Streamflow and Water-Quality Trends of the Rio 

Chama and Rio Grande, Northern and Central New 

Mexico, Water Years 1985 to 2002

U.S. Department of the Interior 

U.S. Geological Survey

Prepared in cooperation with the

CITY OF ALBUQUERQUE

Scientific Investigations Report 2005-5118
Streamflow and Water-Quality Trends of 

the Rio Chama and Rio Grande, Northern 

and Central New Mexico, Water Years 1985 

to 2002

By Jeff B. Langman and Emma O. Nolan

U.S. Department of the Interior 

U.S. Geological Survey

Prepared in cooperation with the

CITY OF ALBUQUERQUE

Scientific Investigations Report 2005-5118
U.S. Department of the Interior

Gale A. Norton, Secretary

U.S. Geological Survey

Dr. R. Patrick Leahy, Acting Director

U.S. Geological Survey, Reston, Virginia: 2005

For sale by U.S. Geological Survey, Information Services 

Box 25286, Denver Federal Center 

Denver, CO 80225

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Although this report is in the public domain, permission must be secured from the individual copyright owners to reproduce any copyrighted materials contained within this report.
CONTENTS

 iii

Page

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

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

Purpose and scope ....................................................................................................................................................... 2

Description of the study area....................................................................................................................................... 2

Physiography..................................................................................................................................................... 2

Climate .............................................................................................................................................................. 2

Streamflow of the Rio Chama and Rio Grande................................................................................................. 2

Influences on streamflow and water quality in the study area........................................................................... 2

Reservoirs................................................................................................................................................ 2

Tributaries ............................................................................................................................................... 5

Ground-water inflows and outflows ........................................................................................................ 5

Evapotranspiration .................................................................................................................................. 6

Irrigation diversions and inflows............................................................................................................. 6

Previous studies................................................................................................................................................. 6

Acknowledgments....................................................................................................................................................... 7

Methods of analysis..................................................................................................................................................... 7

Water-quality spatial trend analysis .................................................................................................................. 7

Streamflow and water-quality seasonal trend analysis...................................................................................... 8

Streamflow and water-quality temporal trend analysis ..................................................................................... 8

Streamflow trends of the Rio Chama and Rio Grande, water years 1985 to 2002................................................................ 8

Seasonal trends in streamflow ..................................................................................................................................... 8

Temporal trends in climate and streamflow ................................................................................................................ 10

Water-quality trends of the Rio Chama and Rio Grande, water years 1985 to 2002 ............................................................ 10

Water-quality spatial trends......................................................................................................................................... 10

Basic water chemistry and physical properties ................................................................................................. 10

Major ions ......................................................................................................................................................... 12

Nutrients, organic carbon, and bacteria............................................................................................................. 12

Trace elements................................................................................................................................................... 12

Radionuclides.................................................................................................................................................... 15

Anthropogenic compounds ............................................................................................................................... 15

Water-quality seasonal trends...................................................................................................................................... 15

Basic water chemistry and physical properties ................................................................................................. 15

Major ions ......................................................................................................................................................... 19

Nutrients, organic carbon, and bacteria............................................................................................................. 19

Trace elements................................................................................................................................................... 19

Radionuclides.................................................................................................................................................... 23

Water-quality temporal trends ..................................................................................................................................... 23

Summary ............................................................................................................................................................................... 26

References cited .................................................................................................................................................................... 26

Supplemental information: Summary statistics and listing of analyzed anthropogenic compounds.................................... 29

FIGURES

1. Map showing selected streamflow and water-quality stations in the study area...................................................... 3

2-12. Graphs showing:

2. Water storage in Heron Lake, El Vado Reservoir, Abiquiu Reservoir, and Cochiti Lake, 1974 to 2002............ 4

3. Seasonal trend of streamflow at the Rio Grande stations of Taos, Otowi, San Felipe, and Albuquerque

and the Rio Chama station of Chamita, water years 1985 to 2002 ................................................................. 9

4. Median ion concentrations for the Rio Grande stations of Taos, Otowi, San Felipe, and Albuquerque

and the Rio Chama station of Chamita, water years 1985 to 2002 ................................................................. 12

5. Total ammonia, total phosphorous, dissolved nitrite plus nitrate, total organic carbon, fecal coliform,

and fecal streptococci concentrations for the Rio Grande stations of Taos, Otowi, San Felipe, and

Albuquerque and the Rio Chama station of Chamita, water years 1985 to 2002............................................ 13
iv 

Page

6. Specific conductance during seasonal periods for the Rio Grande stations of Taos, Otowi, San Felipe,

and Albuquerque and the Rio Chama station of Chamita, water years 1985 to 2002.................................... 17

7. Alkalinity concentrations during seasonal periods for the Rio Grande stations of Taos, Otowi, San Felipe,

and Albuquerque and the Rio Chama station of Chamita, water years 1985 to 2002.................................... 18

8. Seasonal period pH for the Rio Grande stations of Taos, Otowi, San Felipe, and Albuquerque and the

Rio Chama station of Chamita, water years 1985 to 2002 ............................................................................. 20

9. Median ion concentrations during seasonal periods for the Rio Grande stations of Taos, Otowi, San

Felipe, and Albuquerque and the Rio Chama station of Chamita, water years 1985 to 2002........................ 21

10. Seasonal trend of total organic carbon and fecal streptococci for the Rio Grande stations of Taos, Otowi,

and San Felipe and the Rio Chama station of Chamita, water years 1985 to 2002........................................ 22

11. Seasonal trend of manganese concentrations for the Rio Grande stations of Taos, Otowi, and San Felipe

and the Rio Chama station of Chamita, water years 1985 to 2002 ................................................................ 23

12. Seasonal trend of dissolved uranium concentrations for the Rio Grande stations of Otowi and San Felipe,

water years 1985 to 2002................................................................................................................................ 24

TABLES

1. Selected streamflow-gaging stations in the study area ............................................................................................ 5

2. Mean-annual precipitation in the study area............................................................................................................ 11

3. Mean-annual streamflow and streamflow temporal trends in the study area........................................................... 11

4. Annual San Juan-Chama Project streamflow diversion from the Colorado River Basin into the

Rio Grande Basin............................................................................................................................................... 11

5. Median dissolved trace-element concentrations in the Rio Chama and Rio Grande during water years

1985 to 2002 and percentage exceedance of applicable drinking-water standards ........................................... 14

6. Seasonal number of samples collected for aluminum, iron, and manganese analysis for the Rio Grande

stations of Taos, Otowi, San Felipe, and Albuquerque and the Rio Chama station of Chamita during

water years 1985 to 2002 ................................................................................................................................... 14

7. Maximum dissolved radionuclide concentrations detected in the Rio Chama and Rio Grande during water

years 1985 to 2002 and applicable drinking-water standards............................................................................ 16

8. Percentage of anthropogenic compounds detected in samples collected from the Rio Grande stations of

Taos, Otowi, San Felipe, and Albuquerque and the Rio Chama station of Chamita during water years

1985 to 2002 ...................................................................................................................................................... 16

9. Anthropogenic compounds detected in samples from the Rio Grande stations of Taos, Otowi, San Felipe,

and Albuquerque and the Rio Chama station of Chamita during water years 1985 to 2002 and associated

drinking-water standards.................................................................................................................................... 16

10. Results of Seasonal Kendall test (study period) and Mann-Kendall test (seasonal period) for temporal trend

analysis of flow-adjusted concentrations for the Rio Grande stations of Taos, Otowi, San Felipe, and

Albuquerque and the Rio Chama station of Chamita, water years 1985 to 2002.............................................. 25

I-1. Summary statistics of selected water-quality constituents for Rio Grande below Taos Junction Bridge,

water years 1985 to 2002 ................................................................................................................................... 30

I-2. Summary statistics of selected water-quality constituents for Rio Chama near Chamita,

water years 1985 to 2002 ................................................................................................................................... 31

I-3. Summary statistics of selected water-quality constituents for Rio Grande at Otowi Bridge, near

San Ildefonso, water years 1985 to 2002........................................................................................................... 32

I-4. Summary statistics of selected water-quality constituents for Rio Grande at San Felipe,

water years 1985 to 2002 ................................................................................................................................... 33

I-5. Summary statistics of selected water-quality constituents for Rio Grande at Albuquerque,

water years 1985 to 2002 ................................................................................................................................... 34

I-6. Anthropogenic compounds analyzed for in samples collected from the Rio Grande stations of Taos, Otowi,

San Felipe, and Albuquerque and the Rio Chama station of Chamita, water years 1985 to 2002 .................... 35
 v

CONVERSION FACTORS

Inch/pound to SI

Degrees Celsius ( ̊C) may be converted to degrees Fahrenheit ( ̊F) as follows:  ̊F = (1.8 ̊C) +32

Degrees Fahrenheit ( ̊F) may be converted to degrees Celsius ( ̊C) as follows:  ̊C = ( ̊F-32)/1.8

Vertical coordinate information is referenced to the North American Vertical Datum of 1988 (NAVD88).

Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD83).

Elevation, 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).

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

picocuries per liter (pCi/L), or milliequivalents per liter (meq/L).

Multiply By To obtain

Length

inch (in.) 2.54 centimeter (cm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

square mile (mi2) 2.590 square kilometer (km2)

Volume

ounce, fluid (fl. oz) 29.5735 milliliter (mL)

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

Flow Rate

cubic foot per second (ft3/s) 0.02832 cubic meter per second (m3/s)

Radioactivity

picocurie per liter (pCi/L) 0.037 becquerel per liter (Bq/L)
Streamflow and Water-Quality Trends of the Rio Chama 

and Rio Grande, Northern and Central New Mexico, Water 

Years 1985 to 2002

By Jeff B. Langman and Emma O. Nolan

Abstract

The City of Albuquerque plans to divert San Juan-Chama 

Project water from the Rio Grande for potable water use. This 

report examines streamflow and water-quality trends in the Rio 

Chama and the Rio Grande for water years 1985 to 2002 following the implementation of reservoir storage agreements in 

northern and central New Mexico. Streamflow/water-quality 

stations used for this study include the Rio Grande stations of 

Taos, Otowi, San Felipe, and Albuquerque and the Rio Chama 

station of Chamita.

Water years 1985 to 2002 were a period of larger than 

average precipitation and streamflow compared to the stations’ 

historical averages. Annual precipitation and streamflow 

trended downward during the study period because of a drought 

during 1999 to 2002. Streamflow in the Rio Chama and Rio 

Grande was divided into three distinct seasonal periods that corresponded to natural and anthropogenic influences: fall/winter 

baseflow (November through February), snowmelt runoff 

(March through June), and the irrigation/monsoon (July 

through October) seasons. 

A calcium bicarbonate water type was evident at all study 

area stations on the Rio Chama and Rio Grande. Specific conductance increased downstream, but alkalinity and pH did not 

substantially change in the downstream direction. Nearly all 

nitrogen and phosphorous concentrations were less than 1 milligram per liter for all stations. Median trace-element concentrations and maximum radionuclide concentrations did not exceed 

drinking-water standards. Anthropogenic compounds were 

infrequently detected in the Rio Chama and Rio Grande, and 

concentrations did not exceed drinking-water standards.

Water quality in the Rio Chama and Rio Grande varied 

spatially and temporally during water years 1985 to 2002. Specific conductance increased downstream in the Rio Grande during the fall/winter baseflow and snowmelt runoff seasons but 

was similar at the Taos, Otowi, and San Felipe stations during 

the irrigation/monsoon season. This similarity was a result of 

the release of stored water from Abiquiu Reservoir and Cochiti 

Lake, which masked the natural influences that increased specific conductance in the downstream direction during the other 

seasons. During all seasons, pH decreased and major ion concentrations remained stable at the Albuquerque station compared with the San Felipe station, but no single influence could 

be identified that caused these conditions. Manganese and uranium concentrations at the Otowi and San Felipe stations were 

largest during the fall/winter baseflow and smallest during the 

snowmelt runoff, indicating that ground-water inflows likely 

influenced these concentrations.

Water-quality temporal trends were evaluated for selected 

constituents during the study period and during the individual 

seasons. Downward trends in major ion concentrations were 

similar in magnitude at the Taos and Otowi stations, indicating 

that an upstream influence and (or) the downward trend in 

annual precipitation was the main reason(s) for these trends. 

The stations most affected by reservoirs, Chamita and San 

Felipe, were the only stations at which downward trends in 

major ions were apparent for flow-adjusted concentrations but 

not for seasonally correlated flow-adjusted concentrations, 

which indicates fewer seasonal differences at these stations due 

to reservoir operations. 

Introduction

Streamflow and water quality in northern and central New 

Mexico are important because of an increasing population and 

a semiarid climate. The City of Albuquerque implemented a 

strategy in the 1960’s for future use of surface water to supplement ground water as a potable water supply by becoming a 

partner in the San-Juan Chama Project (SJC Project). The SJC 

Project diverts streamflow from three tributaries of the San Juan 

River in southwestern Colorado, transports the water under the 

Continental Divide, and releases the water into the Rio Grande 

Basin through Willow Creek (tributary of the Rio Chama).

The City of Albuquerque has proposed diverting their 

allotment of SJC Project water (48,200 acre-ft per year) from 

the Rio Grande starting in 2006 (City of Albuquerque, 2005). 

Because of the proposed diversion of SJC Project water from 

the Rio Grande, analysis of streamflow and water-quality trends 

in the Rio Chama and Rio Grande is useful for understanding 

spatial and temporal changes that may affect river water use. 

Storage agreements for northern and central New Mexico reservoirs were implemented in the mid-1980’s and incorporated 

into the historical legislative directives that govern water management in the study area. The legislative directives form the 

reservoir operations framework, which influences streamflow 

in the Rio Chama and Rio Grande because of retention of natural riverflows and reservoir delivery obligations to downstream 

users according to various Federal, State, and local agreements. 

The City of Albuquerque has implemented various initiatives under the Water Resources Management Strategy (City of 

Albuquerque, 1997) to ensure a sustainable water supply. In 
2 Trends of the Rio Chama and Rio Grande, Water Years 1985 to 2002

cooperation with the City of Albuquerque, the U.S. Geological 

Survey (USGS) analyzed streamflow and water-quality data in 

the Rio Chama and Rio Grande to provide streamflow and 

water-quality trends to water resource managers so they can 

better understand the variability of the resource.

Purpose and Scope

This report characterizes streamflow and water-quality 

trends (spatial and temporal variability) of the Rio Chama and 

the Rio Grande for the existing (2002) reservoir operations 

framework in northern and central New Mexico during water 

years (October 1 to September 30) 1985 to 2002. The study area 

included the Rio Chama and the Rio Grande in central and 

northern New Mexico (fig. 1). The scope of analysis included 

streamflow and water-quality data collected from October 1, 

1984, to September 30, 2002. Water year 1985 represents the 

start of the existing (2002) framework for reservoir operations 

for Heron Lake, El Vado Reservoir, Abiquiu Reservoir, and 

Cochiti Lake and increased storage of native and non-native 

water in Abiquiu Reservoir (fig. 2). Water year 2002 was 

selected as an end point because it was the last full year of 

streamflow and water-quality data available at the time of analysis. Water-quality data were analyzed by defined categories: 

basic water chemistry and physical properties (specific conductance, alkalinity, pH, dissolved oxygen, chemical oxygen 

demand, and total dissolved solids); major ions; nutrients, 

organic carbon, and bacteria (nitrogen and phosphorous forms, 

total organic carbon (TOC), and fecal bacteria); trace elements; 

radionuclides; and anthropogenic compounds (pesticides and 

volatile and semivolatile organic compounds). 

Description of the Study Area

The study area is defined as the Rio Chama and Rio 

Grande from the Colorado-New Mexico border to the City of 

Albuquerque (fig. 1). The station network for this study consisted of streamflow-gaging stations on the Rio Chama and Rio 

Grande within the study area (table 1; fig. 1).

Physiography

The study area is bordered by the Continental Divide to the 

west and the Sangre de Cristo and Sandia Mountains to the east 

(fig. 1). Elevations in the study area range from about 4,650 to 

greater than 13,000 feet above NAVD88. The Rio Grande is the 

main drainage in the study area, and the Rio Chama is its largest 

tributary in this area. The Rio Grande originates in the San Juan 

Mountains in south-central Colorado, bisects New Mexico, and 

exits the State near El Paso, Texas. The Rio Chama drains 

north-central New Mexico and discharges to the Rio Grande 

near Española, New Mexico (fig. 1).

Climate

Climate in the study area is mostly semiarid with substantial variation in precipitation from the lower valley areas to the 

mountains. Annual precipitation in the mountains can exceed 

40 inches, whereas other areas in the watershed may receive 

less than 10 inches (Natural Resources Conservation Service, 

1999). Most precipitation typically falls during the irrigation/

monsoon season (Western Regional Climate Center, 2002), 

although the largest streamflows typically occur during the 

spring snowmelt runoff. 

Streamflow of the Rio Chama and Rio Grande

Streamflow in the Rio Chama is highly variable; the largest recorded annual-mean streamflow is 1,317 ft3/s and the 

smallest is 145 ft3/s at the Chamita station (period of record 

1913 to 2002). Rio Grande streamflow is similarly variable. The 

Rio Grande at the Taos station is upstream from the major reservoirs in the study area and provides an example of the variability of streamflow for this reach of the river. During the 

period of record (1926 to 2002), the largest annual-mean 

streamflow at the Taos station was 1,840 ft3/s and the smallest 

was 271 ft3/s. 

Influences on Streamflow and Water Quality in the 

Study Area

The Rio Grande begins in the mountains of Colorado and 

is soon altered by the effects of dams, irrigation diversions, and 

channelization. The Rio Grande is fully appropriated; all of its 

annual streamflow volume is accounted for by various compacts, treaties, and individual water rights (Rio Grande Compact Commission, 1999). The streamflow of the Rio Grande 

between the United States and the Republic of Mexico is governed by the 1944 Water Treaty. The interstate flow of the river 

between Colorado, New Mexico, and Texas is governed by the 

1937 Rio Grande Compact. Rio Grande streamflow within the 

study area is appropriated for municipal, agricultural, and recreational uses. 

Reservoirs

Streamflow in the Rio Chama and Rio Grande in the study 

area is regulated with four large reservoirs: Heron Lake, El 

Vado Reservoir, Abiquiu Reservoir, and Cochiti Lake (fig. 1). 

The U.S. Army Corps of Engineers and the Bureau of Reclamation coordinate operation of the reservoirs in the study area to 

allocate available water supplies, provide for irrigation needs, 

maintain flood control, and provide for recreation. Operation of 

the reservoir system is complex because release volumes and 

dates are in continual flux depending on available SJC Project 

water, native Rio Grande water, and the needs of the users. 

The Rio Grande Compact provides the legal framework 

for regulation of equitable apportionment of Rio Grande 

streamflow between States and permits each State to develop
Introduction 3

tud area
1974 1978 1982 1986 1990 1994 1998 

Fi

gure 2. Water storage in Heron Lake, El Vado Reservoir, Abiquiu Reservoir, and Cochiti Lake, 1974 to 2002

0

100,000200,000300,000400,000

0

100,000200,000300,000400,000

0

100,000200,000300,000400,000

0

100,000200,000300,000400,000

Water storage, in acre-feet

Heron LakeEl Vado Reservoir

Abiquiu ReservoirCochiti Lake

Start of existing reservoir operational framework
Introduction 5

and use its water resources provided each State meets its delivery obligations (Rio Grande Compact Commission, 1999). In 

addition to the Rio Grande Compact, operational requirements 

of the reservoirs and diversions that control streamflow in the 

Rio Chama and Rio Grande have a long history of legislative 

directives. A major legislative influence was the approval of the 

SJC Project, which allows for the diversion of streamflow from 

three tributaries of the San Juan River in southwestern Colorado 

into the Rio Grande Basin through the Rio Chama (diversions 

began in 1973). 

More recent legislative actions that influence streamflow 

regulation in the Rio Grande Basin include storage of as much 

as 200,000 acre-ft of SJC Project water in Abiquiu Reservoir 

(Public Law 97-140), which began in 1985, and storage of as 

much as 200,000 acre-ft of Rio Grande Basin water instead of 

SJC Project water in Abiquiu Reservoir (Public Law 100-522), 

which began in 1988. These two operational directives, along 

with prior compacts and treaties, provide the existing operational framework of surface-water regulation in the Rio Chama 

and Rio Grande. Additionally, existing Federal legislation, such 

as the Endangered Species Act, have required adjustments to 

reservoir operations to balance water user needs and environmental needs.

Tributaries

Within the study area, tributaries to the Rio Grande, other 

than the Rio Chama, contribute little to daily streamflow. Only 

Embudo Creek and the Jemez River (fig. 1) provide a mean 

annual streamflow greater than 50 ft3

/s. Numerous intermittent 

and ephemeral drainages flow into the Rio Chama and Rio 

Grande in response to snowmelt or summer thunderstorms. The 

Jemez River drains an area that has geothermal activity and 

contains larger dissolved-solids concentrations and different 

mineral content than the Rio Grande (Trainer and others, 2000). 

Ground-Water Inflows and Outflows

The Rio Grande is hydraulically connected with the surrounding basin-fill aquifer. The basin-fill aquifer is recharged 

along the mountain fronts, and ground water generally flows 

from the mountainous areas toward the Rio Grande (Ellis and 

others, 1993; Anderholm and others, 1995). Ground water in 

the Middle Rio Grande Basin (Cochiti Lake to Albuquerque in 

the study area) predominantly flows north to south but with 

greater east to west direction at the basin margins as a result of 

mountain-front recharge (Plummer and others, 2004).

Follansbee and Dean (1915) determined that the Rio 

Chama is likely a gaining stream from the town of Chama to its 

inflow to the Rio Grande because of ground-water inflows. 

Additional seepage studies between 1966 and 1968 confirmed 

these results and indicated overall gains from La Puente to its 

inflow to the Rio Grande (U.S. Geological Survey, 1968 and 

1969).

From Taos to Cochiti Lake, the Rio Grande is likely a gaining stream overall. Moore and Anderholm (2002) found an 

increase in streamflow greater than what could be attributed to 

inflow from the Rio Chama, indicating other inflows in this 

area. The USGS did find a losing reach in this area during a 

seepage investigation in 2002 (Jack Veenhuis, U.S. Geological 

Survey, written commun., 2003), but also found that earlier 

seepage investigations in 1964 included this reach in a larger 

gaining reach (Jack Veenhuis, written commun., 2002).

From Cochiti Dam to Albuquerque, the interaction of surface water and ground water becomes more complex. In many 

areas of this reach the water table outside the river corridor is 

below the river bottom (Kernodle and Scott, 1986; Kernodle 

and others, 1994). Within the river corridor, the effects of irrigation, drains, river leakage, and evapotranspiration (ET) form 

complex interactions that make it difficult to determine groundwater inflows and outflows. The Rio Grande likely both gains 

and loses streamflow as a result of ground-water inflows and 

Table 1. Selected streamflow-gaging stations in the study area.

[NAD83, North American Datum of 1983; HUC, hydrologic unit code; mi2, square miles; ft, feet; NAVD88, North American Vertical Datum of 1988]

1Drainage area does not include non-contributing areas, closed basins, or out-of-basin areas associated with interbasin transfers.

USGS station 

number

Streamflow-gaging

station name 

Report 

station name 

(fig. 1)

Latitude and 

longitude

(NAD83)

Location 

(county, HUC)

Drainage 

area (mi2

)

1

Elevation

(ft above 

NAVD88)

08276500 Rio Grande below Taos 

Junction Bridge, near Taos

Taos 36 ̊19'12"

105 ̊45'16"

Taos,

13020101

6,790 6,053

08290000 Rio Chama near Chamita Chamita 36 ̊04'26"

106 ̊06'42"

Rio Arriba,

13020102

3,044 5,657

08313000 Rio Grande at Otowi

Bridge, near San Ildefonso

Otowi 35 ̊52'29"

106 ̊08'32"

Santa Fe, 

13020101

11,360 5,491

08319000 Rio Grande at San Felipe San Felipe 35 ̊26'47" 

106 ̊26'26"

Sandoval,

13020201

13,160 5,119

08330000 Rio Grande at Albuquerque Albuquerque 35 ̊05'21" 

106 ̊40'50"

Bernalillo, 

13020203

14,500 4,949
6 Trends of the Rio Chama and Rio Grande, Water Years 1985 to 2002

outflows through this reach. S.S. Papadopulos and Associates 

(2000) determined that the Rio Grande from Cochiti Lake to the 

town of Bernardo typically loses water but does show a gain in 

winter months. The Rio Grande is likely a losing stream overall 

from Cochiti Lake to San Acacia as determined by model simulations (McAda and Barroll, 2002).

Evapotranspiration

Evapotranspiration (ET) from the Rio Chama and the Rio 

Grande corridors is substantial because of the arid climate, reservoirs, broad channel areas, and substantial riparian areas. S.S. 

Papadopulos and Associates (2000) estimated that mean-annual 

riparian ET from 1985 to 1998 was about 155,000 acre-ft for the 

Rio Grande from Cochiti Dam to San Acacia. S.S. Papadopulos 

and Associates (2000) also estimated that mean-annual agricultural ET from 1985 to 1998 was about 192,000 acre-ft in the 

Middle Rio Grande Valley from Cochiti Dam to San Acacia. 

Irrigation Diversions and Inflows

Agricultural areas in the study area rely on diversions of 

Rio Chama and Rio Grande water for irrigation. The agricultural areas and irrigation systems along the Rio Chama and 

from Pilar to Otowi on the Rio Grande are small compared with 

the agricultural areas and irrigation system of the Middle Rio 

Grande Conservancy District (MRGCD), which are located in a 

narrow band of land from Cochiti Lake to Albuquerque in the 

study area. The MRGCD provides water for flood irrigation by 

diverting water from the Rio Grande through a system of canals 

while directing return flows to the Rio Grande through drainage 

ditches and interior and riverside drains. The riverside drains 

also collect water from the interior drains and canals and leakage from the Rio Grande to prevent waterlogging of agricultural 

areas (Kernodle and Scott, 1986). 

Irrigation water applied to fields may return to the river as 

tail water (surface flow) or as ground water discharged to the 

canals and drains. Both pathways have been documented for 

Rio Grande agricultural areas outside the study area (Anderholm, 2002) and are assumed to be present in the study area. For 

this report, “irrigation return flow” indicates either or both of 

the possible pathway sources. Given the different pathways, 

irrigation return flow may occur throughout the year. Tail water 

may contribute return flow during the irrigation season, and 

captured shallow ground water may contribute during the irrigation season and also when diversions are not occurring 

(Anderholm, 2002). Possible influences from irrigation return 

flow and from ground-water inflows from the basin-fill aquifer 

in the Middle Rio Grande Basin are discussed separately.

Previous Studies

Installation of the study area’s reservoirs and the SJC 

Project substantially altered streamflow in the Rio Chama and 

Rio Grande (Mussetter Engineering, Inc., 2002; Langman and 

Anderholm, 2004). Moore and Anderholm (2002) noted that 

streamflow at stations in the study area during 1993 to 1995 was 

smallest during winter months, snowmelt runoff produced the 

largest flows through late spring and early summer, and summer thunderstorms produced large flows of short duration. 

On a regional scale, the USGS has performed water-quality studies as part of the National Water-Quality Assessment 

(NAWQA) Program for the Rio Grande Valley study unit, 

which encompasses the Rio Grande watershed from its headwaters in Colorado to the New Mexico–Texas border. For data collected between 1972 and 1990, Anderholm and others (1995) 

stated that nutrient concentrations in the Rio Grande, with the 

exception of phosphorus, generally remained constant and that 

pesticides were detected infrequently in the study area. Healy 

(1997) noted that dissolved solids, major ions, boron, lithium, 

molybdenum, strontium, and uranium increased in the downstream direction and that pesticides were detected infrequently 

for data collected from 1993 to 1995. For data collected 

between 1992 and 1995, Levings and others (1998) indicated 

that pesticide detections did not exceed U.S. Environmental 

Protection Agency (USEPA) drinking-water standards or applicable Federal or State ambient criteria or guidelines, that 

median nitrogen and phosphorous values were less than 0.12 

mg/L, and that dissolved solids increased in the downstream 

direction. For data collected between 1993 and 1995, Moore 

and Anderholm (2002) found that concentrations of dissolved 

solids, nutrients, and suspended sediment generally increased in 

the downstream direction but that concentrations decreased at 

the Otowi station because of Rio Chama inflow.

In addition to the NAWQA Program, other studies have 

examined Rio Grande water quality in the study area. Mills 

(2003) attributed most downstream increases in chloride concentration in the Rio Grande to ET and an effect on Rio Grande 

chloride loads by the Jemez River. Additionally, agricultural 

drain inflows did not appear to contribute substantial salt loads 

to the Rio Grande in the Albuquerque area, and chloride concentrations were similar or only slightly larger in drains than in 

river water for data collected in 2001 and 2002 (Mills, 2003). 

Passell and others (2004) described upward trends in flowadjusted values/concentrations of specific conductance, dissolved solids, and certain major ions at stations in northern New 

Mexico and downward trends of specific conductance, dissolved solids, and certain major ions at stations in central New 

Mexico for data collected between 1975 and 1999. Langman 

and Anderholm (2004) described an effect on Rio Grande water 

quality due to importation of SJC Project water and seasonal 

effects on water quality due to reservoir releases. 

Besides overall evaluation of water-quality trends, some 

studies have more closely examined possible influences on Rio 

Grande water quality in the study area. Anderholm (1987) indicated that agriculture in the Albuquerque area was likely 

responsible for larger specific-conductance values in shallow 

ground water compared to river values and that the shallow 

ground water might discharge to the river. Anderholm and others (1995) attributed the change in nutrient concentrations 

downstream from Albuquerque to irrigation return flows and 

the City’s wastewater treatment plant. Anderholm (1997) attrib-
Introduction 7

uted major ion concentrations in shallow ground water near the 

river in Albuquerque to the influence of agriculture and the system of canals and drains that recharge shallow ground water. 

Wilcox (1997) presented water-quality data for 1994 to 1996 

for the Rio Grande and MRGCD drains in the Albuquerque area 

that indicated differences between Rio Grande water and drain 

water. 

In addition to river water quality, reservoir water quality 

has been examined in the study area. In 1978-79, nitrogen, 

phosphorus, and iron, individually or combined, were algalgrowth limiters during various seasonal periods in Abiquiu Reservoir and Cochiti Lake (Johnson and Barton, 1980). In 1989, 

the State of New Mexico analyzed water samples from Abiquiu 

Reservoir and said that phosphorus was the limiting nutrient for 

algal growth (Potter and Davis, 1989). In 1991, the State of New 

Mexico indicated that nitrogen and phosphorous concentrations 

in Heron Lake were co-limiting for algal growth and that no 

pesticides were detected in the reservoir (New Mexico Environment Department, 1992). Bolin and others (1987) tried to model 

phosphorous changes in Abiquiu Reservoir and Cochiti Lake 

and found that settling velocities and flushing rates were important for phosphorous removal. Johnson and Barton (1980) 

described dissolved-oxygen stratification near the dam at 

Cochiti Lake during summer months and downward pH values 

with depth. 

Acknowledgments

The authors acknowledge the City of Albuquerque for providing the support to implement this study. In particular, the 

authors express their appreciation to John Stomp, City of Albuquerque Director of Water Resources, for his guidance and support of this study to better understand New Mexico’s water 

resources. 

Methods of Analysis

This study was based entirely on available data. Streamflow data consisted of daily-mean streamflow. Water-quality 

samples were discreet samples collected at Rio Chama and Rio 

Grande stations at different frequencies from October 1, 1984, 

to September 30, 2002. All data are stored in the USGS 

National Water Information System (NWIS) database; stations 

used for this investigation are presented in table 1. All statistical 

analyses were performed using the SPlus 6.1 statistical software 

package created by Insightful Corporation. The Seasonal Kendall test used in this study was applied using the USGS 

ESTREND module for SPlus 6.1.

Exploratory data analysis indicated non-normal data sets 

for streamflow and most water-quality constituents in the study 

area. Because of these non-normal data sets, nonparametric statistics were used for streamflow and water-quality analysis.

Water-quality data were grouped into six categories: basic 

water chemistry and physical properties (specific conductance, 

alkalinity, pH, dissolved oxygen, chemical oxygen demand, and 

total dissolved solids); major ions; nutrients, organic carbon, 

and bacteria (nitrogen and phosphorous forms, total organic 

carbon (TOC), and fecal bacteria); trace elements; radionuclides; and anthropogenic compounds (pesticides and volatile 

and semivolatile organic compounds). 

Water-Quality Spatial Trend Analysis

For all stations, summary statistics (minimum, 25th percentile, median, 75th percentile, and maximum values) were 

calculated for all water-quality constituents for which nine or 

more values were available (Supplemental information). Estimated values (values larger than the method detection level 

(MDL) but smaller than the laboratory reporting level (LRL)) 

were assumed to be actual concentrations. The MDL values 

were substituted for censored (non-detect) data to calculate the 

summary statistics. Because simple substitution of censored 

values with MDL values may result in larger estimates of statistical values (Helsel and Hirsch, 1991), all statistics less than or 

equal to the largest MDL value for that constituent are shown as 

censored data (Supplemental information). 

An MDL is defined as the statistically calculated minimum 

concentration that can be measured with 99 percent confidence 

that the reported value is greater than zero; MDL’s are determined from replicate analyses of small concentration standards 

in a typical representative matrix (Oblinger Childress and others, 1999). An MDL is used to control the reporting of false positives. An LRL is typically twice the MDL and is used to reduce 

reporting of false negatives (Oblinger Childress and others, 

1999). 

Summary statistics were used to evaluate spatial changes 

in water quality from upstream to downstream stations. Median 

values provided a central value for comparison of overall conditions during the study period, and minimum and maximum 

values and interquartile ranges (25th to 75th percentile) provided indicators of constituent variability during the study 

period.

Water-quality concentrations were compared to drinkingwater standards established by the USEPA under the Safe 

Drinking Water Act (U.S. Environmental Protection Agency, 

2004). These standards are not required for streamflow in the 

Rio Chama and Rio Grande, but the standards provide useful 

benchmarks for evaluating the quality of the water for its use as 

drinking water.
8 Trends of the Rio Chama and Rio Grande, Water Years 1985 to 2002

Streamflow and Water-Quality Seasonal Trend 

Analysis

Streamflow and water quality were evaluated for seasonal 

trends using box plots or annual fit lines. Box plots consist of 

the distribution’s median, interquartile range, standard span 

whiskers (interquartile range multiplied by 1.5), and outliers. 

To develop an annual fit line, the concentrations of a constituent 

during the study period were plotted without respect to year, 

and a fit line was applied using the LOESS smooth technique. 

The LOESS smooth technique derives a locally weighted fit 

line that responds to the individual data point and a few neighboring data points. A variable fit window with locally linear fitting was used to create the LOESS fit lines. 

Streamflow and Water-Quality Temporal Trend 

Analysis

Temporal trend analysis consisted of monotonic trend 

analysis using the Seasonal Kendall test or Mann-Kendall test 

to evaluate whether streamflow or flow-adjusted water-quality 

concentrations were increasing (upward trend), decreasing 

(downward trend), or showing no change during the study 

period. Water-quality concentrations were adjusted for streamflow to reduce the variability attributable to streamflow differences. Monotonic trend analysis for flow-adjusted water-quality concentrations during the study period was applied by 

season using the Seasonal Kendall test to reduce the variability 

attributable to seasonal differences. Reduction of the total variability increases the power of the trend analysis and increases 

the probability of detecting a trend that is a result of an influence 

other than seasonal or streamflow differences. Streamflow and 

flow-adjusted concentrations also were analyzed for individual 

seasonal temporal trends by using the Mann-Kendall test to 

evaluate whether the study period temporal trend was representative of trends within the individual seasonal periods. 

Because of non-normal data sets, water-quality concentrations were adjusted for streamflow using the non-parametric 

LOESS smooth technique. The LOESS smooth technique was 

used to derive a locally weighted fit line for determination of 

residuals (differences between the predicted value and the 

actual value). The Seasonal Kendall test applies the Mann-Kendall test to the residual data from each selected seasonal period 

and combines the results for an evaluation of an increase or 

decrease over time. The Mann-Kendall test uses Kendall’s tau 

correlation coefficient with the x-variable as time to test 

whether the y-variable (residuals in this study) tends to increase 

or decrease over time. Kendall’s tau was used to present 

strength of correlation between individual constituents and 

time. Kendall’s tau is a rank method (resistant to outliers) that 

measures the strength of the monotonic relation between two 

variables. The coefficient ranges from +1 (positive relation) to 

-1 (negative relation); values closer to +1 indicate a stronger 

relation. A value of zero indicates no correlation. Generally, a 

coefficient greater than or equal to +0.7 or less than or equal to 

-0.7 indicates a strong correlation for Kendall’s tau (Helsel and 

Hirsch, 1991).

Method detection level values were substituted for censored values for the Seasonal Kendall test provided that a single 

MDL existed for the constituent record. Additionally, the Seasonal Kendall test has certain requirements for the amount and 

distribution of data points based on the number of seasonal periods. Because of these requirements, the Seasonal Kendall test 

was applied only to data sets with a single MDL and with 50 or 

more data points of which at least 95 percent were larger than 

the MDL. The Mann-Kendall test for seasonal temporal trend 

analysis was applied to the same constituents as those selected 

for the Seasonal Kendall test.

A temporal trend in streamflow or water quality was based 

on a p-value (1 - α) less than or equal to 0.10 (90 percent confidence level) for both the Seasonal Kendall and the Mann-Kendall tests. If the p-value was greater than 0.10, the comparison 

was considered to indicate no temporal trend. The trend direction was based on the positive (upward trend) or negative 

(downward trend) value of the Seasonal Kendall or Mann-Kendall test (Kendall’s tau for both tests). The p-value indicates 

whether a trend was statistically significant and that the variability of the constituents could be explained by the relation 

between streamflow or concentration and time. Kendall’s tau 

results (strength of relation) were used to evaluate the magnitude of trends for comparison of sites.

Streamflow Trends of the Rio Chama and 

Rio Grande, Water Years 1985 to 2002

Seasonal Trends in Streamflow

Because of many natural and anthropogenic influences on 

streamflow, seasonal variation of streamflow in the Rio Chama 

and Rio Grande was substantial, and streamflow in the Rio 

Chama and Rio Grande were similar in seasonal patterns (fig. 

3). The annual streamflow pattern in the study area can be 

divided into three distinct seasons: fall/winter baseflow 

(November through February), snowmelt runoff (March 

through June), and the irrigation/monsoon (July through October) seasons (fig. 3). 

Streamflow generally increased in the downstream direction because of surface- and ground-water inflows (fig. 3). 

However, reservoir operations can reduce downstream flows 

during certain periods of the year, such as when streamflow is 

retained in a reservoir for flood protection or snowmelt runoff 

retention. Reservoir operations at Cochiti Lake moderated 

streamflow during the snowmelt runoff, resulting in smaller 

streamflow at the San Felipe station than at the Otowi station 

during this season. Additionally, diversions for agriculture 

along with ET and losses to ground water can reduce instream 

flow at downstream stations, as is evident during the irrigation/

monsoon season when streamflow decreased between San 

Felipe and Albuquerque.
Jan Feb Mar Apr May June July Aug Sept Oct Nov 

0

500

1,0001,5002,0002,5003,0003,5004,0004,500

Median daily-mean streamflow, in cubic feet per second

TCOSA

Snowmelt runoff begins Irrigation deliver

Snowmelt runoff season Irrigation/monsoon season Fall/w

Downstream order of stations

Fall/winter baseflow season

Figure 3 . Seasonal trend of streamflow at the Rio Grande stations of Taos, Otowi, San Felipe, and Albuqueand the Rio Chama station of Chamita, water years 1985 to 2002.

Reservoir operation change
10 Trends of the Rio Chama and Rio Grande, Water Years 1985 to 2002

Temporal Trends in Climate and Streamflow

The climate during the study period ranged from periods of 

above-average rainfall to drought conditions. The period of 

1978 to 1992 was an above-average rainfall period for New 

Mexico (Lewis and Hathaway, 2001). From 1999 to 2002, a 

drought resulted in below-average annual rainfall in New Mexico; water year 2002 was the second driest on record for the 

Southwest (Betancourt, 2003). Passell and others (2004) 

described an upward trend for Rio Grande streamflow from 

1975 to 1999, primarily during January, February, March, September, and October.

Mean-annual precipitation and mean-annual streamflow 

during the study period were larger at all sites and stations than 

during the entire period of record (tables 2 and 3), indicating a 

wetter climate during the study period. Temporal trend analysis 

of mean-annual precipitation, 1985 to 2002 (table 2), indicated 

a downward trend in annual precipitation except for the Red 

River site. Analysis of streamflow trends (table 3) for the study 

period also indicated downward trends except during the irrigation/monsoon season for stations downstream from Taos. These 

downward trends are likely a result of the drought that occurred 

in New Mexico from 1999 to 2002 during the study period. The 

upward trend in streamflow at sites downstream from Taos during the irrigation/monsoon season was likely a result of SJC 

Project water that minimized the natural decrease in streamflow 

that would have occurred without the SJC Project. The drought 

did affect SJC Project water inflow to the Rio Grande Basin, as 

seen by smaller diversions during 2000 and 2002 (table 4), but 

release of multiyear stored water from Heron Lake allowed SJC 

Project water users to receive their full allotment each year 

(total allotment is 96,200 acre-ft). Decreased SJC Project 

inflows to Heron Lake and release of full allotments during the 

drought reduced the water stored in Heron Lake (fig. 2).

Water-Quality Trends of the Rio Chama and 

Rio Grande, Water Years 1985 to 2002

Spatial and temporal trends in water quality were evaluated for Rio Chama and Rio Grande stations for which sufficient water-quality data were available for analysis. The six 

water-quality groups evaluated were basic water chemistry and 

physical properties (specific conductance, alkalinity, pH, dissolved oxygen, chemical oxygen demand, and total dissolved 

solids); major ions; nutrients, organic carbon, and bacteria 

(nitrogen and phosphorous forms, total organic carbon (TOC), 

and fecal bacteria); trace elements; radionuclides; and anthropogenic compounds (pesticides and volatile and semivolatile 

organic compounds).

Water-Quality Spatial Trends

The six water-quality groups were evaluated for changes 

between stations from upstream to downstream in the Rio 

Grande. The effect of the Rio Chama is described by comparison with data from the Rio Grande station upstream from the 

Rio Chama inflow (Taos) and the downstream station (Otowi).

Basic Water Chemistry and Physical Properties

Of all water-quality groups, basic water chemistry and 

physical properties provided the best indication of influences on 

water quality in the Rio Chama and Rio Grande. Median specific conductance in the Rio Chama and Rio Grande ranged 

from 290 to 370 μS/cm (tables I-1 to I-5, Supplemental information) and increased in the downstream direction, likely 

because of surface- and ground-water inflows and ET. Specific 

conductance in the Rio Chama (333-μS/cm median at the 

Chamita station) was larger than that in the Rio Grande 

upstream from the Rio Chama inflow (290-μS/cm median at the 

Taos station). Rio Chama inflow contributed to the increase in 

specific conductance in the Rio Grande (314-μS/cm median at 

the Otowi station). The largest increase in specific conductance 

between Rio Grande stations was between the San Felipe and 

Albuquerque stations, possibly as a result of Jemez River 

inflow, ET, and irrigation return flows (Langman and Anderholm, 2004). Additionally, Plummer and others (2004) measured specific conductance in ground water between San Felipe 

and Albuquerque that ranged from 400 to greater than 1,000

μS/cm. However, Plummer and others presented geochemical 

evidence that the Rio Grande recharges the aquifer from about 

San Felipe through Albuquerque, indicating that ground water 

would not substantially contribute to the Rio Grande through 

this reach.

Median alkalinity in the study area ranged from 94 to 113 

mg/L (tables I-1 to I-5, Supplemental information). Alkalinity 

did not substantially vary from site to site, and median alkalinity 

values increased or decreased only slightly from site to site: an 

8-percent increase from Taos to Otowi, a 6-percent increase 

from Otowi to San Felipe, and a 1-percent decrease from San 

Felipe to Albuquerque. Given the pH ranges described in the 

following paragraph, alkalinity in the Rio Chama and Rio 

Grande is determined by the bicarbonate concentration. 

Median pH in the study area ranged from 7.9 to 8.3 and 

decreased in the downstream direction (tables I-1 to I-5, Supplemental information). As with alkalinity, pH did not substantially vary from site to site and interquartile ranges were 

between 7.8 and 8.5 at all stations. The small ranges of pH and 

alkalinity indicate that natural and anthropogenic influences do 

not affect substantially pH and alkalinity substantially in the 

Rio Grande in the study area.

Streamflow in the Rio Chama and Rio Grande was well 

oxygenated; median dissolved oxygen concentrations ranged 

from 8.6 to 9.4 mg/L and minimum concentrations ranged from 

5.9 to 7.0 mg/L (tables I-1 to I-5, Supplemental information). 

Because minimum dissolved oxygen values were 5.9 mg/L or 

larger at all stations, hypoxic conditions likely do not occur at 

the Rio Chama and Rio Grande stations.
Water-Quality Trends of the Rio Chama and Rio Grande, Water Years 1985 to 2002 11

Table 2. Mean-annual precipitation in the study area.

[in., inches; periods of record are calendar years; p-value significant if less than or equal to 0.10]

1

Precipitation sites are National Weather Service Cooperative Network stations (New Mexico Climate Center, 2004). For analysis of precipitation during the 

study period and periods of record, annual precipitation values were removed when more than 1 month of data was missing.

Table 3. Mean-annual streamflow and streamflow temporal trends in the study area.

[ft3/s, cubic feet per second; p-value significant if less than or equal to 0.10; fall/winter baseflow, November through February; snowmelt runoff, March through 

June; irrigation/monsoon, July through October]

Table 4. Annual San Juan-Chama Project streamflow diversion from the Colorado River Basin into the Rio Grande Basin.

[acre-ft, acre feet]

Precipitation sites1 in 

the study area (fig. 1)

Mean-annual 

precipitation (in.), 

period of record

Mean-annual 

precipitation (in.), 

1984 to 2002

Precipitation 

site period of 

record

Temporal trend, 

1984 to 2002

MannKendall

p-value

Kendall’s 

tau

Chama 20.80 23.56 1914 - 2002 Downward 0.086 -0.286

Abiquiu Dam 9.79 10.30 1958 - 2002 Downward 0.054 -0.322

Red River 20.23 22.90 1918 - 2002 None 0.221 -0.205

Taos 12.24 13.12 1914 - 2002 Downward 0.103 -0.314

Los Alamos 18.25 19.54 1942 - 2002 Downward 0.002 -0.509

Cochiti Lake 12.17 13.16 1975 - 2002 Downward 0.031 -0.372

Albuquerque Airport 8.56 9.65 1914 - 2002 Downward 0.025 -0.374

Station (fig. 1) and 

seasonal period

Mean-annual 

streamflow

(ft3

/s), period

of record

Streamflow 

period of 

record

Mean-annual 

streamflow (ft3

/s), 

water years 1985 

to 2002

Streamflow temporal 

trend, water years 

1985 to 2002

MannKendall pvalue

Kendall’s 

tau

Taos 754 1926 - 2002 837 Downward <0.001 -0.157

Fall/winter baseflow Downward <0.001 -0.207

Snowmelt runoff Downward <0.001 -0.273

Irrigation/monsoon Downward <0.001 -0.166

Chamita 538 1913 - 2002 634 Downward 0.009 -0.022

Fall/winter baseflow Downward <0.001 -0.192

Snowmelt runoff Downward <0.001 -0.114

Irrigation/monsoon Upward <0.001 0.184

Otowi 1,501 1896 - 2002 1,623 Downward <0.001 -0.124

Fall/winter baseflow Downward <0.001 -0.282

Snowmelt runoff Downward <0.001 -0.264

Irrigation/monsoon Upward 0.011 0.036

San Felipe 1,422 1927 - 2002 1,574 Downward <0.001 -0.140

Fall/winter baseflow Downward <0.001 -0.285

Snowmelt runoff Downward <0.001 -0.246

Irrigation/monsoon Upward 0.014 0.035

Albuquerque 1,177 1943 - 2002 1,432 Downward <0.001 -0.158

Fall/winter baseflow Downward <0.001 -0.260

Snowmelt runoff Downward <0.001 -0.244

Irrigation/monsoon None 0.878 -0.002

Year Diversion, acre-ft Year Diversion, acre-ft Year Diversion, acre-ft

1984 113,619 1991 113,389 1998 96,701

1985 91,780 1992 87,064 1999 118,904

1986 89,177 1993 98,812 2000 42,741

1987 83,047 1994 82,193 2001 110,575

1988 63,563 1995 86,268 2002 6,306

1989 50,126 1996 58,528

1990 76,174 1997 142,256
12 Trends of the Rio Chama and Rio Grande, Water Years 1985 to 2002

Major Ions

Streamflow at all Rio Chama and Rio Grande stations was 

of the same calcium bicarbonate water type (fig. 4). Among stations, median concentrations of calcium and sulfate were the 

most variable of the major ions. Bicarbonate was the most prevalent major ion.

Nutrients, Organic Carbon, and Bacteria

All median nitrogen and phosphorous concentrations for 

the Rio Chama and Rio Grande stations were less than or equal 

to 0.40 mg/L, and all concentrations were less than 2 mg/L 

except for one total nitrite plus nitrate (12 mg/L) and one total 

phosphorous (2.8 mg/L) concentration (fig. 5; tables I-1 to I-5, 

Supplemental information). The 12-mg/L total nitrite plus 

nitrate concentration at the San Felipe station (January 1986) 

was the only nitrogen concentration to exceed the dissolved 10-

mg/L drinking-water standard (U.S. Environmental Protection 

Agency, 2004), and the 2.8-mg/L dissolved total phosphorous 

concentration at the Otowi station (July 1991) was the only 

phosphorous concentration to exceed the 0.50-mg/L drinkingwater standard.

Median TOC concentrations were similar at all stations, 

ranging from 3.6 to 5.0 mg/L; the largest median TOC concentration was at the Otowi station (tables I-1 to I-5, Supplemental 

information). Median fecal coliform and median fecal streptococci concentrations increased in the Rio Grande from Taos to 

Otowi. The median fecal coliform concentration at the Otowi 

station (64 colonies per 100 mL) was similar to that at the 

Chamita station (60 colonies per 100 mL) (tables I-1 to I-5, Supplemental information). The increase in TOC, fecal coliform, 

and fecal streptococci concentrations from Taos to Otowi cannot be attributed only to Rio Chama inflow because the distribution of these concentrations at the Otowi station was larger 

than the distribution at the Chamita station (fig. 5). 

Trace Elements

At all stations, median trace-element concentrations did 

not exceed drinking-water standards, and only individual aluminum, iron, and manganese concentrations exceeded standards. For each trace element and each station, the percentage 

of samples exceeding a drinking-water standard was no more 

than 4 percent (table 5). The aluminum drinking-water standard 

(200 μg/L) was exceeded at Otowi (4 percent of samples) and 

San Felipe (3 percent). The iron secondary standard (300 μg/L) 

was exceeded in 1 to 3 percent of samples at all stations except 

the Albuquerque station, at which no single sample exceeded 

the standard. The manganese secondary standard (50 μg/L) was 

exceeded at the Taos (4 percent), Otowi (2 percent), and San 

Felipe (3 percent) stations. Drinking-water standards generally 

were exceeded during the irrigation/monsoon season, and traceelement concentrations larger than drinking-water standards 

were detected only from April through October. Water-quality 

samples analyzed for aluminum, iron, and manganese were distributed nearly evenly across all seasonal periods (table 6).

Figure 4 . Median ion concentrations for the Rio Grande stations of Taos, Otowi, San Felipe, 

and Albuquerque and the Rio Chama station of Chamita, water years 1985 to 2002.

Ca Mg Na Cl SO4 HCO3

0.0

0.5

1.0

1.5

2.0

2.5

Ion concentration, in milliequivalents per liter

Taos

Chamita

Otowi

San Felipe

Albuquerque
0. 00. 51. 01. 52. 0

Total ammonia,

in milligrams per liter as nitrogen

0.000.130.260.390.520.65

Total phosphorus, in milligrams per liter*

0. 00. 20. 40. 6

Dissolved nitrite plus nitrate,

in milligrams per liter as nitrogen*

05

101520

Total organic carbon,

in milligrams per liter*

Figure 5. Total ammonia, total phosphorous, dissolved nitrite plus nitrate, total organic carbon, fecal coliform, and fecal streptococci cfor the Rio Grande stations of Taos, Otowi, San Felipe, and Albuquerque and the Rio Chama station of Chamita, water years 1985 to 

Taos Chamita Otowi San Felipe Albuquerque

1

10

100

1,000

10,000

Fecal coliform, in colonies per 100 milliliters

Taos Chamita Otowi San Feli

1

10

100

1,000

10,000

Fecal streptococci, in colonies per 100 milliliters 

*One large outlier not shown for nitrate plus nitrite, phosphorous, and total organic carbon plots. MDL- largest and smallest method detection levels reporte

MDL

MDL

MDL

No data

1

1

O

IQ
14 Trends of the Rio Chama and Rio Grande, Water Years 1985 to 2002

Table 5. Median dissolved trace-element concentrations in the Rio Chama and Rio Grande during water years 1985 to 2002 and percentage exceedance of applicable drinking-water standards.

[%, percentage of samples that exceeded the drinking-water standard; μg/L, micrograms per liter; NA, none available; <, less than]

1

Drinking-water standard maximum contaminant levels as issued by the U.S. Environmental Protection Agency for National Primary Drinking Water Regulations (U.S. Environmental Protection Agency, 2004). 

2

Drinking-water standard type refers to the U.S. Environmental Protection Agency’s designation for primary, secondary, or action level standard per the National Primary Drinking Water Regulations (U.S. Environmental Protection Agency, 2004).

3

Total and dissolved chromium concentrations were compared to the 100-μg/L total concentration drinking-water standard.

Table 6. Seasonal number of samples collected for aluminum, iron, and manganese analysis for the Rio Grande stations of Taos, Otowi, 

San Felipe, and Albuquerque and the Rio Chama station of Chamita during water years 1985 to 2002.

Station (fig. 1) Taos Chamita Otowi San Felipe Albuquerque Drinkingwater 

standard1

Drinkingwater 

standard 

type2 Constituent Unit Median % Median % Median % Median % Median %

Aluminum μg/L 13 0 4 0 11 4 5 3 NA NA 200 Secondary

Arsenic μg/L 2 0 2 0 2 0 2 0 3 0 10 Primary

Barium μg/L 28 0 71 0 57 0 68 0 NA NA 2,000 Primary

Boron μg/L 40 NA 30 NA 40 NA 40 NA 60 NA NA NA

Chromium3 μg/L 1 0 <1 0 <1 0 <1 0 <1 0 100 Total

Copper μg/L 2.0 0 1.7 0 1.5 0 1.2 0 2.0 0 1,300 Action

Iron μg/L 19 2 16 1 14 2 10 3 14 0 300 Secondary

Manganese μg/L 8.1 4 5.7 0 5.0 2 9.3 3 NA NA 50 Secondary

Molybdenum μg/L 6 NA 1.2 NA NA NA 4.0 NA NA NA NA NA

Nickel μg/L 1.0 NA 1.0 NA 1.00 NA 1.0 NA NA NA NA NA

Zinc μg/L <10 0 3 0 3 0 3 0 3 0 5,000 Secondary

Constituent Taos Chamita Otowi San Felipe Albuquerque

Aluminum total samples 13 16 110 33 4

Fall/winter baseflow 4 7 32 10 1

Snowmelt runoff 5 5 37 10 1

Irrigation/monsoon 4 4 41 13 2

Iron total samples 90 69 139 65 17

Fall/winter baseflow 25 22 43 17 5

Snowmelt runoff 36 27 46 27 8

Irrigation/monsoon 29 20 50 21 4

Manganese total samples 45 46 132 32 4

Fall/winter baseflow 12 15 36 10 1

Snowmelt runoff 18 17 45 10 1

Irrigation/monsoon 15 14 51 12 2
Water-Quality Trends of the Rio Chama and Rio Grande, Water Years 1985 to 2002 15

Radionuclides

Samples for radionuclide analysis were not frequently collected at the stations during the study period. Of the radionuclides analyzed, alpha particles, radium-226, and natural uranium were the most common, and maximum concentrations did 

not exceed drinking-water standards (table 7).

Anthropogenic Compounds

Anthropogenic compounds were rarely detected (table 8), 

and concentrations did not exceed 0.1 μg/L or drinking-water 

standards (table 9). Anthropogenic compounds were analyzed 

only for samples collected between March and September for 

all stations except Chamita, where samples were collected during all months for anthropogenic compound analysis. Nearly all 

analyses were conducted for pesticide compounds only (table I6, Supplemental information), and all detections listed in table 

9 are pesticides.

Water-Quality Seasonal Trends

Five of the six water-quality groups were analyzed for 

changes by season. Data were insufficient for seasonal trend 

analysis of anthropogenic compounds.

Basic Water Chemistry and Physical Properties

Basic water chemistry and physical properties indicate that 

water quality in the study area varied spatially and temporally 

during the study period. Specific conductance increased downstream in the Rio Grande during the fall/winter baseflow and 

snowmelt runoff seasons, but the distribution of specific-conductance values at Taos, Otowi, and San Felipe stations were 

similar during the irrigation/monsoon season (fig. 6). This pattern indicates that influences that increase specific conductance 

in the downstream direction were masked or not present during 

the irrigation/monsoon season. Because of the release of stored 

water from the reservoirs, in particular Abiquiu Reservoir and 

Cochiti Lake, during the irrigation/monsoon season, this stored 

water released from the reservoirs likely was masking the natural influences that increased specific conductance in the downstream direction during the other seasons.

The inflow of the Rio Chama increases specific conductance between the Taos and Otowi stations during the fall/winter baseflow and snowmelt runoff seasons (fig. 6). During the 

irrigation/monsoon season, the specific conductance of Rio 

Chama inflow was similar to that at the Taos station and no 

increase in specific conductance was evident at the Otowi station. The effect of the Rio Chama on specific conductance in the 

Rio Grande was largest during the fall/winter baseflow season, 

when the largest specific conductance was measured at the 

Chamita station.

Specific conductance in the Rio Grande between the 

Otowi and San Felipe stations increased during the fall/winter 

baseflow and snowmelt runoff seasons (fig. 6). Release of 

stored snowmelt runoff from Cochiti Lake during the irrigation/

monsoon season has been shown to decrease specific conductance at the San Felipe station compared with the Otowi station 

during this seasonal period (Langman and Anderholm, 2004). 

Because natural inflows of ground and surface water were 

likely a greater percentage of total flow in the Rio Grande during the fall/winter baseflow and possibly the snowmelt runoff 

seasons, these inflows likely entered the Rio Grande between 

the Otowi and San Felipe stations and increased specific conductance during these seasons. Although evaporation at Cochiti 

Lake was possibly responsible for this increase, it does not seem 

likely because the increase in specific conductance between the 

stations was largest during the snowmelt runoff season and 

when water temperatures were lowest (fall/winter baseflow season). Plummer and others (2004) defined an area east of the Rio 

Grande from Galisteo Creek to Arroyo Tonque that likely discharges ground water to the Rio Grande upstream from the San 

Felipe station. Median specific conductance of ground water in 

this area was greater than 1,200 μS/cm. Water-quality samples 

from Galisteo Creek from 1968 to 1979 also indicated surface 

runoff from this area with relatively large specific conductance 

(five samples ranging from 465 to 1,710 μS/cm) (U.S. Geological Survey, 2004).

Specific conductance in the Rio Grande increased during 

each seasonal period from San Felipe to Albuquerque (fig. 6). 

This increase was likely the result of natural influences such as 

ET and surface inflows such as the Jemez River. The Jemez 

River median specific conductance for data collected during the 

study period was 888 μS/cm (U.S. Geological Survey, 2004). 

Substantial ground-water inflows to the Rio Grande in this area 

are unlikely (Plummer and others, 2004).

The influence of irrigation return flows on specific conductance in the Rio Grande between San Felipe and Albuquerque is not discernible. Specific conductance increased between 

these stations during the fall/winter baseflow when irrigation 

return flows were likely minimal. Although many MRGCD 

canals carry no flow from November through February, they do 

carry flow beginning in March when the MRGCD begins 

diverting water to make irrigation water available to its customers (S.S. Papadopulos and Associates, 2002). Many of the 

drains along the river carry substantial flow throughout the 

year, but flow is likely composed of mostly river leakage 

instead of irrigation return flows during the winter. 

Seasonal patterns of alkalinity in the Rio Chama and Rio 

Grande were similar to seasonal patterns of specific conductance (fig. 7). Alkalinity increased in the Rio Grande in the 

downstream direction during the fall/winter baseflow and 

snowmelt runoff seasons except from San Felipe to Albuquerque and did not increase between stations during the irrigation/

monsoon season. The Rio Chama provided an increase in alkalinity to the Rio Grande only during the fall/winter baseflow 

season, and alkalinity in the Rio Chama was less than that in 

streamflow at the Taos station during the snowmelt runoff and 

irrigation/monsoon seasons. Alkalinity increased from the 

Otowi to San Felipe station during the fall/winter baseflow and 

snowmelt runoff seasons, but an increase is not as apparent during the irrigation/monsoon season.
16 Trends of the Rio Chama and Rio Grande, Water Years 1985 to 2002

Table 7. Maximum dissolved radionuclide concentrations detected in the Rio Chama and Rio Grande during water years 1985 to 2002 and 

applicable drinking-water standards.

[pCi/L, picocuries per liter; μg/L, micrograms per liter; NA, none available]

1

Drinking-water standard maximum contaminant levels as issued by the U.S. Environmental Protection Agency for National Primary Drinking Water Regulations (U.S. Environmental Protection Agency, 2004). 

2

Standard is for radium-226 and radium-228 combined.

Table 8. Percentage of anthropogenic compounds detected in samples collected from the Rio Grande stations of Taos, Otowi, San Felipe, 

and Albuquerque and the Rio Chama station of Chamita during water years 1985 to 2002. 

Table 9. Anthropogenic compounds detected in samples from the Rio Grande stations of Taos, Otowi, San Felipe, and Albuquerque and 

the Rio Chama station of Chamita during water years 1985 to 2002 and associated drinking-water standards.

[recoverable, compounds were partitioned from water sample by C-18 solid phase extraction cartridge; month of detection, month when sample was collected for

each detection; total, unfiltered sample; dissolved, filtered sample; μg/L, micrograms per liter; ----, no detections; NA, not established; E, estimated value less than 

the laboratory reporting level]

Note: all detections are single detections that were produced from one sample

1

Drinking-water standard maximum contaminant levels as issued by the U.S. Environmental Protection Agency for National Primary Drinking Water Regulations (U.S. Environmental Protection Agency, 2004). 

Constituent Unit Taos Chamita Otowi San Felipe Albuquerque Drinking-water standard1

Alpha particles pCi/L NA NA 3.4 NA NA 15

Radium-226 pCi/L 0.05 NA 0.67 0.57 0.37 25 

Uranium μg/L 3.0 4.48 4.90 3.64 3.6 30

Taos Chamita Otowi San Felipe Albuquerque

Total compounds analyzed 166 600 343 60 115

Percentage of compounds detected 0.6 0.5 1.5 1.7 1.7

Compound, 

recoverable Unit

Month of 

detection Taos Chamita Otowi

San 

Felipe Albuquerque

Drinkingwater 

standard1

2,4-D, total μg/L March, March ---- ---- ---- 0.01 0.01 70

Atrazine, dissolved μg/L July ---- E 0.003 ---- ---- ---- 3

DCPA, dissolved μg/L July ---- E 0.003 ---- ---- ---- NA

Diazinon, dissolved μg/L May ---- ---- 0.008 ---- ---- NA

Diazinon, total μg/L September ---- ---- ---- ---- 0.01 NA

EPTC, dissolved μg/L June ---- ---- 0.004 ---- ---- NA

Malathion, dissolved μg/L July ---- ---- 0.007 ---- ---- NA

p,p'-ethyl-DDD, total μg/L September 0.1 ---- ---- ---- ---- NA

Simazine, dissolved μg/L July ---- ---- E 0.003 ---- ---- 4

Tebuthiuron, dissolved μg/L July, April ---- E 0.01 0.01 ---- ---- NA
Water-Quality Trends of the Rio Chama and Rio Grande, Water Years 1985 to 2002 17

150

250

350

450

550

All seasons

150

250

350

450

550

Fall/winter baseflow

150

250

350

450

550

Snowmelt runoff

Taos Chamita Otowi San Felipe Albuquerque

150

250

350

450

550

Irrigation/monsoon

Figure 6. Specific conductance during seasonal periods for the Rio Grande stations of Taos, Otowi, San Felipe,

and Albuquerque and the Rio Chama station of Chamita, water years 1985 to 2002.

Specific conductance, in microsiemens per centimeter at 25 degrees Celsius

1.5 times IQR

1.5 times IQR

50th (median)

75th percentile

25th percentile

Outlier

IQR- interquartile range
18 Trends of the Rio Chama and Rio Grande, Water Years 1985 to 2002

50

90

130

170

Alkalinity concentration, in milligrams per liter as calcium carbonate

All seasons

50

90

130

170

Fall/winter baseflow

50

90

130

170

Snowmelt runoff

Taos Chamita Otowi San Felipe Albuquerque

50

90

130

170

Irrigation/monsoon

Figure 7. Alkalinity concentrations during seasonal periods for the Rio Grande stations of Taos, Otowi, San Felipe, and 

Albuquerque and the Rio Chama station of Chamita, water years 1985 to 2002.

1.5 times IQR

1.5 times IQR

25th percentile

75th percentile

50th (median)

Outlier

IQR- interquartile range
Water-Quality Trends of the Rio Chama and Rio Grande, Water Years 1985 to 2002 19

For all sites except Taos, alkalinity concentrations typically were largest during the fall/winter baseflow season (fig. 

7). Because ground-water inflows likely provide a larger percentage of total streamflow during the fall/winter baseflow, 

these inflows influenced alkalinity in the Rio Chama and Rio 

Grande. Ground-water inflows were diluted during snowmelt 

runoff because of large surface-water inflows, which resulted in 

decreased alkalinity at each site during this season. During the 

irrigation/monsoon season, the effect on alkalinity from the 

release of stored snowmelt runoff from the reservoirs is apparent because alkalinity at Chamita, Otowi, and San Felipe was 

more similar to concentrations during the snowmelt runoff season than to concentrations during the fall/winter baseflow season.

During the snowmelt runoff and irrigation/monsoon seasons, Rio Chama inflow decreased pH in the Rio Grande (fig. 

8). During the fall/winter baseflow season, pH in the Rio 

Chama was similar to or larger than pH in the Rio Grande and 

no change occurred between the Taos and Otowi sites. During 

the fall/winter baseflow and snowmelt runoff seasons, pH values in the Rio Grande at the Otowi and San Felipe stations were 

similar, but during the irrigation/monsoon season, pH decreased 

from Otowi to San Felipe, likely a result of releases from 

Cochiti Lake. 

From San Felipe to Albuquerque, pH decreased during 

each season. Rio Grande pH did not decrease as a result of 

Jemez River inflow because the median pH at the USGS Jemez 

River below Jemez Canyon Dam station (08329000) during the 

study period was 8.2 (range of 7.5 to 9.1). A decrease in pH due 

to ground-water inflows also is unlikely because Plummer and 

others (2004) found evidence that ground water in this reach is 

highly influenced by water infiltrating from the Rio Grande. 

The decrease in pH may be a result of irrigation and drain return 

flow that is composed of shallow ground water captured by 

canals and drains along the river and returned to the river 

throughout the year. 

Major Ions

The calcium bicarbonate water type for streamflow at all 

stations did not change between seasons, although major ion 

concentrations did vary from site to site and among seasons (fig. 

9). Median concentrations that varied the most among sites 

were calcium and sulfate during the fall/winter baseflow and 

snowmelt runoff seasons, and sodium and bicarbonate during 

the irrigation monsoon season. The shift in variability of 

median concentrations was a result of similar concentrations at 

the Chamita site during the snowmelt runoff and irrigation/

monsoon seasons. If median ion concentrations at the Chamita 

site are not considered, calcium, sodium, and bicarbonate were 

the most variable ions during the irrigation/monsoon season.

Median major ion concentrations at the Chamita station 

were similar to Rio Grande concentrations during the fall/winter baseflow and snowmelt runoff seasons (fig. 9). During the 

irrigation/monsoon season, median concentrations at the Rio 

Grande stations increased compared with snowmelt runoff concentrations, but median concentrations at the Chamita station 

did not increase. The snowmelt runoff that was retained in Rio 

Chama reservoirs was released during the irrigation/monsoon 

season, and median concentrations at the Chamita station were 

similar during both seasons.

During the fall/winter baseflow season, median major ion 

concentrations were smallest at the Taos station and increased 

in the downstream direction due to Rio Chama inflow and other 

influences (fig. 9). During the snowmelt runoff season, Rio 

Chama inflow diluted sodium and chloride concentrations in 

the Rio Grande, resulting in smaller median concentrations at 

the Otowi station than those at the Taos station. During the irrigation/monsoon season, reservoir releases from Abiquiu Reservoir on the Rio Chama and from Cochiti Lake on the Rio 

Grande diluted ion concentrations, resulting in smaller magnesium, sodium, and chloride concentrations at the Otowi and San 

Felipe stations compared with those at the Taos station. 

During all seasons, median major ion concentrations were 

the most stable at the Albuquerque station (fig. 9). Median concentrations at Albuquerque did not correspond to seasonal 

changes in concentrations at the San Felipe station. Plummer 

and others (2004) described ranges of major ion concentrations 

in ground water between San Felipe and Albuquerque near the 

river that were larger than those at the San Felipe and Albuquerque stations, but other geochemical data indicate that the Rio 

Grande primarily loses water to the aquifer through this reach. 

Likely a combination of factors such as ET, the Jemez River and 

other surface-water inflows, and irrigation return flows variably 

affect the Rio Grande throughout the year and result in similar 

major ion concentrations at the Albuquerque station during all 

seasons.

Nutrients, Organic Carbon, and Bacteria

Analysis of seasonal trends of nitrogen and phosphorous 

forms was not feasible because of small concentrations and the 

large number of samples with censored values. TOC and fecal 

streptococci provided sufficient data, however, for examination 

of seasonal trends in the Rio Chama and Rio Grande. For both 

constituents, concentrations were smallest during the fall/winter baseflow, increased during the snowmelt runoff, and were 

largest typically during the snowmelt runoff or irrigation/monsoon season (fig. 10). The Rio Chama appears to increase fecal 

streptococci, and Cochiti Lake likely decreases fecal streptococci in the Rio Grande.

Trace Elements

Of the trace elements that exceeded drinking-water standards (aluminum, iron, and manganese), only manganese indicates a seasonal pattern. Manganese concentrations decreased 

during the snowmelt runoff season, began to increase during the 

irrigation/monsoon season, and were largest during the fall/

winter baseflow season (fig. 11). This pattern indicates that 

manganese concentrations in the Rio Grande were diluted during spring runoff and were influenced by ground-water inflows. 
20 Trends of the Rio Chama and Rio Grande, Water Years 1985 to 2002

7.0

7.5

8.0

8.5

pH, in standard units

All seasons

7.0

7.5

8.0

8.5

Fall/winter baseflow

7.0

7.5

8.0

8.5

Snowmelt runoff

Taos Chamita Otowi San Felipe Albuquerque

7.0

7.5

8.0

8.5

Irrigation/monsoon

Figure 8. Seasonal period pH for the Rio Grande stations of Taos, Otowi, San Felipe, and Albuquerque 

and the Rio Chama station of Chamita, water years 1985 to 2002.

9.0

9.0

9.0

9.0

IQR- interquartile range

1.5 times IQR

1.5 times IQR

75th percentile

50th (median)

25th percentile

Outlier
Water-Quality Trends of the Rio Chama and Rio Grande, Water Years 1985 to 2002 21

0.0

0.5

1.0

1.5

2.0

2.5

Ion concentration, in milliequivalents per liter

All seasons Fall/winter baselfow

Ca Mg Na Cl SO4 HCO3

EXPLANATION

0.0

0.5

1.0

1.5

2.0

2.5

Snowmelt runoff

Taos

Chamita

Otowi

San Felipe

Albuquerque

Ca Mg Na Cl SO4 HCO3

Irrigation/monsoon

Figure 9 . Median ion concentrations during seasonal periods for the Rio Grande stations of Taos, Otowi,

San Felipe, and Albuquerque and the Rio Chama station of Chamita, water years 1985 to 2002.
22 Trends of the Rio Chama and Rio Grande, Water Years 1985 to 2002

Jan Feb Mar Apr May June July Aug Sept Oct Nov Dec

1

10

100

1,000

10,000 Fecal streptococci concentration, in colonies per 100 milliliters

Fit lines were created using the LOESS smooth technique. EXPLANATION

0

3

6

9

12

15

Total organic carbon concentration, in milligrams per liter

Taos

Chamita

Otowi

San Felipe

Figure 10. Seasonal trend of total organic carbon and fecal streptococci for the Rio Grande stations of 

Taos, Otowi, and San Felipe and the Rio Chama station of Chamita, water years 1985 to 2002.
Water-Quality Trends of the Rio Chama and Rio Grande, Water Years 1985 to 2002 23

Radionuclides

Uranium is a relatively soluble radionuclide in its highly 

oxidized form (U6+) and is generally present in natural waters 

ranging from 0.1 to 10 μg/L (Hem, 1989). A seasonal trend plot 

of uranium indicates that concentrations fluctuate seasonally 

(fig. 12). Similar to manganese, uranium concentrations in the 

Rio Grande decreased with snowmelt runoff, then increased 

during the irrigation/monsoon season. The largest concentrations were detected during the winter months when streamflow 

was smallest and ground-water inflows were largest. Uranium 

concentrations at Otowi and San Felipe were similar, but the 

range of those at San Felipe was smaller, possibly due to sediment deposition or mixing in Cochiti Lake.

Water-Quality Temporal Trends

Temporal trend analysis was used to detect statistically 

significant increases or decreases in flow-adjusted concentrations during the study period (study period trends) and during 

individual seasons (seasonal trends) at each station. Samples for 

analysis of specific conductance, dissolved oxygen, pH, calcium, magnesium, sodium, sulfate, and chloride were of sufficient number and seasonal representation for analysis of study 

period trends and seasonal trends (table 10).

Study period trends were not significant for specific conductance, dissolved oxygen, and pH. Seasonal trends of these 

constituents were evident at certain stations during specific seasons (table 10), but there was no consistent pattern in seasonal

Jan Feb Mar Apr May June July Aug Sept Oct Nov Dec

EXPLANATION

0

5

10

15

20

25

Dissolved manganese concentration, in micrograms per liter

Taos

Chamita

Otowi

San Felipe

Figure 11. Seasonal trend of manganese concentrations for the Rio Grande stations of Taos, Otowi, and 

 San Felipe and the Rio Chama station of Chamita, water years 1985 to 2002.

Fit lines were created using the LOESS smooth technique.

Method detection level
24 Trends of the Rio Chama and Rio Grande, Water Years 1985 to 2002

trends among stations. Only at the San Felipe station were seasonal trends not detected for these constituents, likely an effect 

of Cochiti Lake. Langman and Anderholm (2004) determined 

that Cochiti Lake has a moderating effect on specific conductance between Otowi and San Felipe because of the retention 

and later release of snowmelt runoff from the reservoir.

Significant decreases in calcium, magnesium, sodium, sulfate, and chloride concentrations were detected for the study 

period and during most seasons at each station (table 10). 

Decreasing trends and similar trend magnitudes (Kendall’s tau) 

for major ion concentrations at Taos and Otowi indicate that 

water-quality influences upstream from the study area and (or) 

the downward trend in annual precipitation (table 2) strongly 

affected major ion concentrations and were likely the main reason(s) for the downward trends in the study area. 

The lack of major ion study period trends at the San Felipe 

station compared with the other stations indicates that the effect 

of either Cochiti Lake or ground-water inflows were masking 

the downward trend at the Taos and Otowi stations. Seasonal 

trends (decreases) at the San Felipe station were detected only 

for calcium, sodium, and sulfate concentrations during the fall/

winter baseflow season. Ground-water inflows during the fall/

winter baseflow season likely diminished during the study 

period because of the downward trend in annual precipitation 

(table 2). Storage and mixing in Cochiti Lake likely minimized 

major ion concentration-trend decreases during the other two 

seasonal periods. 

The stations most affected by reservoirs, Chamita and San 

Felipe, were the only ones at which downward trends in major 

ions were apparent for flow-adjusted concentrations (MannKendall test) during the study period but not for flow-adjusted 

concentrations with seasonal correlation (Seasonal Kendall 

test) (table 10). Study period trends without seasonal correlation 

indicate that flow-adjusted concentrations at the Chamita and 

San Felipe stations were more similar among seasons than concentrations among seasons at the other stations. Although study 

period trends were still apparent at these stations, seasonal differences were reduced due to mixing of seasonal inflows and 

retained reservoir water.

Using multiple trend methods (linear regression, MannKendall test, and Seasonal Kendall test), Passell and others 

(2004) described upward trends in calcium, sodium, magnesium, bicarbonate, and chloride at the Taos station for data collected from 1975 to 1999. The same study described downward

Jan Feb Mar Apr May June July Aug Sept Oct Nov Dec

EXPLANATION

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

Dissolved uranium concentration, in micrograms per liter

Otowi

San Felipe

Fit lines were created using the LOESS smooth technique.

Method detection level

Figure 12. Seasonal trend of dissolved uranium concentrations for the Rio Grande stations of Otowi 

and San Felipe, water years 1985 to 2002.
Table 10. Results of Seasonal Kendall test (study period) and Mann-Kendall test (seasonal period) for temporal trend analysis of flow-adjusted concestations of Taos, Otowi, San Felipe, and Albuquerque and the Rio Chama station of Chamita, water years 1985 to 2002.[Constituent presents results of Seasonal Kendall test for all seasons during the study period (study period trend), and subsequent seasons (italics) present the results of the Mansonal trend); p-value significant if less than or equal to 0.10; tau, Kendall’s tau; ----, no descriptor or value shown because no significant trend; fall/winter baseflow, November thMarch through June; irrigation/monsoon, July through October; NA, not available; <, less than]

1Because of a limited number of data points during water years 1985 and 1986, the number of years for trend analysis of Chamita data was shortened to water years 1986 to 

water years 1987 to 2002 for all other constituents.

2This constituent indicated a trend in flow-adjusted concentrations without seasonal correlation. The values presented for this constituent are uncorrected for seasonal correla

Mann-Kendall test for the study period.

Constituent and 

seasonal period

Taos Chamita1 Otowi San Felipe 

pvalue trend tau p- value trend tau p- value trend tau p- value trend tau 

Specific conductance 0.460 ---- ---- 0.838 ---- ---- 0.522 ---- ---- 0.646 ---- ---- 

Fall/winter baseflow 0.235 ---- ---- 0.418 ---- ---- 0.357 ---- ---- 0.185 ---- ---- Snowmelt runoff 0.809 ---- ---- 0.158 ---- ---- 0.099 Downward -0.145 0.386 ---- ---- Irrigation/monsoon 0.092 Downward -0.210 0.005 Upward 0.302 0.045 Downward -0.179 0.407 ---- ---- 

Dissolved oxygen 0.276 ---- ---- 0.543 ---- ---- 0.516 ---- ---- 0.648 ---- ---- 

Fall/winter baseflow 0.859 ---- ---- 0.003 Downward -0.342 0.385 ---- ---- 0.919 ---- ---- Snowmelt runoff 0.048 Downward -0.227 0.197 ---- ---- 0.001 Downward -0.304 0.778 ---- ---- Irrigation/monsoon 0.897 ---- ---- 0.241 ---- ---- 0.059 Upward 0.177 0.653 ---- ---- 

pH 0.394 ---- ---- 0.370 ---- ---- 0.357 ---- ---- 0.268 ---- ---- 

Fall/winter baseflow 0.797 ---- ---- 0.034 Downward -0.243 0.925 ---- ---- 0.144 ---- ---- Snowmelt runoff 0.773 ---- ---- 0.459 ---- ---- 0.334 ---- ---- 0.241 ---- ---- Irrigation/monsoon 0.897 ---- ---- 0.179 ---- ---- 0.065 Downward -0.171 0.496 ---- ---- 

Calcium 0.047 Downward -0.296 0.256 ---- ---- 0.013 Downward -0.291 0.053 Downward -0.261 

Fall/winter baseflow 0.023 Downward -0.323 0.059 Downward -0.290 0.682 ---- ---- 0.032 Downward -0.347 Snowmelt runoff 0.050 Downward -0.229 0.032 Downward -0.293 0.004 Downward -0.348 0.177 ---- ---- Irrigation/monsoon 0.006 Downward -0.365 0.173 ---- ---- <0.001 Downward -0.429 0.304 ---- ---- 

Magnesium 0.040 Downward -0.289 20.050 Downward -0.243 0.059 Downward -0.235 0.573 ---- ---- 

Fall/winter baseflow 0.021 Downward -0.330 0.052 Downward -0.299 0.018 Downward -0.247 0.218 ---- ---- Snowmelt runoff 0.191 ---- ---- 0.003 Downward -0.407 0.021 Downward -0.235 0.311 ---- ---- Irrigation/monsoon 0.063 Downward -0.249 0.052 Downward -0.316 0.001 Downward -0.311 0.926 ---- ---- 

Sodium 0.042 Downward -0.223 0.148 ---- ---- 0.052 Downward -0.214 20.057 Downward -0.212 

Fall/winter baseflow 0.050 Downward -0.280 0.150 ---- ---- 0.479 ---- ---- 0.080 Downward -0.284 Snowmelt runoff 0.182 --- --- 0.204 ---- ---- 0.010 Downward -0.262 0.388 ---- ---- Irrigation/monsoon 0.144 --- --- 0.060 Downward -0.305 <0.001 Downward -0.393 0.102 ---- ---- 

Sulfate 0.024 Downward -0.282 20.050 Downward -0.243 0.021 Downward -0.268 20.073 Downward -0.200 

Fall/winter baseflow 0.020 Downward -0.333 0.034 Downward -0.325 0.045 Downward -0.209 0.080 Downward -0.284 Snowmelt runoff 0.097 Downward -0.194 0.017 Downward -0.328 0.114 ---- ---- 0.368 ---- ---- Irrigation/monsoon 0.006 Downward -0.365 0.069 Downward -0.295 0.503 ---- ---- 0.607 ---- ---- 

Chloride 0.017 Downward -0.243 0.354 ---- ---- 0.581 ---- ---- 0.101 ---- ---- 

Fall/winter baseflow 0.191 ---- ---- 0.382 ---- ---- 0.430 ---- ---- 0.218 ---- ---- Snowmelt runoff 0.091 Downward -0.200 0.466 ---- ---- 0.012 Downward -0.256 0.708 ---- ---- Irrigation/monsoon 0.114 ---- ---- 0.153 ---- ---- 0.002 Downward -0.306 0.510 ---- ---- 
26 Trends of the Rio Chama and Rio Grande, Water Years 1985 to 2002

trends in calcium, potassium, bicarbonate, and sulfate concentrations and upward trends in chloride and fluoride concentrations at the Otowi station and upward trends in calcium, potassium, bicarbonate, and sulfate concentrations at the San Felipe 

station. From 1975 to 1999, the Taos, Otowi, and San Felipe 

stations had an upward trend in streamflow (Passell and others, 

2004). Given these trends and the differing trends detected during this study, precipitation conditions appear to strongly influence major ion concentrations in the Rio Grande. For this study, 

this effect was particularly apparent during the fall/winter baseflow season when ground-water inflows were the most dominant and likely diminished during the study period because of 

the downward trend in annual precipitation, which appears to 

have resulted in downward trends of most major ion concentrations.

Summary

The City of Albuquerque is planning to divert SJC Project 

water from the Rio Grande for potable water use. The Rio 

Grande is a fully appropriated river and operation of the reservoirs on the river and its tributaries has undergone various 

changes because of water users’ needs, climate variations, and 

coordination of reservoir operations. This report examines 

streamflow and water-quality trends in the Rio Chama and the 

Rio Grande for water years 1985 to 2002 following the implementation of reservoir storage agreements in northern and central New Mexico. Storage agreements for northern and central 

New Mexico reservoirs were implemented in the mid-1980’s 

and incorporated into the historical legislative directives that 

govern water management in the study area. Data for the 

streamflow/water-quality stations of Taos, Otowi, San Felipe, 

and Albuquerque on the Rio Grande and the Rio Chama station 

of Chamita were used for trend analysis. Water-quality constituents were separated into six groups for analysis: basic water 

chemistry and physical properties; major ions; nutrients, 

organic carbon, and bacteria; trace elements; radionuclides; and 

anthropogenic compounds.

Streamflow in the Rio Chama and Rio Grande were 

divided into three distinct seasonal periods that correspond to 

natural and anthropogenic influences: fall/winter baseflow 

(November through February), snowmelt runoff (March 

through June), and the irrigation/monsoon (July through October) seasons. Water years 1985 to 2002 were a period of larger 

than average annual precipitation and streamflow compared to 

the stations’ periods of record. Downward trends in precipitation and streamflow during the study period reflect the drought 

during 1999 to 2002. The SJC Project and release of stored 

snowmelt runoff from the study area during the irrigation season resulted in an upward trend in streamflow during this season compared with downward trends during the remaining seasons.

Water-quality spatial trends indicated a downstream 

increase in specific conductance, and Rio Chama inflow contributed to this increase. Alkalinity and pH did not substantially 

change in the downstream direction. Streamflow at all stations 

was of a calcium bicarbonate water type. Nearly all nitrogen 

and phosphorous concentrations were less than 2 mg/L for all 

stations. Median trace-element concentrations and maximum 

radionuclide concentrations did not exceed drinking-water standards. Anthropogenic compounds were rarely detected, and 

concentrations did not exceed 0.1 μg/L or drinking-water standards

Analysis of seasonal differences indicated that water quality in the Rio Chama and Rio Grande varied temporally and spatially during the study period. Specific conductance increased 

downstream in the Rio Grande during the fall/winter baseflow 

and snowmelt runoff seasons, but was similar at the Taos, 

Otowi, and San Felipe stations during the irrigation/monsoon 

season. This similarity was a result of the release of stored water 

from Abiquiu Reservoir and Cochiti Lake, which masked the 

natural influences that increased specific conductance in the 

downstream direction during the other seasons. During all seasons, pH decreased and major ion concentrations remained stable at the Albuquerque station compared with the San Felipe 

station. Seasonal trends of TOC and fecal streptococci indicated 

smallest concentrations during the fall/winter baseflow season, 

increased concentrations during the snowmelt runoff season, 

and largest concentrations during the snowmelt runoff or irrigation/monsoon season. Manganese and uranium concentrations 

were largest during the fall/winter baseflow season and smallest 

during the snowmelt runoff season, indicating that groundwater inflows influenced concentrations.

Water-quality temporal trends were evaluated for selected 

constituents during the study period and during the individual 

seasons. Although study period trends were not apparent for 

specific conductance, dissolved oxygen, and pH, seasonal 

trends of these constituents were evident at certain stations during certain seasons. Major ion concentrations decreased during 

the study period and during most individual seasons. Downward trends in major ions were similar in magnitude at the Taos 

and Otowi stations, indicating that an upstream influence and 

(or) the downward trend in annual precipitation was likely the 

main reason(s) for these decreases. The stations most affected 

by reservoirs, Chamita and San Felipe, were the only ones at 

which downward trends in major ions were apparent for flowadjusted concentrations but not for seasonally correlated flowadjusted concentrations, which indicated fewer seasonal differences at these stations due to reservoir operations. 

References Cited

Anderholm, S.K., 1987, Reconnaissance of hydrology, land 

use, ground-water chemistry, and effects of land use on 

ground-water chemistry in the Albuquerque-Belen Basin, 

New Mexico: U.S. Geological Survey Water-Resources 

Investigations Report 86-4174, 37 p.

Anderholm, S.K., 1997, Water-quality assessment of the Rio 

Grande Valley, Colorado, New Mexico, and Texas–Shallow 

ground-water quality and land use in the Albuquerque area, 

central New Mexico, 1993: U.S. Geological Survey WaterResources Investigations Report 97-4067, 73 p.
References Cited 27

Anderholm, S.K., 2002, Water-quality assessment of the Rio 

Grande Valley, Colorado, New Mexico, and Texas–Surfacewater quality, shallow ground-water quality, and factors 

affecting water quality in the Rincon Valley, south-central 

New Mexico, 1994-95: U.S. Geological Survey WaterResources Investigations Report 02-4188, 117 p.

Anderholm, S.K., Radell, M.J., and Richey, S.F., 1995, Waterquality assessment of the Rio Grande Valley study unit, Colorado, New Mexico, and Texas–Analysis of selected nutrient, suspended-sediment, and pesticide data: U.S. Geological 

Survey Water-Resources Investigations Report 94-4061, 

203 p.

Betancourt, J.L., 2003, The current drought in historical perspective: Drought Summit presentation, 2003, Southwest 

Drought Summit Summary Report, accessed April 23, 2004, 

at http://www.mpcer.nau.edu/megadrought/

drought_summit_report.

Bolin, S.B., Ward, T.J., and Cole, R.A., 1987, Phosphorous 

models applied to New Mexico reservoirs: Journal of Water 

Resources Planning and Management, v. 113, no. 3, p. 323-

335.

City of Albuquerque, 1997, Water resources management strategy, Public Works Department, accessed June 4, 2003, at 

http://www.cabq.gov/waterresources/strategyindex.html, 

variously paged.

City of Albuquerque, 2005, Strategy index: Water Utility 

Department, Water Resources, accessed March 28, 2005, at 

http://www.cabq.gov/waterresources/strategyindex.html, 

1 p.

Ellis, S.R., Levings, G.W., Carter, L.F., Richey, S.F., and 

Radell, M.J., 1993, Rio Grande Valley, Colorado, New Mexico, and Texas: Water Resources Bulletin, v. 29, no. 4, p. 

617-645.

Follansbee, R., and Dean, H.J., 1915, Water resources of the 

Rio Grande basin: U.S. Geological Survey Water-Supply 

Paper 358, 725 p.

Healy, D.F., 1997, Water-quality assessment of the Rio Grande 

Valley, Colorado, New Mexico, and Texas–Summary and 

analysis of water-quality data for the basic-fixed-station network, 1993-95: U.S. Geological Survey Water-Resources 

Investigations Report 97-4212, 82 p.

Helsel, D.R., and Hirsch, R.M., 1991, Statistical methods in 

water resources, in Hydrologic analysis and interpretation: 

Techniques of Water-Resources Investigations of the United 

States Geological Survey, chap. A3, book 4, 510 p.

Hem, J.D., 1989, Study and interpretation of chemical characteristics of natural water: United States Geological Survey 

Water-Supply Paper 2254, 3d edition, 263 p.

Johnson, G.V., and Barton, L.L., 1980, Role of nitrogen, phosphorous, and iron in occurrence of algal blooms at Abiquiu 

and Cochiti Lakes, New Mexico: Las Cruces, New Mexico, 

Water Resources Research Institute Report No. 185, 153 p.

Kernodle, J.M., McAda, D.P., and Thorn, C.R., 1994, Simulation of ground-water flow in the Albuquerque Basin, central 

New Mexico, 1901-1994, with projections to 2020: U.S. 

Geological Survey Water-Resources Investigations Report 

94-4251, 114 p.

Kernodle, J.M., and Scott, W.B., 1986, Three-dimensional 

model simulation of steady-state ground-water flow in the 

Albuquerque-Belen Basin, New Mexico: U.S. Geological 

Survey Water-Resources Investigations Report 84-4353, 

58 p.

Langman, J.B., and Anderholm, S.K., 2004, Effects of reservoir 

installation, San Juan-Chama Project water and reservoir 

operations on streamflow and water quality in the Rio Chama 

and Rio Grande, northern and central New Mexico, 1938–

2000: U.S. Geological Survey Scientific Investigations 

Report 2004-5188, 47 p. 

Levings, G.W., Healy, D.F., Richey, S.F., and Carter, L.F., 

1998, Water quality in the Rio Grande Valley, Colorado, 

New Mexico, and Texas, 1992-95: U.S. Geological Survey 

Circular 1162, 39 p.

Lewis, K., and Hathaway, D., 2001, Memorandum–Analysis of 

paleo-climate and climate forcing information for New 

Mexico and implications for modeling in the Middle Rio 

Grande: Water Supply Study, S.S. Papadopulos and Associates, Inc., November 8, 2001. 

McAda, D.P., and Barroll, Peggy, 2002, Simulation of groundwater flow in the Middle Rio Grande Basin between Cochiti 

and San Acacia, New Mexico: U.S. Geological Survey 

Water-Resources Investigations Report 02-4200, 81 p.

Mills, S.K., 2003, Quantifying salinization of the Rio Grande 

using environmental tracers: Socorro, New Mexico Institute 

of Mining and Technology, M.S. thesis, 448 p.

Moore, S.J., and Anderholm, S.K., 2002, Spatial and temporal 

variations in streamflow, dissolved solids, nutrients, and suspended sediment in the Rio Grande Valley study unit, Colorado, New Mexico, and Texas, 1993-95: U.S. Geological 

Survey Water-Resources Investigations Report 02-4224, 

52 p.

Mussetter Engineering, Inc., 2002, Geomorphic and sedimentologic investigations of the middle Rio Grande between 

Cochiti Dam and Elephant Butte Reservoir: New Mexico 

Interstate Stream Commission, June 2002, variously paged.

Natural Resources Conservation Service, 1999, New Mexico 

annual precipitation, average annual precipitation, 1961-

1990: map, 1 sheet, scale 1:1,300,00.

New Mexico Climate Center, 2004, New Mexico climate summaries for cooperator stations: Office of State Climatologist, 

New Mexico State University, accessed September 8, 2004, 

at http://weather.nmsu.edu/nmcccooperator/index.html.

New Mexico Environment Department, Water Quality Bureau, 

Surveillance and Standards Section, 1992, Intensive water 

quality stream surveys and lake water quality assessment surveys: NMED/SWQ-92/2.

Oblinger Childress, C.J., Foreman, W.T., Connor, B.F., and 

Maloney, T.J., 1999, New reporting procedures based on 

long-term method detection levels and some considerations 

for interpretations of water-quality data provided by the U.S. 

Geological Survey National Water Quality Laboratory: U.S. 

Geological Survey Open-File Report 99-193, 19 p.
28 Trends of the Rio Chama and Rio Grande, Water Years 1985 to 2002

Passell, H.D., Dahm, C.N., and Bedrick, E.J., 2004, Hydrological and geochemical trends and patterns in the upper Rio 

Grande, 1975 to 1999: Journal of the American Water 

Resources Association, v. 40, no. 1, p. 111-127.

Plummer, L.N., Bexfield, L.M., Anderholm, S.K., Sanford, 

W.E., and Busenberg, E., 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.

Potter, D.U., and Davis, D.R., 1989, New Mexico clean lakes 

program–Lake water quality assessment for FY 89: Surveillance and Standards Section, Surface Water Quality Bureau, 

Environmental Improvement Division, New Mexico Health 

and Environment Department.

Rio Grande Compact Commission, 1999, Report of the Rio 

Grande Compact Commission, 1998, to the governors of 

Colorado, New Mexico, and Texas: 52 p.

S.S. Papadopulos and Associates, Inc., 2000, Middle Rio 

Grande water supply study: Prepared for the U.S. Army 

Corps of Engineers and New Mexico Interstate Stream Commission, contract no. DACW47-99-C-0012.

S.S. Papadopulos and Associates, Inc., 2002, Evaluation of the 

Middle Rio Grande Conservancy District Irrigation System 

and Measurement Program: Prepared for the New Mexico 

Interstate Stream Commission, December 2002.

Trainer, F.W., Rogers, R.J., and Sorey, M.L., 2000, Geothermal 

hydrology of Valles Caldera and the southwestern Jemez 

Mountains, New Mexico: U.S. Geological Survey WaterResources Investigations Report 00-4067, 115 p.

U.S. Environmental Protection Agency, 2004, National primary 

drinking water standards, accessed August 9, 2004, at

http://www.epa.gov/safewater/consumer/mcl.pdf, 6 p.

U.S. Geological Survey, 1968, Water resources data for New 

Mexico, 1967, part 1. Surface water records, 249 p.

U.S. Geological Survey, 1969, Water resources data for New 

Mexico, 1968, part 1. Surface water records, 271 p.

U.S. Geological Survey, 2004, Water quality samples for New 

Mexico, National Water Information System (NWISWeb), 

accessed November 2, 2004, at http://nwis.waterdata.usgs.gov/nm/nwis/qwdata.

Western Regional Climate Center, 2002, Historical climate 

information–Climate of New Mexico: National Oceanic and 

Atmospheric Administration Division of Atmospheric Sciences, accessed October 4, 2002, at http://www.wrcc.dri.edu/

narratives/NEWMEXICO.html.

Wilcox, R.W., 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. 
 29

Supplemental Information:

Summary Statistics and Listing of Analyzed Anthropogenic Compounds

________________________________________________________________________
30 Trends of the Rio Chama and Rio Grande, Water Years 1985 to 2002

Table I-1. Summary statistics of selected water-quality constituents for Rio Grande below Taos Junction Bridge, water years 1985 to 

2002.

[μS/cm, microsiemens per centimeter at 25 degrees Celsius (deg C); mg/L, milligrams per liter; diss., dissolved; <, less than; mL, milliliters; μg/L, micrograms 

per liter]

1

Each data set for antimony, beryllium, cadmium, cobalt, lead, mercury (dissolved and total), selenium, and silver contained less than nine samples greater than 

method detection level.

Summary statistics

Minimum25th 

percentile Median

75th 

percentile

Maximum

Number 

of 

samples

Percentage 

censored 

values

Basic water chemistry and physical properties:

Specific conductance, field (μS/cm) 170 251 290 334 550 95 0

Alkalinity, total, titration to 4.5, lab (mg/L as 

CaCO3)

54 88 99 110 158 88 1

pH, total, field (standard units) 7.2 8.0 8.3 8.5 8.8 98 0

Oxygen, diss. (mg/L) 6.8 8.4 9.4 10.4 18.0 97 0

Chemical oxygen demand, total (mg/L) <10 <10 12 20 40 48 25

Total dissolved solids, 180 deg C (mg/L) 128 164 196 219 257 32 0

Major ions:

Calcium, diss. (mg/L as Ca) 18.0 26.0 29.0 33.0 41.0 89 0

Magnesium, diss. (mg/L as Mg) 3.60 5.40 6.10 7.30 9.20 89 0

Potassium, diss. (mg/L as K) 1.80 2.80 3.10 3.50 8.00 89 0

Sodium, diss. (mg/L as Na) 8.5 16.6 20.0 25.0 72.0 89 0

Bicarbonate, field, diss. (mg/L as HCO3) 55.0 101.5 117.0 125.5 166.0 75 0

Chloride, diss. (mg/L as Cl) 2.60 5.36 6.80 8.10 26.00 89 0

Fluoride, diss. (mg/L as F) <0.10 0.40 0.50 0.70 1.40 89 1

Sulfate, diss. (mg/L as SO4) 17.5 32.0 38.0 48.0 92.0 89 0

Silica, diss. (mg/L as SiO2) 15.0 22.0 25.0 27.0 33.6 89 0

Nutrients, organic carbon, and bacteria:

Nitrogen, ammonia + organic, diss. (mg/L as N) <0.20 <0.20 <0.20 <0.20 0.38 58 76

Nitrogen, ammonia + organic, total (mg/L as N) <0.20 0.20 0.36 0.50 1.00 92 24

Nitrogen, ammonia, diss. (mg/L as N) <0.01 <0.01 0.01 0.02 0.04 67 43

Nitrogen, ammonia, total (mg/L as N) <0.01 0.02 0.03 0.05 0.13 52 10

Nitrogen, NO2 + NO3, diss. (mg/L as N) <0.05 0.10 0.18 0.27 1.90 93 10

Nitrogen, NO2 + NO3, total (mg/L as N) <0.10 0.10 0.20 0.30 0.50 35 11

Phosphorus, diss. (mg/L as P) <0.01 <0.01 0.02 0.03 0.19 58 36

Orthophosphate, diss. (mg/L as P) <0.01 0.02 0.03 0.03 0.10 92 15

Phosphorus, total (mg/L as P) <0.01 0.04 0.06 0.09 0.25 93 5

Organic carbon, total (mg/L as C) 1.5 2.5 3.6 4.7 11.0 56 0

Fecal coliform, 0.7 micron (colonies/100 mL) 1 7 22 84 340 44 7

Fecal streptococci, 0.7 micron (colonies/100 mL) 1 12 25 74 380 45 2

Trace elements1:

Aluminum, diss. (μg/L as Al) 3 9 13 27 88 12 0

Arsenic, diss. (μg/L as As) <1 2 2 2 4 33 3

Arsenic, total (μg/L as As) <1 2 2 2 4 19 5

Barium, diss. (μg/L as Ba) 23 26 28 34 37 13 0

Boron, diss. (μg/L as B) 20 30 40 50 90 60 0

Chromium, diss. (μg/L as Cr) <1 <1 1 1 30 33 48

Copper, diss. (μg/L as Cu) <1 1.1 2.0 2.0 7.0 32 9

Iron, diss. (μg/L as Fe) <10 10 19 36 620 90 4

Manganese, diss. (μg/L as Mn) 1 6 8.1 11 52 45 0

Molybdenum, diss. (μg/L as Mo) <1 4 6 9 89 48 2

Nickel, diss. (μg/L as Ni) <1.0 <1.0 1.0 2.0 2.1 13 46

Zinc, diss. (μg/L as Zn) <10 <10 <10 <10 46 34 79

Uranium (natural), diss. (μg/L as U) 1.0 1.7 2.1 2.6 3.0 16 0
Summary Statistics and Listing of Analyzed Anthropogenic Compounds 31

Table I-2. Summary statistics of selected water-quality constituents for Rio Chama near Chamita, water years 1985 to 2002.

[μS/cm, microsiemens per centimeter at 25 degrees Celsius (deg C); mg/L, milligrams per liter; diss., dissolved; <, less than; mL, milliliters; μg/L, micrograms 

per liter]

1

Each data set for antimony, beryllium, cadmium, cobalt, lead, mercury (dissolved and total), selenium, and silver contained less than nine samples greater than 

method detection level.

Summary statistics

Minimum25th 

percentile Median

75th 

percentile

Maximum

Number 

of 

samples

Percentage 

censored 

values

Basic water chemistry and physical properties:

Specific conductance, lab (μS/cm) 233 297 333 398 540 119 0

Alkalinity, total, titration to 4.5, lab (mg/L as 

CaCO3)

68 84 94 111 168 69 0

pH, total, field (standard units) 7.5 8.0 8.2 8.3 8.8 117 0

Oxygen, diss. (mg/L) 7 8.25 9.4 10.8 14.8 115 0

Chemical oxygen demand, total (mg/L) NA NA NA NA NA 6 50

Total dissolved solids, 180 deg C (mg/L) 152 167 189 222 256 31 0

Major ions:

Calcium, diss. (mg/L as Ca) 26.0 33.0 37.8 43.0 61.0 69 0

Magnesium, diss. (mg/L as Mg) 5.30 6.74 7.50 9.40 14.00 69 0

Potassium, diss. (mg/L as K) 1.30 1.80 2.00 2.40 3.60 68 0

Sodium, diss. (mg/L as Na) 10.0 13.4 17.0 22.0 45.0 69 0

Bicarbonate, field, diss. (mg/L as HCO3) 75 98 110 133 206 64 0

Chloride, diss. (mg/L as Cl) <0.10 2.60 4.04 7.00 50.00 69 1

Fluoride, diss. (mg/L as F) <0.10 0.20 0.20 0.30 0.50 68 1

Sulfate, diss. (mg/L as SO4) 41.0 54.0 65.0 82.0 110.0 69 0

Silica, diss. (mg/L as SiO2) 12.0 13.7 14.0 16.0 21.0 69 0

Nutrients, organic carbon, and bacteria:

Nitrogen, ammonia + organic, diss. (mg/L as N) <0.2 <0.2 <0.2 0.2 0.4 47 70

Nitrogen, ammonia + organic, total (mg/L as N) <0.2 <0.2 0.2 0.3 1.0 47 30

Nitrogen, ammonia, diss. (mg/L as N) <0.01 <0.01 0.02 0.02 0.04 47 38

Nitrogen, ammonia, total (mg/L as N) <0.01 0.01 0.02 0.04 0.06 9 22

Nitrogen, NO2 + NO3, diss. (mg/L as N) <0.05 <0.05 <0.05 <0.05 0.33 47 87

Nitrogen, NO2 + NO3, total (mg/L as N) NA NA NA NA NA NA NA

Phosphorus, diss. (mg/L as P) <0.01 <0.01 0.02 0.02 0.05 47 45

Orthophosphate, diss. (mg/L as P) <0.01 <0.01 <0.01 0.01 0.04 47 55

Phosphorus, total (mg/L as P) <0.01 0.02 0.04 0.08 0.48 47 11

Organic carbon, total (mg/L as C) 3.2 3.5 3.9 5.5 19.0 10 0

Fecal coliform, 0.7 micron (colonies/100 mL) 0 26 60 100 730 45 7

Fecal streptococci, 0.7 micron (colonies/100 mL) 4 42 98 193.5 2500 44 0

Trace elements1:

Aluminum, diss. (μg/L as Al) 1 3 4 6 72 16 0

Arsenic, diss. (μg/L as As) <1 1 2 2 3 26 8

Arsenic, total (μg/L as As) 1 2 2 2 4 11 0

Barium, diss. (μg/L as Ba) 52 63 71 81 119 16 0

Boron, diss. (μg/L as B) <10 20 30 45 80 43 5

Chromium, diss. (μg/L as Cr) <1 <1 <1 1 30 26 73

Copper, diss. (μg/L as Cu) <1 1.0 1.7 2.1 5 26 15

Iron, diss. (μg/L as Fe) <3 9 16 40 330 69 14

Manganese, diss. (μg/L as Mn) 1.8 3.2 5.7 9.0 45.0 46 0

Molybdenum, diss. (μg/L as Mo) <1 <1 1.2 1.7 2.1 16 25

Nickel, diss. (μg/L as Ni) <1.0 1.0 1.0 1.2 2.0 16 19

Zinc, diss. (μg/L as Zn) <1 <1 3 5 16 26 31

Uranium (natural), diss. (μg/L as U) <1.00 <1.00 1.11 2.18 4.48 16 31
32 Trends of the Rio Chama and Rio Grande, Water Years 1985 to 2002

Table I-3. Summary statistics of selected water-quality constituents for Rio Grande at Otowi Bridge, near San Ildefonso, water years 1985 

to 2002.

[μS/cm, microsiemens per centimeter at 25 degrees Celsius (deg C); mg/L, milligrams per liter; diss., dissolved; <, less than; mL, milliliters; μg/L, micrograms 

per liter]

1

Each data set for antimony, beryllium, cadmium, cobalt, lead, mercury (dissolved and total), selenium, and silver contained less than nine samples greater than 

method detection level.

Summary statistics

Minimum25th 

percentile Median

75th 

percentile

Maximum

Number 

of 

samples

Percentage 

censored 

values

Basic water chemistry and physical properties:

Specific conductance, lab (μS/cm) 187 279 314 339 465 172 0

Alkalinity, total, titration to 4.5, lab (mg/L as 

CaCO3)

62 96 107 117 170 137 0

pH, total, field (standard units) 7.2 8.0 8.2 8.3 9.0 164 0

Oxygen, diss. (mg/L) 6.9 8.0 8.8 10.5 16.8 162 0

Chemical oxygen demand, total (mg/L) NA NA NA NA NA NA NA

Total dissolved solids, 180 deg C (mg/L) 131 189 212 229 327 74 0

Major ions:

Calcium, diss. (mg/L as Ca) 20.1 33.6 36.0 40.0 49.0 140 0

Magnesium, diss. (mg/L as Mg) 3.74 6.28 6.80 7.52 9.70 140 0

Potassium, diss. (mg/L as K) 1.60 2.28 2.60 2.88 3.90 140 0

Sodium, diss. (mg/L as Na) 9.6 16 19 22 30 140 0

Bicarbonate, field, diss. (mg/L as HCO3) 76 108 123 133 173 100 0

Chloride, diss. (mg/L as Cl) 2.60 4.50 5.70 7.10 32 137 0

Fluoride, diss. (mg/L as F) <0.10 0.30 0.32 0.40 0.90 137 1

Sulfate, diss. (mg/L as SO4) 21.2 39.1 49.0 56.5 89.0 137 0

Silica, diss. (mg/L as SiO2) 0.1 17.0 19.0 22.0 52.0 140 0

Nutrients, organic carbon, and bacteria:

Nitrogen, ammonia + organic, diss. (mg/L as N) <0.20 <0.20 <0.20 0.20 0.40 63 65

Nitrogen, ammonia + organic, total (mg/L as N) <0.10 0.30 0.38 0.51 1.90 116 12

Nitrogen, ammonia, diss. (mg/L as N) <0.01 <0.01 0.02 0.02 0.36 116 41

Nitrogen, ammonia, total (mg/L as N) <0.01 0.02 0.03 0.04 0.15 70 19

Nitrogen, NO2 + NO3, diss. (mg/L as N) <0.10 <0.10 0.10 0.15 0.34 116 39

Nitrogen, NO2 + NO3, total (mg/L as N) NA NA NA NA NA NA NA

Phosphorus, diss. (mg/L as P) <0.02 <0.02 0.02 0.03 0.16 116 32

Orthophosphate, diss. (mg/L as P) <0.01 <0.01 0.02 0.03 0.1 116 28

Phosphorus, total (mg/L as P) <0.01 0.04 0.08 0.13 2.8 116 3

Organic carbon, total (mg/L as C) 1.8 3.8 5.0 6.3 90.8 63 0

Fecal coliform, 0.7 micron (colonies/100 mL) <10 16 64 140 2,800 123 2

Fecal streptococci, 0.7 micron (colonies/100 mL) <1 34 105 220 6,100 122 1

Trace elements1:

Aluminum, diss. (μg/L as Al) <2 5 11 30 1,900 110 5

Arsenic, diss. (μg/L as As) <1 1 2 2 7 96 7

Arsenic, total (μg/L as As) NA NA NA NA NA NA NA

Barium, diss. (μg/L as Ba) 29 46 57 71 110 110 0

Boron, diss. (μg/L as B) 10 30 40 40 170 113 0

Chromium, diss. (μg/L as Cr) <1 <1 <1 1 3 94 64

Copper, diss. (μg/L as Cu) <1.0 1.1 1.5 3.0 33 94 8

Iron, diss. (μg/L as Fe) <10 10 14 28 1,300 139 23

Manganese, diss. (μg/L as Mn) <1.0 3.0 5.0 8.1 180 132 3

Molybdenum, diss. (μg/L as Mo) NA NA NA NA NA NA NA

Nickel, diss. (μg/L as Ni) <1.00 <1.00 1.00 1.17 13.0 109 44

Zinc, diss. (μg/L as Zn) <1 1 3 6 71 95 18

Uranium (natural), diss. (μg/L as U) <1.00 1.30 2.05 2.72 4.90 84 2
Summary Statistics and Listing of Analyzed Anthropogenic Compounds 33

Table I-4. Summary statistics of selected water-quality constituents for Rio Grande at San Felipe, water years 1985 to 2002.

[μS/cm, microsiemens per centimeter at 25 degrees Celsius (deg C); mg/L, milligrams per liter; diss., dissolved; <, less than; mL, milliliters; μg/L, micrograms 

per liter]

1

Each data set for antimony, beryllium, cadmium, cobalt, lead, mercury (dissolved and total), selenium, and silver contained less than nine samples greater than 

method detection level.

Summary statistics

Minimum25th 

percentile Median

75th 

percentile

Maximum

Number 

of 

samples

Percentage 

censored 

values

Basic water chemistry and physical properties:

Specific conductance, lab (μS/cm) 210 300 336 357 520 104 0

Alkalinity, total, titration to 4.5, lab (mg/L as 

CaCO3)

66 102.25 113 120 135 74 0

pH, total, field (standard units) 7.3 7.9 8.1 8.3 8.8 104 0

Oxygen, diss. (mg/L) 6.5 8.0 9.4 11.2 14.4 101 0

Chemical oxygen demand, total (mg/L) <10 10 10 20 1,800 50 24

Total dissolved solids, 180 deg C (mg/L) 187 210 219.5 225.5 252 10 0

Major ions:

Calcium, diss. (mg/L as Ca) 24.0 34.7 39.0 41.3 49.0 74 0

Magnesium, diss. (mg/L as Mg) 4.60 6.36 7.20 7.70 9.20 74 0

Potassium, diss. (mg/L as K) 1.80 2.60 2.80 3.09 4.00 74 0

Sodium, diss. (mg/L as Na) 11.0 18.0 20.7 22.6 31.0 74 0

Bicarbonate, field, diss. (mg/L as HCO3) 76 120 134 142 248 57 0

Chloride, diss. (mg/L as Cl) 1.80 4.84 5.95 6.93 9.70 74 0

Fluoride, diss. (mg/L as F) 0.20 0.30 0.40 0.40 0.90 66 0

Sulfate, diss. (mg/L as SO4) 29.5 44.5 51.5 60.0 84.0 74 0

Silica, diss. (mg/L as SiO2) 14.9 17.0 18.0 20.0 27.0 66 0

Nutrients, organic carbon, and bacteria:

Nitrogen, ammonia + organic, diss. (mg/L as N) <0.20 <0.20 <0.20 0.21 0.30 26 58

Nitrogen, ammonia + organic, total (mg/L as N) <0.20 0.22 0.30 0.40 1.90 72 14

Nitrogen, ammonia, diss. (mg/L as N) <0.01 <0.01 <0.01 0.02 0.06 46 50

Nitrogen, ammonia, total (mg/L as N) <0.01 0.02 0.03 0.06 0.12 52 6

Nitrogen, NO2 + NO3, diss. (mg/L as N) <0.05 <0.05 0.08 0.10 0.29 72 47

Nitrogen, NO2 + NO3, total (mg/L as N) <0.10 <0.10 <0.10 0.10 12 35 54

Phosphorus, diss. (mg/L as P) <0.02 <0.02 <0.02 0.03 0.05 26 69

Orthophosphate, diss. (mg/L as P) <0.01 <0.01 0.02 0.03 0.06 72 29

Phosphorus, total (mg/L as P) <0.01 0.04 0.05 0.06 0.25 72 6

Organic carbon, total (mg/L as C) 1.8 2.9 3.9 4.7 27 56 0

Fecal coliform, 0.7 micron (colonies/100 mL) <10 12 30 85 7,700 51 2

Fecal streptococci, 0.7 micron (colonies/100 mL) <1 26 66 120 7,000 51 2

Trace elements1:

Aluminum, diss. (μg/L as Al) <1 2 5 11 632 33 12

Arsenic, diss. (μg/L as As) <1 2 2 2 3 52 2

Arsenic, total (μg/L as As) 1 2 2 2 3 28 0

Barium, diss. (μg/L as Ba) 44 65 68 75 116 32 0

Boron, diss. (μg/L as B) 20 30 40 40 60 67 0

Chromium, diss. (μg/L as Cr) <1 <1 <1 1 2 53 72

Copper, diss. (μg/L as Cu) <1.0 1.0 1.2 3.0 9.0 52 9

Iron, diss. (μg/L as Fe) <10 <10 10 18 550 65 25

Manganese, diss. (μg/L as Mn) <1.0 6.3 9.3 13.9 989 32 3

Molybdenum, diss. (μg/L as Mo) 2.0 3.2 4.0 4.3 5.5 32 0

Nickel, diss. (μg/L as Ni) <1.00 <1.00 1.00 1.91 3.00 32 28

Zinc, diss. (μg/L as Zn) <3 <3 3 6 22 52 33

Uranium (natural), diss. (μg/L as U) 0.50 1.84 2.40 3.00 3.64 33 0
34 Trends of the Rio Chama and Rio Grande, Water Years 1985 to 2002

Table I-5. Summary statistics of selected water-quality constituents for Rio Grande at Albuquerque, water years 1985 to 2002.

[μS/cm, microsiemens per centimeter at 25 degrees Celsius (deg C); mg/L, milligrams per liter; diss., dissolved; <, less than; mL, milliliters; μg/L, micrograms 

per liter]

1

Each data set for antimony, beryllium, cadmium, cobalt, lead, mercury (dissolved and total), selenium, and silver contained less than nine samples greater than 

method detection level.

Summary statistics

Minimum25th 

percentile Median

75th 

percentile

Maximum

Number 

of 

samples

Percentage 

censored 

values

Basic water chemistry and physical properties:

Specific conductance, lab (μS/cm) 192 334 370 425 548 98 0

Alkalinity, total, titration to 4.5, lab (mg/L as 

CaCO3)

71 98 112 122 150 22 0

pH, total, field (standard units) 6.8 7.8 7.9 8.1 8.7 80 0

Oxygen, diss. (mg/L) 5.9 8.0 8.6 10.8 13.8 75 0

Chemical oxygen demand, total (mg/L) <10 10 20 30 50 9 22

Total dissolved solids, 180 deg C (mg/L) NA NA NA NA NA NA NA

Major ions:

Calcium, diss. (mg/L as Ca) 27.0 35.5 40.0 42.8 53.0 22 0

Magnesium, diss. (mg/L as Mg) 4.80 6.75 7.05 8.10 9.70 22 0

Potassium, diss. (mg/L as K) 2.50 2.73 2.90 3.40 7.00 22 0

Sodium, diss. (mg/L as Na) 13.0 23.0 24.0 26.8 43.0 22 0

Bicarbonate, field, diss. (mg/L as HCO3) NA NA NA NA NA NA NA

Chloride, diss. (mg/L as Cl) 4.50 7.60 9.80 13.0 22.0 22 0

Fluoride, diss. (mg/L as F) 0.20 0.30 0.35 0.40 0.50 18 0

Sulfate, diss. (mg/L as SO4) 36.0 55.0 59.0 69.8 84.0 22 0

Silica, diss. (mg/L as SiO2) 16.0 17.0 18.5 20.8 22.0 18 0

Nutrients, organic carbon, and bacteria:

Nitrogen, ammonia + organic, diss. (mg/L as N) NA NA NA NA NA NA NA

Nitrogen, ammonia + organic, total (mg/L as N) 0.20 0.30 0.40 0.50 0.80 9 0

Nitrogen, ammonia, diss. (mg/L as N) NA NA NA NA NA NA NA

Nitrogen, ammonia, total (mg/L as N) <0.01 0.02 0.03 0.04 0.07 11 9

Nitrogen, NO2 + NO3, diss. (mg/L as N) <0.10 <0.10 <0.10 0.13 0.22 11 55

Nitrogen, NO2 + NO3, total (mg/L as N) <0.10 <0.10 <0.10 0.10 0.20 11 55

Phosphorus, diss. (mg/L as P) NA NA NA NA NA NA NA

Orthophosphate, diss. (mg/L as P) 0.02 0.03 0.04 0.05 0.07 11 0

Phosphorus, total (mg/L as P) 0.05 0.06 0.09 0.11 0.38 9 0

Organic carbon, total (mg/L as C) 2.2 3.1 4 4.3 4.9 9 0

Fecal coliform, 0.7 micron (colonies/100 mL) NA NA NA NA NA NA NA

Fecal streptococci, 0.7 micron (colonies/100 mL) NA NA NA NA NA NA NA

Trace elements1:

Aluminum, diss. (μg/L as Al) NA NA NA NA NA NA NA

Arsenic, diss. (μg/L as As) <1 3 3 3 4 10 10

Arsenic, total (μg/L as As) <1 3 3 3 4 9 11

Barium, diss. (μg/L as Ba) NA NA NA NA NA NA NA

Boron, diss. (μg/L as B) 20 35 60 78 130 18 0

Chromium, diss. (μg/L as Cr) <1 <1 <1 <10 <10 9 100

Copper, diss. (μg/L as Cu) <1.0 1.0 2.0 3.3 4.0 8 22

Iron, diss. (μg/L as Fe) 9 10 14 28 76 17 0

Manganese, diss. (μg/L as Mn) NA NA NA NA NA NA NA

Molybdenum, diss. (μg/L as Mo) NA NA NA NA NA NA NA

Nickel, diss. (μg/L as Ni) NA NA NA NA NA NA NA

Zinc, diss. (μg/L as Zn) <1 <1 3 5 20 9 33

Uranium (natural), diss. (μg/L as U) NA NA NA NA NA NA NA
Summary Statistics and Listing of Analyzed Anthropogenic Compounds 35

Table I-6. Anthropogenic compounds analyzed for in samples collected from the Rio Grande stations of Taos, Otowi, San Felipe, and Albuquerque and the Rio Chama station of Chamita, water years 1985 to 2002.

[MDL, method detection level; X, analysis performed; group: 1 = pesticides, 2 = total phenols, 3 = polychlorinated napthalenes, 4 = polychlorinated biphenyls; 

diss., dissolved; μg/L, micrograms per liter; <, less than; --, no analysis performed]

Compound Unit MDL Taos Chamita Otowi

San 

Felipe Albuquerque Group

Propachlor, diss. μg/L <0.007 X X X -- -- 1

Butylate, diss. μg/L <0.002 X X X -- -- 1

Simazine, diss. μg/L <0.005 X X X -- -- 1

Prometon, diss. μg/L <0.02 X X X -- -- 1

2-chloro-4-isopropylamino-6-

amino-s-triazine, diss.

μg/L <0.002 X X X -- -- 1

Cyanazine, diss. μg/L <0.004 X X X -- -- 1

Fonofos, diss. μg/L <0.003 X X X -- -- 1

Phenolic compounds, total μg/L <1 -- -- X -- -- 2

alpha-HCH, diss. μg/L <0.002 X X X -- -- 1

p,p’-DDE, diss. μg/L <0.006 X X X -- -- 1

Chlorpyrifos, total μg/L <0.01 X X X X -- 1

Chlorpyrifos, diss. μg/L <0.004 X X X -- -- 1

Disulfoton, total μg/L <0.01 X X X X X 1

Phorate, total μg/L <0.01 X X X X X 1

p,p’-ethyl-DDD, total μg/L <0.1 X X X X X 1

Tribuphos, total μg/L <0.01 X X X X -- 1

Polychlorinated naphthalenes, 

total

μg/L <0.1 X X X X X 3

Aldrin, total μg/L <0.01 X X X X X 1

Lindane, total μg/L <0.010 X X X X X 1

Lindane, diss. μg/L <0.004 X X X -- -- 1

Chlordane (technical), total μg/L <0.1 X X X X X 1

p,p’-DDD, total μg/L <0.010 X X X X X 1

p,p’-DDE, total μg/L <0.010 X X X X X 1

p,p'-DDT, total μg/L <0.010 X X X X X 1

Dieldrin, total μg/L <0.010 X X X X X 1

Dieldrin, diss. μg/L <0.001 X X X -- -- 1

alpha-endosulfan, total μg/L <0.01 X X X X X 1

Endrin, total μg/L <0.01 X X X X X 1

Ethion, total μg/L <0.01 X X X X X 1

Toxaphene, total μg/L <1 X X X X X 1

Heptachlor, total μg/L <0.01 X X X X X 1

Metolachlor, diss. μg/L <0.002 X X X -- -- 1

Heptachlor epoxide, total μg/L <0.010 X X X X X 1

p,p'-methoxychlor, total μg/L <0.010 X X X X X 1

PCB’s, total μg/L <0.1 X X X X X 4

Malathion, total μg/L <0.01 X X X X X 1

Malathion, diss. μg/L <0.005 X X X -- -- 1

Parathion, total μg/L <0.01 X X X X X 1

Parathion, diss. μg/L <0.004 X X X -- -- 1

Diazinon, total μg/L <0.01 X X X X X 1

Diazinon, diss. μg/L <0.002 X X X -- -- 1
36 Trends of the Rio Chama and Rio Grande, Water Years 1985 to 2002

Table I-6. Anthropogenic compounds analyzed for in samples collected from the Rio Grande stations of Taos, Otowi, San Felipe, and Albuquerque and the Rio Chama station of Chamita, water years 1985 to 2002--Concluded.

Compound Unit MDL Taos Chamita Otowi

San 

Felipe Albuquerque Group

Azinphos-methyl, total μg/L <0.1 -- -- -- -- X 1

Methyl parathion, total μg/L <0.01 X X X X X 1

Atrazine, diss. μg/L <0.001 X X X -- -- 1

2,4-D, total μg/L <0.01 X X X X X 1

2,4,5-T, total μg/L <0.01 X X X X X 1

Mirex, total μg/L <0.010 X X X X X 1

Silvex, total μg/L <0.01 X X X X X 1

Carbophenothion, total μg/L <0.01 X X X X X 1

Methyl trithion, total μg/L <0.01 X X X X X 1

Alachlor, diss. μg/L <0.002 X X X -- -- 1

Acetochlor, diss. μg/L <0.002 X X X -- -- 1

Dichlorprop, total μg/L <0.01 X X X X X 1

Fonofos, total μg/L <0.01 X X X X -- 1

Metribuzin, diss. μg/L <0.004 X X X -- -- 1

2,6-diethylaniline, diss. μg/L <0.003 X X X -- -- 1

Trifluralin, diss. μg/L <0.002 X X X -- -- 1

Ethalfluralin, diss. μg/L <0.004 X X X -- -- 1

Phorate, diss. μg/L <0.002 X X X -- -- 1

Terbacil, diss. μg/L <0.007 X X X -- -- 1

Linuron, diss. μg/L <0.002 X X X -- -- 1

Methyl parathion, diss. μg/L <0.006 X X X -- -- 1

EPTC, diss. μg/L <0.002 X X X -- -- 1

Pebulate, diss. μg/L <0.004 X X X -- -- 1

Tebuthiuron, diss. μg/L <0.01 X X X -- -- 1

Molinate, diss. μg/L <0.004 X X X -- -- 1

Ethoprop, diss. μg/L <0.003 X X X -- -- 1

Benfluralin, diss. μg/L <0.002 X X X -- -- 1

Carbofuran, diss. μg/L <0.003 X X X -- -- 1

Terbufos, diss. μg/L <0.01 X X X -- -- 1

Propyzamide, diss. μg/L <0.003 X X X -- -- 1

Disulfoton, diss. μg/L <0.02 X X X -- -- 1

Triallate, diss. μg/L <0.001 X X X -- -- 1

Propanil, diss. μg/L <0.004 X X X -- -- 1

Carbaryl, diss. μg/L <0.003 X X X -- -- 1

Thiobencarb, diss. μg/L <0.002 X X X -- -- 1

DCPA, diss. μg/L <0.002 X X X -- -- 1

Pendimethalin, diss. μg/L <0.004 X X X -- -- 1

Napropamide, diss. μg/L <0.003 X X X -- -- 1

Propargite, diss. μg/L <0.01 X X X -- -- 1

Azinphos-methyl, diss. μg/L <0.001 X X X -- -- 1

cis-permethrin, diss. μg/L <0.005 X X X -- -- 1