREEQC 

simulations (as opposed to the use of laboratory reported 

dissolved-solids concentrations for the ground-water compositions). In some cases, these estimated dissolved-solids concentrations may be slightly less than the values that would be measured in a laboratory because not all constituents are modeled in 

the PHREEQC simulations; however, any differences between 

estimated and measured dissolved-solids concentrations 

would have a fairly small effect on the calculated values of the 

corrosion indices. Two of the indices (LSI and RSI) had a larger 

range for ground water than they did for surface water. The LSIs 

for the surface-water compositions varied from -0.5 to 0.2, with 

all but two values being negative. These indices indicate that 

most of the surface-water compositions would be considered 

mildly corrosive—slightly more corrosive than most groundwater compositions. Calcite SIs are negative for 5 of the 8 

surface-water compositions after simulation of water treatment, 

which is generally consistent with the LSI results (table 7). LKIs 

for the surface-water compositions range from 2.1 to 3.5, and 

RSIs range from 7.6 to 9.1. Both of these indices indicate that 

most or all of the surface-water compositions could be mildly 

to moderately corrosive. Overall, the corrosion indices appear 

to indicate that surface water could generally be slightly more 

corrosive than the ground water currently delivered through the 

Authority’s distribution system. However, model simulations 

indicate that only a relatively small quantity of calcite might be 

dissolved by any of these surface-water compositions before 

the water reached equilibrium with calcite. As a result, calcite 

dissolution might not be sufficient to expose existing pipes to 

substantially increased corrosion.

Ground-Water/Surface-Water Mixtures

In PHREEQC simulations, each treated surface-water 

composition was mixed individually with each of the groundwater compositions that had been simulated to represent partial 

equilibration with atmospheric conditions. For minerals with a 

reasonable potential to form, the SIs that resulted from selected 

mixtures of the solutions in ratios of 9 to 1 and 1 to 9 are shown 

in table 9 (results are not shown for all 160 mixtures). As might 

be expected, the mixtures have positive SIs for most of the same 

minerals that the individual ground-water and surface-water compositions do, generally reflecting most closely the water source 

that makes up 90 percent of the mixture. In particular, mixtures 

that are mostly surface water tend to show no substantial differences from surface-water compositions in terms of the minerals 

that have mostly positive or mostly negative SIs (tables 8 and 9).

Chemical Modeling of Surface Water and Ground-Water/Surface-Water Mixtures 27
Table 9. Saturation indices for selected minerals, as calculated by PHREEQC for selected ground-water/surface-water mixtures. [All mixtures incorporate ground-water samples simulated to be in partial equilibrium with atmospheric conditions and surface-water samples simulated to have undergone treatplant. deg. C, degrees Celsius] Ground-water sample source (from table 1) Surface-water sample source (from table 2) Simulated ratio of ground water to surface water Simulated temperature (deg. C) pH aragonite birnessite calcite chalcedony 

Charles 2 Rio Grande at Albuquerque 8/16/1971 1:9 unaltered 8.00 0.16 6.26 0.30 0.00 Charles 2 Rio Grande at Albuquerque 5/3/1982 1:9 unaltered 8.00 -0.28 8.57 -0.13 -0.07 Charles 2 Rio Grande at Albuquerque 7/15/1986 1:9 unaltered 8.00 -0.43 9.60 -0.28 -0.02 Charles 2 Rio Grande at Albuquerque 11/7/1986 1:9 unaltered 8.00 -0.24 9.92 -0.08 0.07 Charles 2 Rio Grande at Albuquerque 2/3/1987 1:9 unaltered 8.00 -0.31 10.85 -0.15 0.12 Charles 2 Rio Grande at Albuquerque 5/11/1988 1:9 unaltered 8.00 -0.11 7.36 0.03 -0.11 Charles 2 Rio Grande at Albuquerque 11/7/1988 1:9 unaltered 8.00 0.01 8.32 0.16 0.01 Charles 2 Rio Grande at Albuquerque 8/22/1995 1:9 unaltered 8.00 -0.06 6.79 0.08 -0.13 Charles 2 Rio Grande at Albuquerque 8/16/1971 9:1 unaltered 8.06 0.16 6.80 0.30 0.09 Charles 2 Rio Grande at Albuquerque 5/3/1982 9:1 unaltered 8.06 0.11 7.05 0.25 0.09 Charles 2 Rio Grande at Albuquerque 7/15/1986 9:1 unaltered 8.07 0.10 7.16 0.24 0.09 Charles 2 Rio Grande at Albuquerque 11/7/1986 9:1 unaltered 8.07 0.11 7.19 0.26 0.10 Charles 2 Rio Grande at Albuquerque 2/3/1987 9:1 unaltered 8.07 0.11 7.28 0.25 0.11 Charles 2 Rio Grande at Albuquerque 5/11/1988 9:1 unaltered 8.06 0.13 6.92 0.27 0.08 Charles 2 Rio Grande at Albuquerque 11/7/1988 9:1 unaltered 8.06 0.14 7.02 0.28 0.09 Charles 2 Rio Grande at Albuquerque 8/22/1995 9:1 unaltered 8.06 0.13 6.90 0.27 0.08 Charles 2 Rio Grande at Albuquerque 8/16/1971 1:9 2.0 8.03 -0.16 12.04 0.01 0.28 Charles 2 Rio Grande at Albuquerque 5/3/1982 1:9 2.0 8.01 -0.49 12.05 -0.32 0.10 Charles 2 Rio Grande at Albuquerque 7/15/1986 1:9 2.0 8.01 -0.58 12.05 -0.41 0.10 Charles 2 Rio Grande at Albuquerque 11/7/1986 1:9 2.0 8.00 -0.37 12.03 -0.20 0.18 Charles 2 Rio Grande at Albuquerque 2/3/1987 1:9 2.0 8.00 -0.38 12.03 -0.21 0.18 Charles 2 Rio Grande at Albuquerque 5/11/1988 1:9 2.0 8.01 -0.39 12.04 -0.22 0.12 Charles 2 Rio Grande at Albuquerque 11/7/1988 1:9 2.0 8.01 -0.21 12.03 -0.04 0.19 Charles 2 Rio Grande at Albuquerque 8/22/1995 1:9 2.0 8.02 -0.38 12.24 -0.22 0.14 Charles 2 Rio Grande at Albuquerque 8/16/1971 1:9 50.0 7.92 0.41 0.72 0.57 -0.27 Charles 2 Rio Grande at Albuquerque 5/3/1982 1:9 50.0 7.94 0.13 0.79 0.29 -0.46 Charles 2 Rio Grande at Albuquerque 7/15/1986 1:9 50.0 7.94 0.05 0.81 0.21 -0.46 Charles 2 Rio Grande at Albuquerque 11/7/1986 1:9 50.0 7.93 0.24 0.77 0.41 -0.38 Charles 2 Rio Grande at Albuquerque 2/3/1987 1:9 50.0 7.93 0.23 0.77 0.39 -0.38 Charles 2 Rio Grande at Albuquerque 5/11/1988 1:9 50.0 7.94 0.22 0.77 0.38 -0.44 Charles 2 Rio Grande at Albuquerque 11/7/1988 1:9 50.0 7.92 0.38 0.74 0.55 -0.36 Charles 2 Rio Grande at Albuquerque 8/22/1995 1:9 50.0 7.94 0.22 0.96 0.39 -0.42 
Table 9. Saturation indices for selected minerals, as calculated by PHREEQC for selected ground-water/surface-water mixtures.—Continued

Ground-water sample 

source (from table 1) Surface-water sample source (from table 2)

Simulated ratio of 

ground water to 

surface water

Simulated 

temperature 

(deg. C) pH aragonite birnessite calcite chalcedony

Duranes 6 Rio Grande at Albuquerque 8/16/1971 1:9 unaltered 8.01 0.21 6.30 0.35 0.05 Duranes 6 Rio Grande at Albuquerque 5/3/1982 1:9 unaltered 8.02 -0.22 8.62 -0.07 0.01 Duranes 6 Rio Grande at Albuquerque 7/15/1986 1:9 unaltered 8.02 -0.36 9.65 -0.21 0.06 Duranes 6 Rio Grande at Albuquerque 11/7/1986 1:9 unaltered 8.02 -0.18 9.97 -0.03 0.14 Duranes 6 Rio Grande at Albuquerque 2/3/1987 1:9 unaltered 8.02 -0.25 10.90 -0.10 0.19 Duranes 6 Rio Grande at Albuquerque 5/11/1988 1:9 unaltered 8.02 -0.06 7.40 0.08 -0.03 Duranes 6 Rio Grande at Albuquerque 11/7/1988 1:9 unaltered 8.02 0.06 8.36 0.20 0.08 Duranes 6 Rio Grande at Albuquerque 8/22/1995 1:9 unaltered 8.02 -0.01 6.82 0.13 -0.06 Duranes 6 Rio Grande at Albuquerque 8/16/1971 9:1 unaltered 8.21 0.50 7.41 0.64 0.41 Duranes 6 Rio Grande at Albuquerque 5/3/1982 9:1 unaltered 8.22 0.47 7.68 0.61 0.42 Duranes 6 Rio Grande at Albuquerque 7/15/1986 9:1 unaltered 8.22 0.46 7.80 0.60 0.42 Duranes 6 Rio Grande at Albuquerque 11/7/1986 9:1 unaltered 8.22 0.47 7.82 0.61 0.43 Duranes 6 Rio Grande at Albuquerque 2/3/1987 9:1 unaltered 8.22 0.46 7.92 0.61 0.43 Duranes 6 Rio Grande at Albuquerque 5/11/1988 9:1 unaltered 8.21 0.48 7.54 0.62 0.41 Duranes 6 Rio Grande at Albuquerque 11/7/1988 9:1 unaltered 8.21 0.48 7.64 0.62 0.42 Duranes 6 Rio Grande at Albuquerque 8/22/1995 9:1 unaltered 8.21 0.48 7.49 0.62 0.41 Duranes 6 Rio Grande at Albuquerque 8/16/1971 9:1 2.0 8.34 0.36 12.16 0.53 0.64 Duranes 6 Rio Grande at Albuquerque 5/3/1982 9:1 2.0 8.35 0.33 12.16 0.50 0.63 Duranes 6 Rio Grande at Albuquerque 7/15/1986 9:1 2.0 8.35 0.33 12.16 0.50 0.63 Duranes 6 Rio Grande at Albuquerque 11/7/1986 9:1 2.0 8.34 0.34 12.15 0.51 0.63 Duranes 6 Rio Grande at Albuquerque 2/3/1987 9:1 2.0 8.34 0.34 12.14 0.51 0.63 Duranes 6 Rio Grande at Albuquerque 5/11/1988 9:1 2.0 8.34 0.34 12.16 0.51 0.63 Duranes 6 Rio Grande at Albuquerque 11/7/1988 9:1 2.0 8.34 0.35 12.14 0.52 0.63 Duranes 6 Rio Grande at Albuquerque 8/22/1995 9:1 2.0 8.35 0.34 12.19 0.51 0.63 Duranes 6 Rio Grande at Albuquerque 8/16/1971 9:1 50.0 7.96 0.65 0.37 0.82 0.08 Duranes 6 Rio Grande at Albuquerque 5/3/1982 9:1 50.0 7.97 0.63 0.38 0.79 0.07 Duranes 6 Rio Grande at Albuquerque 7/15/1986 9:1 50.0 7.97 0.63 0.38 0.79 0.07 Duranes 6 Rio Grande at Albuquerque 11/7/1986 9:1 50.0 7.97 0.64 0.37 0.80 0.08 Duranes 6 Rio Grande at Albuquerque 2/3/1987 9:1 50.0 7.97 0.64 0.37 0.80 0.08 Duranes 6 Rio Grande at Albuquerque 5/11/1988 9:1 50.0 7.97 0.64 0.38 0.80 0.07 Duranes 6 Rio Grande at Albuquerque 11/7/1988 9:1 50.0 7.96 0.65 0.37 0.81 0.08 Duranes 6 Rio Grande at Albuquerque 8/22/1995 9:1 50.0 7.97 0.64 0.42 0.80 0.07 
Table 9. Saturation indices for selected minerals, as calculated by PHREEQC for selected ground-water/surface-water mixtures.—Continued Ground-water sample source (from table 1) Surface-water sample source (from table 2) Simulated ratio of ground water to surface water Simulated temperature (deg. C) pH aragonite birnessite calcite chalcedon

Leavitt 2 Rio Grande at Albuquerque 8/16/1971 1:9 unaltered 8.01 0.17 6.15 0.31 -0.01 Leavitt 2 Rio Grande at Albuquerque 5/3/1982 1:9 unaltered 8.01 -0.27 8.46 -0.13 -0.08 Leavitt 2 Rio Grande at Albuquerque 7/15/1986 1:9 unaltered 8.01 -0.43 9.49 -0.28 -0.03 Leavitt 2 Rio Grande at Albuquerque 11/7/1986 1:9 unaltered 8.01 -0.23 9.81 -0.08 0.06 Leavitt 2 Rio Grande at Albuquerque 2/3/1987 1:9 unaltered 8.01 -0.31 10.74 -0.15 0.11 Leavitt 2 Rio Grande at Albuquerque 5/11/1988 1:9 unaltered 8.01 -0.11 7.25 0.03 -0.12 Leavitt 2 Rio Grande at Albuquerque 11/7/1988 1:9 unaltered 8.01 0.02 8.21 0.16 0.00 Leavitt 2 Rio Grande at Albuquerque 8/22/1995 1:9 unaltered 8.01 -0.06 6.69 0.08 -0.14 

Leavitt 2 Rio Grande at Albuquerque 8/16/1971 9:1 unaltered 8.18 -0.13 5.99 0.01 0.01 Leavitt 2 Rio Grande at Albuquerque 5/3/1982 9:1 unaltered 8.19 -0.28 6.26 -0.14 0.00 Leavitt 2 Rio Grande at Albuquerque 7/15/1986 9:1 unaltered 8.20 -0.33 6.37 -0.19 0.01 Leavitt 2 Rio Grande at Albuquerque 11/7/1986 9:1 unaltered 8.19 -0.26 6.39 -0.12 0.02 Leavitt 2 Rio Grande at Albuquerque 2/3/1987 9:1 unaltered 8.20 -0.28 6.48 -0.14 0.02 Leavitt 2 Rio Grande at Albuquerque 5/11/1988 9:1 unaltered 8.19 -0.25 6.12 -0.11 0.00 Leavitt 2 Rio Grande at Albuquerque 11/7/1988 9:1 unaltered 8.19 -0.19 6.22 -0.06 0.01 Leavitt 2 Rio Grande at Albuquerque 8/22/1995 9:1 unaltered 8.19 -0.26 6.11 -0.12 0.00 Leavitt 2 Rio Grande at Albuquerque 8/16/1971 1:9 2.0 8.03 -0.16 12.05 0.01 0.28 Leavitt 2 Rio Grande at Albuquerque 5/3/1982 1:9 2.0 8.01 -0.49 12.06 -0.32 0.10 Leavitt 2 Rio Grande at Albuquerque 7/15/1986 1:9 2.0 8.01 -0.59 12.07 -0.42 0.10 Leavitt 2 Rio Grande at Albuquerque 11/7/1986 1:9 2.0 8.01 -0.37 12.04 -0.20 0.17 Leavitt 2 Rio Grande at Albuquerque 2/3/1987 1:9 2.0 8.01 -0.39 12.04 -0.22 0.17 Leavitt 2 Rio Grande at Albuquerque 5/11/1988 1:9 2.0 8.02 -0.40 12.06 -0.23 0.12 Leavitt 2 Rio Grande at Albuquerque 11/7/1988 1:9 2.0 8.02 -0.21 12.04 -0.04 0.19 Leavitt 2 Rio Grande at Albuquerque 8/22/1995 1:9 2.0 8.02 -0.39 12.25 -0.22 0.14 Leavitt 2 Rio Grande at Albuquerque 8/16/1971 1:9 50.0 7.93 0.41 0.73 0.58 -0.28 Leavitt 2 Rio Grande at Albuquerque 5/3/1982 1:9 50.0 7.95 0.13 0.80 0.29 -0.46 Leavitt 2 Rio Grande at Albuquerque 7/15/1986 1:9 50.0 7.95 0.04 0.82 0.20 -0.46 Leavitt 2 Rio Grande at Albuquerque 11/7/1986 1:9 50.0 7.94 0.24 0.78 0.40 -0.38 Leavitt 2 Rio Grande at Albuquerque 2/3/1987 1:9 50.0 7.94 0.22 0.78 0.39 -0.38 Leavitt 2 Rio Grande at Albuquerque 5/11/1988 1:9 50.0 7.94 0.21 0.78 0.38 -0.44 Leavitt 2 Rio Grande at Albuquerque 11/7/1988 1:9 50.0 7.93 0.38 0.75 0.54 -0.37 Leavitt 2 Rio Grande at Albuquerque 8/22/1995 1:9 50.0 7.95 0.22 0.97 0.38 -0.42 
Table 9. Saturation indices for selected minerals, as calculated by PHREEQC for selected ground-water/surface-water mixtures.—Continued

Ground-water sample 

source (from table 1) Surface-water sample source (from table 2)

Simulated ratio of 

ground water to 

surface water

Simulated 

temperature 

(deg. C) Fe(OH)2.7Cl0.3 Fe3(OH)8 ferrihydrite goethite hematite 

Charles 2 Rio Grande at Albuquerque 8/16/1971 1:9 unaltered 9.12 0.17 4.45 8.83 22.67 Charles 2 Rio Grande at Albuquerque 5/3/1982 1:9 unaltered 9.03 -0.38 4.45 8.49 21.95 Charles 2 Rio Grande at Albuquerque 7/15/1986 1:9 unaltered 9.03 -0.62 4.46 8.34 21.62 Charles 2 Rio Grande at Albuquerque 11/7/1986 1:9 unaltered 9.06 -0.72 4.45 8.28 21.50 Charles 2 Rio Grande at Albuquerque 2/3/1987 1:9 unaltered 9.06 -0.95 4.45 8.14 21.19 Charles 2 Rio Grande at Albuquerque 5/11/1988 1:9 unaltered 9.06 -0.08 4.45 8.67 22.34 Charles 2 Rio Grande at Albuquerque 11/7/1988 1:9 unaltered 9.06 -0.33 4.45 8.52 22.01 Charles 2 Rio Grande at Albuquerque 8/22/1995 1:9 unaltered 9.04 0.11 4.45 8.79 22.58 Charles 2 Rio Grande at Albuquerque 8/16/1971 9:1 unaltered 8.00 -2.75 3.50 7.69 20.37 Charles 2 Rio Grande at Albuquerque 5/3/1982 9:1 unaltered 7.97 -2.81 3.50 7.66 20.29 Charles 2 Rio Grande at Albuquerque 7/15/1986 9:1 unaltered 7.97 -2.83 3.50 7.64 20.25 Charles 2 Rio Grande at Albuquerque 11/7/1986 9:1 unaltered 7.97 -2.84 3.50 7.63 20.24 Charles 2 Rio Grande at Albuquerque 2/3/1987 9:1 unaltered 7.97 -2.87 3.50 7.62 20.21 Charles 2 Rio Grande at Albuquerque 5/11/1988 9:1 unaltered 7.97 -2.78 3.50 7.68 20.33 Charles 2 Rio Grande at Albuquerque 11/7/1988 9:1 unaltered 7.98 -2.80 3.50 7.66 20.30 Charles 2 Rio Grande at Albuquerque 8/22/1995 9:1 unaltered 7.97 -2.76 3.50 7.69 20.36 Charles 2 Rio Grande at Albuquerque 8/16/1971 1:9 2.0 9.11 -1.28 4.45 7.95 20.79 Charles 2 Rio Grande at Albuquerque 5/3/1982 1:9 2.0 9.03 -1.25 4.45 7.96 20.81 Charles 2 Rio Grande at Albuquerque 7/15/1986 1:9 2.0 9.03 -1.24 4.46 7.96 20.81 Charles 2 Rio Grande at Albuquerque 11/7/1986 1:9 2.0 9.06 -1.25 4.45 7.96 20.81 Charles 2 Rio Grande at Albuquerque 2/3/1987 1:9 2.0 9.06 -1.24 4.45 7.96 20.81 Charles 2 Rio Grande at Albuquerque 5/11/1988 1:9 2.0 9.06 -1.26 4.45 7.96 20.80 Charles 2 Rio Grande at Albuquerque 11/7/1988 1:9 2.0 9.05 -1.26 4.45 7.95 20.80 Charles 2 Rio Grande at Albuquerque 8/22/1995 1:9 2.0 9.03 -1.26 4.45 7.96 20.80 Charles 2 Rio Grande at Albuquerque 8/16/1971 1:9 50.0 9.14 1.52 4.45 9.66 24.43 Charles 2 Rio Grande at Albuquerque 5/3/1982 1:9 50.0 9.05 1.54 4.45 9.67 24.45 Charles 2 Rio Grande at Albuquerque 7/15/1986 1:9 50.0 9.05 1.55 4.46 9.67 24.45 Charles 2 Rio Grande at Albuquerque 11/7/1986 1:9 50.0 9.08 1.54 4.45 9.66 24.44 Charles 2 Rio Grande at Albuquerque 2/3/1987 1:9 50.0 9.08 1.55 4.45 9.66 24.44 Charles 2 Rio Grande at Albuquerque 5/11/1988 1:9 50.0 9.08 1.53 4.45 9.66 24.44 Charles 2 Rio Grande at Albuquerque 11/7/1988 1:9 50.0 9.08 1.53 4.45 9.66 24.44 Charles 2 Rio Grande at Albuquerque 8/22/1995 1:9 50.0 9.06 1.54 4.45 9.66 24.44 
Table 9. Saturation indices for selected minerals, as calculated by PHREEQC for selected ground-water/surface-water mixtures.—Continued Ground-water sample source (from table 1) Surface-water sample source (from table 2)Simulated ratio of ground water to surface water Simulated temperature (deg. C) Fe(OH)2.7Cl0.3 Fe3(OH)8 ferrihydrite goethite hematite hu

Duranes 6 Rio Grande at Albuquerque 8/16/1971 1:9 unaltered 9.11 0.17 4.45 8.83 22.67 -Duranes 6 Rio Grande at Albuquerque 5/3/1982 1:9 unaltered 9.03 -0.38 4.45 8.49 21.94 -Duranes 6 Rio Grande at Albuquerque 7/15/1986 1:9 unaltered 9.02 -0.63 4.45 8.34 21.61 -Duranes 6 Rio Grande at Albuquerque 11/7/1986 1:9 unaltered 9.05 -0.72 4.45 8.28 21.50 -Duranes 6 Rio Grande at Albuquerque 2/3/1987 1:9 unaltered 9.06 -0.95 4.45 8.14 21.19 -Duranes 6 Rio Grande at Albuquerque 5/11/1988 1:9 unaltered 9.05 -0.09 4.45 8.67 22.33 -Duranes 6 Rio Grande at Albuquerque 11/7/1988 1:9 unaltered 9.05 -0.33 4.45 8.52 22.01 -Duranes 6 Rio Grande at Albuquerque 8/22/1995 1:9 unaltered 9.03 0.10 4.45 8.79 22.58 -Duranes 6 Rio Grande at Albuquerque 8/16/1971 9:1 unaltered 7.93 -2.86 3.46 7.66 20.30 -Duranes 6 Rio Grande at Albuquerque 5/3/1982 9:1 unaltered 7.90 -2.93 3.46 7.62 20.21 -Duranes 6 Rio Grande at Albuquerque 7/15/1986 9:1 unaltered 7.90 -2.96 3.46 7.60 20.17 -Duranes 6 Rio Grande at Albuquerque 11/7/1986 9:1 unaltered 7.91 -2.96 3.46 7.59 20.16 -Duranes 6 Rio Grande at Albuquerque 2/3/1987 9:1 unaltered 7.91 -2.99 3.46 7.58 20.13 -Duranes 6 Rio Grande at Albuquerque 5/11/1988 9:1 unaltered 7.91 -2.89 3.46 7.64 20.26 -Duranes 6 Rio Grande at Albuquerque 11/7/1988 9:1 unaltered 7.91 -2.92 3.46 7.62 20.22 -Duranes 6 Rio Grande at Albuquerque 8/22/1995 9:1 unaltered 7.91 -2.87 3.46 7.65 20.29 -Duranes 6 Rio Grande at Albuquerque 8/16/1971 9:1 2.0 7.83 -4.17 3.40 6.91 18.71 -Duranes 6 Rio Grande at Albuquerque 5/3/1982 9:1 2.0 7.81 -4.17 3.40 6.90 18.70 -Duranes 6 Rio Grande at Albuquerque 7/15/1986 9:1 2.0 7.81 -4.17 3.40 6.90 18.70 -Duranes 6 Rio Grande at Albuquerque 11/7/1986 9:1 2.0 7.82 -4.16 3.40 6.91 18.71 -Duranes 6 Rio Grande at Albuquerque 2/3/1987 9:1 2.0 7.82 -4.16 3.40 6.91 18.71 -Duranes 6 Rio Grande at Albuquerque 5/11/1988 9:1 2.0 7.81 -4.17 3.40 6.91 18.70 -Duranes 6 Rio Grande at Albuquerque 11/7/1988 9:1 2.0 7.82 -4.16 3.40 6.91 18.71 -Duranes 6 Rio Grande at Albuquerque 8/22/1995 9:1 2.0 7.81 -4.17 3.40 6.91 18.70 -Duranes 6 Rio Grande at Albuquerque 8/16/1971 9:1 50.0 8.05 -1.07 3.50 8.72 22.55 -Duranes 6 Rio Grande at Albuquerque 5/3/1982 9:1 50.0 8.02 -1.06 3.50 8.72 22.55 -Duranes 6 Rio Grande at Albuquerque 7/15/1986 9:1 50.0 8.02 -1.06 3.50 8.72 22.55 -Duranes 6 Rio Grande at Albuquerque 11/7/1986 9:1 50.0 8.03 -1.06 3.50 8.72 22.55 -Duranes 6 Rio Grande at Albuquerque 2/3/1987 9:1 50.0 8.03 -1.06 3.50 8.72 22.55 -Duranes 6 Rio Grande at Albuquerque 5/11/1988 9:1 50.0 8.03 -1.07 3.50 8.72 22.55 -Duranes 6 Rio Grande at Albuquerque 11/7/1988 9:1 50.0 8.03 -1.07 3.50 8.72 22.55 -Duranes 6 Rio Grande at Albuquerque 8/22/1995 9:1 50.0 8.02 -1.07 3.50 8.72 22.55 -
Table 9. Saturation indices for selected minerals, as calculated by PHREEQC for selected ground-water/surface-water mixtures.—Continued

Ground-water sample 

source (from table 1) Surface-water sample source (from table 2)

Simulated ratio of 

ground water to 

surface water

Simulated 

temperature 

(deg. C) Fe(OH)2.7Cl0.3 Fe3(OH)8 ferrihydrite goethite hematite 

Leavitt 2 Rio Grande at Albuquerque 8/16/1971 1:9 unaltered 9.12 0.19 4.45 8.85 22.71 Leavitt 2 Rio Grande at Albuquerque 5/3/1982 1:9 unaltered 9.03 -0.35 4.45 8.51 21.98 Leavitt 2 Rio Grande at Albuquerque 7/15/1986 1:9 unaltered 9.03 -0.59 4.46 8.36 21.66 Leavitt 2 Rio Grande at Albuquerque 11/7/1986 1:9 unaltered 9.06 -0.69 4.45 8.30 21.54 Leavitt 2 Rio Grande at Albuquerque 2/3/1987 1:9 unaltered 9.06 -0.92 4.45 8.16 21.23 Leavitt 2 Rio Grande at Albuquerque 5/11/1988 1:9 unaltered 9.06 -0.06 4.45 8.69 22.37 Leavitt 2 Rio Grande at Albuquerque 11/7/1988 1:9 unaltered 9.06 -0.30 4.45 8.54 22.05 Leavitt 2 Rio Grande at Albuquerque 8/22/1995 1:9 unaltered 9.04 0.13 4.45 8.81 22.62 Leavitt 2 Rio Grande at Albuquerque 8/16/1971 9:1 unaltered 7.97 -2.59 3.47 7.82 20.64 Leavitt 2 Rio Grande at Albuquerque 5/3/1982 9:1 unaltered 7.94 -2.66 3.46 7.78 20.56 Leavitt 2 Rio Grande at Albuquerque 7/15/1986 9:1 unaltered 7.94 -2.68 3.46 7.76 20.52 Leavitt 2 Rio Grande at Albuquerque 11/7/1986 9:1 unaltered 7.95 -2.69 3.46 7.76 20.51 Leavitt 2 Rio Grande at Albuquerque 2/3/1987 9:1 unaltered 7.95 -2.71 3.46 7.74 20.48 Leavitt 2 Rio Grande at Albuquerque 5/11/1988 9:1 unaltered 7.95 -2.62 3.46 7.80 20.60 Leavitt 2 Rio Grande at Albuquerque 11/7/1988 9:1 unaltered 7.95 -2.64 3.46 7.78 20.57 Leavitt 2 Rio Grande at Albuquerque 8/22/1995 9:1 unaltered 7.95 -2.60 3.46 7.81 20.63 Leavitt 2 Rio Grande at Albuquerque 8/16/1971 1:9 2.0 9.11 -1.28 4.45 7.95 20.79 Leavitt 2 Rio Grande at Albuquerque 5/3/1982 1:9 2.0 9.03 -1.25 4.45 7.96 20.81 Leavitt 2 Rio Grande at Albuquerque 7/15/1986 1:9 2.0 9.03 -1.24 4.46 7.96 20.81 Leavitt 2 Rio Grande at Albuquerque 11/7/1986 1:9 2.0 9.06 -1.25 4.45 7.96 20.80 Leavitt 2 Rio Grande at Albuquerque 2/3/1987 1:9 2.0 9.06 -1.25 4.45 7.96 20.81 Leavitt 2 Rio Grande at Albuquerque 5/11/1988 1:9 2.0 9.06 -1.26 4.45 7.95 20.80 Leavitt 2 Rio Grande at Albuquerque 11/7/1988 1:9 2.0 9.05 -1.26 4.45 7.95 20.80 Leavitt 2 Rio Grande at Albuquerque 8/22/1995 1:9 2.0 9.03 -1.26 4.45 7.96 20.80 Leavitt 2 Rio Grande at Albuquerque 8/16/1971 1:9 50.0 9.14 1.52 4.45 9.66 24.43 Leavitt 2 Rio Grande at Albuquerque 5/3/1982 1:9 50.0 9.05 1.54 4.45 9.67 24.45 Leavitt 2 Rio Grande at Albuquerque 7/15/1986 1:9 50.0 9.05 1.55 4.46 9.67 24.45 Leavitt 2 Rio Grande at Albuquerque 11/7/1986 1:9 50.0 9.08 1.54 4.45 9.66 24.44 Leavitt 2 Rio Grande at Albuquerque 2/3/1987 1:9 50.0 9.08 1.55 4.45 9.66 24.44 Leavitt 2 Rio Grande at Albuquerque 5/11/1988 1:9 50.0 9.08 1.54 4.45 9.66 24.44 Leavitt 2 Rio Grande at Albuquerque 11/7/1988 1:9 50.0 9.08 1.53 4.45 9.66 24.44 Leavitt 2 Rio Grande at Albuquerque 8/22/1995 1:9 50.0 9.06 1.54 4.45 9.66 24.44 
Table 9. Saturation indices for selected minerals, as calculated by PHREEQC for selected ground-water/surface-water mixtures.—Continued Ground-water sample source (from table 1) Surface-water sample source (from table 2) Simulated ratio of ground water to surface water Simulated temperature (deg. C) manganite Mg-ferrite nsutite py

Charles 2 Rio Grande at Albuquerque 8/16/1971 1:9 unaltered 3.93 14.20 6.85 Charles 2 Rio Grande at Albuquerque 5/3/1982 1:9 unaltered 5.44 12.56 9.16 Charles 2 Rio Grande at Albuquerque 7/15/1986 1:9 unaltered 6.11 11.74 10.19 Charles 2 Rio Grande at Albuquerque 11/7/1986 1:9 unaltered 6.30 11.61 10.51 Charles 2 Rio Grande at Albuquerque 2/3/1987 1:9 unaltered 6.90 10.95 11.44 Charles 2 Rio Grande at Albuquerque 5/11/1988 1:9 unaltered 4.65 13.48 7.94 Charles 2 Rio Grande at Albuquerque 11/7/1988 1:9 unaltered 5.27 12.83 8.91 Charles 2 Rio Grande at Albuquerque 8/22/1995 1:9 unaltered 4.35 14.01 7.38 Charles 2 Rio Grande at Albuquerque 8/16/1971 9:1 unaltered 4.26 11.34 7.38 Charles 2 Rio Grande at Albuquerque 5/3/1982 9:1 unaltered 4.44 11.16 7.64 Charles 2 Rio Grande at Albuquerque 7/15/1986 9:1 unaltered 4.51 11.07 7.75 Charles 2 Rio Grande at Albuquerque 11/7/1986 9:1 unaltered 4.53 11.06 7.78 Charles 2 Rio Grande at Albuquerque 2/3/1987 9:1 unaltered 4.59 10.99 7.87 Charles 2 Rio Grande at Albuquerque 5/11/1988 9:1 unaltered 4.35 11.26 7.51 Charles 2 Rio Grande at Albuquerque 11/7/1988 9:1 unaltered 4.41 11.19 7.61 Charles 2 Rio Grande at Albuquerque 8/22/1995 9:1 unaltered 4.36 11.32 7.49 Charles 2 Rio Grande at Albuquerque 8/16/1971 1:9 2.0 7.66 10.20 12.63 Charles 2 Rio Grande at Albuquerque 5/3/1982 1:9 2.0 7.67 10.11 12.63 Charles 2 Rio Grande at Albuquerque 7/15/1986 1:9 2.0 7.68 10.01 12.64 Charles 2 Rio Grande at Albuquerque 11/7/1986 1:9 2.0 7.66 10.12 12.62 Charles 2 Rio Grande at Albuquerque 2/3/1987 1:9 2.0 7.65 10.11 12.61 Charles 2 Rio Grande at Albuquerque 5/11/1988 1:9 2.0 7.66 10.20 12.63 Charles 2 Rio Grande at Albuquerque 11/7/1988 1:9 2.0 7.65 10.24 12.61 Charles 2 Rio Grande at Albuquerque 8/22/1995 1:9 2.0 7.86 10.21 12.83 Charles 2 Rio Grande at Albuquerque 8/16/1971 1:9 50.0 0.32 17.83 1.31 Charles 2 Rio Grande at Albuquerque 5/3/1982 1:9 50.0 0.39 17.82 1.38 Charles 2 Rio Grande at Albuquerque 7/15/1986 1:9 50.0 0.41 17.72 1.40 Charles 2 Rio Grande at Albuquerque 11/7/1986 1:9 50.0 0.37 17.80 1.35 Charles 2 Rio Grande at Albuquerque 2/3/1987 1:9 50.0 0.37 17.80 1.35 Charles 2 Rio Grande at Albuquerque 5/11/1988 1:9 50.0 0.37 17.89 1.36 Charles 2 Rio Grande at Albuquerque 11/7/1988 1:9 50.0 0.34 17.89 1.33 Charles 2 Rio Grande at Albuquerque 8/22/1995 1:9 50.0 0.55 17.90 1.55 
Table 9. Saturation indices for selected minerals, as calculated by PHREEQC for selected ground-water/surface-water mixtures.—Continued

Ground-water sample 

source (from table 1) Surface-water sample source (from table 2)

Simulated ratio of 

ground water to 

surface water

Simulated 

temperature 

(deg. C) manganite Mg-ferrite nsutite pyrolusite

Duranes 6 Rio Grande at Albuquerque 8/16/1971 1:9 unaltered 3.96 14.26 6.88 8.51Duranes 6 Rio Grande at Albuquerque 5/3/1982 1:9 unaltered 5.48 12.63 9.20 10.14Duranes 6 Rio Grande at Albuquerque 7/15/1986 1:9 unaltered 6.15 11.83 10.23 10.85Duranes 6 Rio Grande at Albuquerque 11/7/1986 1:9 unaltered 6.35 11.68 10.55 11.06Duranes 6 Rio Grande at Albuquerque 2/3/1987 1:9 unaltered 6.95 11.02 11.49 11.71Duranes 6 Rio Grande at Albuquerque 5/11/1988 1:9 unaltered 4.69 13.54 7.98 9.29Duranes 6 Rio Grande at Albuquerque 11/7/1988 1:9 unaltered 5.31 12.89 8.95 9.95Duranes 6 Rio Grande at Albuquerque 8/22/1995 1:9 unaltered 4.38 14.07 7.41 8.95Duranes 6 Rio Grande at Albuquerque 8/16/1971 9:1 unaltered 4.88 11.94 8.00 9.25Duranes 6 Rio Grande at Albuquerque 5/3/1982 9:1 unaltered 5.07 11.78 8.27 9.44Duranes 6 Rio Grande at Albuquerque 7/15/1986 9:1 unaltered 5.14 11.71 8.38 9.52Duranes 6 Rio Grande at Albuquerque 11/7/1986 9:1 unaltered 5.16 11.68 8.41 9.54Duranes 6 Rio Grande at Albuquerque 2/3/1987 9:1 unaltered 5.22 11.62 8.51 9.61Duranes 6 Rio Grande at Albuquerque 5/11/1988 9:1 unaltered 4.97 11.87 8.13 9.35Duranes 6 Rio Grande at Albuquerque 11/7/1988 9:1 unaltered 5.04 11.80 8.23 9.41Duranes 6 Rio Grande at Albuquerque 8/22/1995 9:1 unaltered 4.94 11.93 8.07 9.32Duranes 6 Rio Grande at Albuquerque 8/16/1971 9:1 2.0 8.01 8.92 12.74 12.60Duranes 6 Rio Grande at Albuquerque 5/3/1982 9:1 2.0 8.02 8.92 12.75 12.60Duranes 6 Rio Grande at Albuquerque 7/15/1986 9:1 2.0 8.02 8.92 12.75 12.60Duranes 6 Rio Grande at Albuquerque 11/7/1986 9:1 2.0 8.01 8.92 12.73 12.59Duranes 6 Rio Grande at Albuquerque 2/3/1987 9:1 2.0 8.01 8.92 12.73 12.58Duranes 6 Rio Grande at Albuquerque 5/11/1988 9:1 2.0 8.02 8.92 12.75 12.60Duranes 6 Rio Grande at Albuquerque 11/7/1988 9:1 2.0 8.01 8.92 12.73 12.59Duranes 6 Rio Grande at Albuquerque 8/22/1995 9:1 2.0 8.05 8.93 12.78 12.64Duranes 6 Rio Grande at Albuquerque 8/16/1971 9:1 50.0 0.21 16.20 0.96 4.26Duranes 6 Rio Grande at Albuquerque 5/3/1982 9:1 50.0 0.22 16.21 0.97 4.27Duranes 6 Rio Grande at Albuquerque 7/15/1986 9:1 50.0 0.22 16.21 0.97 4.27Duranes 6 Rio Grande at Albuquerque 11/7/1986 9:1 50.0 0.21 16.21 0.96 4.26Duranes 6 Rio Grande at Albuquerque 2/3/1987 9:1 50.0 0.21 16.21 0.95 4.25Duranes 6 Rio Grande at Albuquerque 5/11/1988 9:1 50.0 0.22 16.21 0.97 4.27Duranes 6 Rio Grande at Albuquerque 11/7/1988 9:1 50.0 0.21 16.21 0.96 4.26Duranes 6 Rio Grande at Albuquerque 8/22/1995 9:1 50.0 0.25 16.22 1.00 4.30
Table 9. Saturation indices for selected minerals, as calculated by PHREEQC for selected ground-water/surface-water mixtures.—Continued Ground-water sample source (from table 1) Surface-water sample source (from table 2) Simulated ratio of ground water to surface water Simulated temperature (deg. C) manganite Mg-ferrite nsutite pyrolusite Leavitt 2 Rio Grande at Albuquerque 8/16/1971 1:9 unaltered 3.86 14.27 6.74 8.41 Leavitt 2 Rio Grande at Albuquerque 5/3/1982 1:9 unaltered 5.37 12.63 9.05 10.02 Leavitt 2 Rio Grande at Albuquerque 7/15/1986 1:9 unaltered 6.04 11.80 10.08 10.73 Leavitt 2 Rio Grande at Albuquerque 11/7/1986 1:9 unaltered 6.24 11.68 10.40 10.94 Leavitt 2 Rio Grande at Albuquerque 2/3/1987 1:9 unaltered 6.83 11.02 11.32 11.58 Leavitt 2 Rio Grande at Albuquerque 5/11/1988 1:9 unaltered 4.58 13.55 7.84 9.18 Leavitt 2 Rio Grande at Albuquerque 11/7/1988 1:9 unaltered 5.20 12.91 8.80 9.84 Leavitt 2 Rio Grande at Albuquerque 8/22/1995 1:9 unaltered 4.29 14.08 7.27 8.84 Leavitt 2 Rio Grande at Albuquerque 8/16/1971 9:1 unaltered 3.83 11.70 6.58 8.15 Leavitt 2 Rio Grande at Albuquerque 5/3/1982 9:1 unaltered 4.01 11.47 6.84 8.34 Leavitt 2 Rio Grande at Albuquerque 7/15/1986 9:1 unaltered 4.09 11.33 6.96 8.42 Leavitt 2 Rio Grande at Albuquerque 11/7/1986 9:1 unaltered 4.10 11.39 6.98 8.43 Leavitt 2 Rio Grande at Albuquerque 2/3/1987 9:1 unaltered 4.16 11.32 7.07 8.49 Leavitt 2 Rio Grande at Albuquerque 5/11/1988 9:1 unaltered 3.92 11.62 6.71 8.24 Leavitt 2 Rio Grande at Albuquerque 11/7/1988 9:1 unaltered 3.98 11.58 6.80 8.30 Leavitt 2 Rio Grande at Albuquerque 8/22/1995 9:1 unaltered 3.93 11.67 6.70 8.25 Leavitt 2 Rio Grande at Albuquerque 8/16/1971 1:9 2.0 7.67 10.20 12.64 12.49 Leavitt 2 Rio Grande at Albuquerque 5/3/1982 1:9 2.0 7.68 10.10 12.65 12.50 Leavitt 2 Rio Grande at Albuquerque 7/15/1986 1:9 2.0 7.69 9.99 12.65 12.51

Leavitt 2 Rio Grande at Albuquerque 11/7/1986 1:9 2.0 7.67 10.11 12.63 12.48Leavitt 2 Rio Grande at Albuquerque 2/3/1987 1:9 2.0 7.67 10.10 12.62 12.48Leavitt 2 Rio Grande at Albuquerque 5/11/1988 1:9 2.0 7.68 10.19 12.64 12.50Leavitt 2 Rio Grande at Albuquerque 11/7/1988 1:9 2.0 7.66 10.23 12.62 12.48Leavitt 2 Rio Grande at Albuquerque 8/22/1995 1:9 2.0 7.87 10.20 12.84 12.69Leavitt 2 Rio Grande at Albuquerque 8/16/1971 1:9 50.0 0.32 17.82 1.32 4.61Leavitt 2 Rio Grande at Albuquerque 5/3/1982 1:9 50.0 0.40 17.80 1.38 4.68Leavitt 2 Rio Grande at Albuquerque 7/15/1986 1:9 50.0 0.42 17.70 1.40 4.70Leavitt 2 Rio Grande at Albuquerque 11/7/1986 1:9 50.0 0.38 17.79 1.36 4.66Leavitt 2 Rio Grande at Albuquerque 2/3/1987 1:9 50.0 0.38 17.79 1.36 4.66Leavitt 2 Rio Grande at Albuquerque 5/11/1988 1:9 50.0 0.38 17.88 1.37 4.67Leavitt 2 Rio Grande at Albuquerque 11/7/1988 1:9 50.0 0.34 17.89 1.33 4.63Leavitt 2 Rio Grande at Albuquerque 8/22/1995 1:9 50.0 0.56 17.89 1.55 4.85
As a result of these similarities, the list of minerals that 

might reasonably dissolve or newly precipitate as the result 

of a change in water source between a ground-water/surfacewater mixture and ground water or surface water alone is the 

same as the list previously discussed for a change between 

ground water and surface water. That is, aragonite, calcite, 

chalcedony, and perhaps Fe3(OH)8 appear to be the primary 

minerals that might dissolve or newly precipitate within the 

distribution system when the source of water is changed. 

Again, of these minerals, only aragonite and calcite have been 

positively identified among mineral precipitates present in the 

Authority’s current distribution system. When heated to 50oC, 

the ground-water/surface-water mixtures also have positive SIs 

for some Mn oxides that have negative SIs for ground-water 

compositions at this temperature. Therefore, precipitation of 

Mn oxides (followed by dissolution upon a change in water 

source) could potentially occur if kinetics of the reactions 

were favorable.

PHREEQC was used to estimate the likely quantity of 

mineral that would precipitate from or be dissolved by the 

simulated ground-water/surface-water compositions. Model 

simulations indicated that the quantity of most minerals precipitated from or dissolved by a ground-water/surface-water 

mixture compared to ground water or surface water alone 

would likely be somewhat larger (about one-half to one order 

of magnitude). For the iron minerals, the quantity precipitated 

from any mixture would be closer to the quantity precipitated 

from surface water alone than from ground water alone; for 

mixtures that are mostly surface water, the quantity precipitated could be as much as one order of magnitude higher than 

for surface water alone.

Corrosion indices calculated for selected ground-water/

surface-water mixtures are shown in table 7. Dissolved-solids 

concentrations for calculation of the LSIs and RSIs were 

estimated from PHREEQC output. As expected, the values of 

all corrosion indices for the mixtures are within the range of 

values obtained for ground-water and surface-water compositions alone. The values calculated for the mixtures closely 

reflect the values calculated for the type of water composing 

the bulk of the mixture. Because most surface-water compositions were found to have corrosion indices indicating a slightly 

greater potential for corrosion compared to most ground-water 

compositions, most ground-water/surface-water mixtures also 

have corrosion indices indicating a slightly greater corrosion 

potential compared to most ground-water compositions. The 

calcite SIs simulated for the mixtures in table 7 are consistent 

with this conclusion.

Potential Chemical Effects of Changes 

in the Source of Water Supply on the 

Distribution System

Based on modeled SIs and kinetic considerations, solid 

phases that appear most likely to either dissolve or newly 

precipitate under assumed distribution-system conditions when 

surface water or ground-water/surface-water mixes are delivered 

through the current distribution system are carbonates (particularly aragonite and calcite). Other types of minerals with some 

potential to dissolve or newly precipitate are a form of silica, 

the Fe-containing mineral Fe3(OH)8, and an aluminum hyroxide 

(gibbsite or diaspore). Dissolution of most of these minerals 

(except the Fe-containing minerals) is not likely to substantially 

affect trace-element concentrations or aesthetic characteristics 

of delivered water and would probably be of concern only if 

the quantities of material precipitated were large enough to 

clog pipes or fixtures. PHREEQC calculations do indicate that 

somewhat larger masses of material would precipitate from 

surface water or ground-water/surface-water mixtures compared 

to ground water alone. Dissolution of the increased mass of Fecontaining minerals precipitated in the system could potentially 

result in discoloration of delivered water and even have some 

effect on trace-element concentrations, depending on the elements that co-precipitated with or sorbed to the minerals.

Under some conditions (particularly, when water is 

heated), Mn oxides might newly precipitate from surface water 

or ground-water/surface-water mixtures and subsequently 

re-dissolve when ground water is the primary source of supply, 

possibly affecting both trace-element concentrations and aesthetic characteristics of delivered water. X-ray diffraction data 

did not show the presence of Mn oxides in any parts of the current distribution system (even at temperatures at which SIs for 

manganese oxides in ground water are positive). However, the 

presence of Mn oxides may not be evident from x-ray diffraction, making it unclear whether precipitation of these minerals 

is kinetically favored under the conditions present. One Mncontaining mineral, rhodochrosite, was identified in the current 

distribution system despite having negative SIs for all groundwater compositions. This mineral would tend to dissolve when 

the primary source of supply changed to surface water.

Based on modeled SIs for calcite combined with calculations of corrosion indices, treated San Juan-Chama water 

from the Rio Grande does not appear likely to be highly corrosive under most conditions, although some samples have 

corrosion indices indicative of mild to moderate corrosivity. 

The results for ground-water/surface-water mixes were 

similar to those for surface water; the calcite SIs in particular 

indicated that the mixtures would not be likely to result in 

substantial calcite dissolution.

Summary

Chemical modeling was used by the U.S. Geological Survey, in cooperation with the Albuquerque Bernalillo 

County Water Utility Authority, to estimate the potential 

chemical effects that could occur in the Authority’s water 

distribution system as a result of changing the source of water 

used for municipal and industrial supply. A variety of water 

samples selected to represent the chemistry of ground water 

currently (2005) delivered by the Authority and of surface 

water that will be delivered starting in 2008 were modeled in 

Summary 37
38 Potential Chemical Effects of Changes in the Source of Water Supply

the software package PHREEQC. The samples were modeled under a variety of conditions (particularly temperature 

and atmospheric-gas pressures) assumed to be present in 

various parts of the distribution system. The surface-water 

samples also were modeled to undergo the treatment processes 

projected to occur at the new water treatment plant. Minerals 

identified as having positive SIs for the simulated groundwater compositions were compared with minerals identified in 

precipitate samples collected from pipes, reservoirs, and one 

water heater associated with the current distribution system. 

Minerals identified as having positive SIs also were compared 

between the simulated ground-water and surface-water compositions, and among these compositions and ground-water/

surface-water mixtures modeled using them. Analysis focused 

on minerals that were kinetically favored to form. Quantities 

of potential precipitate formation and indicators of corrosion 

potential also were compared among ground-water compositions, surface-water compositions, and ground-water/surfacewater mixtures.

For the simulated ground-water compositions, minerals 

that included at least one positive SI and had favorable kinetics for forming substantial quantities of precipitate within the 

Authority’s distribution system were:

•	 calcium carbonate (aragonite or calcite); and

•	 a form of iron oxide or hydroxide (ferrihydrite, 

goethite, hematite, lepidocrocite, maghemite).

Other minerals with positive SIs but uncertain kinetics of formation were a form of silica (chalcedony), a calcium/magnesium 

carbonate (huntite), an aluminum hydroxide (gibbsite or diaspore), 

and various forms of Mn, Cu, and Zn. Minerals with positive SIs 

that were unlikely to form because of known kinetic limitations 

included feldspars, zeolites, clays, and crystalline silica. Of the 

minerals simulated to have positive SIs, the ones identified in 

mineral-precipitate samples from the Authority’s distribution system were aragonite, calcite, goethite, hematite, and lepidocrocite. 

Also identified were amorphous forms of Fe or Fe oxyhydroxides. 

Two minerals, rhodochrosite and gibbsite, that did not have positive SIs for the simulated ground-water compositions also were 

identified in the distribution system; these minerals may have been 

transported into the system.

The minerals with positive SIs for the simulated surfacewater compositions and the simulated ground-water/surfacewater mixtures were quite similar to the minerals with positive 

SIs for the simulated ground-water compositions. Therefore, 

based on the modeled SIs and kinetic considerations, minerals 

that appear most likely to either dissolve or newly precipitate 

under assumed distribution-system conditions when surface 

water or ground-water/surface-water mixtures are delivered 

through the current distribution system are carbonates (particularly aragonite and calcite). Other types of minerals with some 

potential to dissolve or newly precipitate are a form of silica 

(particularly chalcedony), the Fe-containing mineral Fe3(OH)8, 

an aluminum hyroxide (gibbsite or diaspore), and a Mn oxide 

(particularly birnessite or nsutite). Dissolution of most of 

these minerals (except the Fe- or Mn-containing minerals) is 

not likely to substantially affect trace-element concentrations 

or aesthetic characteristics of delivered water, except perhaps 

hardness. These minerals would probably be of concern only 

if the quantities of material precipitated were large enough to 

clog pipes or fixtures. Some Fe-containing minerals that were 

identified in the Authority’s distribution system were associated with relatively high contents of some metals, including 

As, Cr, Cu, Mn, Pb, and Zn. However, these Fe-containing 

minerals were not identified as minerals likely to dissolve 

when the source of water was changed from ground water to 

surface water or a ground-water/surface-water mixture.

PHREEQC calculations indicate that somewhat larger 

masses of material would precipitate from surface water or 

ground-water/surface-water mixtures compared to ground 

water alone. If dissolution of the increased mass of Fecontaining minerals precipitated in the system was to occur, 

aesthetic characteristics and trace-element concentrations of 

delivered water could potentially be adversely affected.

Based on modeled SIs for calcite and additional calculations of corrosion indices (the Langelier Saturation Index, 

Ryznar Stability Index, and Larson-Skold Index), ground 

water, surface water, and ground-water/surface-water mixtures 

are likely to differ only slightly in corrosion potential. Most 

corrosion indices indicate that surface water and ground-water/

surface-water mixtures could be somewhat more corrosive in 

general than ground-water compositions. However, simulated 

calcite SIs show that there should not be a great potential for 

surface water or ground-water/surface-water mixtures to dissolve large quantities of existing calcite and expose pipes to 

substantially increased corrosion.

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W.E., and Busenberg, Eurybiades, 2004, Geochemical 

characterization of ground-water flow in the Santa Fe 

Group aquifer system, Middle Rio Grande Basin, New 

Mexico: U.S. Geological Survey Water-Resources Investigations Report 03-4131, 395 p.

Pough, F.H., 1998, Peterson field guide to rocks and minerals: 

Boston, Houghton Mifflin Company, 542 p.

Price, Steve, and Jefferson, F.T., 1996, Corrosion control 

strategies for changing water supplies in Tucson, Arizona: 

Journal of the New England Water Works Association, v. 

111, no. 3, p. 285–293.

Swanson, W.J., Chowdhury, Z.K., and Davis, S.E., 1998, 

Effect of pH, disinfectant, and corrosion inhibitors on 

distribution system iron release—the Tucson experience, 

in American Water Works Association Annual Conference, 

Dallas, Texas, 1998, Proceedings, v. D: American Water 

Works Association, p. 657–678.

U.S. Environmental Protection Agency, 2006, List of drinking-water contaminants and MCLs, information available 

on the World Wide Web, accessed June 20, 2006, at URL 

http://www.epa.gov/safewater/mcl.html.

Whitworth, Mike, 1996, Hydrogeochemical computer modeling of proposed artificial recharge of the Albuquerque 

aquifer, in Hawley, J.W., and Whitworth, T.M., eds., 

Hydrogeology of potential recharge areas for the basin- and 

valley-fill aquifer systems, and hydrogeochemical modeling 

of proposed artificial recharge of the upper Santa Fe aquifer, 

northern Albuquerque Basin: Socorro, New Mexico Bureau 

of Geology and Mineral Resources Open-File Report 402d, 

variously paged.

Wilcox, Ralph, 1997, Concentrations of selected trace elements and other constituents in the Rio Grande and in fish 

tissue in the vicinity of Albuquerque, New Mexico, 1994 

to 1996: U.S. Geological Survey Open-File Report 97-667, 

173 p.

Xu, Huifang, Buseck, P.R., and Luo, Gufeng, 1998, HRTEM 

investigation of microstructures in length-slow chalcedony: 

American Mineralogist, v. 83, p. 542–545.

References Cited 39
Appendix
Appendix

TITLE Master model

#This file shows PHREEQC input for at least one example of every type of model calculation conducted for the study:

#-Representative surface-water (SW) compositions (numbers 11-18) are defined

#-Representative ground-water (GW) compositions (numbers 80-89) are defined

#-Treatment of representative SW samples is simulated as described in specifications for the proposed SW plant

#-GW samples are simulated at conditions closer to atmospheric equilibrium

#-A selected GW sample near atmospheric equilibrium is mixed with all treated SW samples using a specified ratio

#-Resulting water mixtures are heated and cooled

#-Mixtures are brought into equilibrium with a selected mineral to determine the maximum quantity of precipitate

#

#Selected output for all model calculations is shown, including saturation indices (SIs) for selected minerals,

#chemical parameters needed to perform corrosion calculations, and precipitate mass from equilibrium calculations

#

#The user needs to specify the selected GW solution for mixing, the desired mixing ratio,

#and the selected mineral for equilibration and subsequent output of mass precipitated

#

SOLUTION_SPREAD

-units mg/l

-redox O(0)/O(-2)

Number Alkalinity As Ca Cl F Fe eh pH temperature K Mg 

Mn Na N(5) Si S(6) Al Cu Zn O(0) pe Description

11 163 0.003 70 37 0.7 0.012 7.7 25.5 5.9 9 0.004 60 

28 150 0.005 0.002 0.005 7 12.8640 RGABQ8/16/1971

12 110 0.002 37 5.6 0.4 0.009 8.3 15 2.9 6.7 0.004 16 

17 68 0.005 0.002 0.005 8.3 13.1808 RGABQ5/3/1982

13 99 0.003 28 4.5 0.2 0.02 7.8 10.5 3.1 4.9 0.004 17 

17 45 0.005 0.002 0.005 7.6 14.0767 RGABQ7/15/1986

14 135 0.003 42 12 0.4 0.014 8.05 9 3.4 7 0.004 27 

21 59 0.005 0.002 0.003 9.6 13.9901 RGABQ11/7/1986

15 134 0.003 39 14 0.4 0.012 7.9 5 2.8 6.9 0.004 23 

21 61 0.005 0.002 0.005 11.5 14.5351 RGABQ2/3/1987

16 143 0.003 41 13 0.5 0.01 8.7 20.5 2.6 8.5 0.004 32 

18 76 0.005 0.002 0.005 7.9 12.2968 RGABQ5/11/1988

17 183 0.004 53 13 0.4 0.01 8.46 16 3.8 9.7 0.004 33 

22 73 0.005 0.004 0.005 8.3 12.9325 RGABQ11/7/1988

18 141 0.003 37 7.6 0.4 0.012 7.81 24 3.2 8.3 0.006 24 

19 57 0.02 0.002 0.001 7 12.8783 RGABQ8/22/1995

80 135 0.002 41.07 11.3 0.58 0.007 0.176 7.64 19 1.64 3.9 0.001 23.32 

0.44 31.41 35.7 0.003 0.0005 0.0066 Charles2

81 205 0.004 51.58 14.1 0.46 0.021 0.131 7.48 19 9.51 12.09 0.003 42.5 

0.05 69.62 96 0.003 0.0005 0.001 Duranes6

82 179 0.033 4.42 18.2 1.44 0.003 0.185 8.85 23.8 1.18 0.49 0.001 102.4 

1.28 29.1 65 0.003 0.0005 0.001 Leavitt2

83 133 0.002 37.91 24.3 0.6 0.010 0.161 7.73 22.7 2.81 2.98 0.001 26.9 

0.32 28.1 19.4 0.003 0.0005 0.001 Love5

84 130 0.021 33.63 37.8 0.74 0.011 0.138 7.76 25.7 7.39 7.42 0.001 40.14 

0.22 67.24 43.6 0.003 0.0005 0.0067 Miles1

85 182 0.002 49.4 11.5 0.58 0.003 0.204 7.35 22.5 2.11 7.6 0.001 28.67 

0.87 28.2 55.4 0.003 0.0005 0.001 Ridgecrest1

86 157 0.006 60.99 62.4 0.51 0.018 0.067 7.45 23.3 3 4.71 0.009 40.84 

0.18 35.18 31.3 0.003 0.0005 0.012 Thomas6

87 123 0.008 47.12 19.6 0.48 0.003 0.180 7.91 18 2.67 5.69 0.001 18.25 

0.72 36.7 50.4 0.003 0.0005 0.001 VolAndia3

88 174 0.036 39.54 87.4 1.19 0.013 0.109 7.75 28.7 4.83 5.63 0.018 77.3 

0.05 41.5 37.2 0.003 0.0005 0.001 Walker2

89 158 0.014 20.15 9.33 0.72 0.003 0.206 7.88 24.3 6.43 3.37 0.001 58.02 

0.86 70.1 54.6 0.003 0.0005 0.001 Zamora1

Appendix 41
SELECTED_OUTPUT

-file AllOutput.txt

#

#Output of SIs for all minerals with SI greater than 0.1 for at least one GW or SW composition

#

-si albite(low) analbite analcime annite aragonite birnessite bixbyite\

 Ca-nontronite calcite chalcedony chrysotile CO2(g) cristobalite\

 CupricFerrite CuprousFerrite diaspore diopside dolomite Fe(OH)2.7Cl0.3\

 Fe3(OH)8 ferrihydrite gibbsite(C) goethite halloysite hausmannite\

 hematite huntite jarosite-K K-nontronite kaolinite laumontite leonhardite\

 lepidocrocite maghemite magnesite magnetite manganite Mg-ferrite Mg-nontronite\

 microcline montmorillonite muscovite Na-nontronite nsutite O2(g)\

 pyrolusite pyrophyllite quartz rhodochrosite sanidine(H) sepiolite(c) talc tremolite willemite ZnSiO3

#

#Output for calculating corrosion indices

#

-ph true

-temperature true

-alkalinity true

-ionic_strength true

-totals Al As C Ca Cl Cu F Fe K Mg Mn N Na S Si Zn

-molalities Ca+2 Cl- SO4-2

#

#Output for determining mass of precipitate

#

-equilibrium_phases calcite

PHASES

 Fix_H+

 H+ = H+

 log_k 0

#Simulate treatment plant processes

#

#Add ferric chloride to SW at quantity indicated by design plans (avg 30 mg/L),

#along with sulfuric acid sufficient to bring the pH down to 6

#

42 Potential Chemical Effects of Changes in the Source of Water Supply
USE SOLUTION 11

REACTION 1 Add ferric chloride 

FeCl3

0.185 mmol

EQUILIBRIUM_PHASES

Fix_H+ -6.0 H2SO4 10.

SAVE SOLUTION 21

END

USE SOLUTION 12

REACTION 1 Add ferric chloride 

FeCl3

0.185 mmol

EQUILIBRIUM_PHASES

Fix_H+ -6.0 H2SO4 10.

SAVE SOLUTION 22

END

USE SOLUTION 13

REACTION 1 Add ferric chloride 

FeCl3

0.185 mmol

EQUILIBRIUM_PHASES

Fix_H+ -6.0 H2SO4 10.

SAVE SOLUTION 23

END

USE SOLUTION 14

REACTION 1 Add ferric chloride 

FeCl3

0.185 mmol

EQUILIBRIUM_PHASES

Fix_H+ -6.0 H2SO4 10.

SAVE SOLUTION 24

END

USE SOLUTION 15

REACTION 1 Add ferric chloride 

FeCl3

0.185 mmol

EQUILIBRIUM_PHASES

Fix_H+ -6.0 H2SO4 10.

SAVE SOLUTION 25

END

USE SOLUTION 16

REACTION 1 Add ferric chloride 

FeCl3

0.185 mmol

EQUILIBRIUM_PHASES

Fix_H+ -6.0 H2SO4 10.

SAVE SOLUTION 26

END

USE SOLUTION 17

REACTION 1 Add ferric chloride 

FeCl3

0.185 mmol

EQUILIBRIUM_PHASES

Fix_H+ -6.0 H2SO4 10.

SAVE SOLUTION 27

END

USE SOLUTION 18

REACTION 1 Add ferric chloride 

FeCl3

0.185 mmol

EQUILIBRIUM_PHASES

Fix_H+ -6.0 H2SO4 10.

SAVE SOLUTION 28

END

#

#Add 1.5 mg/L of O3, plus avg. H2O2 dose of 0.2 mg/L, plus 

O2 sufficient to

#bring largest DO up near 24 mg/L (as indicated in design 

plans). Also add

#some organic matter to oxidize (about 0.6 mg/L)

#

USE SOLUTION 21

REACTION 2 Add O3, O2, H2O2 and organic matter

O2

H2O2 .017

O3 .086

CH2O .056

0.360 mmol

SAVE SOLUTION 31

END

USE SOLUTION 22

REACTION 2 Add O3, O2, H2O2 and organic matter

O2

H2O2 .017

O3 .086

CH2O .056

0.360 mmol

SAVE SOLUTION 32

END

USE SOLUTION 23

REACTION 2 Add O3, O2, H2O2 and organic matter

O2

H2O2 .017

O3 .086

CH2O .056

0.360 mmol

SAVE SOLUTION 33

END

USE SOLUTION 24

REACTION 2 Add O3, O2, H2O2 and organic matter

Appendix 43
O2

H2O2 .017

O3 .086

CH2O .056

0.360 mmol

SAVE SOLUTION 34

END

USE SOLUTION 25

REACTION 2 Add O3, O2, H2O2 and organic matter

O2

H2O2 .017

O3 .086

CH2O .056

0.360 mmol

SAVE SOLUTION 35

END

USE SOLUTION 26

REACTION 2 Add O3, O2, H2O2 and organic matter

O2

H2O2 .017

O3 .086

CH2O .056

0.360 mmol

SAVE SOLUTION 36

END

USE SOLUTION 27

REACTION 2 Add O3, O2, H2O2 and organic matter

O2

H2O2 .017

O3 .086

CH2O .056

0.360 mmol

SAVE SOLUTION 37

END

USE SOLUTION 28

REACTION 2 Add O3, O2, H2O2 and organic matter

O2

H2O2 .017

O3 .086

CH2O .056

0.360 mmol

SAVE SOLUTION 38

END

#

#Allow CO2 removal from SW assuming 75% efficiency as 

indicated by design plans,

#and drop O2 back to near 10 mg/L

#

USE SOLUTION 31

EQUILIBRIUM_PHASES 1

CO2(g) -1.85

O2(g) -0.52

SAVE SOLUTION 41

END

USE SOLUTION 32

EQUILIBRIUM_PHASES 1

CO2(g) -2.09

O2(g) -0.52

SAVE SOLUTION 42

END

USE SOLUTION 33

EQUILIBRIUM_PHASES 1

CO2(g) -2.15

O2(g) -0.52

SAVE SOLUTION 43

END

USE SOLUTION 34

EQUILIBRIUM_PHASES 1

CO2(g) -2.04

O2(g) -0.52

SAVE SOLUTION 44

END

USE SOLUTION 35

EQUILIBRIUM_PHASES 1

CO2(g) -2.07

O2(g) -0.52

SAVE SOLUTION 45

END

USE SOLUTION 36

EQUILIBRIUM_PHASES 1

CO2(g) -1.97

O2(g) -0.52

SAVE SOLUTION 46

END

USE SOLUTION 37

EQUILIBRIUM_PHASES 1

CO2(g) -1.88

O2(g) -0.52

SAVE SOLUTION 47

END

USE SOLUTION 38

EQUILIBRIUM_PHASES 1

CO2(g) -1.92

O2(g) -0.52

SAVE SOLUTION 48

END

#

44 Potential Chemical Effects of Changes in the Source of Water Supply
#Add NaOCl at 4 mg/L, H2SiF6 at 1 mg/L, and hydrated lime 

sufficient to bring pH to 8

#

USE SOLUTION 41

REACTION 3 Add NaOCl and H2SiF6

NaOCl

H2SiF6 0.130

0.054 mmol

EQUILIBRIUM_PHASES

Fix_H+ -8.0 Ca(OH)2 10.

SAVE SOLUTION 51

END

USE SOLUTION 42

REACTION 3 Add NaOCl and H2SiF6

NaOCl

H2SiF6 0.130

0.054 mmol

EQUILIBRIUM_PHASES

Fix_H+ -8.0 Ca(OH)2 10.

SAVE SOLUTION 52

END

USE SOLUTION 43

REACTION 3 Add NaOCl and H2SiF6

NaOCl

H2SiF6 0.130

0.054 mmol

EQUILIBRIUM_PHASES

Fix_H+ -8.0 Ca(OH)2 10.

SAVE SOLUTION 53

END

USE SOLUTION 44

REACTION 3 Add NaOCl and H2SiF6

NaOCl

H2SiF6 0.130

0.054 mmol

EQUILIBRIUM_PHASES

Fix_H+ -8.0 Ca(OH)2 10.

SAVE SOLUTION 54

END

USE SOLUTION 45

REACTION 3 Add NaOCl and H2SiF6

NaOCl

H2SiF6 0.130

0.054 mmol

EQUILIBRIUM_PHASES

Fix_H+ -8.0 Ca(OH)2 10.

SAVE SOLUTION 55

END

USE SOLUTION 46

REACTION 3 Add NaOCl and H2SiF6

NaOCl

H2SiF6 0.130

0.054 mmol

EQUILIBRIUM_PHASES

Fix_H+ -8.0 Ca(OH)2 10.

SAVE SOLUTION 56

END

USE SOLUTION 47

REACTION 3 Add NaOCl and H2SiF6

NaOCl

H2SiF6 0.130

0.054 mmol

EQUILIBRIUM_PHASES

Fix_H+ -8.0 Ca(OH)2 10.

SAVE SOLUTION 57

END

USE SOLUTION 48

REACTION 3 Add NaOCl and H2SiF6

NaOCl

H2SiF6 0.130

0.054 mmol

EQUILIBRIUM_PHASES

Fix_H+ -8.0 Ca(OH)2 10.

SAVE SOLUTION 58

END

#

#Bring GW samples closer to equilibration with atmospheric 

conditions

#

USE SOLUTION 80

EQUILIBRIUM_PHASES 1

CO2(g) -3.0

O2(g) -5.0

SAVE SOLUTION 90

END

USE SOLUTION 81

EQUILIBRIUM_PHASES 1

CO2(g) -3.0

O2(g) -5.0

SAVE SOLUTION 91

END

USE SOLUTION 82

EQUILIBRIUM_PHASES 1

CO2(g) -3.0

O2(g) -5.0

SAVE SOLUTION 92

END

USE SOLUTION 83

EQUILIBRIUM_PHASES 1

CO2(g) -3.0

O2(g) -5.0

Appendix 45
SAVE SOLUTION 93

END

USE SOLUTION 84

EQUILIBRIUM_PHASES 1

CO2(g) -3.0

O2(g) -5.0

SAVE SOLUTION 94

END

USE SOLUTION 85

EQUILIBRIUM_PHASES 1

CO2(g) -3.0

O2(g) -5.0

SAVE SOLUTION 95

END

USE SOLUTION 86

EQUILIBRIUM_PHASES 1

CO2(g) -3.0

O2(g) -5.0

SAVE SOLUTION 96

END

USE SOLUTION 87

EQUILIBRIUM_PHASES 1

CO2(g) -3.0

O2(g) -5.0

SAVE SOLUTION 97

END

USE SOLUTION 88

EQUILIBRIUM_PHASES 1

CO2(g) -3.0

O2(g) -5.0

SAVE SOLUTION 98

END

USE SOLUTION 89

EQUILIBRIUM_PHASES 1

CO2(g) -3.0

O2(g) -5.0

SAVE SOLUTION 99

END

#

#Mix treated SW with selected GW

#

MIX 1 Mixing treated RGABQ8/16/1971 with Charles 2

51 9.0

90 1.0

SAVE SOLUTION 201

END

MIX 2 Mixing treated RGABQ5/3/1982 with Charles 2

52 9.0

90 1.0

SAVE SOLUTION 202

END

MIX 3 Mixing treated RGABQ7/15/1986 with Charles 2

53 9.0

90 1.0

SAVE SOLUTION 203

END

MIX 4 Mixing treated RGABQ11/7/1986 with Charles 2

54 9.0

90 1.0

SAVE SOLUTION 204

END

MIX 5 Mixing treated RGABQ2/3/1987 with Charles 2

55 9.0

90 1.0

SAVE SOLUTION 205

END

MIX 6 Mixing treated RGABQ5/11/1988 with Charles 2

56 9.0

90 1.0

SAVE SOLUTION 206

END

MIX 7 Mixing treated RGABQ11/7/1988 with Charles 2

57 9.0

90 1.0

SAVE SOLUTION 207

END

MIX 8 Mixing treated RGABQ8/22/1995 with Charles 2

58 9.0

90 1.0

SAVE SOLUTION 208

END

#

#Heat SW/GW mixture

#

USE SOLUTION 201

REACTION_TEMPERATURE 1

50.0

SAVE SOLUTION 301

END

USE SOLUTION 202

REACTION_TEMPERATURE 1

50.0

SAVE SOLUTION 302

46 Potential Chemical Effects of Changes in the Source of Water Supply
END

USE SOLUTION 203

REACTION_TEMPERATURE 1

50.0

SAVE SOLUTION 303

END

USE SOLUTION 204

REACTION_TEMPERATURE 1

50.0

SAVE SOLUTION 304

END

USE SOLUTION 205

REACTION_TEMPERATURE 1

50.0

SAVE SOLUTION 305

END

USE SOLUTION 206

REACTION_TEMPERATURE 1

50.0

SAVE SOLUTION 306

END

USE SOLUTION 207

REACTION_TEMPERATURE 1

50.0

SAVE SOLUTION 307

END

USE SOLUTION 208

REACTION_TEMPERATURE 1

50.0

SAVE SOLUTION 308

END

#

#Cool SW/GW mixture

#

USE SOLUTION 201

REACTION_TEMPERATURE 1

2.0

SAVE SOLUTION 401

END

USE SOLUTION 202

REACTION_TEMPERATURE 1

2.0

SAVE SOLUTION 402

END

USE SOLUTION 203

REACTION_TEMPERATURE 1

2.0

SAVE SOLUTION 403

END

USE SOLUTION 204

REACTION_TEMPERATURE 1

2.0

SAVE SOLUTION 404

END

USE SOLUTION 205

REACTION_TEMPERATURE 1

2.0

SAVE SOLUTION 405

END

USE SOLUTION 206

REACTION_TEMPERATURE 1

2.0

SAVE SOLUTION 406

END

USE SOLUTION 207

REACTION_TEMPERATURE 1

2.0

SAVE SOLUTION 407

END

USE SOLUTION 208

REACTION_TEMPERATURE 1

2.0

SAVE SOLUTION 408

END

#

#Calculate mass of selected precipitate for heated mix

#

USE SOLUTION 301

EQUILIBRIUM_PHASES 4

calcite 0.0

SAVE SOLUTION 501

END

USE SOLUTION 302

EQUILIBRIUM_PHASES 4

calcite 0.0

SAVE SOLUTION 502

END

USE SOLUTION 303

EQUILIBRIUM_PHASES 4

calcite 0.0

SAVE SOLUTION 503

END

Appendix 47
USE SOLUTION 304

EQUILIBRIUM_PHASES 4

calcite 0.0

SAVE SOLUTION 504

END

USE SOLUTION 305

EQUILIBRIUM_PHASES 4

calcite 0.0

SAVE SOLUTION 505

END

USE SOLUTION 306

EQUILIBRIUM_PHASES 4

calcite 0.0

SAVE SOLUTION 506

END

USE SOLUTION 307

EQUILIBRIUM_PHASES 4

calcite 0.0

SAVE SOLUTION 507

END

USE SOLUTION 308

EQUILIBRIUM_PHASES 4

calcite 0.0

SAVE SOLUTION 508

END

#

#Calculate mass of selected precipitate for cooled mix

#

USE SOLUTION 401

EQUILIBRIUM_PHASES 4

calcite 0.0

SAVE SOLUTION 601

END

USE SOLUTION 402

EQUILIBRIUM_PHASES 4

calcite 0.0

SAVE SOLUTION 602

END

USE SOLUTION 403

EQUILIBRIUM_PHASES 4

calcite 0.0

SAVE SOLUTION 603

END

USE SOLUTION 404

EQUILIBRIUM_PHASES 4

calcite 0.0

SAVE SOLUTION 604

END

USE SOLUTION 405

EQUILIBRIUM_PHASES 4

calcite 0.0

SAVE SOLUTION 605

END

USE SOLUTION 406

EQUILIBRIUM_PHASES 4

calcite 0.0

SAVE SOLUTION 606

END

USE SOLUTION 407

EQUILIBRIUM_PHASES 4

calcite 0.0

SAVE SOLUTION 607

END

USE SOLUTION 408

EQUILIBRIUM_PHASES 4

calcite 0.0

SAVE SOLUTION 608

END

48 Potential Chemical Effects of Changes in the Source of Water Supply
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Bexfield and Anderholm—Potential Chemical Effects of Changes in the Source of Water Supply for Albuquerque—Scientific Investigations Report 2006–5171

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