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 

By Jeff B. Langman and Scott K. Anderholm 

Prepared in cooperation with the 

CITY OF ALBUQUERQUE 

Scientific Investigations Report 2004-5188 

U.S. Department of the Interior 

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

Gale A. Norton, Secretary 

U.S. Geological Survey 

Charles G. Groat, Director 

U.S. Geological Survey, Reston, Virginia: 2004 

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duce any copyrighted materials contained within this report.

 iii 

CONTENTS


Page


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


Introduction 

Effects of reservoir installation, San Juan-Chama Project water, and reservoir operations on streamflow and water


........................................................................................................................................................................... 1


Purpose and scope ....................................................................................................................................................... 1


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


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


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


Legal constraints on streamflow........................................................................................................................ 2


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


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


Irrigation diversions and inflows....................................................................................................................... 5


Treated wastewater and urban runoff ................................................................................................................ 6


Evapotranspiration ............................................................................................................................................ 7


Ground-water inflows........................................................................................................................................ 7


Previous water-quality studies........................................................................................................................... 7


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


Sources and description of data......................................................................................................................... 7


Division of data ................................................................................................................................................. 8


Data comparison................................................................................................................................................ 8


Acknowledgments....................................................................................................................................................... 9


quality in the Rio Chama and Rio Grande ....................................................................................................................... 9


Potential climate bias .................................................................................................................................................. 9


Potential sampling bias ............................................................................................................................................... 9


Streamflow .................................................................................................................................................................. 10


Rio Chama......................................................................................................................................................... 10


Rio Grande ........................................................................................................................................................ 16


Specific conductance................................................................................................................................................... 19


Rio Chama......................................................................................................................................................... 19


Rio Grande ........................................................................................................................................................ 21


pH................................................................................................................................................................................ 21


Rio Chama......................................................................................................................................................... 21


Rio Grande ........................................................................................................................................................ 28


Suspended sediment .................................................................................................................................................... 30


Rio Chama......................................................................................................................................................... 30


Rio Grande ........................................................................................................................................................ 34


Constituent trends and correlation .............................................................................................................................. 37


Summary ............................................................................................................................................................................... 40


References ............................................................................................................................................................................. 41


Supplemental information: LOESS fit lines and study period data ...................................................................................... 43


FIGURES 

1. Map showing streamflow and water-quality sites in the Rio Grande study area..................................................... 3


2.-22. Graphs showing:


2. Water storage in El Vado and Abiquiu Reservoirs, 1965 to 2000................................................................... 9


3. Duration plots of pre- and post-December 1973 daily-mean streamflow at Rio Chama site of La Puente 


and Rio Grande site of Del Norte.............................................................................................................. 10


4. Duration plots of pre- and post-December 1973 daily-mean and sample streamflows for Rio Chama 


sites of Above Abiquiu and Chamita......................................................................................................... 11


5. Duration plots of pre- and post-December 1973 daily-mean and sample streamflows for Rio Grande 


sites of Otowi, San Felipe, Albuquerque, and Bernardo ........................................................................... 12 


6. Monthly and period differences for pre- to post-December 1973 streamflow for Rio Chama sites of 


La Puente, Above Abiquiu, and Chamita.................................................................................................. 14

iv 

Page 

7. Post-December 1973 median daily-mean streamflow for Rio Chama sites of La Puente, Above Abiquiu, 

and Chamita and Rio Chama tributary site of Heron Dam ....................................................................... 15 

8. Monthly and period differences for pre- to post-December 1973 streamflow for Rio Grande sites of 

Del Norte, Taos, Otowi, San Felipe, Albuquerque, and Bernardo ............................................................ 17 

9. Post-December 1973 median daily-mean streamflow for Rio Grande sites of Taos, Otowi, San Felipe, 

Albuquerque, and Bernardo ...................................................................................................................... 18 

10. Monthly and period differences for pre- to post-December 1973 specific conductance for Rio Chama 

site of Chamita .......................................................................................................................................... 20 

11. Post-December 1973 average (LOESS) specific conductance and median daily-mean streamflow for 

Rio Chama sites of La Puente and Chamita.............................................................................................. 22 

12. Monthly and period differences for pre- to post-December 1973 specific conductance for Rio Grande 

sites of Otowi and Bernardo...................................................................................................................... 23 

13. Post-December 1973 average (LOESS) specific conductance and median daily-mean streamflow for 

Rio Grande sites of Taos, Otowi, San Felipe, Albuquerque, Isleta, and Bernardo ................................... 24 

14. Monthly and period differences for pre- to post-December 1973 pH for Rio Chama site of Chamita .......... 25


15. Post-December 1973 average (LOESS) pH and median daily-mean streamflow for Rio Chama sites of 

La Puente and Chamita ............................................................................................................................. 27 

16. Post-December 1973 average (LOESS) water temperature for Rio Chama sites of La Puente and 

Chamita ..................................................................................................................................................... 27 

17. Monthly and period differences for pre- to post-December 1973 pH for Rio Grande sites of Otowi and 

Bernardo.................................................................................................................................................... 29 

18. Post-December 1973 average (LOESS) pH and median daily-mean streamflow for Rio Grande sites 

of Taos, Otowi, San Felipe, Albuquerque, Isleta, and Bernardo ............................................................... 31 

19. Monthly and period differences for pre- to post-December 1973 suspended-sediment concentration 

for Rio Chama sites of Above Abiquiu and Chamita................................................................................ 32 

20. Post-December 1973 average (LOESS) suspended-sediment concentration and median daily-mean 

streamflow for Rio Chama sites of La Puente, Above Abiquiu, and Chamita.......................................... 33 

21. Monthly and period differences for pre- to post-December 1973 suspended-sediment concentration for 

Rio Grande sites of Otowi and Albuquerque ............................................................................................ 35 

22. Post-December 1973 average (LOESS) suspended-sediment concentration and median daily-mean 

streamflow for Rio Grande sites of Taos, Otowi, San Felipe, Albuquerque, Isleta, and Bernardo ........... 36 

23. Map showing pre- to post-December 1973 variations in streamflow, specific-conductance, pH, and 

suspended-sediment distributions in the Rio Grande study area ....................................................................... 38 

24. Map showing post-December 1973 spatial variations in streamflow, specific-conductance, pH, and 

suspended-sediment distributions in the Rio Grande study area ....................................................................... 39 

S-1.-S-4. Graphs showing: 

S-1. LOESS fit lines and post-December 1973 data for specific conductance, pH, and total suspended 

sediment for composite annual year for Rio Chama sites of La Puente, Above Abiquiu, 

and Chamita............................................................................................................................................... 44 

S-2. LOESS fit lines and post-December 1973 data for specific conductance for composite annual year 

for Rio Grande sites of Taos, Otowi, San Felipe, Albuquerque, Isleta, and Bernardo.............................. 45 

S-3. LOESS fit lines and post-December 1973 data for pH for composite annual year for Rio Grande 

sites of Taos, Otowi, San Felipe, Albuquerque, Isleta, and Bernardo....................................................... 46 

S-4. LOESS fit lines and post-December 1973 data for total suspended sediment for composite annual 

year for Rio Grande sites of Taos, Otowi, San Felipe, Albuquerque, Isleta, and Bernardo...................... 47 

TABLES 

1. Selected information for streamflow/water-quality sites in the study area.............................................................. 4 

2. Legislative history of authorization and operations for reservoirs in the Rio Grande study area ........................... 6 

3. Pre- and post-December 1973 streamflow summary statistics for Rio Chama sites of La Puente, Above 

Abiquiu, and Chamita ........................................................................................................................................ 13 

4. Annual-mean streamflow-distribution differences from upstream to downstream for Rio Chama sites of 

La Puente, Above Abiquiu, and Chamita and Rio Grande site of Taos for the post-December 1973 period.... 15 

5. Pre- and post-December 1973 streamflow summary statistics for Rio Grande sites of Taos, Otowi, San Felipe, 

Albuquerque, and Bernardo ............................................................................................................................... 16 
 v 

Page 

6. Annual-mean streamflow-distribution differences from upstream to downstream for Rio Grande sites of Taos, 

Otowi, San Felipe, Albuquerque, and Bernardo for the post-December 1973 period....................................... 18 

7. Pre- and post-December 1973 specific-conductance summary statistics for Rio Chama sites of La Puente and 

Chamita .............................................................................................................................................................. 19 

8. Specific-conductance distribution differences from upstream to downstream for Rio Chama sites of La Puente 

and Chamita and Rio Grande sites of Taos and Otowi for the post-December 1973 period ............................. 20 

9. Heron Lake specific-conductance data .................................................................................................................... 20


10. Pre- and post-December 1973 specific-conductance summary statistics for Rio Grande sites of Taos, Otowi, 

San Felipe, Albuquerque, Isleta, and Bernardo ................................................................................................. 22 

11. Specific-conductance distribution differences from upstream to downstream for Rio Grande sites of Taos, 

Otowi, San Felipe, Albuquerque, Isleta, and Bernardo for the post-December 1973 period ............................ 24 

12. Pre- and post-December 1973 pH summary statistics for Rio Chama sites of La Puente and Chamita ................. 25


13. Distribution differences in pH from upstream to downstream for Rio Chama sites of La Puente and Chamita 

and Rio Grande sites of Taos and Otowi for the post-December 1973 period .................................................. 26 

14. Heron Lake pH data................................................................................................................................................. 26


15. Pre- and post-December 1973 pH summary statistics for Rio Grande sites of Taos, Otowi, San Felipe, 

Albuquerque, Isleta, and Bernardo .................................................................................................................... 28 

16. Distribution differences in pH from upstream to downstream for Rio Grande sites of Taos, Otowi, San Felipe, 

Albuquerque, Isleta, and Bernardo for the post-December 1973 period ........................................................... 30 

17. Pre- and post-December 1973 suspended-sediment summary statistics for Rio Chama sites of La Puente, 

Above Abiquiu, and Chamita............................................................................................................................. 31 

18. Suspended-sediment distribution differences from upstream to downstream for Rio Chama sites of La Puente, 

Above Abiquiu, and Chamita and Rio Grande sites of Taos and Otowi for the post-December 1973 period .. 33 

19. Pre- and post-December 1973 suspended-sediment summary statistics for Rio Grande sites of Taos, Otowi, 

San Felipe, Albuquerque, Isleta, and Bernardo ................................................................................................. 34 

20. Suspended-sediment distribution differences from upstream to downstream for Rio Grande sites of Taos, 

Otowi, San Felipe, Albuquerque, Isleta, and Bernardo for the post-December 1973 period ............................ 36 

21. Streamflow and water-quality correlation in the Rio Chama and Rio Grande during the post-December 

1973 period ........................................................................................................................................................ 40 

CONVERSION FACTORS, ABBREVIATIONS, AND DATUM 

Multiply By To obtain 

inch (in.) 2.54 centimeter (cm) 

foot (ft) 0.3048 meter (m) 

mile (mi) 1.609 kilometer (km) 

acre 4,047 square meter (m2

) 

square mile (mi2) 2.590 square kilometer (km2) 

gallon/day (gal/day) 3.785 liter/day (L/day) 

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

) 

cubic foot per second (ft3

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

milligram per liter (mg/L) 1.0 part per million (ppm) 

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

Horizontal coordinate information is referenced to the North American Datum of 1927 (NAD27). 

Vertical coordinate information is referenced to the National Geodetic Vertical Datum of 1929 (NGVD29). 

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

°C = (°F - 32) / 1.8 

°F = (1.8 × °C) + 32 
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 

By Jeff B. Langman and Scott K. Anderholm 

Abstract 

The coordinated operation of Heron, El Vado, and Abiquiu 

Dams on the Rio Chama and Cochiti Dam on the Rio Grande 

and the importation of Colorado River Basin water by the San 

Juan-Chama Project have altered streamflow and water quality 

of the Rio Chama and Rio Grande in northern and central New 

Mexico. The coordinated retention of streamflow in the four 

reservoirs increased median streamflows, decreased extreme 

flows, and decreased periods of small streamflow; inflow of 

San Juan-Chama Project water increased overall streamflow in 

the Rio Chama and Rio Grande. These changes to streamflow 

decreased specific conductance and suspended-sediment concentration and increased pH in the Rio Chama and the Rio 

Grande. 

Following construction of Heron and Cochiti Dams and 

integration of reservoir operations on the Rio Chama and the 

Rio Grande, the inflow of San Juan-Chama Project water and 

retention of snowmelt runoff influenced water quality. These 

influences varied by season because reservoir releases fluctuated according to downstream user needs and annual streamflow variation. The influences of San Juan-Chama Project water 

and retained snowmelt on water quality diminished with downstream flow as the Rio Grande was subjected to various natural 

and anthropogenic inflows. Because of the variability and type 

of seasonal influences, streamflow did not have a strong annual 

correlation with water quality in the Rio Chama or the Rio 

Grande. 

Introduction 

Streamflow and water quality in northern and central New 

Mexico are extremely important because of limited surfacewater resources and a growing population. Construction and 

operation of reservoirs on the Rio Chama and Rio Grande and 

the importation of Colorado River Basin water by the San JuanChama Project (SJC Project) have likely altered streamflow and 

water quality of the Rio Chama and Rio Grande. These alterations could affect current (2004) and future uses of Rio Chama, 

Rio Grande, and SJC Project water. 

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

Albuquerque, 1997) to ensure a sustainable water supply. The 

U.S. Geological Survey (USGS), in cooperation with the City 

of Albuquerque, investigated alterations and variations in 

streamflow and water quality in the Rio Chama and Rio Grande 

to better understand the effect of reservoir construction and 

operation and the introduction of SJC Project water. 

The introduction of SJC Project water has the potential to 

alter water quality by introducing non-native water of different 

chemical composition. Additionally, the alteration of natural 

streamflow patterns may influence water quality by reducing 

normal seasonal variations such as those that occur during 

snowmelt runoff. It has been shown that operation of dams and 

impoundments can affect water quality through processes such 

as sediment retention, thermal stratification, increased evaporation, decomposition of retained organic material, and nitrogen 

supersaturation (U.S. Environmental Protection Agency, 1975). 

Such processes can occur because incoming water may be 

retained as reservoir storage for flood and sediment control, irrigation, recreation, or municipal supply. 

Substantial alteration of Rio Grande streamflow and suspended sediment has been observed with construction and operation of Cochiti Dam. The magnitude of flood peaks has been 

reduced, suspended-sediment loads and bed material have 

diminished, and channel morphology has been altered downstream from the dam (Mussetter Engineering, Inc., 2002). Construction and operation of Elephant Butte Dam, south of the 

study area, also have altered Rio Grande streamflow and suspended-sediment concentration. The dam reduced peak flows, 

changed sediment transport, and altered stream geometry. The 

installation of the dam also allowed a substantial increase in 

agriculture along the Rio Grande because of increased availability of water for irrigation that resulted in an increase in irrigation-return flows with high salt content (Collier and others, 

1996). 

Purpose and Scope 

This report describes the effects of reservoir installation, 

introduction of SJC Project water, and the coordination of reservoir operations on streamflow, specific conductance, pH, and 

suspended-sediment concentration of the Rio Chama and the 

Rio Grande in northern and central New Mexico. Data collected 

from 1938 to 2000 at Federal and State streamflow-gaging/ 
2 Effects of Reservoir Installation, San Juan-Chama Project Water, and Reservoir Operations 

water-quality sites (sites) on the Rio Chama and the Rio Grande 

were analyzed to evaluate the effects of these influences. 

Description of the Study Area 

The study area includes the Rio Chama watershed from the 

Rio Chama near La Puente to the Rio Chama’s inflow to the Rio 

Grande and the Rio Grande watershed from the Rio Grande at 

Taos Junction Bridge to the Rio Grande Floodway near Bernardo (fig. 1). Additionally, data for the Rio Grande near Del 

Norte in the headwaters of the Rio Grande in Colorado are 

included for climate and streamflow analysis. The surfacewater monitoring network for this report is listed in table 1 and 

shown in figure 1. For this report, streamflow/water-quality 

sites are referred to by the study site name listed in table 1. 

Physiography 

The Continental Divide borders the study area to the west 

and the Sangre de Cristo, Sandia, and Manzano Mountains border it to the east (fig. 1). Elevations in the study area range from 

about 4,650 to 13,000 ft above NGVD29. 

The Rio Grande is the main drainage in the study area, and 

the Rio Chama is its largest tributary in this area (fig. 1). The 

Rio Grande originates in the San Juan Mountains in south-central Colorado. The river flows through south-central Colorado 

and enters northern New Mexico through Sunshine Valley. The 

Rio Grande 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 upstream from Española, New 

Mexico. Most surface-water inflow to the Rio Grande is derived 

from mountains adjacent to the Rio Grande upstream from 

Otowi (Ortiz and Lange, 1996). 

The study area contains four large reservoirs—Heron 

Lake, El Vado Reservoir, Abiquiu Reservoir, and Cochiti Lake 

(fig. 1)—that have the potential to substantially alter streamflow and water quality. Heron Lake is located on Willow Creek 

(a tributary of the Rio Chama); El Vado and Abiquiu Reservoirs 

are located on the Rio Chama downstream from the Willow 

Creek inflow. Cochiti Lake is located on the Rio Grande at 

Cochiti Pueblo downstream from the Rio Chama inflow to the 

Rio Grande. 

Climate 

Climate in the study area is semiarid with substantial variation in precipitation from the lower valley areas to the mountains. This climate results in a highly variable streamflow 

regime. In the headwaters of the Rio Grande, annual precipitation can exceed 50 in., whereas other areas in the watershed 

may receive less than 6 in. (Ellis and others, 1993). Most surface water occurs as snowmelt runoff from March through June. 

Precipitation accumulations are largest during the summer 

monsoon season (July to September), and most of the precipitation during this season falls during July and August (Western 

Regional Climate Center, 2002a). Because of the brevity of 

summer thunderstorms and evapotranspiration (ET), precipitation during the monsoon season contributes less to daily-mean 

streamflow than snowmelt runoff. 

Legal Constraints on Streamflow 

All annual streamflows of the Rio Chama and Rio Grande 

are accounted for by various compacts, treaties, and individual 

water rights. The interstate flow of the Rio Grande between 

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

Grande Compact (Compact). Agreed upon in 1938, the Compact provides the framework for regulation of equitable apportionment of Rio Grande streamflow and permits each State to 

develop and use its water resources, provided each State meets 

its delivery obligations (Rio Grande Compact Commission, 

1998). Table 2 shows applicable legislation and a brief description of the effect of each legislation on reservoirs in the study 

area. 

The SJC Project was authorized by Congress in 1962 to 

divert streamflow from three tributaries of the San Juan River 

in southwestern Colorado in the Colorado River Basin into the 

Rio Chama in the Rio Grande Basin. Minimum instream flows 

are required for the three tributaries. Volumes larger than the 

minimum instream flows are available for diversion and storage 

in Heron Lake. Diversions cannot exceed 1,350,000 acre-ft for 

a 10-year moving average, and annual diversions cannot exceed 

270,000 acre-ft. 

Reservoirs 

Heron Dam was completed in 1971 by the Bureau of Reclamation as part of the SJC Project. The SJC Project provides 

supplemental water supply to contractors such as the City of 

Albuquerque, the City of Santa Fe, and the Middle Rio Grande 

Conservancy District (MRGCD) (U.S. Army Corps of Engineers and others, 2000). The maximum capacity of Heron Lake 

is 401,300 acre-ft, and the firm yield is 96,200 acre-ft. Heron 

Lake is used solely for the storage and delivery of SJC Project 

water for municipal, domestic, industrial, recreational, irrigation, and fish and wildlife purposes (Bureau of Reclamation, 

2002c). SJC Project water is not subject to the provisions of the 

Compact under which El Vado and Abiquiu Reservoirs and 

Cochiti Lake are operated. There is no carryover for SJC Project 

contractor allotment water in Heron Lake, so contractors must 

take delivery of their water by December 31 unless granted a 

waiver. Many contractors store SJC Project water in El Vado 

and Abiquiu Reservoirs. 
Introduction 3 

106 ̊ 

Figure 1. Streamflow and water-quality sites in the Rio Grande study area. 

Rio 

Jose 

Chama 

Rio 

Rio Grande 

San 

Taos 

Conejos 

River 

San Juan Mountains 

Del 

Norte 

Sang

re 

de 

Cr

isto 

M

ountains 

Sangre de Cristo Mountains 

Chama Basin 

Jemez Mountains

Sierra Nacimiento 

Jemez Reservoir 

River 

Santa Fe 

Santa Fe 

San Luis Valley 

Bernardo 

San Juan Mountains 

Rio 

Grande 

G

orge 

Red River 

Trinchera 

Creek 

Franklin Eddy 

Canal 

Continental 

Divide 

Base from U.S. Geological Survey digital data, 1:100,000, 1983 

Chamita 

COLORADO 

NEW MEXICO 

Abiquiu 

Reservoir 

Cochiti 

Pueblo 

Rio Pueblo 

de Taos 

Embudo 

Creek 

Heron 

Lake 

Rio Grande 

Reservoir 

El 

Vado 

Reservoir 

Willow Creek 

Rio Salado 

35 ̊ 

36 ̊ 

37 ̊ 

108 ̊ 

38 107  ̊  ̊ 

Rio 

Puerco 

Isleta 

Isleta 

Diversion

Dam 

Belen 

Dixon Pilar 

Bernalillo 

Los Lunas 

Southside Water 

Reclamation Plant 

Jemez 

River 

Angostura 

Diversion 

Dam 

Albuquerque 

Galisteo Reservoir 

Sunshine 

Valley 

Manzano

Mountains 

Sandia

Mountains 

Chama 

Espanola ~ 

STUDY 

AREA 

BOUNDARY Colorado 

New 

Mexico 

El Paso 

Colorado 

River 

Basin 

EXPLANATION 

Del Norte STREAMFLOW AND 

WATER-QUALITY 

SITE NAME (table 1) 

0 20 40 60

0 20 40 60

80 MILES 

80 KILOMETERS 

Del Norte 

Taos 

Otowi 

San Felipe 

Jemez River 

Cochiti Lake 

Cochiti 

Dam 

Chamita 

Heron 

Dam 

Albuquerque 

Above Abiquiu 

La Puente 

Below Abiquiu 

Bernardo 

Isleta 

Albuquerque 

San Acacia 

Embudo 

Study 

area 

(Rio Grande 

Basin) 
4 Effects of Reservoir Installation, San Juan-Chama Project Water, and Reservoir Operations 

Table 1. Selected information for streamflow/water-quality sites in the study area. 

[USGS, U.S. Geological Survey; NAD27, North American Datum of 1927; mi2, square miles; NGVD29, National Geodetic Vertical Datum of 1929; 

NA, not available] 

DailyLocation mean 

USGS Study site Latitude and (county, Datum stream- Waterstation 

number 

USGS station 

name 

name 

(fig. 1) 

longitude 

(NAD27) 

hydrologic 

unit code) 

Drainage 

area (mi2

)

1 

(feet above 

NGVD29) 

flow 

record 

quality 

record 

08284100 Rio Chama La Puente 36 ̊39'45" Rio Arriba, 480 7,083 1955 ­ 1974 ­

near La Puente 106 ̊37'57" 13020102 2000 2000 

08284520 Willow Creek Heron 36 ̊39'56" Rio Arriba, 193 NA 1971 - None 

below Heron Dam 106 ̊42'13" 13020102 2000 

Dam 

08286500 Rio Chama Above 36 ̊19'06" Rio Arriba, 1,500 6,280 1961 ­ 1962 -

above Abiquiu Abiquiu 106 ̊35'50" 13020102 2000 1985 

Reservoir 

08287000 Rio Chama Below 36 ̊14'12" Rio Arriba, 2,047 6,040 1962 ­ 1976 -

below Abiquiu Abiquiu 106 ̊24'59" 13020102 2000 1985 

Dam 

08290000 Rio Chama Chamita 36 ̊04'26" Rio Arriba, 3,044 5,654 1938 - 1960 -

near Chamita 106 ̊06'40" 13020102 2000 2000 

08220000 Rio Grande Del Norte 37 ̊41'22" Rio Grande, 1,320 7,980 1938 - Not used 

near Del Norte 106 ̊27'38" 13010001 2000 

08276500 Rio Grande Taos 36 ̊19'12" Taos, 6,790 6,050 1938 ­ 1975 -

below Taos 105 ̊45'14" 13020101 2000 2000 

Junction Bridge 

08279000 Embudo Creek Embudo 36 ̊12'39" Rio Arriba, 305 5,859 1938 - Not used 

at Dixon Creek 105 ̊54'47" 13020101 2000 

08313000 Rio Grande at Otowi 35 ̊52'29" Santa Fe, 11,360 5,488 1938 - 1959 -

Otowi Bridge 106 ̊08'30" 13020101 2000 2000 

08317300 Cochiti Lake Cochiti 35 ̊37'01" Sandoval, 11,960 NA Not used 1981 -

near Cochiti Lake 106 ̊18'58" 13020201 2000 

Pueblo 

08317400 Rio Grande Cochiti 35 ̊37'05" Sandoval, 11,960 5,226 1970 ­ 1972 ­

below Cochiti Dam 106 ̊19'24" 13020201 2000 2000 

Dam 

08319000 Rio Grande at San Felipe 35 ̊26'47" Sandoval, 13,160 5,116 1938 - 1970 -

San Felipe 106 ̊26'24" 13020201 2000 2000 

08329000 Jemez River Jemez 35 ̊23'24" Sandoval, 1,038 5,096 1943 - 1966 -

below Jemez River 106 ̊32'03" 13020202 2000 2000 

Canyon Dam 

08330000 Rio Grande at Albuquer­ 35 ̊05'21" Bernalillo, 14,500 4,946 1941 - 1969 -

Albuquerque que 106 ̊40'48" 13020203 2000 2000 

08331000 Rio Grande at Isleta 34 ̊55'14" Bernalillo, 15,160 NA Only 1972 -

Isleta 106 ̊40'44" 13020203 sample 2000 

flow2 

08332010 Rio Grande Bernardo 34 ̊25'01" Socorro, 16,290 4,723 1938 - 1946 -

Floodway near 106 ̊48'00" 13020203 2000 2000 

Bernardo 

1

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


2Streamflow determined only at the time of water-quality sample collection.


Constructed in 1935, El Vado is the oldest reservoir in the water (Bureau of Reclamation, 2002b). Native Rio Chama 

study area and stores native Rio Chama water and SJC Project water is stored in El Vado Reservoir for inflows in excess of 

water for irrigation, recreation, and flood and sediment control required outflows for MRGCD needs and other downstream 

(U.S. Army Corps of Engineers, 1989). El Vado Reservoir is rights including the Compact (Bureau of Land Management, 


owned by the MRGCD and operated by the Bureau of Recla- 1992).


mation. The reservoir has a maximum storage of 180,000 acre­


ft and typically contains about 40,000 acre-ft of SJC Project 

5 

SJC Project water is not governed by the Compact and can 

be released to contractors at any time from storage in El Vado 

Reservoir (U.S. Army Corps of Engineers, 1989). Storage and 

release of native Rio Chama water, however, are governed by 

the Compact. Native Rio Chama water in El Vado Reservoir 

typically is stored during snowmelt runoff and subsequently 

released during the irrigation season (March 1 through November 1) (U.S. Army Corps of Engineers, 1989). During the irrigation season, native Rio Chama inflows as large as 100 ft3/s are 

allowed to pass through the reservoir for downstream senior Rio 

Chama water-right holders. 

In response to problems of poor drainage, flooding, and 

deterioration of agricultural land within central New Mexico, 

the U.S. Army Corps of Engineers (USACE) and Bureau of 

Reclamation cooperatively developed a comprehensive plan 

that included construction of Abiquiu Reservoir in 1963 (U.S. 

Army Corps of Engineers and others, 2000). Abiquiu Reservoir 

is owned and operated by the USACE for flood and sediment 

control and water supply and is the main flood-control structure 

on the Rio Chama. Abiquiu Reservoir has a maximum capacity 

of 1,535,300 acre-ft and a maximum storage capacity of 

140,097 acre-ft for SJC Project water (U.S. Army Corps of 

Engineers, 2000). Abiquiu Reservoir is not capable of storing 

the entire 200,000 acre-ft of SJC Project water as authorized in 

1981 by PL 97-140 (table 2) because of reduced storage capacity from sediment deposition and a lack of full storage easements on the margins of the reservoir (Bureau of Land Management, 1992). 

All native Rio Chama inflows into Abiquiu Reservoir are 

allowed to pass through up to a discharge equal to the downstream channel capacity of 1,800 ft3/s (U.S. Army Corps of 

Engineers, 2000). When inflows into the reservoir exceed 

downstream channel capacity, inflows are partly retained and 

generally released within a 24-hour period after the peak 

inflow, except during snowmelt runoff when water is stored for 

release during the irrigation season (U.S. Army Corps of Engineers, 2000). After July 1, when streamflow in the Rio Grande 

at Otowi Bridge (Otowi site) is less than 1,500 ft3/s, no floodwater is released from Abiquiu Reservoir. 

Congress authorized construction of Cochiti Dam in 1960 

to provide flood and sediment control in the Rio Grande. A recreation pool of 1,200 surface acres was authorized for Cochiti 

Lake in 1964 (table 2) to be supplied with water from the SJC 

Project (U.S. Army Corps of Engineers, 1989). Cochiti Dam 

was completed in 1973 and is operated in conjunction with Galisteo, Jemez, and Abiquiu Reservoirs (fig. 1) for flood and sediment control (U.S. Army Corps of Engineers, 1999). 

Native Rio Grande water is passed through Cochiti Lake 

unless retention is necessary for flood protection. SJC Project 

water can be stored prior to final release to downstream users 

(U.S. Army Corps of Engineers and others, 2000). Snowmelt 

runoff is stored in April and May; water is typically released in 

June and July and may extend into November for irrigation purposes. As with Abiquiu Reservoir, after July 1, when streamflow in the Rio Grande near Otowi Bridge is less than 1,500 

ft3/s, no floodwater is released from Cochiti Lake unless the reservoir has less than 212,000 acre-ft of summer flood storage 

Introduction 

(Bureau of Reclamation, 2002a). Cochiti Lake has a maximum 

capacity of 725,159 acre-ft. 

The USACE allows about 5,000 acre-ft per year of SJC 

Project water to pass from Abiquiu Reservoir to Cochiti Lake to 

replace evaporative losses and protect fisheries. About onethird of this water is released in July, and the remaining water is 

delivered from November to February (Bureau of Reclamation, 

2002c). 

Tributaries 

Within the study area, perennial tributaries to the Rio 

Grande, other than the Rio Chama, are few. Numerous intermittent and ephemeral drainages flow into the Rio Chama and Rio 

Grande in response to snowmelt or summer thunderstorms. 

Only Embudo Creek and the Jemez River (fig. 1) provide an 

annual-mean streamflow greater than 50 ft3/s. 

Embudo Creek has a drainage basin of 305 mi2 at the 

streamflow gage located 0.5 mi upstream from the inflow of 

Embudo Creek to the Rio Grande. The annual-mean streamflow 

is 84.7 ft3/s (1924 to 2000) (Ortiz and others, 2001). Because 

Embudo Creek flows unimpeded from its headwaters in the 

Sangre de Cristo Mountains to its inflow to the Rio Grande near 

Dixon (fig. 1) in a mostly undeveloped watershed, it is assumed 

that the streamflow and water quality of Embudo Creek have 

not changed substantially from 1938 to 2000. 

The Jemez River drainage basin is 1,038 mi2 at the Jemez 

River gage site (2.0 mi upstream from its inflow to the Rio 

Grande) and includes parts of the Jemez and Sierra Nacimiento 

Mountains (fig. 1). The annual-mean streamflow of the Jemez 

River, which may go dry during different periods of the year at 

its inflow to the Rio Grande, is 61.7 ft3/s (1943 to 2000) at the 

Jemez River site; the largest recorded daily-mean streamflow is 

3,640 ft3/s (June 19, 1958) (Ortiz and others, 2001). The river 

enters the Rio Grande between the San Felipe and Albuquerque 

sites (fig. 1). Large flows typically occur in late March, April, 

and May during snowmelt runoff, and additional peak flows 

occur during the monsoon season. The Jemez Canyon Dam and 

Reservoir, completed in 1953, regulates flow for flood and sediment control (U.S. Army Corps of Engineers, 1989). 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). 

Irrigation Diversions and Inflows 

Agricultural areas are located along the Rio Chama from 

Abiquiu Reservoir to the confluence with the Rio Grande and 

along the Rio Grande from Pilar to Otowi and from Cochiti 

Lake to Bernardo (fig. 1). These areas 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 agricultural areas and the irrigation system of the MRGCD. 
6 Effects of Reservoir Installation, San Juan-Chama Project Water, and Reservoir Operations 

Table 2. Legislative history of authorization and operations for reservoirs in the Rio Grande study area. 

[MRGCD, Middle Rio Grande Conservancy District; PL, Federal public law; SJC Project, San Juan-Chama Project] 

Legislation Date Effect on reservoirs in the study area 

MRGCD initiative 1935 Completion of El Vado Dam. 

Rio Grande Compact 1938 Authorized water delivery obligations between Colorado, New Mexico, and Texas. 

Flood Control Act (PL 80­

858) 

1948 Authorized comprehensive plan for improvement of Rio Grande Basin with a focus 

on flood control. 

Upper Colorado River Basin 

Compact 

1949 Set New Mexico’s share of Upper Colorado river water at 11.25 percent. 

Flood Control Act (PL 81­

516) 

1950 Authorized construction of Abiquiu Dam. 

River and Harbor and Flood 

Control Act (PL 86-645) 

1960 Set operating criteria for Abiquiu Dam and retention of floodwater during summer 

months for carryover storage under certain conditions. Authorized construction and 

operation parameters of Cochiti Dam. 

PL 87-483 1962 Authorized SJC Project (including Heron Dam) that allows importing water from 

San Juan Basin of the Colorado River to the Rio Chama to supply specific municipal and irrigation users in the Rio Grande Basin. Set minimum instream-flow 

requirements for the Navajo and Little Navajo Rivers and Rio Blanco. 

PL 88-293 1964 Authorized permanent pool in Cochiti Lake for recreation, fish, and wildlife. 

City of Albuquerque Resolution 1974 Committed the City’s allotment of SJC Project water to the establishment of an 

incidental recreational lake at Abiquiu Reservoir as a result of the annual storage. 

Water Supply Storage (PL 

97-140) 

1981 Authorized the storage of as much as 200,000 acre-feet of SJC Project water in 

Abiquiu Reservoir. 

PL 100-522 1988 Authorized the storage of as much as 200,000 acre-feet of Rio Grande Basin water 

in Abiquiu Reservoir instead of SJC Project water if space is available. 

Wild and Scenic River Designations (PL 100-633) 1988 Designated three reaches of the Rio Chama upstream from Abiquiu Reservoir as 

wild and scenic river with recreational purposes. 

Within the study area, the MRGCD provides irrigation 

water for agricultural purposes in a narrow band of land from 

Cochiti Lake to Bernardo (fig. 1). The MRGCD diverts water 

from the Rio Grande immediately downstream from Cochiti 

Dam, at the Angostura Diversion Dam about 5 mi north of Bernalillo, and at the Isleta Diversion Dam about one-half mi 

downstream from the Isleta site. 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 infiltrating water from 

the interior drains and canals and leakage from the Rio Grande 

to prevent waterlogging of agricultural areas (Kernodle and 

Scott, 1986). The riverside drains discharge to the Rio Grande 

at multiple locations in the study area. 

Treated Wastewater and Urban Runoff 

The City of Albuquerque operates the Southside Water 

Reclamation Plant, the largest wastewater-treatment facility in 

New Mexico, with a capacity to process 76 million gal/day 

(City of Albuquerque, 2002). Initially built in 1962, the plant 

was expanded periodically to increase treatment and receive all 

wastewater collected within the city limits. In 2001, continuous 

outflow at the Southside Water Reclamation Plant typically 

ranged from 80 to 90 ft3/s. Within the study area, this treated 

wastewater is a larger daily-mean inflow to the Rio Grande 

than any other except the Rio Chama. 
7 

The City of Albuquerque has a large storm-water collection system that discharges to the Rio Grande. The largest conveyance channel collects storm-water runoff from more than 60 

percent of the land area within the city limits. This channel typically has no measurable flow, but peak storm flows may 

exceed 4,000 ft3/s for very brief periods of time (less than 1 

hour) and can be substantially larger than flows in the Rio 

Grande during these events (Ortiz and others, 2001). Because of 

the episodic nature of storm-water runoff and the limitations of 

water-quality data, any influence on water quality from urban 

storm water is difficult to detect and is not discussed in this 

report. 

Evapotranspiration 

Evapotranspiration (sum of evaporation and transpiration, 

or ET) affects water quality by increasing constituent concentrations in water. Reservoirs in the study area provide substantial surface area for evaporation. Annual pan evaporation has 

averaged 51.72 in. for El Vado Reservoir (1923–2000), 63.72 

in. for Abiquiu Reservoir (1957–2000), and 81.10 in. for 

Cochiti Lake (1975–2000) (Western Regional Climate Center, 

2002b). ET from the Rio Chama and Rio Grande is substantial 

because of climate, reservoirs, and the broad channel areas and 

riparian corridor. The Action Committee of the Middle Rio 

Grande Water Assembly (1999) estimated that 75,000 to 

195,000 acre-ft of water is lost to ET annually from the river 

channel and along the riparian corridor of the Rio Grande from 

Otowi to San Acacia (located about 13 mi south of Bernardo 

and outside the study area; fig. 1). 

Ground-Water Inflows 

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

recharged along the mountain fronts, and ground water generally flows from the mountain areas toward the Rio Grande (Ellis 

and others, 1993; Anderholm and others, 1995). 

Follansbee and Dean (1915) determined that the Rio 

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

inflow to the Rio Grande. Various reaches of the Rio Chama 

showed seepage losses to ground water, but overall the river 

showed a 55-percent net gain of streamflow from ground-water 

inflows. 

From Taos to Cochiti Lake (fig. 1), the Rio Grande is 

likely a gaining stream. Moore and Anderholm (2002) found an 

increase in streamflow greater than what could be attributed to 

the 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). 

Introduction 

From Cochiti Lake to Bernardo (fig. 1), the interaction of 

surface water and ground water becomes increasingly 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 ET form complex interactions that make determining ground-water inflows difficult. The 

Rio Grande likely both gains and loses streamflow as a result of 

ground-water inflows and outflows through this reach. Veenhuis (2002) calculated a net loss of streamflow in the Albuquerque area during the winter months from 1996 to 2000, and 

Thorn (1995) calculated net losses in the Albuquerque area for 

all four seasons from 1989 to 1995. The Rio Grande is likely a 

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

Previous Water-Quality Studies 

Water quality in the study area has been studied for various 

constituents over variable lengths of time. Nutrient, suspendedsediment, and pesticide concentrations and trends in the Rio 

Grande from 1972 to 1990 were analyzed by Anderholm and 

others (1995). Healy (1997) assessed dissolved solids, major 

constituents, nutrients, trace elements, and suspended-sediment 

concentrations from 1993 to 1995 for spatial variations and 

streamflow relations. Pesticides, volatile organic compounds, 

and nutrients in the Rio Grande from 1992 to 1995 were summarized by Levings and others (1998). Dissolved solids, nutrients, and suspended-sediment concentrations and loads in the 

Rio Grande from 1993 to 1995 were studied by Moore and 

Anderholm (2002). Miller and others (1997) presented traceelement and suspended-sediment data from 1994 for the upper 

Rio Grande in New Mexico. Trace-element concentrations and 

streamflow in the Rio Grande from 1994 to 1996 in the greater 

Albuquerque area were presented by Kelly and Taylor (1996) 

and Wilcox (1997). Passell and others (2004) evaluated hydrological and geochemical trends and patterns in the upper Rio 

Grande for streamflow and water-quality data collected from 

1975 to 1999. 

Methods of Analysis 

Sources and Description of Data 

This study was based on available data. Daily-mean 

streamflow data were collected from 1938 to 2000, and waterquality samples were collected at the selected sites during different time periods and at different frequencies from 1946 to 

2000. Not all sites had sufficient sample populations of the 

selected constituents; thus, the data for these sites were not used 

for analysis. Site information and periods of record for available 

streamflow and water-quality data are shown in table 1. 
8 Effects of Reservoir Installation, San Juan-Chama Project Water, and Reservoir Operations 

Streamflow values used in this study are instream values 

that do not account for adjacent flow in drains, canals, and 

ditches. Flow in adjacent channels may return to the main channel upstream, downstream, or between sites used in this study 

for comparison of changes in the daily-mean streamflow. The 

total cross-sectional streamflow (instream flow plus flow in 

drains, canals, and ditches) is not used for comparison because 

the use of total cross-sectional streamflow would mask the 

effect of diversions and return flows on water quality, which is 

available only for instream flow. 

Specific conductance, pH, and total suspended-sediment 

concentration (suspended-sediment concentration) have been 

the primary water-quality data collected at each site. Because of 

the large sample populations, these three water-quality constituents were used in conjunction with streamflow to determine 

changes in the Rio Chama and Rio Grande from 1938 to 2000. 

All data are stored in the USGS National Water Information 

System (NWIS) database. 

Division of Data 

Streamflow and water-quality data from 1938 to 2000 

were divided into two periods: pre-December 1973 and postDecember 1973. This division is based on the beginning of regulated streamflow in the Rio Grande at Cochiti Lake on December 1, 1973. Installation of Heron and Cochiti Dams began a 

period of new reservoir operation and reservoir operational 

integration on the Rio Chama and Rio Grande that was not 

present before 1973 when only El Vado and Abiquiu Reservoirs 

existed. With the installation of Heron and Cochiti Dams, reservoir operation at the existing dams changed as storage and 

release volumes increased (fig. 2). Although Heron Reservoir 

was in operation in 1971, the diversion, storage, and discharge 

of SJC Project water was not fully implemented until 1973. 

Data Comparison 

Summary statistics (minimum, 25th percentile, median, 

75th percentile, and maximum values) provide an overview of 

streamflow and water-quality data for the pre- and post-December 1973 periods. The two periods were compared for monthly 

and overall period distributions using step-trend analysis that 

employed the two-tail Wilcoxon rank sum test and the HodgesLehmann estimator. The non-parametric Wilcoxon rank sum 

test was used to determine whether two sample populations 

came from the same population or whether they differed in central value (central location of sample population distribution). 

The test jointly ranks the sample populations, then compares the 

sum of the ranks for each population. The Hodges-Lehmann 

estimator was used to determine the direction of change 

(increase or decrease) in distributions (sample populations) and 

provide an estimate of the size of the change. The Hodges-Lehmann estimator is calculated by determining the median of all 

possible pair-wise differences between individual data points in 

each distribution. The estimator is insensitive to non-normal 

distribution characteristics such as skewness. 

For this study, a statistical difference in distributions was 

based on a p-value (1 – α) less than or equal to 0.10 for all twoway tests (90-percent confidence interval). If the p-value was 

greater than 0.10, the comparison was considered to show no 

difference in distributions (“no difference” or “no significance”). If the p-value was greater than 0.05 and less than or 

equal to 0.10, an increase or decrease in distributions was considered “marginally significant.” If the p-value was greater than 

0.01 and less than or equal to 0.05, the change in distributions 

was considered “significant.” If the p-value was less than or 

equal to 0.01, the change in distributions was considered 

“highly significant.” 

One-tail Wilcoxon rank sum tests were used for comparison of data distributions from two sites (upstream and downstream) during the same time period. Two-tail tests were first 

used to determine a difference in distributions, and one-tail tests 

were used to determine the direction (increase or decrease) of 

change. The Wilcoxon signed rank test was used for comparing 

upstream to downstream streamflow because of the logical pairing of daily mean values. A difference in distributions was considered significant if the one-tail test produced a p-value less 

than or equal to 0.05. 

The LOESS smooth technique was used to analyze seasonal streamflow and water-quality variation. Data for each site 

were plotted by month and day without regard for year, and a 

LOESS (local) smooth technique was applied to produce a fit 

line of the data. LOESS fit lines use a locally weighted smoothing technique to provide a flexible fit line that responds to the 

individual data point and a few neighboring data points. A variable fit window with locally quadratic fitting was used to create 

the LOESS fit lines. The LOESS fit line represents long-term 

average seasonal constituent concentrations for the specified 

period. To show adequacy of fit, LOESS fit lines and the study 

period data are presented by constituent in the Supplemental 

Information section at the back of this report. 

Kendall’s tau correlation coefficient was used to present 

strength of correlation between streamflow and the individual 

water-quality constituents. Kendall’s tau is a rank method 

(resistant to outliers) that measures the strength of the monotonic relation between two sample populations. 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 equal to or 

greater than +0.7 or equal to or less than -0.7 indicates a strong 

correlation for Kendall’s tau (Helsel and Hirsch, 1991). 
Effects of Reservoir Installation, San Juan-Chama Project Water, and Reservoir Operations on Streamflow and Water Quality 9 

400,000 

300,000 

200,000 

100,000 

0 

1965 1970 1975 1980 1985 1990 1995 2000 

Abiquiu Reservoir 

El Vado Reservoir 

Figure 2. Water storage in El Vado and Abiquiu Reservoirs, 1965 to 2000. WATER STORAGE, IN ACRE-FEET 

Acknowledgments 

The authors acknowledge the City of Albuquerque for the 

foresight and support to implement this study. In particular, the 

authors express their appreciation to John Stomp, City of Albuquerque Director of Water Resources, for his support of the 

study to better understand the State of New Mexico’s water 

resources. The authors also thank Don Gallegos of the USACE 

for his insightful contribution to reservoir operations in northern and central New Mexico. 

from any reservoirs or large diversions, and the Rio Grande near 

Del Norte drains the headwaters of the Rio Grande in the San 

Juan Mountains (fig. 1). Several small reservoirs are located on 

the Rio Grande and its tributaries upstream from Del Norte; 

however, there is little change in annual storage in these reservoirs (Rio Grande Compact Commission, 1998), and the reservoirs are considered to have insignificant storage capacity relative to the streamflow of the Rio Grande at this location. 

There were only small differences in the distributions of 

daily-mean streamflow between the pre- and post-December 

1973 periods for the sites of La Puente and Del Norte (fig. 3). 

With little difference in streamflow at the La Puente and Del 

Effects of Reservoir Installation, San Juan- Norte sites between the two periods, climate was assumed not 

to be a major influence. Most differences in streamflow in the

Chama Project Water, and Reservoir pre- and post-December 1973 periods for sites downstream 

Operations on Streamflow and Water from the reservoirs can then be attributed to the effects of reservoir installation and operation and the SJC Project. A potential

Quality climate bias is further explored in the Streamflow section of this 

Potential Climate Bias 

A concern when comparing streamflow and water-quality 

data between the pre- and post-December 1973 periods is the 

potential for a climate bias. If climate were the major influence 

in creating differences in streamflow between the two periods, 

the effect of reservoirs or the SJC Project could not be accurately evaluated. Streamflow at the La Puente and Del Norte 

sites was examined for differences between the pre- and postDecember 1973 periods. 

The Rio Chama near La Puente drains the headwaters of 

the Rio Chama in the southern San Juan Mountains upstream 

report. 

Potential Sampling Bias 

For valid comparison, water-quality samples must have 

been collected during streamflows that were representative of 

daily-mean streamflow distributions for the pre- and postDecember 1973 periods. If sample-streamflow distributions 

were similar to daily-mean streamflow distributions for each of 

the pre- and post-December 1973 periods, then comparison of 

water-quality data for those two periods was assumed valid and 

not biased. 
10 Effects of Reservoir Installation, San Juan-Chama Project Water, and Reservoir Operations 

10,000 

8,000 

6,000 

4,000 

2,000 

0 

La Puente 1955 to 1973 

La Puente 1974 to 2000 

Del Norte 1938 to 1973 

Del Norte 1974 to 2000 

0 25 50 75 100 

PERCENTAGE OF TIME INDICATED STREAMFLOW WAS EQUALED OR EXCEEDED 

Figure 3. Duration plots of pre- and post-December 1973 daily-mean streamflow at Rio Chama site of

 La Puente and Rio Grande site of Del Norte. 

DAILY-MEAN STREAMFLOW,

IN CUBIC FEET PER SECOND 

Sample-streamflow distributions were similar to dailymean streamflow distributions except at the San Felipe site and 

to a lesser extent at the Chamita, Albuquerque, and Bernardo 

sites during the pre-December 1973 period (figs. 4 and 5). The 

San Felipe pre-December 1973 sampling distribution lacked 

sufficient samples for comparison of pre- to post-December 

1973 periods. The large (less than 25-percent frequency) preDecember 1973 streamflow samples from Chamita, Albuquerque, and Bernardo were overrepresented in the sample-streamflow distributions. However, the overall sample-streamflow 

distributions were generally similar to the daily-mean streamflow distribution. No sampling bias was apparent that would 

reduce the validity of the pre- to post-December 1973 comparison of streamflow and water-quality constituents at sites with 

sufficient sample populations in both periods. 

Streamflow 

Rio Chama 

Installation and operation of the Rio Chama reservoirs and 

implementation of the SJC Project increased overall streamflow 

in the Rio Chama but decreased the largest streamflows downstream from the reservoirs. Streamflow at La Puente, upstream 

from the reservoirs, was slightly larger in post-December 1973 

median and interquartile range, and streamflow at Above 

Abiquiu and Chamita, downstream from the reservoirs, was 

substantially larger in post-December 1973 medians and interquartile ranges (table 3). The maximum streamflow increased at 

La Puente and at Above Abiquiu, but the maximum streamflow 

decreased at Chamita. 
Effects of Reservoir Installation, San Juan-Chama Project Water, and Reservoir Operations on Streamflow and Water Quality 11 

0 

2,000 

4,000 

6,000 

8,000 

0 

1,000 

2,000 

3,000 

4,000

STREAMFLOW, IN CUBIC FEET PER SECOND

Chamita 

Above Abiquiu Daily mean streamflow 1962 to 1973 

Sample streamflow 1962 to 1973 

Daily mean streamflow 1974 to 2000 

Sample streamflow 1974 to 2000 

Daily mean streamflow 1962 to 1973 

Sample streamflow 1962 to 1973 

Daily mean streamflow 1974 to 2000 

Sample streamflow 1974 to 2000 

0 25 50 75 100


PERCENTAGE OF TIME INDICATED STREAMFLOW WAS EQUALED OR EXCEEDED


Figure 4. Duration plots of pre- and post-December 1973 daily-mean and sample streamflows for

 Rio Chama sites of Above Abiquiu and Chamita. 
12 Effects of Reservoir Installation, San Juan-Chama Project Water, and Reservoir Operations STREAMFLOW, IN CUBIC FEET PER SECOND 

12,000 

9,000 

6,000 

3,000 

0 

10,000 

8,000 

6,000 

4,000 

2,000 

0 

10,000 

8,000 

6,000 

4,000 

2,000 

0 

16,000 

12,000 

8,000 

4,000 

0 

Otowi 

San Felipe 

Albuquerque 

Bernardo 

Daily mean streamflow 1962 to 1973 

Sample streamflow 1962 to 1973 

Daily mean streamflow 1974 to 2000 

Sample streamflow 1974 to 2000 

Daily mean streamflow 1962 to 1973 

Sample streamflow 1962 to 1973 

Daily mean streamflow 1974 to 2000 

Sample streamflow 1974 to 2000 

Daily mean streamflow 1962 to 1973 

Sample streamflow 1962 to 1973 

Daily mean streamflow 1974 to 2000 

Sample streamflow 1974 to 2000 

Daily mean streamflow 1962 to 1973 

Sample streamflow 1962 to 1973 

Daily mean streamflow 1974 to 2000 

Sample streamflow 1974 to 2000 

0 25 50 75 100


PERCENTAGE OF TIME INDICATED STREAMFLOW WAS EQUALED OR EXCEEDED


Figure 5. Duration plots of pre- and post-December 1973 daily-mean and sample streamflows for

 Rio Grande sites of Otowi, San Felipe, Albuquerque, and Bernardo. 
Effects of Reservoir Installation, San Juan-Chama Project Water, and Reservoir Operations on Streamflow and Water Quality 13 

Table 3. Pre- and post-December 1973 streamflow summary statistics for Rio Chama sites of La Puente, Above Abiquiu, and Chamita. 

[ft3/s, cubic feet per second; pre, pre-December 1973; post, post-December 1973] 

La Puente La Puente Above Abiquiu Chamita 

Streamflow (ft3/s) pre post Above Abiquiu pre post Chamita pre post 

Minimum 4 4 8 19 0.5 17 

25th percentile 45 51 69 131 63 142 

Median 76 85 122 249 166 384 

75th percentile 220 280 416 651 640 852 

Maximum 6,690 7,720 6,180 6,480 8,760 3,567 

Number of values 6,636 9,801 4,505 9,801 13,098 9,801 

The annual-mean streamflow distributions for the Rio 

Chama increased from pre- to post-December 1973 for all sites 

affected by the reservoirs (fig. 6). The annual-mean streamflow 

distribution did not increase at the La Puente site. Increases in 

streamflow distributions at Above Abiquiu and Chamita were 

highly significant for all months except November at the Above 

Abiquiu site. For sites affected by the reservoirs, the largest 

monthly increases generally were during snowmelt runoff in 

March through July (fig. 6). Monthly increases at the La Puente 

site also were highly significant during snowmelt runoff, 

although smaller than those at Above Abiquiu and Chamita, 

indicating some climate influence. 

Annual-mean streamflow distributions increased downstream in the Rio Chama in the post-December 1973 period 

(table 4), indicating likely surface- and ground-water inflows 

and the effect of the addition of SJC Project water. Because the 

median daily-mean streamflow of 384 ft3/s at Chamita was 

equal to about 70 percent of the median daily-mean streamflow 

of 530 ft3/s at Taos, the Rio Chama has a large influence on Rio 

Grande streamflow and water quality. 

Post-December 1973 median daily-mean streamflow at La 

Puente was largest during snowmelt runoff from March through 

July with peak flows in May and small flows during all other 

months (fig. 7). Streamflow was less than 100 ft3/s at the La 

Puente site from August through February. During the peak of 

snowmelt runoff, median daily-mean streamflow at La Puente 

was greater than 2,500 ft3/s, larger than all other Rio Chama 

sites in the post-December 1973 period. 

Storage of SJC Project water and snowmelt runoff in El 

Vado and Abiquiu Reservoirs affected downstream flow (fig. 

7). El Vado Reservoir operations decreased streamflow in the 

Rio Chama from March to June (comparing the streamflow at 

Above Abiquiu to the streamflows at La Puente and Heron 

Dam) by storing part of the SJC Project water and snowmelt 

runoff. The reservoir increased streamflow in the Rio Chama 

from June to February as stored water was released. The maximum release from Abiquiu Dam was restricted to 1,800 ft3/s 

because of downstream channel capacity. This restriction 

resulted in larger releases from Abiquiu Reservoir prior to and 

after the snowmelt runoff peak and during summer months than 

releases from El Vado Reservoir. Streamflow greater than 

1,800 ft3/s at the Chamita site during peak snowmelt runoff is 

attributable to tributary inflows between Abiquiu Reservoir and 

the Chamita site. 
14 Effects of Reservoir Installation, San Juan-Chama Project Water, and Reservoir Operations 

JAN FEB MAR APR MAY JUNE JULY AUG SEPT OCT NOV DEC PERIOD

Above Abiquiu 

La Puente 

DAILY-MEAN STREAMFLOW DIFFERENCE (HODGES-LEHMANN ESTIMATOR), IN CUBIC FEET PER SECOND -100 

100 

300 

500 

-100 

100 

300 

500 

-100 

100 

300 

500 Chamita 

ANNUAL 

MEAN 

EXPLANATION 

WILCOXON RANK SUM TEST 

Highly significant (p <_ 0.01) 

Significant (0.01 < p <_ 0.05) 

No significance (p > 0.10) 

Figure 6. Monthly and period differences for pre- to post-December 1973 streamflow for

 Rio Chama sites of La Puente, Above Abiquiu, and Chamita. 
Effects of Reservoir Installation, San Juan-Chama Project Water, and Reservoir Operations on Streamflow and Water Quality 15 

Table 4. Annual-mean streamflow-distribution differences from upstream to downstream for Rio Chama sites of La Puente, Above 

Abiquiu, and Chamita and Rio Grande site of Taos for the post-December 1973 period. 

[<, less than] 

Wilcoxon signed rank test La Puente to Above Abiquiu to Chamita compared 

(one way) Above Abiquiu Chamita with Taos 

Difference in streamflow Increase Increase Increase 

distributions 

P-value <0.001 <0.001 <0.001 

JAN FEB MAR APR MAY JUNE JULY AUG SEPT OCT NOV DEC 

Figure 7. Post-December 1973 median daily-mean streamflow for Rio Chama sites of La Puente,

 Above Abiquiu, and Chamita and Rio Chama tributary site of Heron Dam. 

La Puente 

Above Abiquiu 

Chamita 

Heron Dam

MEDIAN DAILY-MEAN STREAMFLOW, IN CUBIC FEET PER SECOND

0 

500 

1,000 

1,500 

2,000 

2,000 

3,000 

3,500 

4,000 

4,500 
16 Effects of Reservoir Installation, San Juan-Chama Project Water, and Reservoir Operations 

Rio Grande 

The operation of Rio Chama reservoirs, the Rio Grande 

reservoir of Cochiti Lake, and the addition of SJC Project water 

generally increased streamflow in the Rio Grande. Median 

streamflows and interquartile ranges increased and maximum 

streamflows decreased from pre- to post-December 1973 for all 

sites on the Rio Grande influenced by the reservoirs: Otowi, San 

Felipe, Albuquerque, and Bernardo (table 5). Minimum, 

median, and interquartile ranges in the post-1973 period were 

larger at the Taos site, upstream from the reservoirs, but these 

increases were smaller than increases at sites affected by the 

reservoirs. 

Annual-mean streamflow distributions for the Rio Grande 

increased from pre- to post-December 1973 at all sites affected 

by the reservoirs and the SJC Project (fig. 8). There was no significant increase in annual-mean streamflow distributions at the 

Del Norte and Taos sites. Increases in streamflow distributions 

at the Rio Grande sites of Otowi, San Felipe, Albuquerque, and 

Bernardo were highly significant during all months except at 

San Felipe in November. The largest monthly increases were 

during snowmelt runoff in March through July. At the Del 

Norte and Taos sites, increases in streamflow were significant 

during snowmelt runoff, although much smaller than those at 

the sites downstream from the reservoirs, indicating some climate influence. 

Median daily-mean streamflow of the Rio Grande 

increased by a factor of two from Taos to Otowi (from 530 to 

1,050 ft3/s), was similar between Otowi and San Felipe (1,050 

to 1,020 ft3/s), decreased from San Felipe to Albuquerque 

(1,020 to 874 ft3/s), and increased from Albuquerque to Bernardo (874 to 920 ft3

/s) during the post-December 1973 period 

(table 5). 

Changes in annual-mean streamflow distributions were 

similar to changes in median streamflow (table 6). However, 

streamflow distribution from Otowi to San Felipe decreased, 

and from Albuquerque to Bernardo did not change. 

Much of the increase in streamflow from Taos to Otowi is 

due to the inflow of the Rio Chama, whereas the decrease 

between Otowi and San Felipe is a result of ET and the Cochiti 

Dam MRGCD diversion. The decrease in streamflow between 

San Felipe and Albuquerque is a result of ET and MRGCD 

diversions and possible ground-water losses. The lack of difference in streamflow between Albuquerque and Bernardo is 

likely a result of riverside drain inflows, ground-water inflows, 

and the Southside Water Reclamation Plant inflow balanced by 

ET and the Isleta MRGCD diversion. 

Median daily-mean streamflow at all Rio Grande sites 

responded similarly to snowmelt runoff in the post-December 

1973 period as streamflow increased in March and peaked in 

May (fig. 9). The largest median daily-mean peak streamflow 

was about 4,500 ft3/s at the Otowi site. Rio Grande sites downstream from Otowi were moderated because of Cochiti Dam. 

Streamflows were less than 1,500 ft3/s from July 1 to March 1 

at all sites. Streamflows decreased abruptly after July 1 when 

floodwater releases from Abiquiu Reservoir and Cochiti Lake 

were halted. 

Table 5. Pre- and post-December 1973 streamflow summary statistics for Rio Grande sites of Taos, Otowi, San Felipe, Albuquerque, and 

Bernardo. 

[ft3/s, cubic feet per second; pre, pre-December 1973; post, post-December 1973] 

San San Albu- Albu- Ber- BerStreamflow Taos Taos Otowi Otowi Felipe Felipe querque querque nardo nardo 

(ft3

/s) pre post pre post pre post pre post pre post 

Minimum 159 171 106 195 54 67 0.1 0.1 0.1 72 

25th percen- 300 351 510 740 507 724 240 549 154 472 

tile 

Median 448 530 740 1,050 755 1,020 606 874 575 920 

75th percen- 648 835 1,320 1,650 1,340 1,640 1,070 1,640 1,060 1,704 

tile 

Maximum 9,730 8,120 22,000 12,000 21,300 8,095 20,600 8,650 19,600 9,208 

Number of 13,118 9,435 13,118 9,801 13,118 9,801 11,598 9,801 11,657 9,801 

values 
Effects of Reservoir Installation, San Juan-Chama Project Water, and Reservoir Operations on Streamflow and Water Quality 17 DAILY-MEAN STREAMFLOW DIFFERENCE (HODGES-LEHMANN ESTIMATOR), IN CUBIC FEET PER SECOND 

-100 

100 

300 

500 

700 

900 

-100 

100 

300 

500 

700 

900 

-100 

100 

300 

500 

700 

900 

Del Norte 

Otowi 

Albuquerque 

Taos 

San Felipe 

Bernardo 

JAN


FEB


MAR


APR


MAY


JUNE


JULY


AUG


SEPT

OCT

NOV

DEC

PERIOD

ANNUAL

MEAN

JAN


FEB


MAR


APR


MAY


JUNE


JULY


AUG


SEPT

OCT

NOV

DEC

PERIOD

ANNUAL

MEAN 

EXPLANATION 

Highly significant (p <_ 0.01) 

Significant (0.01 < p <_ 0.05) 

Marginally significant (0.05 < p <_ 0.10) 

No significance (p > 0.10) 

Figure 8. Monthly and period differences for pre- to post-December 1973 streamflow for Rio Grande

 sites of Del Norte, Taos, Otowi, San Felipe, Albuquerque, and Bernardo. 

WILCOXON RANK SUM TEST 
18 Effects of Reservoir Installation, San Juan-Chama Project Water, and Reservoir Operations 

Table 6. Annual-mean streamflow-distribution differences from upstream to downstream for Rio Grande sites of Taos, Otowi, San Felipe, 

Albuquerque, Isleta, and Bernardo for the post-December 1973 period. 

[<, less than] 

Wilcoxon signed rank test Taos to Otowi to San San Felipe to Albuquerque to 

(one way) Otowi Felipe Albuquerque Bernardo 

Difference in streamflow dis- Increase Decrease Decrease No difference 

tributions 

P-value < 0.001 < 0.001 < 0.001 0.173 

JAN FEB MAR APR MAY JUNE JULY AUG SEPT OCT NOV DEC 

Figure 9. Post-December 1973 median daily-mean streamflow for Rio Grande sites of Taos,

 Otowi, San Felipe, Albuquerque, and Bernardo. 

Taos 

Otowi 

San Felipe 

Albuquerque 

Bernardo 

4,500 

4,000 

3,500 

3,000 

2,500 

2,000 

1,500 

1,000 

500 

MEDIAN DAILY-MEAN STREAMFLOW, IN CUBIC FEET PER SECOND 

0
Effects of Reservoir Installation, San Juan-Chama Project Water, and Reservoir Operations on Streamflow and Water Quality 19 

Inflow from the Rio Chama to the Rio Grande was about 

35 percent of Otowi’s streamflow from October through February with only a small increase in December (fig. 9). Beginning 

in March, the Rio Chama carried snowmelt runoff and SJC 

Project water to the Rio Grande (about 50 percent of Otowi’s 

streamflow) with a substantial reduction by July 1. 

The trend for streamflow in the Rio Grande was similar to 

that observed in the Rio Chama near Chamita. The Otowi and 

San Felipe sites substantially increased in streamflow in March 

and decreased July 1 (fig. 9). Water was stored in Cochiti Lake 

mostly from March through May and released mostly in June, 

as shown by the difference between Otowi and San Felipe 

streamflows. MRGCD irrigation water from the Rio Grande 

was diverted from mid-May through the end of October, as 

shown by the difference in streamflows between the San Felipe 

and the Albuquerque and Bernardo sites. This trend was especially apparent on November 1 when streamflow at San Felipe, 

Albuquerque, and Bernardo increased as irrigation diversions 

stopped. Streamflow increased between Albuquerque and Bernardo from November 1 to mid-March and can be attributed to 

the Southside Water Reclamation Plant, riverside drain inflows, 

and potential ground-water inflows. 

Specific Conductance 

Rio Chama 

Specific conductance at the Chamita site decreased in 

median value, interquartile range, and maximum value from the 

pre- to post-December 1973 period (table 7). Decreases in specific-conductance distribution at Chamita were highly significant from the pre- to post-December 1973 period and highly 

significant in January through March and July through December (fig. 10). Specific conductance did not change significantly 

in April and June, but an increase was highly significant in May. 

These significant decreases and increase exemplify the effect of 

reservoir operations as released SJC Project water and retained 

snowmelt decreased specific conductance in the Rio Chama 

throughout the year except when streamflow was retained during the snowmelt runoff. 

Post-December 1973 specific conductance in the Rio 

Chama increased from La Puente to Chamita (table 8) and indicated that specific conductance in inflows of ground water, tributaries, and SJC Project water likely were larger than in native 

upper Rio Chama water (La Puente). Specific conductance of 

ground water and tributaries between La Puente and Chamita is 

unknown. Data retrieved from the U.S. Environmental Protection Agency STORET Legacy database for Heron Lake 

(table 9) indicated a median of 312 μS/cm, which was larger 

than the 190-μS/cm median for La Puente (table 7). The inflow 

of ground water and (or) tributaries to the Rio Chama between 

the La Puente and Chamita sites also likely increased specific 

conductance because the median specific conductance (353 

μg/L) in water at the Chamita site was larger than that in Heron 

Lake. 

Specific conductance increased downstream from Abiquiu 

Reservoir in the post-December 1973 period. The median specific conductance at the Above Abiquiu site was 357 μS/cm 

from 1976 to 1985. For the same period at the Below Abiquiu 

site, the median was 355 μS/cm. The median for the Chamita 

site from 1976 to 1985 was 440 μS/cm. The similar medians for 

Above Abiquiu and Below Abiquiu and the increase in median 

specific conductance from Below Abiquiu to Chamita indicate 

that most of the increase in specific conductance in the Rio 

Chama was likely a result of ground-water and tributary inflow 

downstream from Abiquiu Reservoir. Comparison of specificconductance distributions for the Rio Chama (Chamita) and Rio 

Grande (Taos and Otowi) (table 8) indicates that specific conductance in the Rio Chama was larger than that in the Rio 

Grande and that the inflow of the Rio Chama was diluted with 

mixing of Rio Grande water. 

Table 7. Pre- and post-December 1973 specific-conductance summary statistics for Rio Chama sites of La Puente and Chamita. 

[μS/cm, microsiemens per centimeter at 25 degrees Celsius; pre-, pre-December 1973; post, post-December 1973; NA, not available] 

Specific 

conductance La Puente La Puente Chamita 

(μS/cm) pre post Chamita pre post 

Minimum NA 46 132 176 

25th percentile NA 148 328 300 

Median NA 190 523 353 

75th percentile NA 230 676 473 

Maximum NA 375 1,000 864 

Number of values 0 73 207 253 
20 Effects of Reservoir Installation, San Juan-Chama Project Water, and Reservoir Operations 

JAN FEB MAR APR MAY JUNE JULY AUG SEPT OCT NOV DEC PERIOD 

EXPLANATION 

WILCOXON RANK SUM TEST 

Highly significant (p <_ 0.01) 

No significance (p > 0.10) 

Figure 10. Monthly and period differences for pre- to post-December 1973 specific conductance for

 Rio Chama site of Chamita. 

Table 8. Specific-conductance distribution differences from upstream to downstream for Rio Chama sites of La Puente and Chamita and 

Rio Grande sites of Taos and Otowi for the post-December 1973 period. 

[<, less than] SPECIFIC-CONDUCTANCE DIFFERENCE (HODGES-LEHMANN ESTIMATOR),

IN MICROSIEMENS PER CENTIMETER

AT 25 DEGREES CELSIUS 

-300 

-200 

-100 

0 

100 

Wilcoxon rank sum test 

(one way) La Puente to Chamita 

Chamita compared with 

Taos 

Chamita compared with 

Otowi 

Difference in specific-conductance 

distributions 

Increase Decrease Decrease 

P-value < 0.001 < 0.001 < 0.001 

Table 9. Heron Lake specific-conductance data. 

[Retrieved from U.S. Environmental Protection Agency STORET Legacy Data Center; cond., conductance; μS/cm, microsiemens per centimeter at 25 degrees 

Celsius] 

Sample Sample Sample Sample 

depth depth depth depth 

Constituent 8/26/87 (feet) 5/14/91 (feet) 8/14/91 (feet) 10/29/91 (feet) 

Heron Lake: sample location is Heron deep, located near the dam 

Specific cond. 305-352 0 - 108 325 - 0 - 148 286 - 328 0 - 148 293 - 326 0 - 148 

(μS/cm) 347 

Heron Lake: sample location is Heron shallow, located in the northeastern part of the reservoir 

Specific cond. 305 - 0 - 29 308 - 0 - 49 274 - 306 0 - 56 292 - 292 0 - 52 

(μS/cm) 305 342 
Effects of Reservoir Installation, San Juan-Chama Project Water, and Reservoir Operations on Streamflow and Water Quality 21 

Post-December 1973 specific conductance decreased at 

the La Puente and Chamita sites during the snowmelt runoff 

(fig. 11). Following the streamflow peak in May, specific conductance increased as streamflow decreased. Specific-conductance values were largest from January through March when 

ground-water and tributary inflows composed the majority of 

streamflow in the Rio Chama. 

Rio Grande 

Specific-conductance medians decreased from pre- to 

post-December 1973 for the Rio Grande sites of Otowi, Isleta, 

and Bernardo (table 10). Maximum specific conductance 

decreased at Otowi and Bernardo but slightly increased at 

Isleta. Specific-conductance distributions decreased significantly from the pre- to post-December 1973 period at Otowi 

and Bernardo (fig. 12). Specific-conductance distribution also 

significantly decreased between the two periods for the Isleta 

site (p-value less than 0.001), but data were insufficient for 

monthly comparisons of distributions. Specific-conductance 

distribution decreases at Otowi were significant or highly significant during all months except April. Decreases at Bernardo 

were marginally significant to highly significant during January, June, August, September, October, and December (fig. 12). 

The differences in magnitude and significance in pre- to postDecember 1973 monthly decreases in specific conductance at 

Otowi and Bernardo show the lessening effect of the reservoirs 

further downstream as the Rio Grande was influenced by other 

inflows. 

Specific conductance increased in the downstream direction in the Rio Grande during the post-December 1973 period 

(table 11). The increase in median specific conductance from 

Taos to Otowi (from 281 to 329 μS/cm) was likely a result of 

Rio Chama inflow (353 μS/cm at the Chamita site). The small 

median increase from the Otowi to San Felipe site (329 to 340 

μS/cm) was likely a result of storage, mixing, and ET at Cochiti 

Lake and ET within the channel corridor. 

The San Felipe to Albuquerque reach of the Rio Grande 

has the potential for substantial ET because of a broad, flat 

channel, but the reach also contains the inflow from the Jemez 

River. Inflow from the Jemez River is small compared with the 

Rio Grande. The larger specific conductance of the Jemez River 

(1,240-μS/cm median specific conductance and 4,700-μS/cm 

maximum specific conductance during the post-December 

1973 period), however, may have increased median specific 

conductance in the Rio Grande from San Felipe to Albuquerque 

(from 340 to 368 μS/cm) in addition to increases caused by ET 

and irrigation-return flows. 

The increase in median specific conductance from Albuquerque (368 μS/cm) to Isleta (425 μS/cm) and Bernardo (491 

μS/cm) was likely a result of ET, treated wastewater inflow, and 

irrigation-return flows. Wilcox (1997) measured specific conductance ranging from 764 to 836 μS/cm (median of 816 

μS/cm) for the City of Albuquerque’s Southside Water Reclamation Plant and ranging from 398 to 486 μS/cm (median of 

432 μS/cm) for the riverside drains in the Albuquerque area. 

Seasonal variation of average specific conductance in the 

post-December 1973 period was similar for all sites on the Rio 

Grande (fig. 13). Specific conductance decreased with the 

beginning of snowmelt runoff in March, was smallest in May 

and June, and gradually increased throughout the summer 

months as releases from the reservoirs declined in volume. By 

September, specific-conductance values at all sites were similar 

to those prior to snowmelt runoff. 

The larger specific conductance at Otowi compared with 

that at San Felipe from mid-June through July was likely a 

result of snowmelt runoff storage in Cochiti Lake. The difference in specific conductance between Otowi and San Felipe in 

March was small but began to increase in April as a greater 

amount of snowmelt runoff passed the Otowi site and part of 

this runoff was stored in Cochiti Lake (shown by the difference 

in streamflow at the Otowi and San Felipe sites). Streamflow at 

San Felipe was generally smaller than streamflow at Otowi during this period but was equal to or greater than streamflow at 

Otowi after mid-June with release of stored snowmelt runoff. 

With this shift in streamflow at San Felipe in mid-June, specific 

conductance at San Felipe decreased to concentrations smaller 

than those observed at Otowi as retained snowmelt was released 

from Cochiti Lake. 

pH 

Rio Chama 

From the pre- to post-December 1973 period in water collected from the Rio Chama near Chamita (table 12), pH 

increased for all statistical values (minimum, 25th percentile, 

median, 75th percentile, and maximum). The increase in pH at 

the Chamita site was highly significant from the pre- to postDecember 1973 period and highly significant in every month 

except December (significant) (fig. 14). The largest increases 

were in October and November, and the smallest increase was 

in July. 

The post-December 1973 pH in the Rio Chama increased 

from La Puente to Chamita (table 13). The increase was likely 

a result of inflow of SJC Project water because pH was larger in 

Heron Lake (8.45 median pH, table 14) than pH at the La Puente 

site. Ground-water and tributary inflows between La Puente and 

Chamita also could increase pH, although no data were available for comparison. 

For the post-December 1973 period, there was no difference in pH distributions at Chamita compared with the Taos and 

Otowi sites (table 13). This lack of difference indicates that the 

increase in pH in water at the Chamita site from the pre- to postDecember 1973 period resulted in a pH in the Rio Chama that 

was similar to pH in the Rio Grande at Taos. Therefore, mixing 

of Rio Chama and Rio Grande water did not result in pH 

changes at Otowi. 
22 Effects of Reservoir Installation, San Juan-Chama Project Water, and Reservoir Operations SPECIFIC CONDUCTANCE, IN MICROSIEMENS PER CENTIMETER AT 25 DEGREES CELSIUS

MEDIAN DAILY-MEAN STREAMFLOW,

IN CUBIC FEET PER SECOND 

JAN FEB MAR APR MAY JUNE JULY AUG SEPT OCT NOV DEC 

75 

150 

225 

300 

375 

450 

525 

600 

500 

1,000 

1,500 

2,000 

2,500 

3,000 

3,500 

4,000 

4,500 

0 

EXPLANATION 

SPECIFIC STREAMFLOW 

CONDUCTANCE 

La Puente La Puente 

Chamita Chamita 

Figure 11. Post-December 1973 average (LOESS) specific conductance and median daily-mean


 streamflow for Rio Chama sites of La Puente and Chamita.


Table 10. Pre- and post-December 1973 specific-conductance summary statistics for Rio Grande sites of Taos, Otowi, San Felipe, Albuquerque, Isleta, and Bernardo. 

[μS/cm, microsiemens per centimeter at 25 degrees Celsius; pre, pre-December 1973; post, post-December 1973; NA, not available] 

Specific San San Albu- Albu- Ber- Berconductance Taos Taos Otowi Otowi Felipe Felipe querque querque Isleta Isleta nardo nardo 

( μS/cm) pre post pre post pre post pre post pre post pre post 

Minimum NA 144 200 165 NA 173 NA 192 245 220 289 224 

25th percen- NA 220 335 288 NA 303 NA 329 367 379 406 417 

tile 

Median NA 281 386 329 NA 340 NA 368 486 425 520 491 

75th percen- NA 329 442 370 NA 376 NA 425 580 470 644 575 

tile 

Maximum NA 550 1,310 628 NA 520 NA 570 690 720 1,940 865 

Number of 0 200 982 381 1 190 2 103 31 289 160 219 

values 
Effects of Reservoir Installation, San Juan-Chama Project Water, and Reservoir Operations on Streamflow and Water Quality 23 

Bernardo 

JAN FEB MAR APR MAY JUNE JULY AUG SEPT OCT NOV DEC PERIOD

WILCOXON RANK SUM TEST 

EXPLANATION 

No significance (p > 0.10) 

Highly significant (p <_ 0.01) 

Significant (0.01 < p <_ 0.05) 

Marginally significant (0.05 < p <_ 0.10) 

SPECIFIC-CONDUCTANCE DIFFERENCE (HODGES-LEHMANN ESTIMATOR),

IN MICROSIEMENS PER CENTIMETER AT 25 DEGREES CELSIUS -200 

-150 

-100 

-50 

0 

50 

Otowi 

-200 

-150 

-100 

-50 

0 

50 

Figure 12. Monthly and period differences for pre- to post-December 1973 specific conductance

 for Rio Grande sites of Otowi and Bernardo. 
24 Effects of Reservoir Installation, San Juan-Chama Project Water, and Reservoir Operations 

Table 11. Specific-conductance distribution differences from upstream to downstream for Rio Grande sites of Taos, Otowi, San Felipe, 

Albuquerque, Isleta, and Bernardo for the post-December 1973 period. 

[<, less than] 

Wilcoxon rank sum test (one Taos to Otowi to San San Felipe to Albuquerque to Isleta to 

way) Otowi Felipe Albuquerque Isleta Bernardo 

Difference in specific-conduc- Increase Increase Increase Increase Increase 

tance distributions 

P-value < 0.001 0.015 < 0.001 < 0.001 < 0.001 

SPECIFIC CONDUCTANCE, IN MICROSIEMENS PER CENTIMETER

AT 25 DEGREES CELSIUS

MEDIAN DAILY-MEAN STREAMFLOW,

IN CUBIC FEET PER SECOND

0 

500 

1,000 

1,500 

2,000 

2,500 

3,000 

3,500 

4,000 

4,500 

75 

150 

225 

300 

375 

450 

525 

600 

JAN FEB MAR APR MAY JUNE JULY AUG SEPT OCT NOV DEC 

EXPLANATION 

SPECIFIC 

CONDUCTANCE STREAMFLOW 

Taos Taos 

Otowi Otowi 

San Felipe San Felipe 

Albuquerque Albuquerque 

Isleta Bernardo 

Bernardo 

Figure 13. Post-December 1973 average (LOESS) specific conductance and median daily-mean

 streamflow for Rio Grande sites of Taos, Otowi, San Felipe, Albuquerque, Isleta,

 and Bernardo. 
Effects of Reservoir Installation, San Juan-Chama Project Water, and Reservoir Operations on Streamflow and Water Quality 25 

Table 12. Pre- and post-December 1973 pH summary statistics for Rio Chama sites of La Puente and Chamita. 

[pre, pre-December 1973; post, post-December 1973; NA, not available] 

pH (standard La Puente La Puente Chamita 

units) pre post Chamita pre post 

Minimum NA 6.3 6.9 7.5 

25th percentile NA 7.7 7.4 8 

Median NA 8.0 7.6 8.2 

75th percentile NA 8.2 7.8 8.4 

Maximum NA 8.8 8.5 8.8 

Number of values 0 124 181 146 

JAN FEB MAR APR MAY JUNE JULY AUG SEPT OCT NOV DEC PERIOD 

EXPLANATION 

WILCOXON RANK SUM TEST 

Highly significant (p <_ 0.01) 

Significant (0.01 < p <_ 0.05) 

Figure 14. Monthly and period differences for pre- to post-December 1973 pH for Rio Chama site

 of Chamita. 

pH DIFFERENCE

(HODGES-LEHMANN ESTIMATOR),

IN STANDARD UNITS 

-0.1 

0.0 

0.1 

0.2 

0.3 

0.4 

0.5 

0.6 

0.7 

0.8 

0.9 
26 Effects of Reservoir Installation, San Juan-Chama Project Water, and Reservoir Operations 

Table 13. Distribution differences in pH from upstream to downstream for Rio Chama sites of La Puente and Chamita and Rio Grande sites 

of Taos and Otowi for the post-December 1973 period. 

[<, less than] 

Wilcoxon rank sum test (one 

way) La Puente to Chamita 

Chamita compared 

with Taos 

Chamita compared with 

Otowi 

Difference in pH distributions Increase No difference No difference 

P-value < 0.001 0.463 0.145 

Table 14. Heron Lake pH data. 

[Retrieved from U.S. Environmental Protection Agency STORET Legacy Data Center; pH in standard units] 

Sample Sample Sample 

depth depth depth Sample 

Constituent 8/26/87 (feet) 5/14/91 (feet) 8/14/91 (feet) 10/29/91 depth (feet) 

Heron Lake: sample location is Heron deep, located near the dam 

pH 8.40 0 8.60 0 8.48 0 8.43 0 

Heron Lake: sample location is Heron shallow, located in the northeastern part of the reservoir 

pH 8.30 0 8.65 0 8.47 0 8.38 0 

In the post-December 1973 period, seasonal variations in 

pH at the La Puente and Chamita sites were not similar due to 

reservoir operations (fig. 15). The pH at La Puente was typically smaller than at Chamita except from June through August, 

and pH data for both sites indicate an inverse relation to streamflow. The pH in water from the La Puente site was smallest in 

early May just before the streamflow peak and largest in July 

following the end of snowmelt runoff. The values of pH in 

water at Chamita were smallest in June following the streamflow peak and largest in late October when reservoir releases 

were at a minimum. 

The pH was typically smaller at the La Puente site than pH 

at the Chamita site except during summer months when pH at 

the La Puente site exceeded pH at the Chamita site from midJune through mid-August (fig. 15). Following the peak of 

snowmelt runoff, biological productivity likely increased at the 

La Puente site as instream temperatures increased, thereby producing greater photosynthesis and an increase in pH. Biological 

productivity in a watershed continually changes with variable 

inputs of nutrients and energy, given natural seasonal variations 

(Black, 1996). With increased photosynthesis, pH increases as 

hydrogen-ion concentrations decrease as dissolved carbon 

dioxide decreases (Hem, 1989). 

Following the pH peak at La Puente in July, pH decreased 

through August, remained stable in September, and decreased 

from October through December (fig. 15). The decrease in pH 

from mid-July through August is consistent with biological 

productivity as an influence on pH. Streamflow was stable during this period, indicating that ground-water and tributary 

inflows also were stable. Biological productivity may have 

peaked in July and decreased through August as a result of 

decreasing temperature (fig. 16). Following the decrease, pH 

remained relatively constant from late August through midOctober (fig. 15). The decrease in pH from mid-October 

through December was likely a result of another decrease in 

biological activity as water temperature further decreased (fig. 

16). 

The assumption of biological activity as an influence on 

pH in the Rio Chama is not as straightforward at the Chamita 

site. At this site, pH increased in late summer and fall as streamflow decreased to a minimum following summer reservoir 

releases and also decreased in early spring (fig. 15) as stream 

temperatures began to increase (fig. 16). The pH was largest 

when streamflow was smallest but did not correlate with the 

streamflow temperature peak as observed with the La Puente 

site (fig. 16). The retention and later release of snowmelt runoff 

from Abiquiu Reservoir appears to depress pH values at the 

Chamita site through the warm summer months. The shift in pH 

from the La Puente site to the Chamita site is likely a result of 

reservoir releases that controlled stream temperature, nutrient 

loads, and biological activity downstream from Abiquiu Dam. 
Effects of Reservoir Installation, San Juan-Chama Project Water, and Reservoir Operations on Streamflow and Water Quality 27 MEDIAN DAILY-MEAN STREAMFLOW, IN CUBIC FEET PER SECOND 

0 

500 

1,000 

1,500 

2,000 

2,500 

3,000 

3,500 

4,000 

4,500 

7.7 

7.8 

7.9 

8.0 

8.1 

8.2 

8.3 

8.4 

8.5 

pH, IN STANDARD UNITS 

JAN FEB MAR APR MAY JUNE JULY AUG SEPT OCT NOV DEC 

EXPLANATION 

pH STREAMFLOW 

La Puente La Puente 

Chamita Chamita 

Figure 15. Post-December 1973 average (LOESS) pH and median daily-mean streamflow for Rio Chama

 sites of La Puente and Chamita. 

TEMPERATURE, IN DEGREES

CELSIUS 

0

5

10

15

20

25

La Puente 

Chamita 

JAN


FEB


MAR


APR


MAY


JUNE


JULY


AUG


SEPT


OCT


NOV


DEC


Figure 16. Post-December 1973 average (LOESS) water temperature for

 Rio Chama sites of La Puente and Chamita. 
28 Effects of Reservoir Installation, San Juan-Chama Project Water, and Reservoir Operations 

Rio Grande 

For the Rio Grande sites downstream from the reservoirs, 

median pH was 7.7 or 7.8 during the pre-December 1973 period 

and ranged from 8.0 to 8.2 for the post-December 1973 period 

(table 15). The 25th and 75th percentile pH values increased at 

Otowi, Isleta, and Bernardo between the two periods. The pH at 

Otowi indicated a highly significant increase from pre- to postDecember 1973 for all monthly distributions (fig. 17). Although 

the 25th percentile, median, and 75th percentile pH values all 

increased by 0.3 unit at the Isleta site (table 15), the overall pH 

distribution decreased from the pre- to post-December 1973 

period (highly significant, p-value less than 0.001). The pH 

increase at Bernardo was highly significant from pre- to postDecember 1973, but monthly distributions were a mixture of no 

significance to highly significant increases (fig. 17). 

No downstream trend in pH was evident for the Rio 

Grande sites during the post-December 1973 period as was 

observed with specific conductance. The distributions of pH in 

the Rio Grande were similar for Taos and Otowi, decreased 

from Otowi to San Felipe, were similar for San Felipe and Albuquerque, decreased from Albuquerque to Isleta, and increased 

from Isleta to Bernardo (table 16). The decrease in pH from 

Otowi to San Felipe could have been a result of storage in 

Cochiti Lake. The pH at the Cochiti Lake site ranged from 7.2 

to 9.0 with a median of 7.9, and pH at the Cochiti Dam site 

ranged from 7.8 to 8.3 with a median of 7.9. The median pH values for Cochiti Lake and Cochiti Dam were smaller than the 

Otowi site median pH of 8.2. 

Stratification of Cochiti Lake may be causing smaller pH 

values near the bottom of the reservoir because of hypoxic or 

anoxic conditions. Under hypoxic conditions, pH may decrease 

as carbon dioxide increases with biological respiration (Black, 

1996). In July 1999, June 2000, and September 2000, near the 

dam in Cochiti Lake, water-quality depth profiles showed dissolved-oxygen stratification (K. Bennett, U.S. Army Corps of 

Engineers, written commun., 2002). Additionally, Johnson and 

Barton (1980) found dissolved-oxygen stratification near the 

dam at Cochiti Lake during summer months and decreasing pH 

values with depth. Stratification occurred only during summer 

months, which likely limited the decrease in pH, and is the reason why median pH concentrations from Otowi to San Felipe 

decreased by only 0.1 standard unit (distribution decrease was 

significant; p-value of 0.01). 

The decrease in pH from Albuquerque to Isleta (table 15) 

and the subsequent increase at Bernardo were probably an 

effect of the inflow from the City of Albuquerque’s Southside 

Water Reclamation Plant between Albuquerque and Isleta and 

riverside drain inflows or ground-water additions between 

Isleta and Bernardo. Wilcox (1997) measured pH values ranging from 6.55 to 7.33 (median of 6.99) at the Southside Water 

Reclamation Plant from 1994 to 1996, which were smaller than 

the median pH value at the Albuquerque site. Wilcox (1997) 

also measured pH ranging from 7.33 to 8.37 (median of 7.84) 

for riverside drains in the Albuquerque area during the same 

period, yet these values do not indicate a possible increase in pH 

from riverside drain inflows between Isleta and Bernardo. The 

remaining potential sources of a larger pH inflow between Isleta 

and Bernardo could be additional downstream riverside drain 

inflows or possibly biological activity in this reach of the Rio 

Grande due to an increase in nutrients (Moore and Anderholm, 

2002). 

Table 15. Pre- and post-December 1973 pH summary statistics for Rio Grande sites of Taos, Otowi, San Felipe, Albuquerque, Isleta, and 

Bernardo. 

[pre, pre-December 1973; post, post-December 1973; NA, not available] 

Albu- AlbuSan San quer­ quer- Ber- BerpH (standard Taos Taos Otowi Otowi Felipe Felipe que que Isleta Isleta nardo nardo 

units) pre post pre post pre post pre post pre post pre post 

Minimum NA 7.1 6.8 6.6 NA 7.3 NA 6.8 6.7 6.6 7.1 6.8 

25th percen- NA 7.9 7.6 8.0 NA 7.9 NA 7.9 7.5 7.8 7.6 7.8 

tile 

Median NA 8.2 7.8 8.2 NA 8.1 NA 8.1 7.7 8.0 7.8 8.1 

75th percen- NA 8.4 8.0 8.3 NA 8.3 NA 8.2 7.8 8.1 7.9 8.4 

tile 

Maximum NA 8.9 9.2 8.9 NA 8.8 NA 8.7 8.4 8.5 8.5 9.5 

Number of 0 204 1,007 355 1 189 2 85 31 289 162 183 

values 
Effects of Reservoir Installation, San Juan-Chama Project Water, and Reservoir Operations on Streamflow and Water Quality 29 

Otowi 

pH DIFFERENCE (HODGES-LEHMANN ESTIMATOR), IN STANDARD UNITS -0.1 

0. 

0.1 

0.2 

0.3 

0.4 

0.5 

-0.1 

0. 

0.1 

0.2 

0.3 

0.4 

0.5 

0.6 

0.7 

0.8 

Bernardo 

JAN FEB MAR APR MAY JUNE JULY AUG SEPT OCT NOV DEC PERIOD 

EXPLANATION 

WILCOXON RANK SUM TEST 

Highly significant (p <_ 0.01) 

Significant (0.01 < p <_ 0.05) 

Marginally significant (0.05 < p <_ 0.10) 

No significance (p > 0.10) 

Figure 17. Monthly and period differences for pre- to post-December 1973 pH for Rio Grande

 sites of Otowi and Bernardo. 
30 Effects of Reservoir Installation, San Juan-Chama Project Water, and Reservoir Operations 

Table 16. Distribution differences in pH from upstream to downstream for Rio Grande sites of Taos, Otowi, San Felipe, Albuquerque, Isleta, and Bernardo for the post-December 1973 period. 

[<, less than] 

Wilcoxon rank sum 

test (one way) Taos to Otowi Otowi to San Felipe 

San Felipe to 

Albuquerque 

Albuquerque to 

Isleta 

Isleta to 

Bernardo 

Difference in pH distributions No difference Decrease No difference Decrease Increase 

P-value 0.230 0.010 0.070 0.001 < 0.001 

A consistent seasonal pattern did not exist between sites 

on the Rio Grande for post-December 1973 pH except for 

decreases during snowmelt runoff (fig. 18). At all sites pH 

decreased slightly during snowmelt runoff, although at each 

site the timing of this decrease was different. The smallest and 

least variation in pH was at Isleta, likely a result of continuous 

Southside Water Reclamation Plant inflow. The pH at the Taos 

site indicated that pH in the Rio Grande upstream from inflow 

from the Rio Chama was smallest from January to July and 

largest from August to December; a similar trend was observed 

only at the Bernardo site. 

The pH at the Otowi, San Felipe, and Albuquerque sites 

had little seasonal variability (fig. 18). At Otowi, pH values 

were larger than those at San Felipe except during May and 

June, the peak of snowmelt runoff. During snowmelt runoff, 

pH at Otowi decreased more than at the San Felipe site because 

the decrease in pH at San Felipe was moderated by mixing of 

inflow and water stored in Cochiti Lake. The difference in pH 

at Otowi and San Felipe generally increased throughout the 

summer months and into the fall, supporting the assertion that 

hypoxic or anoxic conditions in the reservoir were producing 

smaller pH values in the Rio Grande downstream from the reservoir. The decrease in pH between the San Felipe and Albuquerque sites from January through August was not due to 

inflow of the Jemez River. Median pH of the Jemez River in the 

post-December 1973 period was 8.2 (compared with 8.1 for 

San Felipe and Albuquerque), and a comparison of pH distributions for the San Felipe and Jemez River sites indicated larger 

pH for the Jemez River (p-value of 0.02). 

The pH at the Bernardo site was more variable throughout 

the seasons compared with all other sites, and this variability 

likely resulted from riverside drain inflows and biological 

activity. The increase in pH beginning in June was likely a 

result of riverside drain inflows, and the large pH values at Bernardo during August and September were likely a biological 

effect from increased instream temperatures, smaller streamflow, and increased nutrients. 

Suspended Sediment 

Rio Chama 

All suspended-sediment statistical values (minimum, 25th 

percentile, median, 75th percentile, and maximum) for the Rio 

Chama sites of Above Abiquiu and Chamita were smaller during the post-December 1973 period than during the pre-December 1973 period (table 17). Suspended-sediment concentrations 

at Above Abiquiu decreased highly significantly between the 

two periods, but monthly distributions ranged from no significance to highly significant (fig. 19). The decrease in suspended-sediment concentrations at the Chamita site was highly 

significant from the pre- to post-December 1973 period for all 

months except January (marginally significant) and July (marginally significant). The largest decreases in suspended-sediment concentrations between the two periods were in August at 

Chamita and in September at Above Abiquiu. 

Suspended-sediment concentrations increased from La 

Puente to Above Abiquiu and from Above Abiquiu to Chamita 

in the post-December 1973 period (table 18). Additionally, suspended-sediment concentrations at Chamita were larger than at 

Taos and smaller than at Otowi. The difference in suspendedsediment concentration distributions between Chamita and the 

Rio Grande sites (table 18) indicates that the Rio Chama provided additional sediment to the Rio Grande but that Rio 

Chama inflow did not account for all the suspended-sediment 

concentration increase between Taos and Otowi. 

During the post-December 1973 period, seasonal concentrations in suspended sediment in the Rio Chama peaked twice 

at Above Abiquiu and Chamita but only once at the La Puente 

site (fig. 20). Suspended-sediment concentration at La Puente 

peaked during snowmelt runoff in early May prior to the 

streamflow peak in mid-May. Additionally, suspended-sediment concentrations at La Puente were much smaller with little 

variation compared with those at the other sites. Suspendedsediment concentrations at the Above Abiquiu and Chamita 

sites peaked in April, more than 1 month before the snowmelt 

runoff peak. The peaks in suspended-sediment concentration 

prior to streamflow peaks indicate that the carrying capacity of 

streamflow exceeded the supply of available sediment during 

this time. The second peak at the Above Abiquiu and Chamita 

sites during the monsoon season was about 60 percent of the 

first peak (fig. 20). 
Effects of Reservoir Installation, San Juan-Chama Project Water, and Reservoir Operations on Streamflow and Water Quality 31 MEDIAN DAILY-MEAN STREAMFLOW, IN CUBIC FEET PER SECOND 

0 

500 

1,000 

1,500 

2,000 

2,500 

3,000 

3,500 

4,000 

4,500 

7.7 

7.8 

7.9 

8.0 

8.1 

8.2 

8.3 

8.4 

8.5

pH, IN STANDARD UNITS 

JAN FEB MAR APR MAY JUNE JULY AUG SEPT OCT NOV DEC 

EXPLANATION 

pH STREAMFLOW 

Taos Taos 

Otowi Otowi 

San Felipe San Felipe 

Albuquerque Albuquerque 

Isleta Bernardo 

Bernardo 

Figure 18. Post-December 1973 average (LOESS) pH and median daily-mean streamflow for Rio Grande

 sites of Taos, Otowi, San Felipe, Albuquerque, Isleta, and Bernardo. 

Table 17. Pre- and post-December 1973 suspended-sediment summary statistics for Rio Chama sites of La Puente, Above Abiquiu, and 

Chamita. 

[mg/L, milligrams per liter; pre, pre-December 1973; post, post-December 1973; NA, not available] 

Suspended La Puente La Puente Above Abiquiu Above Abiquiu Chamita 

sediment (mg/L) pre post pre post Chamita pre post 

Minimum NA 1 50 4 100 21 

25th percentile NA 10 875 39 995 89 

Median NA 17 2,050 111 2,910 209 

75th percentile NA 39 7,768 367 6,665 658 

Maximum NA 703 70,800 14,300 47,500 14,500 

Number of values 0 74 104 105 127 199 
32 Effects of Reservoir Installation, San Juan-Chama Project Water, and Reservoir Operations TOTAL SUSPENDED-SEDIMENT CONCENTRATION DIFFERENCE (HODGES-LEHMANN ESTIMATOR), IN MILLIGRAMS PER LITER -15,000 

-10,750 

-6,500 

-2,250 

2,000 

-15,000 

-10,750 

-6,500 

-2,250 

2,000 

Above Abiquiu 

Chamita 

JAN FEB MAR APR MAY JUNE JULY AUG SEPT OCT NOV DEC PERIOD 

WILCOXON RANK SUM TEST 

EXPLANATION 

Highly significant (p <_ 0.01) 

Significant (0.01 < p <_ 0.05) 

Marginally significant (0.05 < p <_ 0.10) 

No significance (p > 0.10) 

Figure 19. Monthly and period differences for pre- to post-December 1973 suspended-sediment

 concentration for Rio Chama sites of Above Abiquiu and Chamita. 
Effects of Reservoir Installation, San Juan-Chama Project Water, and Reservoir Operations on Streamflow and Water Quality 33 

Table 18. Suspended-sediment distribution differences from upstream to downstream for Rio Chama sites of La Puente, Above Abiquiu, 

and Chamita and Rio Grande sites of Taos and Otowi for the post-December 1973 period. 

[<, less than] 

Wilcoxon rank sum test 

(one way) 

La Puente to Above 

Abiquiu 

Above Abiquiu to 

Chamita 

Chamita compared 

with Taos 

Chamita compared 

with Otowi 

Difference in suspendedsediment distributions Increase Increase Decrease Increase 

P-value < 0.001 < 0.001 < 0.001 < 0.001 

JAN FEB MAR APR MAY JUNE JULY AUG SEPT OCT NOV DEC 

MEDIAN DAILY-MEAN STREAMFLOW,

IN CUBIC FEET PER SECOND

0 

500 

1,000 

1,500 

2,000 

2,500 

3,000 

3,500 

4,000 

4,500 

TOTAL SUSPENDED-SEDIMENT CONCENTRATION,

IN MILLIGRAMS PER LITER 

0 

125 

250 

375 

500 

625 

750 

875 

1,000 

EXPLANATION 

SUSPENDED STREAMFLOW 

SEDIMENT 

La Puente La Puente 

Above Abiquiu Above Abiquiu 

Chamita Chamita 

Figure 20. Post-December 1973 average (LOESS) suspended-sediment concentration and median

 daily-mean streamflow for Rio Chama sites of La Puente, Above Abiquiu, and Chamita. 
34 Effects of Reservoir Installation, San Juan-Chama Project Water, and Reservoir Operations 

Rio Grande 

Median and 25th and 75th percentile values of suspendedsediment concentrations decreased from the pre- to postDecember 1973 period for the Rio Grande sites of Otowi, San 

Felipe, Albuquerque, and Bernardo (table 19). The median 

decrease was largest at Bernardo and smallest at Otowi. Maximum concentrations decreased at all sites except San Felipe, 

which is likely a result of the small number of samples collected 

during the pre-December 1973 period. Decreases in suspendedsediment concentrations at the Otowi and Albuquerque sites 

were highly significant between the two periods and ranged 

from no significance to highly significant for the monthly distributions (fig. 21). Suspended-sediment concentrations 

decreased from the pre- to post-December 1973 period for San 

Felipe (highly significant) and Bernardo (highly significant). 

Suspended-sediment concentrations for the Rio Grande 

alternately increased and decreased in the downstream direction 

in the post-December 1973 period (table 20). The effect of 

Cochiti Lake as a sediment control was evident with the 

decrease in concentrations between Otowi and San Felipe. 

In the post-December 1973 period, the seasonal variation 

in Rio Grande suspended-sediment concentration (fig. 22) was 

a different pattern than what was observed in the Rio Chama. 

Suspended-sediment concentrations in the Rio Grande peaked 

only once (snowmelt runoff) at all sites except Otowi, which 

peaked twice. Concentrations were typically smallest at the 

Taos site. The largest suspended-sediment concentrations were 

at the Otowi site except during November through January 

when the concentrations were larger at the Bernardo site. Suspended-sediment concentrations at Otowi peaked early in May 

before the streamflow peak in mid-May and also peaked in 

August during the monsoon season. The two suspended-sediment concentration peaks at the Otowi site are likely a result of 

the Rio Chama, which also showed two peaks. Concentrations 

at the San Felipe site were similar to those at the Taos site, but 

two small increases in suspended sediment occurred in May and 

August at the San Felipe site. 

Suspended-sediment concentrations were larger at the 

Albuquerque site during all months than concentrations at the 

San Felipe (upstream) and Isleta (downstream) sites (fig. 22). 

Concentrations did not increase at the Isleta site during snowmelt runoff or the monsoon season. Suspended-sediment concentrations increased from Isleta to Bernardo and increased at 

the Bernardo site during the snowmelt runoff, monsoon season, 

and in winter. 

Table 19. Pre- and post-December 1973 suspended-sediment summary statistics for Rio Grande sites of Taos, Otowi, San Felipe, Albuquerque, Isleta, and Bernardo. 

[mg/L, milligrams per liter; pre, pre-December 1973; post, post-December 1973; NA, not available] 

Albu- AlbuSuspended San San quer­ quer- Ber- Bersediment Taos Taos Otowi Otowi Felipe Felipe que que Isleta Isleta nardo nardo 

(mg/L) pre post pre post pre post pre post pre post pre post 

Minimum NA 4 40 14 565 5 77 9 NA 8 283 10 

25th percen- NA 19 746 228 1,705 35 1,235 169 NA 113 1,875 208 

tile 

Median NA 36 1,590 625 2,295 61 2,280 411 NA 193 3,260 461 

75th percen- NA 77 4,553 1,770 2,690 137 3,805 1,135 NA 510 5,955 965 

tile 

Maximum NA 24,700 163,00 45,300 2,990 14,300 76,600 45,800 NA 10,100 31,100 28,800 

0 

Number of 0 131 140 352 12 181 96 479 0 214 59 412 

values 
Effects of Reservoir Installation, San Juan-Chama Project Water, and Reservoir Operations on Streamflow and Water Quality 35 

JAN FEB MAR APR MAY JUNE JULY AUG SEPT OCT NOV DEC PERIOD

TOTAL SUSPENDED-SEDIMENT CONCENTRATION DIFFERENCE

(HODGES-LEHMANN ESTIMATOR), IN MILLIGRAMS PER LITER

Otowi 

Albuquerque 

-8,000 

-6,000 

-4,000 

-2,000 

0 

2,000 

-8,000 

-6,000 

-4,000 

-2,000 

0 

2,000 

EXPLANATION 

WILCOXON RANK SUM TEST 

Highly significant (p <_ 0.01) 

Significant (0.01 < p <_ 0.05) 

Marginally significant (0.05 < p <_ 0.10) 

No significance (p > 0.10) 

Figure 21. Monthly and period differences for pre- to post-December 1973 suspended-sediment

 concentration for Rio Grande sites of Otowi and Albuquerque. 
36 Effects of Reservoir Installation, San Juan-Chama Project Water, and Reservoir Operations 

Table 20. Suspended-sediment distribution differences from upstream to downstream for Rio Grande sites of Taos, Otowi, San Felipe, Albuquerque, Isleta, and Bernardo for the post-December 1973 period. 

[<, less than] 

Wilcoxon rank sum test 

(one way) Taos to Otowi 

Otowi to San 

Felipe 

San Felipe to 

Albuquerque 

Albuquerque to 

Isleta 

Isleta to 

Bernardo 

Difference in suspendedsediment distributions Increase Decrease Increase Decrease Increase 

P-value <0.001 <0.001 <0.001 <0.001 <0.001 

TOTAL SUSPENDED-SEDIMENT CONCENTRATION,

IN MILLIGRAMS PER LITER

MEDIAN DAILY-MEAN STREAMFLOW, IN CUBIC FEET PER SECOND

0 

500 

1,000 

1,500 

2,000 

2,500 

3,000 

3,500 

4,000 

4,500 

125 

250 

375 

500 

625 

750 

875 

1,000 

0 

JAN FEB MAR APR MAY JUNE JULY AUG SEPT OCT NOV DEC 

EXPLANATION 

SUSPENDED 

SEDIMENT STREAMFLOW 

Taos Taos 

Otowi Otowi 

San Felipe San Felipe 

Albuquerque Albuquerque 

Isleta Bernardo 

Bernardo 

Figure 22. Post-December 1973 average (LOESS) suspended-sediment concentration and median

 daily-mean streamflow for Rio Grande sites of Taos, Otowi, San Felipe, Albuquerque,

 Isleta, and Bernardo. 
Effects of Reservoir Installation, San Juan-Chama Project Water, and Reservoir Operations on Streamflow and Water Quality 37 

Peaks of suspended-sediment concentrations during snowmelt runoff were most visible at sites that have instream sediment sources (unstable channel configurations that allow aggradation and degradation) and upstream tributary inflows. The 

smallest suspended-sediment concentrations through most of 

the seasons were at the Taos site because the site is located 

downstream from the Rio Grande Gorge (fig. 1), a stable channel area where the Rio Grande flows through a basalt canyon 

with few inflows. In contrast, the Otowi site is located in a narrow valley flood plain where the river has downcut into basin 

fill and the upstream reach receives multiple inflows of intermittent and ephemeral tributaries draining the river valley. Nordin and Beverage (1965) determined that the Rio Grande channel near Otowi increased in bed shear stress and bed-material 

size as streamflow increased. This increase in bed shear stress 

indicated scour and channel alteration with larger streamflows. 

Culbertson and Dawdy (1964) observed an accumulation of 

sediment in the Rio Grande between the confluence of the Rio 

Chama and the Otowi site. 

The difference in suspended-sediment concentrations 

between the San Felipe and Albuquerque sites may have been a 

result of channel characteristics, bed material, and sedimentstarved water discharged from Cochiti Lake. Lagasse (1980) 

found that cross-sectional profiles of the Rio Grande from 

Cochiti Lake to the San Felipe site did not substantially change 

from 1971 to 1980 (before and after installation of Cochiti 

Dam), but cross-sectional profiles of the Rio Grande from San 

Felipe to Albuquerque showed substantial alteration, indicating 

aggradation and degradation of the channel through this reach. 

Culbertson and Dawdy (1964) described the channel at the San 

Felipe site as stable with little evidence of aggradation and degradation. 

Water discharged from Cochiti Lake was likely mostly 

sediment free, did not suspend much sediment prior to reaching 

the San Felipe site, then suspended sediment from San Felipe to 

Albuquerque where channel sediment was freely available. 

Suspended-sediment concentration also likely increased 

between San Felipe and Albuquerque because of inflows from 

tributaries. 

The decrease in suspended-sediment concentration 

between the Albuquerque and Isleta sites was unusual because 

this reach of the river does not substantially change in morphology or gradient (Lagasse, 1980). This decrease may partly be a 

result of local channel geometry or local influences such as 

operation of the MRGCD Isleta Diversion Dam (fig. 1) or 

inflows of treated wastewater from the Southside Water Reclamation Plant (median of 24.5 mg/L; Wilcox, 1997) and riverside drains (median of 68.5 mg/L; Wilcox, 1997). 

At the Bernardo site, suspended-sediment concentration 

increased with increasing streamflow during snowmelt runoff, 

but did not increase during the monsoon season (fig. 22). The 

lack of increase during the monsoon season is similar to the lack 

of increase in suspended-sediment concentration observed at 

the Albuquerque site during this period. Suspended-sediment 

concentrations at Bernardo increased when MRGCD diversions 

were halted (November to March), indicating that the smaller, 

wetted channel area and smaller streamflow during the diversions did not have sufficient instream sediment or velocity compared with the larger, wetted channel area during snowmelt runoff and when diversions were not occurring. 

Minor increases in suspended-sediment concentration that 

did occur during the monsoon season were a result of intermittent and ephemeral streams contributing brief inflows to the Rio 

Grande. These inflows contribute little surface water to the Rio 

Grande (typically flow for 1 day or less in response to precipitation), but the inflows can have large concentrations of suspended sediment (Healy, 1997). Inflows from these streams can 

result in deposition of sediment in the Rio Grande channel that 

is subsequently resuspended and transported during larger Rio 

Grande streamflows. Nordin and Beverage (1965) described 

how tributary runoff during thunderstorms in the monsoon season caused sharp peaks in streamflow and suspended-sediment 

concentration in these intermittent and ephemeral streams. 

Constituent Trends and Correlation 

Temporal variations of streamflow, specific conductance, 

pH, and suspended-sediment concentration followed similar 

trends as the Rio Chama and Rio Grande responded to reservoir 

installation, SJC Project water, and reservoir operations. 

Streamflow and pH distributions increased and specific conductance and suspended-sediment distributions decreased at all 

sites from the pre- to the post-December 1973 period (fig. 23). 

In the post-December 1973 period, the effects of reservoirs 

and SJC Project water created different overall and seasonal 

responses depending on proximity to certain reservoirs. Streamflow, specific conductance, and suspended-sediment concentration increased downstream in the Rio Chama and in the Rio 

Grande at Otowi (fig. 24) because of the introduction of SJC 

Project water and retention of snowmelt runoff in the Rio 

Chama reservoirs. The pH increased from Above Abiquiu to 

Chamita, but this increase did not affect the Rio Grande because 

no increase was observed from Taos to Otowi. 

Effects of the reservoirs and SJC Project water were not as 

apparent in the Rio Grande as they were in the Rio Chama (fig. 

24). Specific conductance increased downstream at all sites, but 

streamflow, pH, and suspended-sediment concentration indicated increases, decreases, and no change from site to site from 

Otowi to Bernardo. The alteration of streamflow and water 

quality in the Rio Grande as a result of the reservoirs and SJC 

Project water is demonstrated by the changes in these constituents from Otowi to San Felipe, but the effects of the reservoirs 

and SJC Project water are reduced or reversed because of additional influences on the Rio Grande downstream from San 

Felipe. 
Taos to Otowi

TRATION

NAME (table 1)

M

ountains 

38 Effects of Reservoir Installation, San Juan-Chama Project Water, and Reservoir Operations

EXPLANATION 

Del Norte	 STREAMFLOW AND WATER­


QUALITY SITE


STREAMFLOW OR CONCEN


DISTRIBUTION


Increase


Decrease


NA Not available


Streamflow 

Specific conductance 

pH 

Suspended sediment 

Chamita

 Otowi 

Bernardo

 Isleta 

Rio 

Jose 

Chama 

Rio 

Rio Grande 

San 

Taos 

Conejos 

River 

San Juan Mountains 

Del 

Norte 

Sang

re 

de 

Cr

isto 

Sangre de Cristo M

San Juan Mountains 

R

Trinchera Reservoir 

Willow Creek 

Galisteo Reservoir 

Valley 

Del Norte 

Below Abiquiu 

ountains 

Chama Basin 

Continental 

u Jemez Mountains

Sierra Nacimiento 

Jemez Reservoir 

e

River m

e

z

S n

iv r 

a

ta Fe 

Santa Fe 

San Luis Valley 

Rio Salado 

Bernardo 

io 

Gr

G

ande 

orge 

Red River 

Creek 

Franklin

dE

dy 

n l Ca

a

Divide 

Base from U.S. Geological Survey digital data, 1:100,000, 1983 

Chamita 

COLORADO 

NEW MEXICO 

Abiquiu 

Reservoir 

Cochiti 

Pueblo 

Va Rio do Pueblo 

de Taos 

Embudo 

Creek 

Heron Heron

Lake 

Rio Grande 

El 

Reservoir 

35 ̊ 

36 ̊ 

37 ̊ 

108 ̊ 

107 ̊ 

Southside W BOUNDARY ater 

38 ̊ 

106 ̊ 

Albuquerque STUDY 

AREA 

Rio 

P

rco 

Isleta 

Isleta Diversion

Dam 

Belen 

Pilar 

Bernalillo 

Los Lunas 

Reclamation Plant 

R

e

anzano

M

Dixon 

J

e

Angostura 

Diversion 

Dam 

Albuquerque 

Sunshine 

M

ountains 

Sandia

Mountains 

Taos 

Otowi 

San Felipe 

Jemez River 

Cochiti Lake 

Cochiti 

Dam 

Chamita 

Dam 

Above Abiquiu 

La Puente 

Bernardo 

Isleta 

Chama 

Embudo 

Espanola ~ 

Streamflow 

Specific conductance 

pH 

Suspended sediment 

Streamflow NA 

Specific conductance 

pH 

Suspended sediment NA 

Streamflow 

Specific conductance 

pH 

Suspended sediment 

0 20 40 60 80 MILES 

0 20 40 60 80 KILOMETERS 

 Figure 23. Pre- to post-December 1973 variations in streamflow, specific-conductance,

 pH, and suspended-sediment distributions in the Rio Grande study area. 
Taos to Otowi

Taos to Otowi

Taos to Otowi

Effects of Reservoir Installation, San Juan-Chama Project Water, and Reservoir Operations on Streamflow and Water Quality 39 

EXPLANATION 

Del Norte	 STREAMFLOW AND STREAMFLOW OR CONCENTRATION 

WATER-QUALITY DISTRIBUTION 

SITE NAME (table 1) La Puente to Above Abiquiu No change 

Streamflow 

Decrease NA Not available 

Specific conductance 

pH	 NA 

Suspended sediment 

Increase 

Streamflow 

Specific conductance 

pH (La Puente to Chamita) 

Above Abiquiu to Chamita 

Suspended sediment 

Streamflow (Albuquerque

 to Bernardo) 

Specific conductance 

Rio 

Jose 

Chama 

Rio 

Rio Grande 

San 

Taos 

Conejos 

River 

San Juan Mountains 

Del 

Norte 

Sang

re 

de 

Cr

isto 

M

ountains 

Sangre de Cristo Mountains 

Chama Basin 

Jemez Mountains

Sierra Nacimiento 

Jemez Reservoir 

San Juan Mountains 

R

ivide 

R

River R

e

S n

e

iv

a

ta Fe 

Santa Fe 

San Luis Valley 

Rio Salado 

Bernardo 

io Gr

G

ande 

orge Red River 

Trinchera 

Creek 

Frank

a

E

Lake Dam 

lin

ddy 

C

nal 

Continental 

D

Base from U.S. Geological Survey digital data, 1:100,000, 1983 

Chamita 

COLORADO 

NEW MEXICO 

Abiquiu 

Reservoir 

Cochiti 

Pueblo 

Rio Pueblo 

de Taos 

Embudo 

io 

Creek 

Heron 

Rio Grande 

Reservoir 

El 

Vado 

Reservoir 

Willow Creek 

Heron 

35 ̊ 

36 ̊ 

37 ̊ 

108 ̊ 

107 ̊ 

Southside Water BOUNDARY 

38 ̊ 

106 ̊ 

Albuquerque STUDY 

AREA 

Puerco 

Isleta 

Isleta 

Diversion

Dam 

Belen 

Dixon Pilar 

Bernalillo 

Los Lunas 

Reclamation Plant 

J z

r 

anzano 

em

Angostura 

Diversion 

Dam 

Albuquerque 

Galisteo Reservoir 

Sunshine 

Valley 

M

M

ountains 

Sandia 

Mountains 

Del Norte 

Taos 

Otowi 

San Felipe 

Jemez River 

Cochiti Lake 

Cochiti 

Dam 

Chamita 

Above Abiquiu 

La Puente 

Below Abiquiu 

Bernardo 

Isleta 

Embudo 

Chama 

Espanola ~ 

pH 

0 20 40 60 80 MILES 

Suspended sediment 

0 20 40 60 80 KILOMETERS 

Taos to Otowi

Streamflow 

Specific conductance 

pH 

Suspended sediment 

 Otowi to San Felipe 

Streamflow 

Specific conductance 

pH 

Suspended sediment 

San Felipe to Albuquerque 

Streamflow 

Specific conductance 

pH 

Suspended sediment 

Albuquerque to Isleta 

Streamflow NA 

Specific conductance 

pH 

Suspended sediment 

Isleta to Bernardo 

Figure 24. Post-December 1973 spatial variations in streamflow, specific-conductance,

 pH, and suspended-sediment distributions in the Rio Grande study area. 
40 Effects of Reservoir Installation, San Juan-Chama Project Water, and Reservoir Operations 

Rio Chama and Rio Grande streamflow indicated some 

correlation with water quality during certain seasons (figs. 11, 

13, 15, 18, 20, and 22). Because of the variability and type of 

seasonal influences—snowmelt runoff, reservoir releases, monsoon precipitation, and irrigation diversions and return 

flows—streamflow and the water-quality constituents of specific conductance, pH, and suspended-sediment concentration 

in the Rio Chama and the Rio Grande did not demonstrate a 

strong annual correlation (table 21), although the small p-values 

associated with the correlation coefficients indicate that relations do exist between streamflow and water quality. Correlations might exist for specific seasonal periods; however, these 

periods of strong correlation likely vary by site and constituent. 

Summary 

Streamflow and water quality in northern and central New 

Mexico are extremely important because of limited surfacewater resources and a growing population. Construction and 

operation of reservoirs on the Rio Chama and Rio Grande and 

the importation of Colorado River Basin water by the SJC 

Project can affect current (2004) and future uses of Rio Chama, 

Rio Grande, and SJC Project water. Prior to this study, the effect 

of the coordinated operation of Heron, El Vado, Abiquiu, and 

Cochiti Dams and the implementation of the SJC Project on 

streamflow and water quality in the Rio Chama and Rio Grande 

had not been fully documented. Evaluation of streamflow and 

water-quality data prior to and after the coordination of the 

dams and the implementation of SJC Project water indicated 

that streamflow patterns and water quality of the Rio Chama 

and the Rio Grande had been altered. 

The combined effect of reservoir installation and operation 

and diversion of Colorado River Basin water into the Rio 

Grande Basin by the SJC Project was a decrease in extreme 

streamflows, an increase in median streamflows, and a decrease 

in periods of historically small streamflows. Inflow of SJC 

Project water increased annual streamflow volumes in the Rio 

Chama and Rio Grande, and reservoir storage increased median 

streamflows by retaining large flows and modifying reservoir 

releases to conform to channel capacities for flood protection. 

The SJC Project and Heron, El Vado, Abiquiu, and Cochiti 

Dams decreased streamflow variability and increased median 

streamflows in the study area. These changes to streamflow 

resulted in an overall decrease in specific conductance and suspended-sediment concentration and an increase in pH in the Rio 

Chama and the Rio Grande. 

Following construction of Heron and Cochiti Dams and 

operational integration of the reservoirs on the Rio Chama and 

the Rio Grande, water quality was influenced by the inflow of 

Colorado River Basin water by the SJC Project, retention of 

snowmelt runoff, and to a lesser degree, by reservoir storage. 

The non-native water of the SJC Project was different from 

native Rio Chama and Rio Grande water. Retention of snowmelt runoff in the reservoirs influenced overall water quality in 

the Rio Chama and Rio Grande by distributing the normal dilution effect of snowmelt from the snowmelt runoff period to 

year-round. This dilution effect decreased downstream with 

influences such as the MRGCD and the City of Albuquerque’s 

Southside Water Reclamation Plant. Most changes in water 

quality attributable to the reservoirs were not evident in the Rio 

Grande at the Bernardo site. 

The non-native water of the SJC Project and retained 

snowmelt provided a variable influence on water quality 

throughout the seasons because of managed releases from 

Heron Lake, El Vado Reservoir, Abiquiu Reservoir, and 

Cochiti Lake that fluctuated according to downstream user 

needs and reservoir inflows. The influence of SJC Project water 

and retained snowmelt on specific conductance, pH, and suspended-sediment concentration diminished with downstream 

flow as the Rio Grande was subjected to various natural and 

anthropogenic inflows. Cochiti Lake storage contributed to a 

small but identifiable influence on water quality because of 

hypoxic conditions in the reservoir during summer months. 

Because of the variability and type of seasonal influences, 

streamflow did not strongly correlate annually with water quality in the Rio Chama or the Rio Grande. 

Table 21. Streamflow and water-quality correlation in the Rio Chama and Rio Grande during the post-December 1973 period. 

[<, less than] 

Streamflow 

correlation Above 

(Kendall’s tau) Abiquiu Chamita Otowi San Felipe Albuquerque Isleta Bernardo 

Specific conduc­ -0.53 -0.57 -0.45 -0.49 -0.33 -0.58 -0.54 

tance 0.000 0.000 0.000 0.000 0.000 0.000 0.000 

p-value 

pH NA -0.14 -0.11 -0.06 -0.27 0.04 -0.14 

p-value 0.025 0.004 0.243 0.000 0.306 0.004 

Suspended sedi­ 0.26 0.14 0.19 0.23 0.22 0.32 0.15 

ment 0.000 0.004 0.000 0.000 0.000 0.000 0.000 

p-value 
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References 41 

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Supplemental Information 43


Supplemental Information


LOESS Fit Lines and Study Period Data

TOTAL SUSPENDED-SEDIMENT SPECIFIC CONDUCTANCE, IN

CONCENTRATION, MICROSIEMENS PER CENTIMETER

IN MILLIGRAMS PER LITER pH, IN STANDARD UNITS AT 25 DEGREES CELSIUS

800 La Puente Chamita 

580 

360 

140 

-80 

8.8 La Puente Chamita 

8.4 

8.0 

7.6 

7.2 

6.8 

6.4 

6.0 

900 La Puente Above Abiquiu Reservoir 

750 

600 

450 

300 

150 

0 

JAN


FEB


MAR


APR


TOTAL SUSPENDED-SEDIMENT MAY

CONCENTRATION,

IN MILLIGRAMS PER LITER JUNE

900 

750 

600 

450 

300 

150 

0 JULY

JAN AUG

44 Effects of Reservoir Installation, San Juan-Chama Project Water, and Reservoir Operations 

Figure S-1. LOESS fit lines and post-December 1973 data for specific conductance, pH, and total

 suspended sediment for composite annual year for Rio Chama sites of La Puente,

 Above Abiquiu, and Chamita. 

Chamita FEB SEPT MAR OCT

APR


MAY


JUNE


JULY


AUG


SEPT

OCT

NOV

DEC 

NOV


DEC


JAN


FEB


MAR


APR


MAY


JUNE


JULY


AUG


SEPT

OCT

NOV

DEC 
700

LOESS Fit Lines and Study Period Data 45 

Taos Otowi 

SPECIFIC CONDUCTANCE, IN MICROSIEMENS PER CENTIMETER AT 25 DEGREES CELSIUS

550


400


250


100


San Felipe Albuquerque 

700


550


400


250


100


Isleta Bernardo 

700


550


400


250


100


JAN


FEB


MAR


APR


MAY


JUNE

JULY

AUG

SEPT

OCT

NOV

DEC

JAN


FEB


MAR


APR


MAY


JUNE

JULY

AUG

SEPT

OCT

NOV

DEC 

Figure S-2. LOESS fit lines and post-December 1973 data for specific conductance for composite

 annual year for Rio Grande sites of Taos, Otowi, San Felipe, Albuquerque, Isleta,

 and Bernardo. 
46 Effects of Reservoir Installation, San Juan-Chama Project Water, and Reservoir Operations 

9.8 Taos Otowi 

9.1 

8.4 

7.7 

7.0 

9.8 San Felipe Albuquerque 

pH, IN STANDARD UNITS 9.1 

8.4 

7.7 

7.0 

9.8 

9.1 

8.4 

7.7 

7.0 

Isleta Bernardo 

JAN


FEB


MAR


APR


MAY


JUNE

JULY

AUG

SEPT

OCT

NOV

DEC

JAN


FEB


MAR


APR


MAY


JUNE

JULY

AUG

SEPT

OCT

NOV

DEC 

Figure S-3. LOESS fit lines and post-December 1973 data for pH for composite annual year for Rio

 Grande sites of Taos, Otowi, San Felipe, Albuquerque, Isleta, and Bernardo. 
LOESS Fit Lines and Study Period Data 47 

105


Taos Otowi 

104


TOTAL SUSPENDED-SEDIMENT CONCENTRATION (LOG SCALE), IN MILLIGRAMS PER LITER 103


102


101


105


San Felipe Albuquerque 

104


103


102


101


105


Isleta Bernardo 

104


103


102


101


JAN


FEB


MAR


APR


MAY


JUNE

JULY

AUG

SEPT

OCT

NOV

DEC

JAN


FEB


MAR


APR


MAY


JUNE

JULY

AUG

SEPT

OCT

NOV

DEC 

Figure S-4. LOESS fit lines and post-December 1973 data for total suspended sediment for composite

 annual year for Rio Grande sites of Taos, Otowi, San Felipe, Albuquerque, Isleta, and

 Bernardo.