Prepared in cooperation with the Southern Ute Tribe and the Bureau of Reclamation

Water-Quality Data Collected from Vallecito Reservoir, 

Its Inflows and Outflow, Southwestern Colorado, 1999–2002

Data Series 305

U.S. Department of the Interior

U.S. Geological Survey
Water-Quality Data Collected from 

Vallecito Reservoir, Its Inflows and 

Outflow, Southwestern Colorado, 

1999–2002

By Anthony J. Ranalli

Prepared in cooperation with the Southern Ute Tribe and the

Bureau of Reclamation

Data Series 305

U.S. Department of the Interior

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

DIRK KEMPTHORNE, Secretary

U.S. Geological Survey

Mark D. Myers, Director

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

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Suggested citation:

Ranalli, Anthony J., 2008, Water-quality data collected from Vallecito Reservoir, its inflows and outflow, southwestern 

Colorado, 1992–2002: U.S. Geological Survey Data Series 305, 76 p.
iii

Contents

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

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

Purpose and Scope .......................................................................................................................................1

Sampling Locations, Dates of Collection, and Project Responsibilities ...............................................2

Methods of Data Collection .......................................................................................................................30

Stream Samples and Field Properties.............................................................................................30

Reservoir Samples and Field Properties.........................................................................................30

Sample Processing and Shipment............................................................................................................31

Laboratory Analysis.....................................................................................................................................32

Field Blank and Field Replicate Data Collection and Interpretation ...................................................32

Analysis of Field Blanks.....................................................................................................................56

Analysis of Field Replicates ..............................................................................................................58

Analysis of pH and Specific Conductance Standard Reference Samples by the Hydrolab ...........59

Summary........................................................................................................................................................61

Acknowlegments .........................................................................................................................................62

References Cited..........................................................................................................................................63

Appendix........................................................................................................................................................65

Figures

1. Map showing water-quality sample-collection locations, 1999–2002.................................3

2. Comparison of Hydrolab measurements of the low ionic strength standard to 

the accepted value of the standard.........................................................................................60

3. Difference between the value of the specific conductance standard and the 

Hydrolab reading of the specific conductance standard....................................................61

Tables

1. Water-quality sample-collection locations, 1999–2002..........................................................4

2. Water-quality data collected from the inflows and outflow of Vallecito Reservoir...........5

3. Total metals data collected from Vallecito Reservoir in 1999..............................................22

4. Water-quality data collected from Vallecito Reservoir South, 2000–2002 ........................24

5. Fecal coliform and E. coli data collected from sites in and near Vallecito Reservoir,

2000–2002 .....................................................................................................................................30

6. Data needed for the calculation of the Carlson Trophic State Index in Vallecito 

Reservoir, 2000–2002 ..................................................................................................................31

7. Constituents and properties measured in the water-quality monitoring of Vallecito

Reservoir, its inflows and outflow, 1999–2002........................................................................33

8. Field blanks collected from stream and reservoir sampling sites, 1999–2002..................36
iv

9. Field replicates collected from stream and reservoir sampling sites, 1999–2002 ...........41

10. Upper confidence limits for contamination by nutrients and metals in specified

percentiles of all samples based on data for field blanks ...................................................56

11. Ninety-five percent confidence intervals about a single sample.......................................59

12. Differences in the measurement of pH and specific-conductance standards by 

the Hydrolab ................................................................................................................................60

Appendix Table

Field property data measured in Vallecito Reservoir, 2000–2002 ................................................65

Conversion Factors and Abbreviations

Inch/Pound to SI

Multiply By To obtain

Length

inch 2.54 centimeter (cm)

inch 25.4 millimeter (mm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Volume

gallon (gal) 3.785 liter (L) 

gallon (gal) 0.003785 cubic meter (m3) 

cubic inch (in3) 0.01639 liter (L)

Flow rate

foot per second (ft/s) 0.3048 meter per second (m/s)

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

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

°F=(1.8×°C)+32

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

°C=(°F–32)/1.8

Vertical coordinate information is referenced to the North American Vertical Datum of 1988 

(NAVD 88).

Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD 83).

Abbreviations

mg/L, milligrams per liter

μg/L, micrograms per liter

mL, milliliters
Abstract

The Pine River Watershed Stakeholders Group was 

created in December 1997 to allow local participation in 

addressing water-quality issues in Los Piños River watershed, 

including Vallecito Reservoir in southwestern Colorado. One 

water-quality issue identified by the stakeholder group is to 

increase the understanding of the current water quality of 

Vallecito Reservoir, its two major inflows, and its outflow. The 

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

from the Pine River Watershed Stakeholders Group and the 

U.S. Environmental Protection Agency (USEPA), U.S. Bureau 

of Reclamation (BOR), Colorado Department of Public Health 

and Environment (CDPHE), Pine River Irrigation District, 

Southern Ute Tribe, San Juan Basin Health Department, and 

San Juan Resource Conservation and Development, collected water-quality samples from Vallecito Reservoir, its 

two major inflows, and its outflow between August 1999 and 

November 2002 at about monthly intervals from April through 

November. The water-quality samples were analyzed for total 

and dissolved metals (aluminum, arsenic, cadmium, copper, 

chromium, iron, lead, manganese, mercury, nickel, silver, and 

zinc), dissolved major ions (calcium, magnesium, sodium, 

potassium, chloride, bicarbonate, and sulfate), dissolved silica, 

dissolved organic carbon (DOC), ultraviolet (UV) absorbance at 

254 and 280 nanometers, nutrients (total organic nitrogen, dissolved organic nitrogen, dissolved ammonia, dissolved nitrate, 

total phosphorus, dissolved phosphorus, and orthophosphate), 

chlorophyll-a (reservoir only), and suspended sediment (inlets 

to the reservoir only). Measurements of field properties (pH, 

specific conductance, water temperature, and dissolved oxygen) 

were also made at each sampling site each time a water-quality 

sample was collected.

This report documents (1) sampling sites and times of 

sample collection, (2) sample-collection methods, (3) laboratory analytical methods, and (4) responsibilities of each 

agency/group involved in the project. The report also provides 

the environmental and quality-control data collected during 

the project and provides an interpretation of the quality-control 

data (field blanks and field duplicates) to assess the quality of 

the environmental data. This report provides a baseline data set 

against which future changes in water quality can be assessed.

Introduction

The water quality of the Vallecito Reservoir watershed in southwestern Colorado was initially studied by the 

U.S. Geological Survey (USGS) during July 1996 to July 1997, 

in cooperation with the Pine River Irrigation District, to assess 

the suitability of the reservoir as a potential source of drinking 

water (Ranalli and Evans, 1999). As a result of this study, in 

December 1997 a group of residents in and around Bayfield, 

Colo., created the Pine River Watershed Stakeholders Group. 

The stakeholders group was created to facilitate local participation in addressing water-quality issues in Los Piños River 

watershed, which includes Vallecito Reservoir.

An important issue of concern to the stakeholders is the 

potential effect that population growth and development within 

the Vallecito Reservoir watershed might have on the water quality of Vallecito Reservoir, its two major inflows (Vallecito Creek 

and Los Piños River), and Los Piños River downstream from the 

reservoir (hereinafter referred to as the study area). To address 

this issue, the stakeholders envisioned a long-term water-quality 

monitoring project of the study area and initiated water-quality 

sampling in August 1999. The overall objectives of water-quality 

monitoring are to (1) characterize the current water quality of 

the study area and (2) periodically monitor the water quality of 

the study area over time to document trends in water quality and 

the causes for the trends if they occur. The water-quality monitoring conducted in 1999–2002 was done in cooperation with 

the USGS, U.S. Environmental Protection Agency (USEPA), 

U.S. Bureau of Reclamation (BOR), Colorado Department of 

Public Health and Environment (CDPHE), Pine River Irrigation 

District, Southern Ute Tribe, San Juan Basin Health Department, 

San Juan Resource Conservation and Development, and volunteers from the Pine River Watershed Stakeholders Group.

Purpose and Scope

The purpose of this report is to document the (1) sampling 

locations and times of sample collection, (2) sample-collection 

methods, (3) laboratory analytical methods, and (4) responsibilities of each agency/group involved in the project. The report 

also provides the environmental and quality-control data collected during the project and provides an interpretation of the 

Water-Quality Data Collected from Vallecito Reservoir, 

Its Inflows and Outflow, Southwestern Colorado, 

1999–2002

By Anthony J. Ranalli
2 Water-Quality Data Collected from Vallecito Reservoir, Its Inflows and Outflow, Southwestern Colorado, 1999–2002 

quality-control data (field blanks and field duplicates) needed 

to assess the quality of the environmental data. Thus, the 

information provided in the report facilitates assessment of the 

quality of the environmental data collected during 1999–2002 

and allows the water-quality data collected during 1999–2002 

to serve as a baseline data set against which future changes in 

water quality can be assessed.

Sampling Locations, Dates of Collection, 

and Project Responsibilities

The objectives of the water-quality characterization 

of the study area were achieved by analyzing water-quality 

samples collected approximately monthly from April through 

November (1999–2002) at various reservoir stages and 

streamflows from Vallecito Reservoir, its two major inlets, and 

its outlet (fig. 1 and table 1) for a variety of water-quality constituents and field properties. The water-quality constituents 

measured at each site are described in the Laboratory Analysis 

section. The USGS, USEPA, CDPHE, and the volunteers 

participated in the collection and analysis of the water-quality 

samples. The participation of each agency involved in datacollection activities and the volunteers from 1999 to 2002 is 

described below. The timing of any activity that did not occur 

continuously from 1999 to 2002 is noted.

The USGS:

1. Provided the volunteers with the equipment and training needed to collect and process nutrient, dissolved 

organic carbon (DOC), UV absorbance, and chlorophyll-a

samples and to measure depth profiles of pH, specific 

conductance, water temperature, and dissolved oxygen 

in Vallecito Reservoir. The USGS also provided the 

volunteers with sample bottles, filter pump, and 0.45-μm 

capsule filters.

2. Collected and processed water-quality samples 

from Vallecito Creek near Bayfield, Colo., and analyzed the samples for major ions, metals, nutrients, 

DOC, and suspended sediment as part of the USGS 

Hydrologic Benchmark Network program (Cobb and 

Biesecker, 1971).

3. Collected and processed water-quality samples from 

Los Piños River above Vallecito Reservoir near Bayfield, 

Colo. (2000–2002) and analyzed the samples for nutrients, DOC, UV absorbance, and suspended sediment.

4. Supervised the collection of water-quality samples 

from Vallecito Reservoir by the volunteers and analyzed 

the samples for nutrients, DOC, UV absorbance, and 

chlorophyll-a.

5. Supervised the collection of water-quality samples from 

Los Piños River below Vallecito Reservoir near Bayfield, 

Colo., by the volunteers and analyzed the samples for 

nutrients, DOC, and UV absorbance.

6. Shipped the nutrient, DOC, UV absorbance, and 

chlorophyll-a samples collected from all sampling sites to 

the USGS National Water-Quality Laboratory (NWQL) in 

Lakewood, Colo., for analysis in thermally insulated coolers that contained sufficient ice to keep samples at less 

than 4 degrees Celsius for the duration of the trip.

7. Provided blank water for the field blanks. Inorganic blank 

water was used for the major ion, metal, and nutrient field 

blanks. Pesticide-grade volatile organic carbon (VOC) 

free water was used for the DOC and UV absorbance 

blanks. Both types of water were obtained from the USGS 

water-quality service unit in Ocala, Fla.

The USEPA:

1. Trained the volunteers on how to use the bottles and preservatives for the collection of total and dissolved metal 

samples and on how to fill out the required USEPA chainof-custody forms.

2. Provided the volunteers with the sample bottles for the 

collection of total and dissolved metal samples that were 

shipped to and analyzed by the USEPA laboratory in 

Golden, Colo.

3. Analyzed water-quality samples collected from Los Piños 

River above Vallecito Reservoir near Bayfield, Colo., Los 

Piños River below Vallecito Reservoir near Bayfield, Colo., 

and Vallecito Reservoir for total and dissolved metals.

The CDPHE:

1. Collected and processed water-quality samples from 

Vallecito Creek near mouth and Los Piños River above 

Vallecito Reservoir (just upstream from where both 

streams empty into Vallecito Reservoir) and analyzed 

these samples for major ions, metals, nutrients, and fecal 

coliform and E. coli bacteria at the CDPHE laboratory in 

Denver, Colo.

2. Analyzed water-quality samples collected from Vallecito 

Reservoir for fecal coliform and E. coli bacteria at the 

San Juan Basin Health Department in Durango, Colo.

The CDPHE collected water-quality samples at the 

mouths of Vallecito Creek and Los Piños River where most 

of the development in the watershed has occurred (fig. 1). 

The USGS and CDPHE sampling sites on Vallecito Creek 

and Los Piños River bracket this development, and collecting samples upstream and downstream from potential sources 

of contamination associated with development could provide 

evidence of any adverse effects development might have on 

water quality.

The Volunteers:

1. Collected and processed water-quality samples from 

Vallecito Reservoir and Los Piños River below Vallecito 

Reservoir near Bayfield, Colo., according to USGS and 

USEPA protocols. In 1999, the volunteers collected waterquality samples for total metals only from the Vallecito 

Reservoir North, Vallecito Reservoir Center, and Vallecito 

Reservoir South sampling sites.
Sampling Locations, Dates of Collection, and Project Responsibilities 3

Figure 1. Water-quality sample-collection locations, 1999–2000.

2. Measured depth profiles of pH, specific conductance, 

water temperature, and dissolved oxygen at the Vallecito 

reservoir North, Center, and South sampling sites with a 

multiconstituent water-quality probe (Hydrolab) approximately biweekly from May to October.

3. Delivered the samples for metal, nutrient, DOC, UV 

absorbance, and chlorophyll-a analysis to USGS personnel for transport to and analysis by the USGS National 

Water Quality Laboratory in Denver, Colo.

4. Collected and processed water-quality samples for analysis 

of fecal coliform and E. coli bacteria from the Vallecito 

Reservoir South sampling site, Vallecito Reservoir just 

downstream from the mouth of Vallecito Creek, and 

Vallecito Reservoir just downstream from the mouth of 

Los Piños River and delivered these samples to the San Juan 

Basin Health Department in Durango, Colo., for analysis.

The BOR:

1. Provided funding for the collection of water-quality samples following the Missionary Ridge wildfire in June 2002. 

These samples were collected in July, August, September, 

and October 2002.

The water-quality data that were collected during this 

study are available in this report (tables 2–4) and in the USGS 

and USEPA databases. All data analyzed by the USGS and 

USEPA are available at waterdata.usgs.gov/nwis/, and all 

data collected and analyzed by the CDPHE is in the USEPA 

STORET database at www.epa.gov/storet. These data can be 

downloaded from these databases by using the site IDs listed 

in table 1. The fecal coliform and E. coli bacteria data are 

given in table 5. Values of pH, specific conductance, water 

temperature, and dissolved oxygen measured in Vallecito 

Reservoir are given in the Appendix.

C O L O R A D O

LOCATION OF STUDY AREA

LA PLATA CO.

Denver

Grand

Junction

SAN JUAN NATIONAL FOREST

107°37'30"

36°26'15"

36°22'30"

107°30'

0

0 1 2 3 KILOMETERS

1 2 MILES

EXPLANATION

USGS water-quality 

 sampling site and name

CDPHE water-quality

 sampling site and name

Hydrolab measurement only

Los Piños River

above Vallecito

Reservoir RPS9380

Los Piños River 

above Vallecito 

Reservoir near 

Bayfield, CO 

9352800

Vallecito Creek near

mouth before entering

reservoir RPS9370

Los Pinos River below

Vallecito Reservoir near 

Bayfield, CO 372236107344400

Vallecito 

Reservoir

South

Vallecito 

Reservoir

Center

Vallecito 

Reservoir

North

Vallecito Creek near

Bayfield, CO 9352900

Vallecito

Reservoir

Los Piños River

Los Piños River

Vallecito Creek
Table 1. Water-quality sample-collection locations, 1999–2000. Site name Site type and sampling agency Site ID Latitude Longitude 

Vallecito Creek near Bayfield, CO Stream—USGS 9352900 37o28'39" 107o32'35" Located at the Vallecito Creek near mouth before entering reservoir Stream—CDPHE RPS9370 Located at bridLos Pinos River above Vallecito Reservoir near Bayfield, CO Stream—USGS 9352800 37o24'53" 107o30'46" Located at the 

Wilderness 

Los Pinos River above Vallecito Reservoir Stream—CDPHE RPS9380 Located at the 

Campgroun

Vallecito Reservoir North Reservoir—USGS/Volunteers 372433107324300 37o24'33" 107o32'43" Vallecito Reservoir Center Reservoir—USGS/Volunteers 372346107330200 37o23'46" 107o33'02" Vallecito Reservoir South Reservoir—USGS/Volunteers 372300107335700 37o23'00" 107o33'57" Los Pinos River below Vallecito Reservoir near Bayfield, CO Stream—Volunteers 372236107344400 37o22'36" 107o34'44" Located about 

from powerp
Sampling Locations, Dates of Collection, and Project Responsibilities 5

Table 2. Water-quality data collected from the inflows and outflow of Vallecito Reservoir, 1999–2000.

[ft3/s, cubic feet per second; μS/m, microsiemens per centimeter; C, Celsius; mg/L, milligrams per liter; μg/L, micrograms per liter; nm, nanometers; mL, milliliters; 

-, no data; <, less than; E, estimated]

Date Time 

Instantaneous

discharge

(ft3/s)

pH,

field

(standard

units)

Specific

conductance,

field

(μS/cm

25 degrees C)

Water

temperature

(degrees C)

Dissolved

oxygen

(mg/L)

pH,

laboratory

(standard

units)

Specific

conductance,

laboratory

(μS/cm

25 degrees C)

Calcium,

dissolved

(mg/L)

Magnesium,

dissolved

(mg/L)

Potassium,

dissolved

(mg/L)

Vallecito Creek near Bayfield, CO (9352900)

04/21/1999 1430 150 7 63 4 10.1 7.6 69 9.09 1.91 0.52

05/13/1999 1045 240 7.7 70 3.3 10 7.9 71 9.04 1.85 0.46

06/08/1999 1045 450 7.5 53 3.5 11.6 7.3 56 6.99 1.55 0.31

06/30/1999 1045 368 6.9 41 6.3 10.3 7.7 42 4.59 1.26 0.3

08/10/1999 1130 646 7.3 54 9.5 8.8 7.2 55 6.94 1.64 0.44

08/23/1999 1300 368 7.6 67 10 9 7.9 69 9.32 1.88 0.45

05/18/2000 1145 210 7.4 61 3.1 10.4 8 64 7.79 1.76 0.46

06/06/2000 1045 292 7.3 42 5.4 9.8 7.6 43 4.88 1.26 0.37

07/11/2000 1030 55 7.5 55 10.6 8.6 7.9 57 6.73 1.54 0.42

08/22/2000 1600 59 7.4 61 14.2 8.1 7.9 65 7.69 1.71 0.5

04/12/2001 1030 50 7.6 71 0.8 10.8 7.6 78 9.92 2.03 0.62

05/17/2001 1530 764 7.2 55 5.5 9.8 7 56 6.97 1.51 0.43

06/14/2001 1100 314 7 49 2.9 10.9 7.3 50 6.21 1.48 0.36

07/17/2001 1200 144 6.1 46 8.9 9.4 7 46 5.26 1.42 0.36

08/16/2001 1030 225 7.4 59 7.8 9.7 7.5 61 7.64 1.71 0.42

09/18/2001 945 52 7.1 71 7.4 9.3 7.6 69 8.65 1.98 0.51

10/17/2001 1445 24 7.5 87 5.1 10.3 7.8 81 10.3 2.28 0.57

05/22/2002 1100 107 7.8 54 2.5 10.7 - - 5.66 1.69 0.43

07/30/2002 1000 27 7.6 74 12 8.5 - - 8.77 2.01 0.6

08/29/2003 830 19 7.5 70 11 8.4 - - 9.04 1.98 0.6

09/19/2002 915 75 7.5 63 5 10.7 - - 7.47 1.89 0.5

10/30/2002 1500 - - - - - 8.0 67 7.63 1.82 0.47

Date Time 

Sodium,

dissolved

(mg/L)

Alkalinity,

mg/L as

CaCO3

laboratory

Alkalinity,

mg/L as

CaCO3

field

Chloride,

dissolved

(mg/L)

Sulfate,

dissolved

(mg/L)

Silica,

dissolved

(mg/L)

Ammonia 

+ org-N,

dissolved

(mg/L 

as N)

Ammonia 

+ org-N,

total

(mg/L 

as N)

Ammonia,

dissolved

(mg/L 

as N)

Nitrite 

+ nitrate,

dissolved

(mg/L 

as N)

Nitrite

dissolved,

(mg/L 

as N)

Vallecito Creek near Bayfield, CO (9352900)

04/21/1999 1430 0.78 - 28 0.21 4.1 3.81 E0.07 0.1 0.003 0.088 <0.001

05/13/1999 1045 0.7 - 27 0.26 4.9 3.61 E0.06 0.12 0.002 0.087 <0.001

06/08/1999 1045 0.48 - 17 0.33 5.7 2.73 E0.07 <0.1 0.003 0.119 0.001

06/30/1999 1045 0.43 12 11 0.11 6.5 2.17 <0.1 E0.07 0.003 0.093 0.001

08/10/1999 1130 0.59 - 18 0.11 6.3 3 E0.1 0.17 0.007 0.063 0.001

08/23/1999 1300 0.64 - 24 0.13 6 3.66 <0.1 0.15 <0.002 0.048 <0.001

05/18/2000 1145 0.6 20 21 E0.22 5.8 3.11 E0.07 <0.1 <0.002 0.121 <0.001

06/06/2000 1045 0.42 11 12 <0.29 6 2.33 <0.1 0.1 0.005 0.125 <0.001

07/11/2000 1030 0.7 18 21 E0.14 6.5 3.17 <0.1 E0.07 0.003 0.079 <0.001

08/22/2000 1600 0.73 20 19 E0.14 8 3.19 <0.1 <0.1 <0.002 0.141 <0.001

04/12/2001 1030 1.05 - 23 0.32 7.98 4.08 <0.1 E0.06 0.005 0.132 -

05/17/2001 1530 0.5 - 18 0.2 6.3 3.1 E0.06 0.1 0.005 0.115 -

06/14/2001 1100 0.49 - 15 0.16 6.1 2.89 <0.1 E0.05 <0.002 0.1 -

07/17/2001 1200 0.52 - 14 0.11 8.63 2.62 <0.1 E0.04 0.003 0.073 -

08/16/2001 1030 0.58 - 20 0.12 7.29 3.16 E0.07 E0.05 <0.002 0.079 -

09/18/2001 945 0.81 - 23 0.21 9.58 3.62 <0.1 <0.08 <0.002 0.078 -

10/17/2001 1445 1.01 - 28 0.3 10.1 3.92 <0.1 <0.1 <0.015 0.115 -

05/22/2002 1100 0.65 - 12 0.19 10.3 3.02 <0.1 <0.1 <0.015 0.152 -

07/30/2002 1000 0.97 - 22 0.25 10.7 3.69 E0.06 <0.1 <0.015 0.143 <0.002

08/29/2003 830 1.08 24 25 0.44 9.8 3.7 <0.1 E0.06 <0.015 0.145 <0.002

09/19/2002 915 0.84 19 - E0.28 10.3 3.6 <0.1 <0.1 <0.015 0.191 <0.002

10/30/2002 1500 0.9 - - E0.14 8.8 3.7 <0.1 E0.06 <0.015 0.168 <0.002
6 Water-Quality Data Collected from Vallecito Reservoir, Its Inflows and Outflow, Southwestern Colorado, 1999–2002 

Table 2. Water-quality data collected from the inflows and outflow of Vallecito Reservoir, 1999–2000.—Continued

[ft3/s, cubic feet per second; μS/m, microsiemens per centimeter; C, Celsius; mg/L, milligrams per liter; μg/L, micrograms per liter; nm, nanometers; mL, milliliters; 

-, no data; <, less than; E, estimated]

Date Time 

Orthophosphate,

dissolved

(mg/L as P)

Phosphorus,

dissolved

(mg/L)

Phosphorus,

total

(mg/L )

Organic

carbon,

dissolved

(mg/L)

Organic

carbon,

total

(mg/L)

Ultraviolet

absorbance

at 254 nm

Ultraviolet

absorbance

at 280 nm

Aluminum,

dissolved

(μg/L)

Aluminum,

total

(μg/L)

Antimony,

dissolved

(μg/L)

Antimony,

total

(μg/L)

Vallecito Creek near Bayfield, CO (9352900)

04/21/1999 1430 0.001 <0.004 0.008 1.9 - - - 34 - <1 -

05/13/1999 1045 <0.001 <0.004 0.007 2.3 - - - 45 - <1 -

06/08/1999 1045 <0.001 0.004 0.005 1.4 - - - 46 - <1 -

06/30/1999 1045 0.001 <0.004 0.004 0.6 - 0.014 - 36 - <1 -

08/10/1999 1130 0.001 <0.004 0.026 1.4 - 0.05 - 64 - <1 -

08/23/1999 1300 <0.001 <0.004 <0.004 1.5 - 0.053 - 71 - <1 -

05/18/2000 1145 <0.001 <0.006 <0.008 1.7 - 0.043 0.027 55 - <1 -

06/06/2000 1045 <0.001 <0.006 <0.008 0.8 - 0.017 0.011 <44 - <1 -

07/11/2000 1030 0.001 <0.006 <0.008 0.5 - 0.013 0.01 34 - <1 -

08/22/2000 1600 <0.001 <0.006 <0.008 0.6 - 0.011 0.009 30 - <1 -

04/12/2001 1030 <0.007 <0.006 E0.002 1.2 - 0.031 0.022 - - - -

05/17/2001 1530 <0.007 <0.006 0.011 2 - 0.072 0.054 80 - - -

06/14/2001 1100 <0.007 <0.006 0.004 0.9 - 0.027 0.002 40 - - -

07/17/2001 1200 <0.007 <0.006 E0.002 0.7 - 0.01 0.007 60 - - -

08/16/2001 1030 <0.007 <0.006 E0.004 1.9 - 0.03 0.017 50 - - -

09/18/2001 945 <0.007 <0.006 <0.004 0.6 - 0.014 0.01 30 - - -

10/17/2001 1445 <0.007 <0.004 E0.003 0.6 - 0.009 0.004 - - - -

05/22/2002 1100 <0.007 <0.004 0.004 0.8 - 0.016 0.011 30 - - -

07/30/2002 1000 <0.007 <0.004 <0.004 0.5 - 0.011 0.008 - - - -

08/29/2003 830 <0.007 <0.004 <0.004 0.9 E0.4 0.01 0.008 18 21 - -

09/19/2002 915 <0.007 <0.004 <0.004 0.8 0.8 0.011 0.008 32 128 - -

10/30/2002 1500 <0.007 <0.004 <0.004 0.6 0.64 0.015 0.011 27 83 - -

Date Time 

Arsenic,

dissolved

(μg/L)

Arsenic,

total

(μg/L)

Barium,

dissolved

(μg/L)

Barium,

total

(μg/L)

Beryllium,

dissolved

(μg/L)

Beryllium,

total

(μg/L)

Cadmium,

dissolved

(μg/L)

Cadmium,

total

(μg/L)

Chromium,

dissolved

(μg/L)

Chromium,

total

(μg/L)

Copper,

dissolved

(μg/L)

Vallecito Creek near Bayfield, CO (9352900)

04/21/1999 1430 <1 - 13 - <1 - <1 - <1 - <1

05/13/1999 1045 <1 - 13 - <1 - <1 - <1 - <1

06/08/1999 1045 <1 - 10 - <1 - <1 - - - <1

06/30/1999 1045 <1 - 9 - <1 - <1 - <1 - <1

08/10/1999 1130 <1 - 12 - <1 - <1 - <1 - <1

08/23/1999 1300 <1 - 13 - <1 - <1 - <1 - <1

05/18/2000 1145 <2 - 11 - <1 - <1 - <0.8 - <1

06/06/2000 1045 <2 - 8 - <1 - <1 - <0.8 - <1

07/11/2000 1030 <2 - 11 - <1 - <1 - <0.8 - <1

08/22/2000 1600 <2 - 13 - <1 - <1 - <0.8 - <1

04/12/2001 1030 - - - - - - - - - - -

05/17/2001 1530 - - - - - - - - - - -

06/14/2001 1100 - - - - - - - - - - -

07/17/2001 1200 - - - - - - - - - - -

08/16/2001 1030 - - - - - - - - - - -

09/18/2001 945 - - - - - - - - - - -

10/17/2001 1445 - - - - - - - - - - -

05/22/2002 1100 - - - - - - - - - - -

07/30/2002 1000 - - - - - - - - - - -

08/29/2003 830 E0.2 <2 - - - - <0.04 <0.04 - - 0.4

09/19/2002 915 E0.1 <2 - - - - <0.04 E0.02 - - 0.5

10/30/2002 1500 <0.3 <2 - - - - <0.04 <0.04 - - 0.4
Sampling Locations, Dates of Collection, and Project Responsibilities 7

Table 2. Water-quality data collected from the inflows and outflow of Vallecito Reservoir, 1999–2000.—Continued

[ft3/s, cubic feet per second; μS/m, microsiemens per centimeter; C, Celsius; mg/L, milligrams per liter; μg/L, micrograms per liter; nm, nanometers; mL, milliliters; 

-, no data; <, less than; E, estimated]

Date Time 

Copper,

total

(μg/L)

Iron,

dissolved

(μg/L)

Iron,

total

(μg/L)

Lead,

dissolved

(μg/L)

Lead,

total

(μg/L)

Manganese,

dissolved

(μg/L)

Manganese,

total

(μg/L)

Mercury,

dissolved

(μg/L)

Mercury,

total

(μg/L)

Molybdenum,

dissolved

(μg/L)

Molybdenum,

total

(μg/L)

Vallecito Creek near Bayfield, CO (9352900)

04/21/1999 1430 - 11 - <1 - 3.4 - - - <1 -

05/13/1999 1045 - 11 - <1 - 8.1 - - - <1 -

06/08/1999 1045 - 13 - <1 - 20 - - - <1 -

06/30/1999 1045 - <10 - <1 - 22.2 - - - <1 -

08/10/1999 1130 - E6 - <1 - 18.6 - - - <1 -

08/23/1999 1300 - <10 - <1 - 12 - - - <1 -

05/18/2000 1145 - E10 - <1 - 24.1 - - - <1 -

06/06/2000 1045 - <10 - <1 - 24.6 - - - <1 -

07/11/2000 1030 - <10 - <1 - 3.8 - - - <1 -

08/22/2000 1600 - <10 - <1 - 6.9 - - - 1 -

04/12/2001 1030 - - - - - - - - - - -

05/17/2001 1530 - 30 - - - 23.4 - - - - -

06/14/2001 1100 - <10 - - - 20.6 - - - - -

07/17/2001 1200 - <10 - - - 19.9 - - - - -

08/16/2001 1030 - <10 - - - 15.9 - - - - -

09/18/2001 945 - <10 - - - 10 - - - - -

10/17/2001 1445 - - - - - - - - - - -

05/22/2002 1100 - <10 - - - 40.5 - - - - -

07/30/2002 1000 - <10 - - - - - - - - -

08/29/2003 830 E0.4 <10 <12 <0.08 <1 0.7 1.8 - - - -

09/19/2002 915 <0.6 <10 51 <0.08 <1 16.7 17.7 - - - -

10/30/2002 1500 0.8 <10 40 <0.08 <0.06 11.2 12.6 - - - -

Date Time 

Nickel,

dissolved

(μg/L)

Nickel,

total

(μg/L)

Selenium,

dissolved

(μg/L)

Selenium,

total

(μg/L)

Silver,

dissolved

(μg/L)

Silver,

total

(μg/L)

Zinc,

dissolved

(μg/L)

Zinc,

total

(μg/L)

Uranium

(natural),

dissolved

(μg/L)

Uranium

(natural),

total

(μg/L)

Suspended

sediment

(mg/L )

Vallecito Creek near Bayfield, CO (9352900)

04/21/1999 1430 <1 - <1 - <1 - <1 - <1 - -

05/13/1999 1045 <1 - <1 - <1 - 1.2 - <1 - -

06/08/1999 1045 1.48 - <1 - <1 - 3 - <1 - -

06/30/1999 1045 2.54 - <1 - <1 - 3.8 - <1 - -

08/10/1999 1130 2.01 - <1 - <1 - 2 - <1 - -

08/23/1999 1300 1.72 - <1 - <1 - 1.7 - <1 - -

05/18/2000 1145 1.6 - <2 - <1 - 4.9 - <1 - 1.6

06/06/2000 1045 2.25 - <2 - <1 - 6.5 - <1 - 6.5

07/11/2000 1030 1.43 - <2 - <1 - 1.2 - <1 - 1.1

08/22/2000 1600 <1 - <2 - <1 - <1 - <1 - 0.4

04/12/2001 1030 - - - - - - - - - 1.6

05/17/2001 1530 - - - - - - 2.5 - - - 9.5

06/14/2001 1100 - - - - - - 3.1 - - - 3.0

07/17/2001 1200 - - - - - - 3.3 - - - 1.3

08/16/2001 1030 - - - - - - 2.1 - - - 1.4

09/18/2001 945 - - - - - - 1.7 - - - 0.7

10/17/2001 1445 - - - - - - - - - 1.8

05/22/2002 1100 - - - - - - 5.2 - - - 1.1

07/30/2002 1000 - - - - - - - - - 0.2

08/29/2003 830 - - - - - - 1.4 2 - - 0.1

09/19/2002 915 - - - - - - 3.3 4 - - 0.8

10/30/2002 1500 - - - - - - 2.2 3 - - 0.1
8 Water-Quality Data Collected from Vallecito Reservoir, Its Inflows and Outflow, Southwestern Colorado, 1999–2002 

Table 2. Water-quality data collected from the inflows and outflow of Vallecito Reservoir, 1999–2000.—Continued

[ft3/s, cubic feet per second; μS/m, microsiemens per centimeter; C, Celsius; mg/L, milligrams per liter; μg/L, micrograms per liter; nm, nanometers; mL, milliliters; 

-, no data; <, less than; E, estimated]

Date Time 

Instantaneous

discharge

(ft3/s)

pH,

field

(standard

units)

Specific

conductance,

field

(μS/cm

25 degrees C)

Water

temperature

(degrees C)

Dissolved

oxygen

(mg/L(

pH,

laboratory

(standard

units)

Specific

conductance,

laboratory

(μS/cm

25 degrees C)

Calcium,

dissolved

(mg/L)

Magnesium,

dissolved

(mg/L)

Potassium,

dissolved

(mg/L)

Los Piños River above Vallecito Reservoir near Bayfield, CO (9352800)

05/18/2000 1430 296 7.5 66 9.0 9.2 - - - - 0.86

06/06/2000 1330 289 7.6 56 12.7 8.4 - - - - -

07/11/2000 1415 53.5 7.9 93 21.0 7.1 - - - - 1.01

08/22/2000 1315 52.1 8.0 88 18.6 7.5 - - - - -

04/12/2001 1430 84.5 7.8 100 3.5 10.4 - - - - -

05/17/2001 1215 1100 7.5 54 6 9.5 - - - - -

06/14/2001 1330 500 7.4 50 8.3 9.3 - - - - -

07/17/2001 1445 131 6.5 71 15.2 7.7 - - - - -

08/16/2001 1245 232 7.7 60 13.8 7.9 - - - - -

09/18/2001 1245 60.6 7.9 84 13.1 8.0 - - - - -

10/17/2001 1015 38.6 7.4 95 5.5 10.4 - - - - -

05/22/2002 1400 79.8 7.9 62 12 8.8 - - - - -

07/30/2002 1315 19.6 8.1 107 20.8 6.9 - - - - -

08/29/2002 1045 14.2 8.3 105 16 7.9 - - 16.6 2.43 1.16

09/19/2002 1200 47.7 8.1 81 11.5 8.8 - - 11.3 1.82 1.02

10/30/2002 1235 46 - - - - 6.5 80.8 10.8 1.7 0.89

Date Time 

Sodium,

dissolved

(mg/L)

Alkalinity,

laboratory

(mg/L as

CaCO3)

Alkalinity,

field

(mg/L as

CaCO3)

Chloride,

dissolved

(mg/L)

Sulfate,

dissolved

(mg/L)

Silica,

dissolved

(mg/L)

Ammonia 

+ org-N,

dissolved

(mg/L 

as N)

Ammonia 

+ org-N,

total

(mg/L 

as N)

Ammonia,

dissolved

(mg/L 

as N)

Nitrite 

+ nitrate,

dissolved

(mg/L 

as N)

Nitrite,

dissolved

(mg/L 

as N)

Los Piños River above Vallecito Reservoir near Bayfield, CO (9352800)

05/18/2000 1430 - - 29 - - - 0.109 0.105 <0.002 0.007 0.001

06/06/2000 1330 - - 24 - - - E0.063 0.126 0.039 0.020 <0.001

07/11/2000 1415 - - 40 - - - E0.074 E0.086 <0.002 0.009 <0.001

08/22/2000 1315 - - 37 - - - E0.069 E0.084 0.005 0.015 <0.001

04/12/2001 1430 - - 34 - - - E0.07 0.1 0.007 0.094 0.001

05/17/2001 1215 - - 23 - - - 0.15 0.18 0.006 0.033 <0.001

06/14/2001 1330 - - 20 - - - E0.1 0.12 0.002 0.016 <0.001

07/17/2001 1445 - - 30 - - - E0.06 0.09 0.002 0.012 0.002

08/16/2001 1245 - - 28 - - - E0.09 0.09 0.003 0.015 <0.001

09/18/2001 1245 - - 34 - - - E0.08 0.1 0.003 0.056 0.001

10/17/2001 1015 - - 39 - - - <0.1 <0.1 <0.015 0.019 <0.002

05/22/2002 1400 - - 28 - - - 0.12 E0.07 <0.015 0.018 <0.002

07/30/2002 1315 - - 48 - - - E0.08 0.1 <0.015 <0.013 <0.002

08/29/2002 1045 2.04 53 50 0.95 3.6 8.2 <0.1 E0.05 <0.015 E0.009 <0.002

09/19/2002 1200 1.6 E39 - 0.99 3.4 7.4 E0.07 E0.05 <0.015 0.015 <0.002

10/30/2002 1235 1.56 - - E0.19 3.7 7.7 E0.06 E0.07 <0.015 E0.015 <0.002
Sampling Locations, Dates of Collection, and Project Responsibilities 9

Table 2. Water-quality data collected from the inflows and outflow of Vallecito Reservoir, 1999–2000.—Continued

[ft3/s, cubic feet per second; μS/m, microsiemens per centimeter; C, Celsius; mg/L, milligrams per liter; μg/L, micrograms per liter; nm, nanometers; mL, milliliters; 

-, no data; <, less than; E, estimated]

Date Time 

Orthophosphate,

dissolved

(mg/L 

as P)

Phosphorus,

dissolved

(mg/L)

Phosphorus,

total

(mg/L)

Organic

carbon,

dissolved

(mg/L)

Organic

carbon,

total

(mg/L)

Ultraviolet

absorbance

at 254 nm

Ultraviolet

absorbance

at 280 nm

Aluminum,

dissolved

(μg/L)

Aluminum,

total

(μg/L)

Antimony,

dissolved

(μg/L)

Antimony,

total

(μg/L)

Los Piños River above Vallecito Reservoir near Bayfield, CO (9352800)

05/18/2000 1430 0.001 0.003 0.012 2.6 - 0.076 0.050 20 69 - -

06/06/2000 1330 <0.001 0.003 0.013 2.0 - 0.070 0.054 - - - -

07/11/2000 1415 0.002 <0.006 <0.008 1.2 - 0.031 0.024 15 18 - -

08/22/2000 1315 0.001 <0.006 E0.005 1.3 - 0.032 0.024 <10 21 - -

04/12/2001 1430 <0.007 <0.006 0.005 1.7 - 0.038 0.028 - - - -

05/17/2001 1215 <0.007 E0.005 0.043 3.0 - 0.122 0.091 - - - -

06/14/2001 1330 <0.007 E0.004 0.019 2.1 - 0.078 0.059 28 144 - -

07/17/2001 1445 <0.007 E0.004 0.007 1.4 - 0.035 0.026 - - - -

08/16/2001 1245 <0.007 E0.003 0.024 2.0 - 0.055 0.041 - - - -

09/18/2001 1245 <0.007 E0.003 E0.003 - - - - - - - -

10/17/2001 1015 <0.007 <0.004 <0.004 0.8 - 0.020 0.012 - - - -

05/22/2002 1400 <0.007 E0.003 0.007 1.5 - 0.043 0.032 <20 - - -

07/30/2002 1315 0.013 0.017 0.026 1.0 - 0.031 0.023 - - - -

08/29/2002 1045 E0.006 0.008 0.011 0.9 1.4 0.021 0.017 5 43 - -

09/19/2002 1200 <0.007 E0.003 0.005 1.1 1.2 0.025 0.019 4 30 - -

10/30/2002 1235 <0.007 E0.002 E0.003 1.0 1.0 0.025 0.019 3 64 - -

Date Time 

Arsenic,

dissolved

(μg/L)

Arsenic,

total

(μg/L)

Barium,

dissolved

(μg/L)

Barium,

total

(μg/L)

Beryllium,

dissolved

(μg/L)

Beryllium,

total

(μg/L)

Cadmium,

dissolved

(μg/L)

Cadmium,

total

(μg/L)

Chromium,

dissolved

(μg/L)

Chromium,

total

(μg/L)

Copper,

dissolved

(μg/L)

Los Piños River above Vallecito Reservoir near Bayfield, CO (9352800)

05/18/2000 1430 - - - - - - <0.2 <0.2 <0.4 <0.4 <2

06/06/2000 1330 - - - - - - - - - - -

07/11/2000 1415 <1 <1 - - - - <0.2 <0.2 <0.4 <0.4 <2

08/22/2000 1315 <1 <1 - - - - <0.2 <0.2 <0.4 <0.4 <2

04/12/2001 1430 - - - - - - - - - - -

05/17/2001 1215 - - - - - - - - - - -

06/14/2001 1330 <1 <1 - - - - <0.3 <0.3 <0.4 <0.4 1.1

07/17/2001 1445 - - - - - - - - - - -

08/16/2001 1245 - - - - - - - - - - -

09/18/2001 1245 - - - - - - - - - - -

10/17/2001 1015 - - - - - - - - - - -

05/22/2002 1400 - - - - - - - - - - -

07/30/2002 1315 - - - - - - - - - - -

08/29/2002 1045 0.2 <2 - - - - <0.04 <0.04 - - 0.3

09/19/2002 1200 E0.1 <2 - - - - <0.04 <0.04 - - 0.3

10/30/2002 1235 E0.1 <2 - - - - <0.04 <0.04 - - E0.2
10 Water-Quality Data Collected from Vallecito Reservoir, Its Inflows and Outflow, Southwestern Colorado, 1999–2002 

Table 2. Water-quality data collected from the inflows and outflow of Vallecito Reservoir, 1999–2000.—Continued

[ft3/s, cubic feet per second; μS/m, microsiemens per centimeter; C, Celsius; mg/L, milligrams per liter; μg/L, micrograms per liter; nm, nanometers; mL, milliliters; 

-, no data; <, less than; E, estimated]

Date Time 

Copper,

total

(μg/L)

Iron,

dissolved

(μg/L)

Iron,

total

(μg/L)

Lead,

dissolved

(μg/L)

Lead,

total

(μg/L)

Manganese,

dissolved

(μg/L)

Manganese,

total

(μg/L)

Mercury,

dissolved

(μg/L)

Mercury,

total

(μg/L)

Molybdenum,

dissolved

(μg/L)

Molybdenum,

total

(μg/L)

Los Piños River above Vallecito Reservoir near Bayfield, CO (9352800)

05/18/2000 1430 <2 39.0 113 <1.5 <1.5 2.6 7.2 - <0.02 - -

06/06/2000 1330 - - - - - - - - - - -

07/11/2000 1415 <2 15.2 31 <1.5 <1.5 4.6 4.1 - <0.02 - -

08/22/2000 1315 <2 19.5 49.9 <1.5 <1.5 5.5 7.7 - <0.04 - -

04/12/2001 1430 - - - - - - - - - - -

05/17/2001 1215 - - - - - - - - - - -

06/14/2001 1330 5.8 21.3 162.6 <2 <2 4.2 10.2 - <0.1 - -

07/17/2001 1445 - - - - - - - - - - -

08/16/2001 1245 - - - - - - - - - - -

09/18/2001 1245 - - - - - - - - - - -

10/17/2001 1015 - - - - - - - - - - -

05/22/2002 1400 - 16 - - - E2.8 - - - - -

07/30/2002 1315 - - - - - - - - - - -

08/29/2002 1045 E0.3 15 66 <0.08 <1 10 12.7 - - - -

09/19/2002 1200 <0.6 25 62 <0.08 <1 6.2 7.7 - - - -

10/30/2002 1235 E0.4 19 101 <0.08 0.09 4.3 7.2 - - - -

Date Time 

Nickel,

dissolved

(μg/L)

Nickel,

total

(μg/L)

Selenium,

dissolved

(μg/L)

Selenium,

total

(μg/L)

Silver,

dissolved

(μg/L)

Silver,

total

(μg/L)

Zinc,

dissolved

(μg/L)

Zinc,

total

(μg/L)

Uranium

(natural),

dissolved

(μg/L)

Uranium

(natural),

total

(μg/L)

Suspended

sediment

(μg/L)

Los Piños River above Vallecito Reservoir near Bayfield, CO (9352800)

05/18/2000 1430 0.4 0.6 - - <0.8 <0.8 <2 3.7 - - 3.9

06/06/2000 1330 - - - - - - - - - - 3.6

07/11/2000 1415 0.5 <0.4 - - <0.8 <0.8 <2 4.2 - - 1.5

08/22/2000 1315 0.5 0.6 - - <0.8 <0.8 <2 <2 - - 0.7

04/12/2001 1430 - - - - - - - - - - 1.7

05/17/2001 1215 - - - - - - - - - - 59.7

06/14/2001 1330 <0.4 0.4 - - <0.8 <0.8 <2 8.2 - - 6.1

07/17/2001 1445 - - - - - - - - - - 1.7

08/16/2001 1245 - - - - - - - - - - 10.8

09/18/2001 1245 - - - - - - - - - - 1.2

10/17/2001 1015 - - - - - - - - - - 1.3

05/22/2002 1400 - - - - - - 1 - - - 1.1

07/30/2002 1315 - - - - - - - - - - 5.7

08/29/2002 1045 - - - - - - <1 1 - - 2.3

09/19/2002 1200 - - - - - - <1 <1 - - 1.7

10/30/2002 1235 - - - - - - <1 E1 - - 0.5
Sampling Locations, Dates of Collection, and Project Responsibilities 11

Table 2. Water-quality data collected from the inflows and outflow of Vallecito Reservoir, 1999–2000.—Continued

[ft3/s, cubic feet per second; μS/m, microsiemens per centimeter; C, Celsius; mg/L, milligrams per liter; μg/L, micrograms per liter; nm, nanometers; mL, milliliters; 

-, no data; <, less than; E, estimated]

Date Time 

Instantaneous

discharge

(ft3/s)

pH,

field

(standard

units)

Specific

conductance,

field

(μS/cm

25 degrees C)

Water

temperature

(degrees C)

Dissolved

oxygen

(mg/L)

pH,

laboratory

(standard

units)

Specific

conductance,

laboratory

(μS/cm

25 degrees C)

Calcium,

dissolved

(mg/L)

Magnesium,

dissolved

(mg/L)

Potassium,

dissolved

(mg/L)

Los Piños River below Vallecito Reservoir near Bayfield, CO (372236107344400)

05/19/2000 1200 - - - - - - - - - 0.80

06/06/2000 1130 - - - - - - - - - 0.78

07/11/2000 1130 - 6.8 79 7.6 9.1 - - - - 0.74

08/22/2000 1100 - - - - - - - - - 0.80

05/17/2001 1100 - 7.7 78 7.9 8.5 - - - - 0.74

06/14/2001 1000 - 7.6 67 9.9 8.4 - - - - 0.67

07/17/2001 1030 - 7.1 66 11 6.6 - - - - 0.63

08/16/2001 1100 - 7.2 64 14.5 7 - - - - 0.70

09/18/2001 1100 - - - - - - - - - 0.69

10/17/2001 1100 - - - - - - - - - 1.05

05/22/2002 1000 - 7.2 90 12.1 7.2 - - - - -

07/31/2002 1000 - - - - - - - - - -

08/29/2002 1030 - 9.1 123 17.6 7.3 - 441 18.6 2.8 1.1

09/19/2002 1000 - 7.5 135 15.2 7.2 - 133 19.0 2.8 1.2

11/01/2002 1300 - - 120 8.9 - 6.9 117 16.4 2.55 0.89

Date Time 

Sodium,

dissolved

(mg/L)

Alkalinity,

mg/L as

CaCO3

laboratory

Alkalinity,

mg/L as 

CaCO3

field

Chloride,

dissolved

(mg/L)

Sulfate,

dissolved

(mg/L)

Silica,

dissolved

(mg/L)

Ammonia 

+ org-N,

dissolved

(mg/L 

as N)

Ammonia 

+ org-N,

total

(mg/L 

as N)

Ammonia,

dissolved

(mg/L 

as N)

Nitrite 

+ nitrate,

dissolved

(mg/L 

as N)

Nitrite,

dissolved

(mg/L 

as N)

Los Piños River below Vallecito Reservoir near Bayfield, CO (372236107344400)

05/19/2000 1200 - - - - - - E0.068 E0.096 0.008 0.005 <0.001

06/06/2000 1130 - - - - - - E0.063 0.123 0.013 0.014 <0.001

07/11/2000 1130 - - - - - - E0.09 0.117 0.008 0.013 0.001

08/22/2000 1100 - - - - - - E0.084 0.126 0.005 0.008 <0.001

05/17/2001 1100 - - - - - - 0.13 0.19 0.013 0.048 0.001

06/14/2001 1000 - - - - - - E0.08 0.13 0.007 0.044 <0.001

07/17/2001 1030 - - - - - - 0.2 0.12 0.012 0.044 0.004

08/16/2001 1100 - - - - - - E0.1 0.11 0.003 0.039 <0.001

09/18/2001 1100 - - - - - - <0.1 E0.04 0.004 0.011 0.001

10/17/2001 1100 - - - - - - E0.1 0.13 <0.015 <0.013 <0.002

05/22/2002 1000 - - - - - - E0.07 E0.07 <0.015 <0.013 <0.002

07/31/2002 1000 - - - - - - E0.09 0.16 0.017 <0.013 E0.002

08/29/2002 1030 1.5 57 - 0.6 6.4 2.3 0.1 0.2 <0.015 <0.013 E0.002

09/19/2002 1000 1.5 E57 - 0.4 6.8 3.2 0.2 0.2 0.040 0.037 0.003

11/01/2002 1300 1.41 - - 0.31 6.9 4.5 0.1 0.2 E0.008 0.028 0.003
12 Water-Quality Data Collected from Vallecito Reservoir, Its Inflows and Outflow, Southwestern Colorado, 1999–2002 

Table 2. Water-quality data collected from the inflows and outflow of Vallecito Reservoir, 1999–2000.—Continued

[ft3/s, cubic feet per second; μS/m, microsiemens per centimeter; C, Celsius; mg/L, milligrams per liter; μg/L, micrograms per liter; nm, nanometers; mL, milliliters; 

-, no data; <, less than; E, estimated]

Date Time 

Orthophosphate,

dissolved

(mg/L

as P)

Phosphorus,

dissolved

(mg/L)

Phosphorus,

total

(mg/L)

Organic

carbon,

dissolved

(mg/L)

Organic

carbon,

total

(mg/L)

Ultraviolet

absorbance

at 254 nm

Ultraviolet

absorbance

at 280 nm

Aluminum,

dissolved

(μg/L)

Aluminum,

total

(μg/L)

Antimony,

dissolved

(μg/L)

Antimony,

total

(μg/L)

Los Piños River below Vallecito Reservoir near Bayfield, CO (372236107344400)

05/19/2000 1200 <0.001 <0.006 E0.005 1.9 - 0.040 0.020 20 64 - -

06/06/2000 1130 <0.001 <0.006 E0.004 1.9 - 0.055 0.042 21 65 - -

07/11/2000 1130 0.003 0.008 E0.005 1.8 - 0.052 0.039 15 27 - -

08/22/2000 1100 0.001 <0.006 0.009 1.6 - 0.033 0.023 24 32 - -

05/17/2001 1100 <0.007 E0.003 0.011 2.3 - 0.069 0.051 24 144 - -

06/14/2001 1000 <0.007 <0.006 0.006 2.3 - 0.078 0.059 45 93 - -

07/17/2001 1030 <0.007 <0.006 0.004 2.4 - 0.068 0.051 32 51 - -

08/16/2001 1100 <0.007 <0.006 0.005 1.9 - 0.047 0.034 13 34 - -

09/18/2001 1100 <0.007 <0.006 <0.004 - - - - 19 39 - -

10/17/2001 1100 <0.007 <0.004 0.005 1.6 - 0.036 0.022 <10 30 - -

05/22/2002 1000 <0.007 <0.004 0.006 1.4 - 0.028 0.019 - - - -

07/31/2002 1000 <0.007 0.006 0.015 1.3 - 0.044 0.034 50.7 - - -

08/29/2002 1030 E0.004 0.009 0.022 1.6 2.0 0.042 0.030 7.4 30.3 - -

09/19/2002 1000 0.020 0.029 0.041 1.8 2.3 0.053 0.038 11.6 82.7 - -

11/01/2002 1300 0.008 0.014 0.025 1.6 1.6 0.045 0.033 7.4 57 - -

Date Time 

Arsenic,

dissolved

(μg/L)

Arsenic,

total

(μg/L)

Barium,

dissolved

(μg/L)

Barium,

total

(μg/L)

Beryllium,

dissolved

(μg/L)

Beryllium,

total

(μg/L)

Cadmium,

dissolved

(μg/L)

Cadmium,

total

(μg/L)

Chromium,

dissolved

(μg/L)

Chromium,

total

(μg/L)

Copper,

dissolved

(μg/L)

Los Piños River below Vallecito Reservoir near Bayfield, CO (372236107344400)

05/19/2000 1200 <1 <1 - - - - <0.2 <0.2 <0.4 <0.4 <2

06/06/2000 1130 <1 <1 - - - - <0.2 0.2 <0.4 <0.4 <2

07/11/2000 1130 <1 <1 - - - - <0.2 <0.2 <0.4 <0.4 <2

08/22/2000 1100 <1 <1 - - - - <0.2 <0.2 <0.4 <0.4 <2

05/17/2001 1100 <1 <1 - - - - <0.3 <0.3 <0.4 <0.4 1.3

06/14/2001 1000 <1 <1 - - - - <0.3 <0.3 <0.4 <0.4 1.2

07/17/2001 1030 <1 <1 - - - - <0.3 <0.3 <0.4 <0.4 1.0

08/16/2001 1100 <1 <1 - - - - <0.3 <0.3 <0.4 <0.4 <0.6

09/18/2001 1100 <1 <1 - - - - <0.3 <0.3 <0.4 0.5 1.4

10/17/2001 1100 <1 <1 - - - - <0.3 <0.3 <0.4 <0.4 2.9

05/22/2002 1000 - - - - - - - - - - -

07/31/2002 1000 - - - - - - - - - - -

08/29/2002 1030 0.7 <2 - - - - <0.04 <0.04 - - 0.4

09/19/2002 1000 0.7 <2 - - - - <0.04 <0.04 - - 0.5

11/01/2002 1300 0.7 <2 - - - - <0.04 0.04 - - 0.5
Sampling Locations, Dates of Collection, and Project Responsibilities 13

Table 2. Water-quality data collected from the inflows and outflow of Vallecito Reservoir, 1999–2000.—Continued

[ft3/s, cubic feet per second; μS/m, microsiemens per centimeter; C, Celsius; mg/L, milligrams per liter; μg/L, micrograms per liter; nm, nanometers; mL, milliliters; 

-, no data; <, less than; E, estimated]

Date Time

Copper,

total

(μg/L)

Iron,

dissolved

(μg/L)

Iron,

total

(μg/L)

Lead,

dissolved

(μg/L)

Lead,

total

(μg/L)

Manganese,

dissolved

(μg/L)

Manganese,

total

(μg/L)

Mercury,

dissolved

(μg/L)

Mercury,

total

(μg/L)

Molybdenum,

dissolved

(μg/L)

Los Piños River below Vallecito Reservoir near Bayfield, CO (372236107344400)

05/19/2000 1200 <2 5.0 49.0 <1.5 <1.5 0.7 11.9 - <0.02 -

06/06/2000 1130 5.9 11 59.0 <1.5 <1.5 1.6 12.4 - <0.02 -

07/11/2000 1130 <2 8.3 41.2 <1.5 <1.5 32.5 54.4 - <0.02 -

08/22/2000 1100 <2 6.0 39.4 <1.5 <1.5 14.9 56.5 - <0.04 -

05/17/2001 1100 2.1 14.6 142.3 <2 <2 2.4 17.6 - <0.1 -

06/14/2001 1000 1.7 17.1 63.9 <2 <2 2.0 7.3 - <0.1 -

07/17/2001 1030 1.2 15.9 40.5 <2 <2 7.8 14.7 - <0.2 -

08/16/2001 1100 1.2 15.4 52.5 <2 <2 11.8 38.4 - <0.2 -

09/18/2001 1100 4.4 4.4 36.0 <2 <2 1.9 19.7 - <0.2 -

10/17/2001 1100 1.6 6.8 42.7 <2 <2 2.5 21.8 - <0.2 -

05/22/2002 1000 - E6 - - - E1.8 - - - -

07/31/2002 1000 - <10 - - - 8.3 - - - -

08/29/2002 1030 E0.41 E9 53.9 <0.08 <1 16.6 71.4 - - -

09/19/2002 1000 <0.6 15.7 107 <0.08 <1 28.9 42.8 - - -

11/01/2002 1300 0.6 <10 78 <0.08 0.13 3.3 94.7 - - -

Date Time

Molybdenum,

total

(μg/L)

Nickel,

dissolved

(μg/L)

Nickel,

total

(μg/L)

Selenium,

dissolved

(μg/L)

Selenium,

total

(μg/L)

Silver,

dissolved

(μg/L)

Silver,

total

(μg/L)

Zinc,

dissolved

(μg/L)

Zinc,

total

(μg/L)

Uranium

(natural),

dissolved

(μg/L)

Uranium

(natural),

total

(μg/L)

Los Piños River below Vallecito Reservoir near Bayfield, CO (372236107344400)

05/19/2000 1200 - 0.6 1.1 - - <0.8 <0.8 <2 6.1 - -

06/06/2000 1130 - 0.8 6.2 - - <0.8 <0.8 4.7 7.6 - -

07/11/2000 1130 - 1.1 1.0 - - <0.8 <0.8 <2 5.0 - -

08/22/2000 1100 - 0.7 0.9 - - <0.8 <0.8 <2 2.7 - -

05/17/2001 1100 - 0.6 0.6 - - <0.8 <0.8 <2 4.1 - -

06/14/2001 1000 - 0.7 0.7 - - <0.8 <0.8 <2 <2 - -

07/17/2001 1030 - 1.3 1.1 - - <0.8 <0.8 <2 <2 - -

08/16/2001 1100 - 1.0 1.1 - - <0.8 <0.8 <2 2.9 - -

09/18/2001 1100 - 0.9 0.9 - - <0.8 <0.8 <2 <2 - -

10/17/2001 1100 - 0.5 0.9 - - <0.8 <0.8 <2 <2 - -

05/22/2002 1000 - - - - - - - 2.9 - - -

07/31/2002 1000 - - - - - - - 1.1 - - -

08/29/2002 1030 - - - - - - - 3.2 <1 - -

09/19/2002 1000 - - - - - - - <1 <1 - -

11/01/2002 1300 - - - - - - - <1 E2 - -
14 Water-Quality Data Collected from Vallecito Reservoir, Its Inflows and Outflow, Southwestern Colorado, 1999–2002 

Table 2. Water-quality data collected from the inflows and outflow of Vallecito Reservoir, 1999–2000.—Continued

[ft3/s, cubic feet per second; μS/m, microsiemens per centimeter; C, Celsius; mg/L, milligrams per liter; μg/L, micrograms per liter; nm, nanometers; mL, milliliters; 

-, no data; <, less than; E, estimated]

Date Time pH

Specific

conductance

(μS/cm)

Dissolved

oxygen

(mg/L)

Water

temperature

(degrees C)

Escherichia

coli

(#/100 mL)

Fecal

coliform

(#/100 mL)

Total

coliform

(#/100 mL)

Dissolved 

solids,

filterable

(mg/L)

Total 

suspended 

solids,

non-filterable

(mg/L)

Hardness,

(Ca + Mg)

(mg/L)

Alkalinity,

(mg/L)

Vallecito Creek near mouth before entering reservoir—RPS9370

01/20/1999 1520 7.3 - 11.6 1 - Non-detect - 42 Non-detect 39 32

02/24/1999 1225 7.7 88 12 2.1 - Non-detect - 68 Non-detect 38 -

03/17/1999 1410 - 88 10.1 4.5 - Non-detect - 62 Non-detect 36 32

04/14/1999 1430 - 81 10.5 7.1 - Non-detect - 43 Non-detect 34 34

05/13/1999 1115 - 82 10.6 5 - 0 - 55 Non-detect 34 32

06/17/1999 1000 8 52 10.2 5.2 - 2 - 32 Non-detect 21 20

07/14/1999 1350 7.5 52 8.5 10.5 - Non-detect - 35 Non-detect 20 18

08/24/1999 1010 8 76 8.8 9.7 - 4 - 44 Non-detect 32 28

10/21/1999 1235 7.6 97 10.6 5.8 - Non-detect - 62 Non-detect 39 36

11/08/1999 1635 7.6 101 9.8 6.1 - Non-detect - 58 Non-detect 43 38

12/14/1999 1155 7.7 - 11 1.5 - 4 - 52 Non-detect 46 30

01/19/2000 1225 7.52 106 11.3 2.4 - Non-detect - 57 10 47 42

02/15/2000 1210 8.1 110 10.92 4.6 - Non-detect - 68 Non-detect 48 46

04/18/2000 1310 8.02 71 9.41 6.1 - Non-detect - 43 Non-detect 30 24

05/18/2000 1110 7.32 68 10.17 4.3 - Non-detect - 37 Non-detect 28 20

06/06/2000 930 7.16 45 9.61 5.7 - Non-detect - 22 Non-detect 17 12

07/26/2000 845 7.53 78 8.14 11.2 - 9 - 69 Non-detect 32 26

08/16/2000 1455 7.6 82 7.5 18.1 - 15 - 58 Non-detect 34 28

09/27/2000 1625 7.08 62 8.32 9.3 - 15 - 37 Non-detect 26 16

01/19/2001 1535 7.34 84 11.55 0.1 - - - 46 Non-detect 35 28

02/12/2001 1625 8.27 82 10.78 0.3 - Non-detect - 41 Non-detect 32 26

03/14/2001 1125 7.67 85 9.96 2.9 - Non-detect - 54 Non-detect 32 28

04/17/2001 1300 7.28 77 10.78 5.9 - Non-detect - 49 Non-detect 33 28

05/17/2001 920 7.08 59 10.88 4.4 Non-detect Non-detect 44 47 Non-detect 25 20

06/14/2001 1120 7.49 55 10.36 4.1 Non-detect - 30.5 35 Non-detect 23 16

07/26/2001 1140 7.53 53 8.48 12 20.2 - 58.1 37 Non-detect 21 16

08/16/2001 925 7.33 65 8.63 8.7 14.6 - 816.4 40 Non-detect 26 20

09/18/2001 1700 7.3 76 7.78 12.8 3.1 - - 40 Non-detect 31 24

11/06/2001 1445 8.1 83 9.61 8.1 1 - - 64 Non-detect 36 31

12/18/2001 1005 7.28 82 11.21 0.9 Non-detect - 41 44 Non-detect 36 30

01/15/2002 1125 7.87 94 11.6 1.1 1 - 21.6 53 Non-detect 41 34

02/13/2002 1115 7.91 100 10.99 1.9 Non-detect - 17.3 53 Non-detect 42 38

03/13/2002 850 7.16 97 10.92 1.3 Non-detect - - 52 Non-detect 41 32

05/15/2002 1015 7.58 52 9.76 5.9 - - - 26 Non-detect 20 6

06/06/2002 1000 8.06 58 9.21 9.1 - - - 33 Non-detect 23 26

07/23/2002 1155 8.65 112 8.57 16.1 - - - 54 Non-detect 45 40

08/21/2002 1240 7.88 98 5.95 15.6 25.6 - 1,413.6 54 Non-detect 41 32
Sampling Locations, Dates of Collection, and Project Responsibilities 15

Table 2. Water-quality data collected from the inflows and outflow of Vallecito Reservoir, 1999–2000.—Continued

[ft3/s, cubic feet per second; μS/m, microsiemens per centimeter; C, Celsius; mg/L, milligrams per liter; μg/L, micrograms per liter; nm, nanometers; mL, milliliters; 

-, no data; <, less than; E, estimated]

Date Time

Sulfate,

total

(mg/L)

Nitrogen,

NH3 + NH4

(mg/L as N)

Nitrogen,

NO2 + NO3

(mg/L as N)

Nitrogen, 

total

Kjeldahl

(mg/L as N)

Phosphorus,

total

(mg/L as P)

Aluminum,

dissolved

(μg/L)

Aluminum,

total

(μg/L)

Arsenic,

dissolved

(μg/L)

Arsenic,

total

(μg/L)

Vallecito Creek near mouth before entering reservoir—RPS9370

01/20/1999 1520 8 Non-detect 0.21 Non-detect Non-detect Non-detect - Non-detect -

02/24/1999 1225 7 Non-detect 0.14 Non-detect Non-detect Non-detect - Non-detect -

03/17/1999 1410 6 Non-detect 0.19 Non-detect Non-detect Non-detect - Non-detect -

04/14/1999 1430 5 Non-detect 0.12 Non-detect Non-detect 57 - Non-detect -

05/13/1999 1115 5 Non-detect 0.16 Non-detect 0.01 81 - Non-detect -

06/17/1999 1000 6 Non-detect 0.2 Non-detect Non-detect 51 - Non-detect -

07/14/1999 1350 6 Non-detect 0.16 Non-detect Non-detect 69 - Non-detect -

08/24/1999 1010 5 0.01 0.1 - 0.01 88 150 Non-detect Non-detect

10/21/1999 1235 7 Non-detect 0.18 - 0.02 Non-detect - Non-detect -

11/08/1999 1635 6 Non-detect 0.15 - 0.03 Non-detect - Non-detect -

12/14/1999 1155 7 Non-detect 0.19 - Non-detect Non-detect - Non-detect -

01/19/2000 1225 6 Non-detect 0.19 - 0.01 Non-detect - Non-detect -

02/15/2000 1210 7 Non-detect 0.19 - 0.03 Non-detect - Non-detect -

04/18/2000 1310 Non-detect Non-detect 0.32 - 0.01 92 - Non-detect -

05/18/2000 1110 Non-detect Non-detect 0.13 - Non-detect 65 - Non-detect -

06/06/2000 930 5 Non-detect 0.17 - 0.05 Non-detect - Non-detect -

07/26/2000 845 9 Non-detect 0.14 - 0.01 Non-detect - Non-detect -

08/16/2000 1455 Non-detect Non-detect 0.13 - 0.03 Non-detect - Non-detect -

09/27/2000 1625 8 Non-detect 0.17 - 0.02 Non-detect - Non-detect -

01/19/2001 1535 7 Non-detect 0.21 - 0.03 Non-detect - Non-detect -

02/12/2001 1625 7 Non-detect 0.21 - 0.02 Non-detect - Non-detect -

03/14/2001 1125 7 Non-detect 0.19 - Non-detect Non-detect - Non-detect -

04/17/2001 1300 6 Non-detect 0.15 - 0.02 87 - Non-detect -

05/17/2001 920 Non-detect Non-detect 0.15 - 0.01 59 - Non-detect -

06/14/2001 1120 6 Non-detect 0.14 - Non-detect Non-detect - Non-detect -

07/26/2001 1140 7 Non-detect Non-detect - 0.04 Non-detect - Non-detect -

08/16/2001 925 6 Non-detect Non-detect - 0.02 47 - Non-detect -

09/18/2001 1700 12 Non-detect Non-detect - 0.07 57 - Non-detect -

11/06/2001 1445 10 Non-detect Non-detect - Non-detect Non-detect - Non-detect -

12/18/2001 1005 9 Non-detect Non-detect - Non-detect Non-detect - Non-detect -

01/15/2002 1125 10 Non-detect Non-detect - Non-detect Non-detect - Non-detect -

02/13/2002 1115 10 Non-detect Non-detect - Non-detect Non-detect - Non-detect -

03/13/2002 850 10 Non-detect Non-detect - Non-detect Non-detect - Non-detect -

05/15/2002 1015 9 Non-detect Non-detect - Non-detect Non-detect - Non-detect -

06/06/2002 1000 8 Non-detect Non-detect - Non-detect Non-detect - Non-detect -

07/23/2002 1155 10 0.07 Non-detect - Non-detect Non-detect - Non-detect -

08/21/2002 1240 9 Non-detect Non-detect - Non-detect Non-detect - Non-detect -
16 Water-Quality Data Collected from Vallecito Reservoir, Its Inflows and Outflow, Southwestern Colorado, 1999–2002 

Table 2. Water-quality data collected from the inflows and outflow of Vallecito Reservoir, 1999–2000.—Continued

[ft3/s, cubic feet per second; μS/m, microsiemens per centimeter; C, Celsius; mg/L, milligrams per liter; μg/L, micrograms per liter; nm, nanometers; mL, milliliters; 

-, no data; <, less than; E, estimated]

Date Time

Cadmium,

dissolved

(μg/L)

Cadmium,

total

(μg/L)

Copper,

dissolved

(μg/L)

Copper,

total

(μg/L)

Iron,

dissolved

(μg/L)

Iron,

total

(μg/L)

Lead,

dissolved

(μg/L)

Lead,

total

(μg/L)

Manganese,

dissolved

(μg/L)

Vallecito Creek near mouth before entering reservoir—RPS9370

01/20/1999 1520 Non-detect - Non-detect - - 15 Non-detect Non-detect

02/24/1999 1225 Non-detect - Non-detect - - 22 Non-detect Non-detect

03/17/1999 1410 Non-detect - Non-detect - - 16 Non-detect Non-detect

04/14/1999 1430 Non-detect - Non-detect - - 750 Non-detect Non-detect

05/13/1999 1115 Non-detect - Non-detect - - 180 Non-detect 6

06/17/1999 1000 Non-detect - Non-detect - - 140 Non-detect 22

07/14/1999 1350 Non-detect - Non-detect - - 45 Non-detect 9

08/24/1999 1010 Non-detect Non-detect Non-detect Non-detect 17 56 Non-detect Non-detect 10

10/21/1999 1235 Non-detect - Non-detect - Non-detect 13 Non-detect Non-detect

11/08/1999 1635 Non-detect - Non-detect - Non-detect Non-detect Non-detect Non-detect

12/14/1999 1155 Non-detect - Non-detect - Non-detect Non-detect Non-detect Non-detect

01/19/2000 1225 Non-detect - Non-detect - Non-detect Non-detect Non-detect Non-detect

02/15/2000 1210 Non-detect - Non-detect - Non-detect Non-detect Non-detect Non-detect

04/18/2000 1310 Non-detect - Non-detect - 43 59 Non-detect 4

05/18/2000 1110 Non-detect - Non-detect - 19 72 Non-detect 17

06/06/2000 930 Non-detect - Non-detect - Non-detect 56 Non-detect 19

07/26/2000 845 Non-detect - Non-detect - Non-detect Non-detect Non-detect Non-detect

08/16/2000 1455 Non-detect - Non-detect - Non-detect Non-detect Non-detect Non-detect

09/27/2000 1625 Non-detect - Non-detect - Non-detect 27 Non-detect 11

01/19/2001 1535 Non-detect - Non-detect - Non-detect 15 Non-detect Non-detect

02/12/2001 1625 Non-detect - Non-detect - Non-detect Non-detect Non-detect Non-detect

03/14/2001 1125 Non-detect - Non-detect - 11 19 Non-detect Non-detect

04/17/2001 1300 Non-detect - Non-detect - 40 89 Non-detect 4

05/17/2001 920 Non-detect - Non-detect - 43 310 Non-detect 18

06/14/2001 1120 Non-detect - Non-detect - Non-detect 46 Non-detect 15

07/26/2001 1140 Non-detect - Non-detect - Non-detect 22 Non-detect 7

08/16/2001 925 Non-detect - 4 - Non-detect 56 Non-detect 11

09/18/2001 1700 Non-detect - Non-detect - Non-detect 19 Non-detect 7

11/06/2001 1445 Non-detect - Non-detect - Non-detect Non-detect Non-detect Non-detect

12/18/2001 1005 Non-detect - Non-detect - Non-detect Non-detect Non-detect Non-detect

01/15/2002 1125 Non-detect - Non-detect - Non-detect Non-detect Non-detect Non-detect

02/13/2002 1115 Non-detect - Non-detect - Non-detect Non-detect Non-detect Non-detect

03/13/2002 850 Non-detect - Non-detect - Non-detect Non-detect Non-detect Non-detect

05/15/2002 1015 Non-detect - Non-detect - Non-detect 140 Non-detect 26

06/06/2002 1000 Non-detect - Non-detect - 8 46 Non-detect 12

07/23/2002 1155 Non-detect - Non-detect - Non-detect 24 Non-detect 3

08/21/2002 1240 Non-detect - Non-detect - 4 20 Non-detect 3
Sampling Locations, Dates of Collection, and Project Responsibilities 17

Table 2. Water-quality data collected from the inflows and outflow of Vallecito Reservoir, 1999–2000.—Continued

[ft3/s, cubic feet per second; μS/m, microsiemens per centimeter; C, Celsius; mg/L, milligrams per liter; μg/L, micrograms per liter; nm, nanometers; mL, milliliters; 

-, no data; <, less than; E, estimated]

Date Time

Manganese,

total

(μg/L)

Mercury,

dissolved

(μg/L)

Mercury,

total

(μg/L)

Selenium,

dissolved

(μg/L)

Selenium,

total

(μg/L)

Silver,

dissolved

(μg/L)

Silver,

total

(μg/L)

Zinc,

dissolved

(μg/L)

Zinc,

total

(μg/L)

Vallecito Creek near mouth before entering reservoir—RPS9370

01/20/1999 1520 - - Non-detect Non-detect - Non-detect - 11 -

02/24/1999 1225 - - Non-detect Non-detect - Non-detect - 12 -

03/17/1999 1410 - - Non-detect Non-detect - Non-detect - 15 -

04/14/1999 1430 - - Non-detect Non-detect - Non-detect - 11 -

05/13/1999 1115 - - Non-detect Non-detect - Non-detect - 12 -

06/17/1999 1000 - - Non-detect Non-detect - Non-detect - 11 -

07/14/1999 1350 - - Non-detect Non-detect - Non-detect - Non-detect -

08/24/1999 1010 12 - Non-detect Non-detect Non-detect Non-detect Non-detect 12 13

10/21/1999 1235 - - Non-detect Non-detect - Non-detect - Non-detect -

11/08/1999 1635 - - Non-detect Non-detect - Non-detect - 13 -

12/14/1999 1155 - - Non-detect Non-detect - Non-detect - 16 -

01/19/2000 1225 - - Non-detect Non-detect - Non-detect - 19 -

02/15/2000 1210 - - Non-detect Non-detect - Non-detect - 15 -

04/18/2000 1310 - - Non-detect Non-detect - Non-detect - 14 -

05/18/2000 1110 - - Non-detect Non-detect - Non-detect - 11 -

06/06/2000 930 - - Non-detect Non-detect - Non-detect - Non-detect -

07/26/2000 845 - - Non-detect Non-detect - Non-detect - Non-detect -

08/16/2000 1455 - - Non-detect Non-detect - Non-detect - 13 -

09/27/2000 1625 - - Non-detect Non-detect - Non-detect - 15 -

01/19/2001 1535 - Non-detect - Non-detect - Non-detect - 14 -

02/12/2001 1625 - Non-detect - Non-detect - Non-detect - Non-detect -

03/14/2001 1125 - Non-detect - Non-detect - Non-detect - Non-detect -

04/17/2001 1300 - Non-detect - Non-detect - Non-detect - Non-detect -

05/17/2001 920 - Non-detect - Non-detect - Non-detect - Non-detect -

06/14/2001 1120 - Non-detect - Non-detect - Non-detect - Non-detect -

07/26/2001 1140 - Non-detect - Non-detect - Non-detect - Non-detect -

08/16/2001 925 - Non-detect - Non-detect - Non-detect - Non-detect -

09/18/2001 1700 - Non-detect - Non-detect - Non-detect - Non-detect -

11/06/2001 1445 - Non-detect - Non-detect - Non-detect - Non-detect -

12/18/2001 1005 - Non-detect - Non-detect - Non-detect - Non-detect -

01/15/2002 1125 - Non-detect - Non-detect - Non-detect - Non-detect -

02/13/2002 1115 - Non-detect - Non-detect - Non-detect - Non-detect -

03/13/2002 850 - Non-detect - Non-detect - Non-detect - Non-detect -

05/15/2002 1015 - Non-detect - Non-detect - Non-detect - Non-detect -

06/06/2002 1000 - Non-detect - Non-detect - Non-detect - Non-detect -

07/23/2002 1155 - Non-detect - Non-detect - Non-detect - Non-detect -

08/21/2002 1240 - Non-detect - Non-detect - Non-detect - Non-detect -
18 Water-Quality Data Collected from Vallecito Reservoir, Its Inflows and Outflow, Southwestern Colorado, 1999–2002 

Table 2. Water-quality data collected from the inflows and outflow of Vallecito Reservoir, 1999–2000.—Continued

[ft3/s, cubic feet per second; μS/m, microsiemens per centimeter; C, Celsius; mg/L, milligrams per liter; μg/L, micrograms per liter; nm, nanometers; mL, milliliters; 

-, no data; <, less than; E, estimated]

Date Time pH

Specific

conductance

(μS/cm)

Dissolved

oxygen

(mg/L)

Water

temperature

(degrees C)

Escherichia

coli

(#/100 mL)

Fecal

coliform

(#/100 mL)

Total

coliform

(#/100 mL)

Dissolved

solids,

filterable

(mg/L)

Total

suspended

solids,

non-filterable

(mg/L)

Hardness

(Ca + Mg)

(mg/L)

Los Piños River above Vallecito Reservoir—RPS9380

02/24/1999 1305 7.5 111 12.3 0.4 - Non-detect - 82 Non-detect 50

03/17/1999 1445 112 10 4.6 - Non-detect - 80 Non-detect 45

04/14/1999 1510 103 9.6 9.2 - Non-detect - 58 Non-detect 43

05/13/1999 1030 88 10.7 5.2 - 4 - 64 Non-detect 37

06/17/1999 - 7.6 9.8 6.3 - 26 - 37 Non-detect 20

07/14/1999 1420 7.9 74 7.91 13.8 - 23 - 51 Non-detect 29

08/24/1999 1100 7.94 76 9.5 11.7 - 43 - 52 Non-detect 33

10/21/1999 1310 8 98 10.9 4.9 - Non-detect - 64 Non-detect 38

11/08/1999 1705 7.9 116 9.9 6.6 - 9 - 58 Non-detect 50

12/14/1999 1230 7.3 126 12.2 0.1 - Non-detect - 76 Non-detect 58

01/19/2000 1310 7 111 12.76 0.1 - Non-detect - 62 Non-detect 52

02/15/2000 1255 7.65 117 12.33 1.1 - 4 - 78 Non-detect 52

04/18/2000 1350 8.54 93 9.23 6.8 - Non-detect - 58 Non-detect 40

05/18/2000 1200 7.84 68 8.2 6.1 - Non-detect - 44 Non-detect 28

06/06/2000 1015 7.43 56 9.3 8.5 - 4 - 34 Non-detect 22

07/26/2000 930 7.96 107 8.14 12.7 - 150 - 84 Non-detect 45

08/16/2000 1530 8.61 102 7.29 20.1 - 23 - 72 Non-detect 42

09/27/2000 1655 7.89 87 7.85 12.7 - 15 - 53 Non-detect 37

01/19/2001 1620 7.13 107 12.14 0 - Non-detect - 61 Non-detect 44

02/12/2001 1715 7.25 97 10.86 0 - Non-detect - 60 Non-detect 43

03/14/2001 1220 7.07 105 10.24 2.5 - Non-detect - 64 Non-detect 41

04/17/2001 1345 7.28 103 10.14 8.4 - Non-detect - 69 Non-detect 44

05/17/2001 1000 7.8 55 10.96 4.5 5 43 91 55 10 22

06/14/2001 1030 7.5 52 9.59 5.9 2 - 204.6 42 Non-detect 21

07/26/2001 1305 8.27 86 7.86 15.6 14.2 - 533.5 63 Non-detect 35

08/16/2001 1010 7.49 63 7.95 11.1 45.2 - Present >QL 49 Non-detect 25

09/18/2001 1730 7.79 89 7.66 15.2 Non-detect - - 62 Non-detect 38

11/06/2001 1515 7.82 100 10.45 6.3 9.7 - - 73 Non-detect 43

12/18/2001 1055 7.11 107 11.76 0 3.1 - 150 66 Non-detect 48

01/15/2002 1200 7.73 111 12.33 0 1 - 38.8 63 Non-detect 50

02/13/2002 1200 7.6 120 11.9 0 Non-detect - 42.8 75 Non-detect 54

03/13/2002 945 8.02 110 11.72 0.1 4.1 - - 67 Non-detect 49

05/15/2002 1120 7.63 56 8.93 9.3 - - - 40 Non-detect 22

07/23/2002 1240 8.74 113 6.54 17.3 - - - 69 Non-detect 47

08/21/2002 1330 8.36 117 5.48 17.5 10.4 - 1,553.07 73 Non-detect 49

11/13/2002 1400 8.11 94 10.5 2.26 2 - 131.7 63 Non-detect 41
Sampling Locations, Dates of Collection, and Project Responsibilities 19

Table 2. Water-quality data collected from the inflows and outflow of Vallecito Reservoir, 1999–2000.—Continued

[ft3/s, cubic feet per second; μS/m, microsiemens per centimeter; C, Celsius; mg/L, milligrams per liter; μg/L, micrograms per liter; nm, nanometers; mL, milliliters; 

-, no data; <, less than; E, estimated]

Date Time Alkalinity

(mg/L)

Sulfate,

total

(mg/L)

Nitrogen,

NH3 + NH4

(mg/L as N)

Nitrogen,

NO2 + NO3

(mg/L as N)

Nitrogen,

total

Kjeldahl

(mg/L as N)

Phosphorus,

total

(mg/L as P)

Aluminum,

dissolved

(μg/L)

Aluminum,

total

(μg/L)

Arsenic,

dissolved

(μg/L)

Arsenic,

total

(μg/L)

Los Piños River above Vallecito Reservoir—RPS9380

02/24/1999 1305 50 5 Non-detect Non-detect Non-detect Non-detect Non-detect - Non-detect -

03/17/1999 1445 46 Non-detect Non-detect 0.06 Non-detect Non-detect Non-detect - Non-detect -

04/14/1999 1510 48 Non-detect 0.24 0.06 Non-detect Non-detect Non-detect - Non-detect -

05/13/1999 1030 40 5 Non-detect 0.08 Non-detect 0.02 65 - Non-detect -

06/17/1999 - 28 Non-detect Non-detect 0.11 Non-detect Non-detect Non-detect - Non-detect -

07/14/1999 1420 34 Non-detect Non-detect 0.06 Non-detect Non-detect Non-detect - Non-detect -

08/24/1999 1100 38 Non-detect 0.01 Non-detect - 0.01 Non-detect 62 Non-detect Non-detect

10/21/1999 1310 42 Non-detect Non-detect 0.06 - 0.13 Non-detect - Non-detect -

11/08/1999 1705 50 Non-detect Non-detect 0.06 - 0.03 Non-detect - Non-detect -

12/14/1999 1230 54 5 Non-detect 0.12 - 0.01 Non-detect - Non-detect -

01/19/2000 1310 50 Non-detect Non-detect 0.12 - Non-detect Non-detect - Non-detect -

02/15/2000 1255 48 5 Non-detect 0.11 - 0.02 Non-detect - Non-detect -

04/18/2000 1350 40 Non-detect Non-detect 0.05 - 0.01 90 - Non-detect -

05/18/2000 1200 28 Non-detect Non-detect Non-detect - Non-detect Non-detect - Non-detect -

06/06/2000 1015 22 Non-detect Non-detect Non-detect - 0.05 Non-detect - Non-detect -

07/26/2000 930 46 Non-detect Non-detect Non-detect - 0.02 Non-detect - Non-detect -

08/16/2000 1530 42 6 Non-detect Non-detect - 0.01 Non-detect - Non-detect -

09/27/2000 1655 38 Non-detect Non-detect 0.05 - 0.02 Non-detect - Non-detect -

01/19/2001 1620 48 Non-detect Non-detect 0.13 - 0.04 Non-detect - Non-detect -

02/12/2001 1715 46 Non-detect Non-detect 0.11 - 0.02 Non-detect - Non-detect -

03/14/2001 1220 42 Non-detect Non-detect 0.09 - Non-detect Non-detect - Non-detect -

04/17/2001 1345 46 Non-detect Non-detect 0.1 - 0.02 87 - Non-detect -

05/17/2001 1000 22 Non-detect Non-detect 0.07 - 0.04 72 - Non-detect -

06/14/2001 1030 20 Non-detect Non-detect 0.06 - Non-detect Non-detect - Non-detect -

07/26/2001 1305 40 Non-detect Non-detect Non-detect - 0.01 Non-detect - Non-detect -

08/16/2001 1010 28 Non-detect Non-detect Non-detect - 0.02 Non-detect - Non-detect -

09/18/2001 1730 38 3 Non-detect Non-detect - 0.07 Non-detect - Non-detect -

11/06/2001 1515 45 5 Non-detect Non-detect - Non-detect Non-detect - Non-detect -

12/18/2001 1055 48 10 Non-detect Non-detect - Non-detect Non-detect - Non-detect -

01/15/2002 1200 48 5 Non-detect Non-detect - Non-detect Non-detect - Non-detect -

02/13/2002 1200 56 6 Non-detect Non-detect - Non-detect Non-detect - Non-detect -

03/13/2002 945 50 5 Non-detect Non-detect - Non-detect Non-detect - Non-detect -

05/15/2002 1120 22 Non-detect Non-detect Non-detect - Non-detect Non-detect - Non-detect -

07/23/2002 1240 46 4 Non-detect Non-detect - Non-detect Non-detect - Non-detect -

08/21/2002 1330 52 4 Non-detect Non-detect - 0.02 Non-detect - Non-detect -

11/13/2002 1400 38 5 Non-detect Non-detect - Non-detect Non-detect - Non-detect -
20 Water-Quality Data Collected from Vallecito Reservoir, Its Inflows and Outflow, Southwestern Colorado, 1999–2002 

Table 2. Water-quality data collected from the inflows and outflow of Vallecito Reservoir, 1999–2000.—Continued

[ft3/s, cubic feet per second; μS/m, microsiemens per centimeter; C, Celsius; mg/L, milligrams per liter; μg/L, micrograms per liter; nm, nanometers; mL, milliliters; 

-, no data; <, less than; E, estimated]

Date Time

Cadmium,

dissolved

(μg/L)

Cadmium,

total

(μg/L)

Copper,

dissolved

(μg/L)

Copper,

total

(μg/L)

Iron,

dissolved

(μg/L)

Iron,

total

(μg/L)

Lead,

dissolved

(μg/L)

Lead,

total

(μg/L)

Maganese,

dissolved

(μg/L)

Los Piños River above Vallecito Reservoir—RPS9380

02/24/1999 1305 Non-detect - Non-detect - - 62 Non-detect - Non-detect

03/17/1999 1445 Non-detect - Non-detect - - 47 Non-detect - Non-detect

04/14/1999 1510 Non-detect - Non-detect - - 100 Non-detect - Non-detect

05/13/1999 1030 Non-detect - Non-detect - - 560 Non-detect - Non-detect

06/17/1999 - Non-detect - Non-detect - - 140 Non-detect - Non-detect

07/14/1999 1420 Non-detect - Non-detect - - 110 Non-detect - Non-detect

08/24/1999 1100 Non-detect Non-detect Non-detect Non-detect 56 110 Non-detect Non-detect Non-detect

10/21/1999 1310 Non-detect - Non-detect - 20 37 Non-detect - Non-detect

11/08/1999 1705 Non-detect - Non-detect - 13 20 Non-detect - Non-detect

12/14/1999 1230 Non-detect - Non-detect - Non-detect 18 Non-detect - 4

01/19/2000 1310 Non-detect - Non-detect - 11 29 Non-detect - Non-detect

02/15/2000 1255 Non-detect - Non-detect - Non-detect 15 Non-detect - Non-detect

04/18/2000 1350 Non-detect - Non-detect - 65 160 Non-detect - Non-detect

05/18/2000 1200 Non-detect - Non-detect - 51 110 Non-detect - Non-detect

06/06/2000 1015 Non-detect - Non-detect - 29 97 Non-detect - Non-detect

07/26/2000 930 Non-detect - Non-detect - 11 15 Non-detect - Non-detect

08/16/2000 1530 Non-detect - Non-detect - 18 26 Non-detect - Non-detect

09/27/2000 1655 Non-detect - Non-detect - 19 55 Non-detect - 4

01/19/2001 1620 Non-detect - Non-detect - 12 12 Non-detect - Non-detect

02/12/2001 1715 Non-detect - Non-detect - 13 20 Non-detect - Non-detect

03/14/2001 1220 Non-detect - Non-detect - 17 27 Non-detect - Non-detect

04/17/2001 1345 Non-detect - Non-detect - 54 140 Non-detect - Non-detect

05/17/2001 1000 Non-detect - Non-detect - 57 560 Non-detect - Non-detect

06/14/2001 1030 Non-detect - Non-detect - 24 150 Non-detect - Non-detect

07/26/2001 1305 Non-detect - Non-detect - 17 37 Non-detect - Non-detect

08/16/2001 1010 Non-detect - Non-detect - 27 240 Non-detect - 2

09/18/2001 1730 Non-detect - Non-detect - 20 36 Non-detect - 4

11/06/2001 1515 Non-detect - Non-detect - Non-detect 22 Non-detect - 4

12/18/2001 1055 Non-detect - Non-detect - Non-detect 15 Non-detect - 3

01/15/2002 1200 Non-detect - Non-detect - Non-detect 20 Non-detect - 4

02/13/2002 1200 Non-detect - Non-detect - Non-detect 16 Non-detect - 4

03/13/2002 945 Non-detect - Non-detect - Non-detect 19 Non-detect - 6

05/15/2002 1120 Non-detect - 4 - 21 81 Non-detect - Non-detect

07/23/2002 1240 Non-detect - Non-detect - 9 15 Non-detect - Non-detect

08/21/2002 1330 Non-detect - Non-detect - 16 78 Non-detect - 8

11/13/2002 1400 Non-detect - Non-detect - 21 500 Non-detect - 3
Sampling Locations, Dates of Collection, and Project Responsibilities 21

Table 2. Water-quality data collected from the inflows and outflow of Vallecito Reservoir, 1999–2000.—Continued

[ft3/s, cubic feet per second; μS/m, microsiemens per centimeter; C, Celsius; mg/L, milligrams per liter; μg/L, micrograms per liter; nm, nanometers; mL, milliliters; 

-, no data; <, less than; E, estimated]

Date Time

Manganese,

total

(μg/L)

Mercury,

dissolved

(μg/L)

Mercury,

total

(μg/L)

Selenium,

dissolved

(μg/L)

Selenium,

total

(μg/L)

Silver,

dissolved

(μg/L)

Silver,

total

(μg/L)

Zinc,

dissolved

(μg/L)

Zinc,

total

(μg/L)

Los Piños River above Vallecito Reservoir—RPS9380

02/24/1999 1305 - - Non-detect Non-detect - Non-detect - 19 -

03/17/1999 1445 - - Non-detect Non-detect - Non-detect - 14 -

04/14/1999 1510 - - Non-detect Non-detect - Non-detect - 11 -

05/13/1999 1030 - - Non-detect Non-detect - Non-detect - 14 -

06/17/1999 - - - Non-detect Non-detect - Non-detect - Non-detect -

07/14/1999 1420 - - Non-detect Non-detect - Non-detect - Non-detect -

08/24/1999 1100 7 - Non-detect Non-detect - Non-detect Non-detect 11 12

10/21/1999 1310 - - Non-detect Non-detect - Non-detect - 17 -

11/08/1999 1705 - - Non-detect Non-detect - Non-detect - 16 -

12/14/1999 1230 - - Non-detect Non-detect - Non-detect - Non-detect -

01/19/2000 1310 - - Non-detect Non-detect - Non-detect - Non-detect -

02/15/2000 1255 - - Non-detect Non-detect - Non-detect - Non-detect -

04/18/2000 1350 - - Non-detect Non-detect - Non-detect - 17 -

05/18/2000 1200 - - Non-detect Non-detect - Non-detect - 11 -

06/06/2000 1015 - - Non-detect Non-detect - Non-detect - Non-detect -

07/26/2000 930 - - Non-detect Non-detect - Non-detect - 17 -

08/16/2000 1530 - - Non-detect Non-detect - Non-detect - 15 -

09/27/2000 1655 - - Non-detect Non-detect - Non-detect - 17 -

01/19/2001 1620 - Non-detect - Non-detect - Non-detect - 11 -

02/12/2001 1715 - Non-detect - Non-detect - Non-detect - Non-detect -

03/14/2001 1220 - Non-detect - Non-detect - Non-detect - Non-detect -

04/17/2001 1345 - Non-detect - Non-detect - Non-detect - 12 -

05/17/2001 1000 - Non-detect - Non-detect - Non-detect - Non-detect -

06/14/2001 1030 - Non-detect - Non-detect - Non-detect - Non-detect -

07/26/2001 1305 - Non-detect - Non-detect - Non-detect - Non-detect -

08/16/2001 1010 - Non-detect - Non-detect - Non-detect - Non-detect -

09/18/2001 1730 - Non-detect - Non-detect - Non-detect - Non-detect -

11/06/2001 1515 - Non-detect - Non-detect - Non-detect - Non-detect -

12/18/2001 1055 - Non-detect - Non-detect - Non-detect - 11 -

01/15/2002 1200 - Non-detect - Non-detect - Non-detect - Non-detect -

02/13/2002 1200 - Non-detect - Non-detect - Non-detect - Non-detect -

03/13/2002 945 - Non-detect - Non-detect - Non-detect - Non-detect -

05/15/2002 1120 - Non-detect - Non-detect - Non-detect - Non-detect -

07/23/2002 1240 - Non-detect - Non-detect - Non-detect - Non-detect -

08/21/2002 1330 - Non-detect - Non-detect - Non-detect - Non-detect -

11/13/2002 1400 - Non-detect - Non-detect - Non-detect - Non-detect -
22 Water-Quality Data Collected from Vallecito Reservoir, Its Inflows and Outflow, Southwestern Colorado, 1999–2002 

Table 3. Total metals data collected from Vallecito Reservoir in 1999.

[μg/L, micrograms per liter; <, less than]

Site name Date Time

Sampling 

depth

(feet)

Aluminum,

total

(μg/L)

Arsenic,

total

(μg/L)

Cadmium,

total

(μg/L)

Vallecito Reservoir North 08/24/1999 0930 2 59 <2 <0.1

Vallecito Reservoir North 08/24/1999 0930 16 52 <2 <0.1

Vallecito Reservoir North 08/24/1999 0930 31.5 50 <2 <0.1

Vallecito Reservoir North 09/21/1999 1130 2 49 <2 <0.1

Vallecito Reservoir North 09/21/1999 1132 15 47 <2 <0.1

Vallecito Reservoir North 09/21/1999 1134 24 53 <2 <0.1

Vallecito Reservoir North 10/19/1999 1010 2 72 <1 <0.1

Vallecito Reservoir North 10/19/1999 1012 15 69 <1 <0.1

Vallecito Reservoir North 11/30/1999 1200 2 <10 <1 <0.2

Vallecito Reservoir North 11/30/1999 1150 23 30 <1 <0.2

Vallecito Reservoir Center 08/24/1999 0900 2 62 <2 <0.1

Vallecito Reservoir Center 08/24/1999 0900 20 57 <2 <0.1

Vallecito Reservoir Center 08/24/1999 0900 66 120 <2 <0.1

Vallecito Reservoir Center 09/21/1999 1045 2 47 <2 <0.1

Vallecito Reservoir Center 09/21/1999 1047 30 45 <2 <0.1

Vallecito Reservoir Center 09/21/1999 1049 53 <45 <2 <0.1

Vallecito Reservoir Center 10/19/1999 0945 2 62 <1 <0.1

Vallecito Reservoir Center 10/19/1999 0947 52 75 <1 <0.1

Vallecito Reservoir Center 11/30/1999 1140 2 <10 <1 <0.2

Vallecito Reservoir Center 11/30/1999 1130 40 19 <1 <0.2

Vallecito Reservoir South 08/24/1999 0805 2 63 <2 <0.1

Vallecito Reservoir South 08/24/1999 0805 23 65 <2 <0.1

Vallecito Reservoir South 08/24/1999 0805 92 <45 <2 <0.1

Vallecito Reservoir South 09/21/1999 0930 2 <45 <2 <0.1

Vallecito Reservoir South 09/21/1999 0932 53 <45 <2 <0.1

Vallecito Reservoir South 09/21/1999 0934 73 <45 <2 <0.1

Vallecito Reservoir South 10/19/1999 0930 2 62 <1 <0.1

Vallecito Reservoir South 10/19/1999 0932 64 67 <1 <0.1

Vallecito Reservoir South 11/30/1999 1050 2 <10 <1 <0.2

Vallecito Reservoir South 11/30/1999 1100 73 445 <1 <0.2
Sampling Locations, Dates of Collection, and Project Responsibilities 23

Table 3. Total metals data collected from Vallecito Reservoir in 1999.—Continued

[μg/L, micrograms per liter; <, less than]

Chromium,

total

(μg/L)

Copper,

total

(μg/L)

Iron,

total

(μg/L)

Lead,

total

(μg/L)

Manganese,

total

(μg/L)

Mercury,

total

(μg/L)

Nickel,

total

(μg/L)

Potassium,

total

(mg/L)

Silver,

total

(μg/L)

Zinc,

total

(μg/L)

<5 <1 30 <1 2 - <5 0.7 <0.1 <5

<5 <1 30 <1 2 - <5 0.7 <0.1 <5

<5 <1 70 <1 7 - <5 0.7 <0.1 <5

<5 <1 30 <1 8 <0.1 <5 0.6 <0.1 <5

<5 <1 50 <1 8 <0.1 <5 0.6 <0.1 <5

<5 <1 40 <1 8 <0.1 <5 0.6 <0.1 <5

<5 <1 40 2 18 <0.1 <5 1.3 <0.1 <5

<5 <1 50 <1 19 <0.1 <5 1.5 <0.1 36

<0.4 <0.6 26 <1.5 7 <0.5 <0.4 0.44 <0.8 7.5

1.4 2.8 39 100.1 7.8 <0.5 <0.4 0.51 <0.8 34.7

<5 <1 30 <1 2 - <5 0.7 <0.1 <5

<5 <1 30 <1 2 - <5 0.7 <0.1 <5

<5 <1 20 <1 46 - <5 0.7 <0.1 <5

<5 <1 30 <1 5 <0.1 <5 0.6 <0.1 <5

<5 <1 40 <1 14 <0.1 <5 0.6 <0.1 <5

<5 <1 50 <1 20 <0.1 <5 0.6 <0.1 <5

<5 <1 40 <1 18 <0.1 <5 1.1 <0.1 15

5 <1 80 <1 17 <0.1 <5 1.1 <0.1 20

<0.4 <0.6 24 <1.5 6.8 <0.05 0.4 0.42 <0.8 7.6

0.4 4.2 34 <1.5 8.0 <0.05 <0.4 0.50 <0.8 10.9

<5 <1 30 <1 2 - <5 0.7 <0.1 <5

<5 <1 30 <1 2 - <5 0.7 <0.1 <5

<5 <1 50 <1 44 - <5 0.7 <0.1 <5

<5 <1 40 <1 5 <0.1 <5 0.6 <0.1 <5

<5 <1 50 <1 20 <0.1 <5 0.7 <0.1 <5

<5 <1 60 <1 39 0.2 <5 0.7 <0.1 6

<5 <1 40 <1 20 <0.1 <5 1.2 <0.1 7

<5 <1 40 <1 20 <0.1 <5 1.2 <0.1 <5

<0.4 2.2 28 <1.5 6.8 <0.05 <0.4 0.39 <0.8 13.8

<0.4 1.8 796 <1.5 58.0 <0.05 0.9 0.52 <0.8 16.8
24 Water-Quality Data Collected from Vallecito Reservoir, Its Inflows and Outflow, Southwestern Colorado, 1999–2002 

Table 4. Water-quality data collected from Vallecito Reservoir South, 2000–2002.

[μS/cm, microsiemens per centimeter; C, Celsius; mg/L, milligrams per liter; nm, nanometers; mL, milliliters; <, less than; -, no data]

Date Time

Sampling

depth

(feet)

pH,

field

(standard

units)

Specific

conductance,

field

(μS/cm

25 degrees C)

Water

temperature

(degrees C)

Dissolved

oxygen

(mg/L)

pH,

laboratory

(standard

units)

Specific

conductance,

laboratory

(μS/cm

25 degrees C)

05/19/2000 1100 2 7.9 87 10.7 9.3 - -

05/19/2000 1110 85 7.1 81 8.6 7.0 - -

06/06/2000 1000 2 8.3 84 16.0 8.3 - -

06/06/2000 1015 25 7.5 77 11.3 7.8 - -

06/06/2000 1030 98 7.1 81 8.6 7.0 - -

07/11/2000 0930 2 7.8 86 19.7 7.0 - -

07/11/2000 1000 25 7.3 82 18.5 7.2 - -

07/11/2000 1030 78 6.3 81 9.8 4.9 - -

08/22/2000 0930 2 6.9 84 19.5 7.2 - -

08/22/2000 1000 43 6.6 86 18.5 5.1 - -

08/22/2000 1015 70 6.2 82 9.7 0.7 - -

05/17/2001 1000 2 8.2 81 12.7 8.7 - -

05/17/2001 1015 25 - - - - - -

05/17/2001 1030 70 7.4 89 6.2 7.8 - -

06/14/2001 0915 2 7.8 64 13.4 7.8 - -

06/14/2001 0900 45 7.6 64 10.3 8 - -

06/14/2001 0845 85 7.5 70 8.6 7.3 - -

07/17/2001 0930 2 8.2 67 19.3 7 - -

07/17/2001 0940 40 7.1 62 12.5 5.8 - -

07/17/2001 1000 88 7.8 67 9.9 5.4 - -

08/16/2001 1000 5 8.4 68 19.4 6.9 - -

08/16/2001 1015 65 7.0 64 12.1 4.4 - -

08/16/2001 1025 85 6.8 66 10.3 3.4 - -

09/18/2001 1000 2 - - - - - -

09/18/2001 1020 - - - - - - -

09/18/2001 1030 73 - - - - - -

10/17/2001 1000 2 8 68 12.2 7.2 - -

10/17/2001 1010 35 7.8 68 12.2 6.9 - -

10/17/2001 1020 70 - - - - - -

05/22/2002 0900 2 7.9 87 12.4 7.2 - -

05/22/2002 0910 - - - - - - -

05/22/2002 0920 65 7.3 89 10.2 6.6 - -

07/31/2002 0900 2 - - - - - -

07/31/2002 0915 20 - - - - - -

07/31/2002 0930 40 - - - - - -

08/29/2002 0900 2 8.8 123 17.6 6.2 - 130

08/29/2002 0930 28 9.4 122 17.4 5.5 - 219

09/19/2002 0900 2 7.3 136 15.2 6.4 - 133

09/19/2002 0930 40 7.1 123 14.4 4.4 - 124

10/29/2002 0900 2 - - - - 7.7 118

10/29/2002 0930 40 - - - - 6.3 115
Sampling Locations, Dates of Collection, and Project Responsibilities 25

Table 4. Water-quality data collected from Vallecito Reservoir South, 2000–2002.—Continued

[μS/cm, microsiemens per centimeter; C, Celsius; mg/L, milligrams per liter; nm, nanometers; mL, milliliters; <, less than; -, no data]

Calcium,

dissolved

(mg/L)

Magnesium,

dissolved

(mg/L)

Potassium,

dissolved

(mg/L)

Sodium,

dissolved

(mg/L)

Alkalinity,

mg/L as

CaCO3

laboratory

Chloride,

dissolved

(mg/L)

Sulfate,

dissolved

(mg/L)

Silica,

dissolved

(mg/L)

Ammonia 

+ org-N,

dissolved

(mg/L as N)

Ammonia 

+ org-N,

total

(mg/L as N)

- - 0.80 - - - - - 0.1 0.12

- - 0.81 - - - - - E0.08 0.1

- - 0.76 - - - - - E0.07 0.13

- - 0.75 - - - - - <0.1 0.16

- - 0.78 - - - - - E0.07 0.11

- - 0.85 - - - - - 0.16 0.11

- - 0.74 - - - - - 0.31 0.14

- - 0.76 - - - - - 0.11 0.13

- - 0.87 - - - - - 0.14 0.15

- - 0.83 - - - - - 0.11 0.12

- - 0.84 - - - - - 0.13 0.16

- - 0.73 - - - - - 0.12 1.1

- - 0.74 - - - - - E0.1 0.14

- - 0.78 - - - - - E0.08 0.13

- - 0.65 - - - - - 0.1 0.11

- - 0.67 - - - - - E0.09 0.15

- - 0.69 - - - - - 0.1 0.13

- - 0.64 - - - - - E0.06 0.09

- - 0.63 - - - - - E0.09 0.1

- - 0.62 - - - - - E0.09 0.08

- - 0.68 - - - - - 0.1 0.09

- - 0.70 - - - - - E0.09 0.11

- - 0.73 - - - - - E0.1 0.118

- - 0.67 - - - - - E0.06 0.1

- - 0.70 - - - - - E0.07 E0.07

- - 0.69 - - - - - E0.06 E0.04

- - 0.73 - - - - - E0.07 E0.1

- - 0.71 - - - - - <0.1 E0.09

- - 0.74 - - - - - 0.14 E0.1

- - - - - - - - E0.07 E0.07

- - - - - - - - E0.07 E0.06

- - - - - - - - E0.06 E0.07

- - - - - - - - <0.1 0.14

- - - - - - - - E0.05 0.12

- - - - - - - - 0.17 0.23

18.8 2.8 1.1 1.6 58 0.65 6.4 2.3 0.1 0.2

18.3 2.8 1.1 1.5 57 0.65 6.2 2.6 0.1 0.2

18.7 2.7 1.2 1.5 E57 0.46 6.8 3.3 0.167 0.222

17.2 2.6 1.1 1.4 E51 0.42 7.1 3.9 0.215 0.268

16.1 2.52 0.97 1.41 - 0.32 6.8 4.4 <0.1 0.170

16.7 2.59 0.97 1.44 - 0.31 6.7 4.5 0.110 0.172
26 Water-Quality Data Collected from Vallecito Reservoir, Its Inflows and Outflow, Southwestern Colorado, 1999–2002 

Table 4. Water-quality data collected from Vallecito Reservoir South, 2000–2002.—Continued

[μS/cm, microsiemens per centimeter; C, Celsius; mg/L, milligrams per liter; nm, nanometers; mL, milliliters; <, less than; -, no data]

Date Time 

Ammonia,

dissolved

(mg/L as N)

Nitrite 

+ nitrate,

dissolved

(mg/L as N)

Nitrite,

dissolved

(mg/L as N)

Orthophosphate,

dissolved

(mg/L as P)

Phosphorus,

dissolved

(mg/L)

Phosphorus,

total

(mg/L)

Organic

carbon,

dissolved

(mg/L)

05/19/2000 1100 0.003 <0.005 <0.001 <0.001 <0.006 0.008 2.0

05/19/2000 1110 0.009 <0.005 <0.001 <0.001 <0.006 E0.006 1.8

06/06/2000 1000 0.009 <0.005 <0.001 <0.001 <0.006 E0.006 2.1

06/06/2000 1015 0.006 <0.005 <0.001 <0.001 <0.006 0.009 -

06/06/2000 1030 0.014 0.012 <0.001 <0.001 <0.006 E0.004 1.9

07/11/2000 0930 0.012 0.005 0.001 0.003 <0.006 E0.006 1.8

07/11/2000 1000 0.013 0.011 0.001 0.013 0.022 E0.004 1.7

07/11/2000 1030 0.017 0.018 0.001 0.002 <0.006 E0.004 1.8

08/22/2000 0930 0.006 <0.005 <0.001 0.002 <0.006 E0.006 1.6

08/22/2000 1000 0.016 0.008 0.002 0.002 <0.006 E0.007 1.6

08/22/2000 1015 0.031 0.112 <0.001 0.002 E0.005 0.015 1.7

05/17/2001 1000 0.006 0.009 0.001 <0.007 <0.006 0.008 2.5

05/17/2001 1015 0.01 0.033 0.001 <0.007 <0.006 0.011 2.3

05/17/2001 1030 0.009 0.057 0.001 <0.007 <0.006 0.016 1.8

06/14/2001 0915 <0.002 0.021 <0.001 <0.007 E0.004 0.009 2.2

06/14/2001 0900 0.007 0.036 <0.001 <0.007 <0.006 0.007 2.3

06/14/2001 0845 0.003 0.025 <0.001 <0.007 E0.003 0.011 2.3

07/17/2001 0930 <0.002 0.007 0.002 <0.007 <0.006 <0.004 3.1

07/17/2001 0940 0.019 0.032 0.003 <0.007 <0.006 0.004 3.4

07/17/2001 1000 0.002 0.010 0.002 <0.007 <0.006 E0.002 2.6

08/16/2001 1000 0.002 0.005 <0.001 <0.007 <0.006 E0.003 2.2

08/16/2001 1015 0.002 0.064 <0.001 <0.007 <0.006 0.004 2.1

08/16/2001 1025 0.005 0.095 <0.001 <0.007 <0.006 0.006 2.2

09/18/2001 1000 0.002 0.009 0.001 <0.007 <0.006 E0.002 -

09/18/2001 1020 0.005 0.01 0.001 <0.007 <0.006 <0.004 -

09/18/2001 1030 <0.002 0.013 0.001 <0.007 <0.006 E0.003 -

10/17/2001 1000 <0.015 <0.013 <0.002 <0.007 <0.004 0.006 1.5

10/17/2001 1010 <0.015 <0.013 <0.002 <0.007 E0.004 0.008 1.4

10/17/2001 1020 <0.015 <0.013 <0.002 <0.007 <0.004 0.005 1.6

05/22/2002 0900 <0.015 <0.013 <0.002 <0.007 E0.003 0.006 1.5

05/22/2002 0910 <0.015 <0.013 <0.002 <0.007 <0.004 0.005 1.5

05/22/2002 0920 <0.015 <0.013 <0.002 <0.007 <0.004 0.006 1.5

07/31/2002 0900 <0.015 <0.013 <0.002 <0.007 0.005 0.01 1.4

07/31/2002 0915 <0.015 <0.013 <0.002 <0.007 E0.004 0.011 1.5

07/31/2002 0930 0.089 E0.012 0.008 0.007 0.009 0.019 1.4

08/29/2002 0900 <0.015 <0.013 <0.002 <0.007 0.008 0.019 1.7

08/29/2002 0930 0.022 0.015 0.003 0.007 0.012 0.023 1.6

09/19/2002 0900 0.044 0.039 0.003 0.021 0.029 0.040 1.8

09/19/2002 0930 0.098 0.072 0.004 0.023 0.031 0.050 1.8

10/29/2002 0900 E0.014 0.030 0.003 0.008 0.014 0.020 1.5

10/29/2002 0930 0.015 0.031 0.003 0.009 0.016 0.023 1.6
Sampling Locations, Dates of Collection, and Project Responsibilities 27

Table 4. Water-quality data collected from Vallecito Reservoir South, 2000–2002.—Continued

[μS/cm, microsiemens per centimeter; C, Celsius; mg/L, milligrams per liter; nm, nanometers; mL, milliliters; <, less than; -, no data]

Organic

carbon,

total

(mg/L)

Ultraviolet

absorbance

at 254 nm

Ultraviolet

absorbance

at 280 nm

Aluminum,

dissolved

(μg/L)

 Aluminum,

total

(μg/L)

Arsenic,

dissolved

(μg/L)

Arsenic,

total

(μg/L)

Cadmium,

dissolved

(μg/L)

Cadmium,

total

(μg/L)

- 0.054 0.032 27 43 <1 <1 <0.2 <0.2

- 0.037 0.018 12 24 <1 <1 <0.2 <0.2

- 0.056 0.041 45 59 <1 <1 <0.2 <0.2

- - - 30 64 <1 <1 <0.2 <0.2

- 0.051 0.039 18 47 <1 <1 <0.2 <0.2

- 0.044 0.032 36 49 <1 <1 <0.2 <0.2

- 0.052 0.039 17 24 <1 <1 <0.2 <0.2

- 0.053 0.039 15 23 <1 <1 <0.2 <0.2

- 0.033 0.023 24 44 <1 <1 <0.2 <0.2

- 0.032 0.022 <10 36 <1 <1 <0.2 <0.2

- 0.044 0.032 <10 33 <1 <1 <0.2 <0.2

- 0.065 0.048 21 85 <1 <1 <0.3 <0.3

- 0.071 0.054 24 96 <1 <1 <0.3 <0.3

- 0.048 0.036 <10 61 <1 <1 <0.3 <0.3

- 0.073 0.055 57 91 <1 <1 <0.3 <0.3

- 0.076 0.057 46 91 <1 <1 <0.3 <0.3

- 0.074 0.055 46 137 <1 <1 <0.3 <0.3

- 0.053 0.04 49 62 <1 <1 <0.3 <0.3

- 0.060 0.045 42 49 <1 <1 <0.3 <0.3

- 0.056 0.040 27 50 <1 <1 <0.3 <0.3

- 0.038 0.026 43 61 <1 <1 <0.3 <0.3

- 0.051 0.037 11 31 <1 <1 <0.3 <0.3

- 0.056 0.041 16 29 <1 <1 <0.3 <0.3

- - - 26 38 <1 <1 <0.3 0.7

- - - 25 41 <1 <1 <0.3 0.3

- - - <10 23 <1 <1 <0.3 0.3

- 0.036 0.022 11 21 <1 <1 <0.3 <0.3

- 0.037 0.024 11 21 <1 <1 <0.3 <0.3

- 0.036 0.023 <10 22 <1 <1 <0.3 <0.3

- 0.028 0.019 20 - - - - -

- 0.03 0.02 20 - - - - -

- 0.028 0.019 <20 - - - - -

- 0.036 0.027 E10 - - - - -

- 0.037 0.027 <20 - - - - -

- 0.039 0.028 <20 - - - - -

1.9 0.042 0.030 6.7 26.1 0.7 4 <0.04 <0.04

2.0 0.042 0.030 8.8 25.0 0.8 <2 <0.04 <0.04

2.7 0.053 0.038 11.2 84.2 0.7 <2 <0.04 <0.04

2.2 0.056 0.041 10.3 115.4 0.7 <2 <0.04 <0.04

1.6 0.044 0.032 10.9 36.9 0.6 <2 <0.04 0.04

2.0 0.044 0.032 10.6 35.9 0.6 <2 <0.04 <0.04
28 Water-Quality Data Collected from Vallecito Reservoir, Its Inflows and Outflow, Southwestern Colorado, 1999–2002 

Table 4. Water-quality data collected from Vallecito Reservoir South, 2000–2002.—Continued

[μS/cm, microsiemens per centimeter; C, Celsius; mg/L, milligrams per liter; nm, nanometers; mL, milliliters; <, less than; -, no data]

Date Time 

Chromium,

dissolved

(μg/L)

Chromium,

total

(μg/L)

Copper,

dissolved

(μg/L)

Copper,

total

(μg/L)

Iron,

dissolved

(μg/L)

Iron,

total

(μg/L)

Lead,

dissolved

(μg/L)

05/19/2000 1100 <0.4 <0.4 <2 <2 6.0 43.0 <1.5

05/19/2000 1110 <0.4 <0.4 <2 <2 4.0 26.0 <1.5

06/06/2000 1000 <0.4 0.6 <2 2.7 9 39.0 <1.5

06/06/2000 1015 <0.4 <0.4 <2 <2 11 55 <1.5

06/06/2000 1030 <0.4 <0.4 <2 <2 7 54.0 <1.5

07/11/2000 0930 <0.4 <0.4 <2 <2 <4 22.9 <1.5

07/11/2000 1000 <0.4 <0.4 <2 <2 9.0 33.9 <1.5

07/11/2000 1030 <0.4 <0.4 <2 <2 10.0 47.6 <1.5

08/22/2000 0930 <0.4 <0.4 <2 <2 7.3 36.1 <1.5

08/22/2000 1000 <0.4 <0.4 <2 <2 7.2 50.6 <1.5

08/22/2000 1015 <0.4 <0.4 <2 <2 9.0 85.5 <1.5

05/17/2001 1000 <0.4 <0.4 1.3 0.8 10.0 67.2 <2

05/17/2001 1015 <0.4 <0.4 0.8 1.5 12.7 97.1 <2

05/17/2001 1030 <0.4 <0.4 1.0 1.6 7.8 71.1 <2

06/14/2001 0915 <0.4 <0.4 1.2 1.8 14.4 42.8 <2

06/14/2001 0900 <0.4 <0.4 1.3 1.7 17.5 58.9 <2

06/14/2001 0845 <0.4 <0.4 2.1 1.5 21.0 107.8 <2

07/17/2001 0930 <0.4 <0.4 1.6 1.1 8.7 22.1 <2

07/17/2001 0940 <0.4 <0.4 1.2 1.7 11.7 31.5 <2

07/17/2001 1000 <0.4 <0.4 0.9 1.9 17.2 45.1 <2

08/16/2001 1000 <0.4 <0.4 <0.6 1.0 4.1 17.2 <2

08/16/2001 1015 <0.4 <0.4 <0.6 <0.6 14.7 43.3 <2

08/16/2001 1025 <0.4 <0.4 1.4 <0.6 13.8 51.7 <2

09/18/2001 1000 <0.4 <0.4 4.1 1.3 5.1 26.8 <2

09/18/2001 1020 <0.4 <0.4 0.8 2.4 4.6 26.9 <2

09/18/2001 1030 <0.4 <0.4 1.2 2.0 5.6 42.4 <2

10/17/2001 1000 <0.4 <0.4 2.0 1.0 7.8 38.7 <2

10/17/2001 1010 <0.4 <0.4 0.5 2.7 6.5 37.3 <2

10/17/2001 1020 <0.4 <0.4 0.7 2.1 7.0 40.9 <2

05/22/2002 0900 - - - - E9 - -

05/22/2002 0910 - - - - E10 - -

05/22/2002 0920 - - - - <10 - -

07/31/2002 0900 - - - - <10 - -

07/31/2002 0915 - - - - <10 - -

07/31/2002 0930 - - - - <10 - -

08/29/2002 0900 - - 0.4 E0.55 E7 52.2 <0.08

08/29/2002 0930 - - 0.4 E0.43 <10 45.4 <0.08

09/19/2002 0900 - - 0.5 <0.6 20.5 116.6 E0.07

09/19/2002 0930 - - 0.5 0.63 35.5 215.7 <0.08

10/29/2002 0900 - - 0.4 1.1 E10 71.5 <0.08

10/29/2002 0930 - - 0.5 0.65 11.7 65.7 <0.08
Sampling Locations, Dates of Collection, and Project Responsibilities 29

Table 4. Water-quality data collected from Vallecito Reservoir South, 2000–2002.—Continued

[μS/cm, microsiemens per centimeter; C, Celsius; mg/L, milligrams per liter; nm, nanometers; mL, milliliters; <, less than; -, no data]

Lead,

total

(μg/L)

Manganese,

dissolved

(μg/L)

Manganese,

total

(μg/L)

Mercury,

dissolved

(μg/L)

Mercury,

total

(μg/L)

Nickel,

dissolved

(μg/L)

Nickel,

total

(μg/L)

Silver,

dissolved

(μg/L)

Silver,

total

(μg/L)

Zinc,

dissolved

(μg/L)

Zinc,

total

(μg/L)

<1.5 1.0 8.1 - <0.02 0.8 0.9 <0.8 <0.8 2.0 10.0

<1.5 0.3 6.7 - <0.02 0.5 1.8 <0.8 <0.8 2.3 5.3

<1.5 1.3 5.9 - 0.12 0.9 1.8 <0.8 <0.8 <2 2.5

<1.5 0.7 8.4 - <0.02 1.1 0.8 <0.8 <0.8 5.4 40.7

<1.5 0.6 11.4 - <0.02 0.8 0.6 <0.8 <0.8 2.5 9.2

<1.5 0.5 10.5 - <0.02 1.0 0.9 <0.8 <0.8 <2 <2

<1.5 24.3 43.8 - <0.02 0.9 0.9 <0.8 <0.8 <2 <2

<1.5 66.0 105.0 - 0.39 1.0 1.0 <0.8 <0.8 2.0 2.6

<1.5 1.0 14.6 - <0.04 0.6 0.9 <0.8 <0.8 4.3 3.4

<1.5 21.1 41.3 - 0.15 0.8 0.7 <0.8 <0.8 <2 2.1

<1.5 986.8 1,036 - 0.10 0.9 1.0 <0.8 <0.8 3.3 6.7

<2 0.7 8.0 <0.1 <0.1 0.8 <0.4 <0.8 <0.8 <2 3.7

<2 0.4 9.6 <0.1 <0.1 0.7 0.5 <0.8 <0.8 <2 3.8

<2 1.2 15.5 <0.1 0.10 0.6 0.4 <0.8 <0.8 <2 3.6

<2 1.5 4.1 <0.1 <0.1 0.9 0.7 <0.8 <0.8 <2 <2

<2 2.0 6.5 <0.1 <0.1 1.1 0.6 <0.8 <0.8 <2 <2

<2 4.7 8.6 <0.1 <0.1 0.8 0.9 <0.8 <0.8 <2 <2

<2 3.9 5.6 <0.2 <0.2 1.2 1.2 <0.8 <0.8 <2 <2

<2 7.0 12.0 <0.2 <0.2 1.2 1.2 <0.8 <0.8 <2 <2

<2 10.6 19.9 <0.2 <0.2 1.0 1.1 <0.8 <0.8 <2 <2

<2 <0.4 3.0 - <0.2 1.1 1.2 <0.8 <0.8 <2 2.8

<2 4.7 29.1 - <0.2 0.8 1.1 <0.8 <0.8 <2 2.5

<2 15.8 116.7 - <0.2 1.1 0.9 <0.8 <0.8 <2 <2

<2 0.9 9.1 - <0.2 0.7 0.7 <0.8 <0.8 <2 4.5

<2 0.5 8.2 - <0.2 0.7 0.6 <0.8 <0.8 <2 <2

<2 0.5 110.0 - <0.2 0.5 0.5 <0.8 <0.8 <2 <2

<2 0.6 21.3 <0.2 <0.2 1.0 1.0 <0.8 <0.8 <2 <2

<2 0.5 20.8 <0.2 <0.2 0.8 0.8 <0.8 <0.8 <2 <2

<2 1.7 39.2 <0.2 <0.2 0.7 0.9 <0.8 <0.8 <2 <2

- 3.8 - - - - - - - <1 -

- 3.9 - - - - - - - 3.5 -

- <2 - - - - - - - 4.4 -

- 12.7 - - - - - - - <1 -

- 14.1 - - - - - - - <1 -

- E2.1 - - - - - - - <1 -

<1 9.6 63.9 - - - - - - 1.8 <1

<1 10.8 153.7 - - - - - - 1.1 <1

<1 16.7 44.6 - - - - - - 1.8 1.3

<1 34.5 146 - - - - - - 1.0 <1

0.13 81.2 103.8 - - - - - - <1 <2

0.07 81.3 - - - - - - <1 <2
30 Water-Quality Data Collected from Vallecito Reservoir, Its Inflows and Outflow, Southwestern Colorado, 1999–2002 

Methods of Data Collection

Water-quality samples were collected for the analysis of 

total and dissolved metals, total and dissolved nutrients, DOC, 

UV absorbance, suspended sediment, chlorophyll-a, and fecal 

coliform bacteria. Field measurements of pH, specific conductance, water temperature and dissolved oxygen also were 

made. This section describes how the water-quality samples 

were collected and how the field measurements were made.

Stream Samples and Field Properties

USGS personnel collected water-quality samples from 

Vallecito Creek near Bayfield, Colo., and from Los Piños 

River above Vallecito Reservoir near Bayfield, Colo., 

by using the equal-width-increment sampling method as 

described in section 4.1.1.A of Wilde and Radtke (1998). A 

stream discharge measurement was made at each site on each 

sampling date as described in Rantz and others (1982). Samples for suspended sediment were collected using the equalwidth-increment sampling method described in Edwards and 

Glysson (1988).

Field measurements of pH, specific conductance, water 

temperature, and dissolved oxygen were done at each site on 

each sampling date. Water-quality samples were collected 

in a 4-liter churn, and samples for the determination of pH 

and specific conductance were drawn off from the spigot of 

the churn (before filtering of the water sample) and placed 

into 250-mL beakers. A Beckman pH meter using a Markson 

M788B pH probe was used to measure pH. Specific conductance was measured with a WTW, Model LF 318 specificconductance meter. The pH and specific-conductance meters 

were calibrated once a day using standards obtained from the 

USGS water-quality service unit in Ocala, Fla., following the 

procedures described in USGS TWRI book 9, National Field 

Manual for the Collection of Water-Quality Data (Wilde and 

Radtke, 1998). The pH of the buffers used for the calibration 

of the pH meter was 7.00 and 10.00. Following calibration a 

pH buffer of 4.00 was measured as a check on the calibration. 

The values of the specific-conductance standards used for 

calibration were 50 μS/cm, 100 μS/cm, and 252 μS/cm. Water 

temperature and dissolved oxygen were measured in-situ. An 

ASTM certified mercury thermometer was used for measuring water temperature. A YSI model 50B meter was used for 

measuring dissolved oxygen and was calibrated at each site.

CDPHE personnel collected water-quality samples from 

Vallecito Creek near the mouth and Los Piños River near the 

mouth just upstream from the point where both streams empty 

into Vallecito Reservoir monthly from 1999 to 2002. The 

methods used by the CDPHE to collect and process the waterquality samples are described in the quality-assurance project 

plan for the Colorado nonpoint-source monitoring program 

(1994).

The volunteers collected water-quality samples from 

Los Piños River below Vallecito Reservoir near Bayfield, Colo. 

Because of the high streamflow velocity at this site, discharge 

measurements were not made, and water-quality samples 

were collected from the streambank by immersing the churn 

splitter into the stream. Field measurements of pH, specific 

conductance, water temperature, and dissolved oxygen were 

made by immersing the Hydrolab at a point in the stream near 

the streambank where the probes were fully under the water 

and allowed to stabilize for 1 to 2 minutes before the readings 

were recorded.

Reservoir Samples and Field Properties

The volunteers used a Kemmerer sampler to collect 

water-quality samples 2 feet below the surface (epilimnion) 

and 2 feet from the bottom (hypolimnion) of the Vallecito 

Reservoir South sampling site. Water-quality samples were 

also collected from within the thermocline (the area between 

the epilimnion and the hypolimnion characterized by a steep 

decline in temperature with depth; also known as the metalimnion) when the reservoir was thermally stratified (about 

June–September). The volunteers also collected samples for 

chlorophyll-a analysis; measured the depth of light penetration 

in the reservoir with a Secchi disk (20-centimeter-diameter 

black-and-white disk); and measured depth profiles of pH, 

specific conductance, water temperature, and dissolved oxygen, with a Hydrolab. The volunteers calibrated the Hydrolab 

each day before sample collection according to the methods 

described by Hydrolab Corporation (1993). The pH standards 

used in the calibration of the Hydrolab had values of 7.00 and 

10.00 pH units. The specific-conductance standard used in the 

calibration of the Hydrolab had a value of 100 microsiemens 

per centimeter at 25 degrees Celsius.

Chlorophyll-a measurements are an indication of the 

algal biomass in the reservoir. The amount of algal growth 

in a reservoir can be directly influenced by human activities that release nutrients into the reservoir, such as effluents 

from sewage-treatment plants, leakage from septic systems, and runoff of fertilizers from lawns and agricultural 

Table 5. Fecal coliform and E. coli data collected from sites in and 

near Vallecito Reservoir, 2000–2002.

Date

Vallecito 

Reservoir

South

Vallecito 

Reservoir 

near mouth of 

Los Pinos River

Vallecito 

Reservoir 

near mouth of 

Vallecito Creek

Bacteria 

type

Fecal coliform and E. coli colonies per 100 mL

05/19/2000 <3 <3 <3 Fecal

06/06/2000 <3 <3 <3 Fecal

07/17/2001 <1 <1 <1 E. coli

08/16/2001 <1 3.1 <1 E. coli

09/18/2001 - 1.0 <1 E. coli

10/17/2001 <3 <1 <3 Fecal

05/22/2002 <1 <1 <1 E. coli

07/31/2002 1.0 8.6 7.4 E. coli

08/29/2002 <1 1.0 2.0 E. coli

09/19/2002 1.0 <1 3.1 E. coli

10/29/2002 <1 6.3 1.0 E. coli
Sample Processing and Shipment 31

fields. Samples for chlorophyll-a analysis were collected 

from the Vallecito Reservoir South sampling site using a 

Kemmerer sampler. One liter of sample was filtered through a 

47-millimeter glass-fiber filter that was placed on a filter funnel attached to a hand pump.

The depth of light penetration in the reservoir was 

determined by lowering the Secchi disk into the reservoir 

from the shaded side of the boat until the disk disappeared. The 

Secchi disk was then raised until it became visible again. The 

depth at which the Secchi disk became visible was recorded 

as the depth of light penetration. The chlorophyll-a data, the 

Secchi-disk depth data, and the total phosphorus concentration 

measured within 2 feet of the surface (table 6) can be used to 

evaluate the trophic status of the reservoir according to Carlson’s 

Trophic State Index (Carlson, 1977).

Whenever water-quality samples were collected from 

the Vallecito Reservoir South sampling site, depth profiles 

of pH, specific conductance, water temperature, and dissolved oxygen were measured with the Hydrolab at the south, 

center, and north sampling sites in Vallecito Reservoir (fig. 1). 

Measurements of pH, specific conductance, water temperature, and dissolved oxygen were made at about 3-ft intervals 

with the Hydrolab; the probe was allowed to equilibrate for 

1 to 2 minutes at each measurement point until stabilized 

readings were obtained. Depth profiles of these field properties were also monitored about biweekly from the peak of 

snowmelt runoff in June to the fall turnover of the reservoir 

in October. In August 1996 the concentration of dissolved 

oxygen was near zero near the bottom of the reservoir at the 

south sampling site. Therefore, the biweekly depth profiles 

were completed to document the onset and duration of low 

dissolved-oxygen conditions.

Sample Processing and Shipment

Samples collected by USGS personnel from Vallecito 

Creek near Bayfield, Colo., and from Los Piños River above 

Vallecito Reservoir near Bayfield, Colo., for the analysis 

of inorganic constituents were processed as described in 

Horowitz and others (1994). In 2000, water-quality samples 

for DOC and UV absorbance analysis were collected and 

processed as described in section 5.2.2.C of Wilde and others (1998). Beginning in 2001, DOC and UV absorbance 

samples were processed as described in the USGS Office 

of Water Quality Technical Memorandum 2000.08, “New 

method for particulate carbon and particulate nitrogen” 

(http://water.usgs.gov/admin/memo/QW/qw00.08.html). 

Processing of the samples collected from both of these sites 

occurred in the field immediately after sample collection.

Samples collected by CDPHE personnel from Vallecito 

Creek near the mouth and Los Piños River near the mouth 

were processed according to the quality-assurance project plan 

for the Colorado nonpoint-source monitoring program (1994). 

Processing of the samples collected from both of these sites 

occurred in the field immediately after sample collection.

Initial processing of water-quality samples collected 

from Vallecito Reservoir occurred while the volunteers were 

on the boat. Samples for total metal analyses were poured 

from the Kemmerer sampler into a 1-liter cubitainer provided 

by the USEPA. Samples for total nutrient analyses were 

poured from the Kemmerer sampler into a 125-mL translucent polyethylene bottle provided by the USGS. Samples to 

be analyzed for dissolved metals, dissolved nutrients, DOC, 

and UV absorbance were poured from the Kemmerer sampler 

into 1-liter Teflon bottles provided by the USGS. Back on 

shore, samples collected by the volunteers from the Vallecito 

Reservoir South sampling site and from Los Pinos River below 

Vallecito Reservoir near Bayfield, Colo., were processed in 

the garage of one of the volunteers. The samples for dissolved 

constituents were filtered from the Teflon bottle into other 

sample bottles using the equipment and techniques described 

by Horowitz and others (1994). The dissolved metal samples 

were filtered into a 1-liter cubitainer. The total and dissolved 

metal samples were preserved by adding 1 mL of concentrated nitric acid to the sample. The dissolved nutrient samples 

were filtered into a 125-mL brown polyethylene bottle. The 

DOC samples were filtered into a 125-mL amber glass bottle, 

and the UV absorbance samples were filtered into a separate 

125-mL amber glass bottle.

All samples that were to be analyzed by the USGS and 

USEPA laboratories were placed in disposable trash bags, 

sealed, and then placed in coolers filled with enough ice to 

keep the temperature below 4 degrees Celsius. The glass-fiber 

filter to be analyzed for chlorophyll-a was wrapped in aluminum foil and placed into a separate cooler filled with dry ice. 

Samples were driven back to Denver, Colo., by USGS personnel and delivered to the USGS and USEPA laboratories the 

day after samples were collected.

Table 6. Data needed for the calculation of the Carlson Trophic 

State Index in Vallecito Reservoir, 2000–2002.

[<, less than; E, estimated; -, no data; μg/L, micrograms per liter; mg/L, 

milligrams per liter]

Date

Secchi disk 

depth

(feet)

Chlorophyll-a

(μg/L)

Total 

phosphorus

(mg/L as P)

05/19/2000 - - 0.008

06/06/2000 15 0.67 E0.006

07/11/2000 9.5 <0.1 E0.006

08/22/2000 17 0.84 E0.006

05/17/2001 7 1.04 0.008

06/14/2001 13 0.82 0.009

07/17/2001 13 1.22 <0.004

08/16/2001 12 0.96 E0.0029

09/18/2001 19 <0.10 E0.0022

10/17/2001 14 0.48 0.006

05/22/2002 14 0.46 0.006

07/31/2002 5.5 - 0.010

08/29/2002 12 0.92 0.019

09/19/2002 5.5 0.34 0.040

10/29/2002 - E0.31 0.020
32 Water-Quality Data Collected from Vallecito Reservoir, Its Inflows and Outflow, Southwestern Colorado, 1999–2002 

Laboratory Analysis

All water-quality samples were analyzed for pH, specific 

conductance, alkalinity, dissolved and total metals, dissolved and 

total nutrients (nitrogen and phosphorus), DOC, UV absorbance 

at 254 and 280 nanometers, and suspended sediment (inflow 

sites only) by either the USGS, USEPA, or CDPHE (table 7).

USGS personnel at the NWQL in Lakewood, Colo., 

analyzed water-quality samples collected from (1) Vallecito 

Creek near Bayfield, Colo., for major cations and anions, metals, nutrients, DOC, UV absorbance, and suspended sediment; 

(2) Los Piños River above Vallecito Reservoir near Bayfield, 

Colo., for nutrients, DOC, UV absorbance, and suspended 

sediment; (3) Vallecito Reservoir for nutrients, DOC, UV 

absorbance, and chlorophyll-a; and (4) Los Piños River below 

Vallecito Reservoir near Bayfield, Colo., for nutrients, DOC, 

and UV absorbance. All USGS laboratory analytical methods 

are described in Fishman (1993). Chlorophyll-a concentrations were measured by the NWQL using high-performance 

liquid chromatography followed by fluorometry as described 

in Britton and Greeson (1987).

USEPA personnel analyzed water-quality samples collected from Los Piños River above Vallecito Reservoir near 

Bayfield, Colo., Vallecito Reservoir South sampling site, and 

Los Piños River below Vallecito Reservoir near Bayfield, 

Colo., downstream from the dam for major ions and metals at 

the USEPA laboratory in Golden, Colo. A description of the 

analytical methods used by the USEPA is in Keith (1996).

CDPHE personnel analyzed water-quality samples 

collected from Vallecito Creek near mouth before entering Vallecito Reservoir and Los Piños River above Vallecito 

Reservoir at the CDPHE laboratory in Denver, Colo. The 

analytical methods used by the CDPHE are described in the 

quality-assurance project plan for the Colorado nonpointsource monitoring program (1994). The fecal coliform and 

E. coli bacteria analyses were completed by the San Juan 

Basin Health Department, a division of the CDPHE, using the 

multiple-tube fermentation technique described in Standard 

Methods (American Public Health Association, 1998).

Field Blank and Field Replicate Data 

Collection and Interpretation

Field blanks and field replicates were collected during this study to quantify the errors involved in collecting, 

processing, transporting, and analyzing the samples (tables 8 

and 9). Any measurement has an error associated with it that 

cannot be eliminated, but the error can be quantified so that 

appropriate interpretations of the environmental data can be 

made. Bias and variability are two components of the error 

associated with any water-quality measurement. Bias is the 

systematic error inherent in a method or measurement system 

and may be either positive (contamination) or negative (loss). 

Variability is the random error in independent measurements 

that results from repeated application of the measurement 

process under specified conditions.

In water-quality studies, two types of samples are needed: 

environmental samples and quality-control samples. Environmental samples fulfill the scientific objective(s) of the study. 

Quality-control samples provide estimates of the bias and 

variability of the environmental data. Field blanks are samples 

that are intended to be free of the analyte(s) of interest. Field 

blanks are analyzed to test for bias that could occur from the 

introduction of contamination into environmental samples in 

any stage of the sample-collection, processing, transportation, 

and analysis processes. Field replicates are samples that are 

collected in the same manner as the environmental samples 

and intended to be identical in composition. Field replicates 

are used to estimate the variability of the sample-collection 

and analysis process.

Since 1963, the USGS has been collecting and analyzing water-quality samples from Vallecito Creek as part of the 

Hydrologic Benchmark Network program (Cobb and Biesecker, 

1971). Although water-quality sample-collection methods 

and laboratory analysis methods have changed over the years, 

sample collection and analysis have been done in a consistent 

manner since the USGS began using a parts per billion sampling protocol at Vallecito Creek in 1993 (Horowitz and others, 

1994). The USGS parts per billion sampling protocol is a set of 

guidelines and procedures developed by the USGS to produce 

filtered inorganic-constituent data that are defensible and interpretable at the microgram-per-liter level.

The field blank and field replicate data collected from 

Vallecito Reservoir and the stream sampling sites were analyzed 

separately because the equipment used to collect samples from 

Vallecito Reservoir was different from the equipment used to 

collect samples from the stream sites as described previously. 

However, the water-quality sample-collection procedures and 

the laboratory analysis have been done consistently since 1993. 

Therefore, field blanks and field replicates collected in the 

1996–97 study and in this study from the Vallecito Reservoir 

South sampling site were pooled together, and field blanks 

and field replicates collected in the 1996–97 study and in this 

study from the stream-sampling sites (Vallecito Creek near 

Bayfield, Colo., Los Piños River above Vallecito Reservoir 

near Bayfield, Colo., and Los Piños River below Vallecito 

Reservoir near Bayfield, Colo.) study were pooled to determine 

the magnitude of bias and variability in the environmental data. 

Field blank data and field replicate data should only be pooled 

together from sampling sites at which similar equipment was 

used. However, as the analysis in the next section will show, 

except for total nickel and total zinc in samples collected from 

the Vallecito Reservoir South sampling site, there is a lack of 

evidence of contamination affecting the interpretation of the 

environmental data. Therefore, the environmental data collected from all sampling sites (Vallecito Reservoir and the three 

stream sites) can be considered comparable. The CDPHE did 

not collect field blanks from Vallecito Creek near mouth and 

Los Piños River above Vallecito Reservoir but did collect a 

few field replicates from these sampling sites. It should also be 

noted that if data collection resumes at some point in the future 

using similar sample collection and analysis methods then all 

of the field blank and field replicate data collected since 1993, 

including the field blanks and field replicates collected in this 

study, could be pooled together.
Field Blank and Field Replicate Data Collection and Interpretation 33

Table 7. Constituents and properties measured in the water-quality monitoring of Vallecito Reservoir, its inflows and outflow, 

1999–2002.—Continued

[μS/cm, microsiemens per centimeter at 25o Celsius; mg/L, milligrams per liter; μg/L, micrograms per liter; nm, nanometers; --, no data]

Constituents and properties Reporting limit Analytical laboratory and method

Vallecito Creek near Bayfield, Colorado

pH 0.10 pH units USGS National Water-Quality Laboratory, Fishman, 1993

Specific conductance 2.6 μS/cm USGS National Water-Quality Laboratory, Fishman, 1993

Alkalinity 1 mg/L USGS National Water-Quality Laboratory, Fishman, 1993

Aluminum, dissolved 1.000 μg/L USGS National Water-Quality Laboratory, Fishman, 1993

Calcium, dissolved 0.020 mg/L USGS National Water-Quality Laboratory, Fishman, 1993

Chloride, dissolved 0.29 mg/L USGS National Water-Quality Laboratory, Fishman, 1993

Iron, dissolved 10.000 μg/L USGS National Water-Quality Laboratory, Fishman, 1993

Magnesium, dissolved 0.12 mg/L USGS National Water-Quality Laboratory, Fishman, 1993

Manganese, dissolved 1.000 μg/L USGS National Water-Quality Laboratory, Fishman, 1993

Potassium, dissolved 0.24 mg/L USGS National Water-Quality Laboratory, Fishman, 1993

Silica, dissolved 0.09 mg/L USGS National Water-Quality Laboratory, Fishman, 1993

Sodium, dissolved 0.09 mg/L USGS National Water-Quality Laboratory, Fishman, 1993

Sulfate, dissolved 0.31 mg/L USGS National Water-Quality Laboratory, Fishman, 1993

Zinc, dissolved 1.000 μg/L USGS National Water-Quality Laboratory, Fishman, 1993

Dissolved organic carbon 0.33 mg/L USGS National Water-Quality Laboratory, Fishman, 1993

Ultraviolet absorbance at 254 nm - USGS National Water-Quality Laboratory, Fishman, 1993

Nitrogen, ammonia dissolved 0.002 mg/L USGS National Water-Quality Laboratory, Fishman, 1993

Nitrogen, ammonia + organic nitrogen, total 0.10 mg/L USGS National Water-Quality Laboratory, Fishman, 1993

Nitrogen, ammonia + organic nitrogen, dissolved 0.10 mg/L USGS National Water-Quality Laboratory, Fishman, 1993

Nitrogen, nitrite + nitrate, dissolved 0.005 mg/L USGS National Water-Quality Laboratory, Fishman, 1993

Total phosphorus 0.008 mg/L USGS National Water-Quality Laboratory, Fishman, 1993

Phosphorus, dissolved 0.006 mg/L USGS National Water-Quality Laboratory, Fishman, 1993

Phosphorus, phosphate, ortho, dissolved 0.001 mg/L USGS National Water-Quality Laboratory, Fishman, 1993

Suspended sediment 0.5 mg/L USGS Sediment Laboratory

Vallecito Creek near mouth before entering reservoir

Aluminum, dissolved 50 μg/L CDPHE—USEPA Method 200.7 

Arsenic, dissolved 1 μg/L CDPHE—USEPA Method 200.8 

Cadmium, dissolved 0.3 μg/L CDPHE—USEPA Method 200.8 

Copper, dissolved 4 μg/L CDPHE—USEPA Method 200.8 

Hardness - CDPHE—USEPA Method 200.7 

Iron, total recoverable 10 μg/L CDPHE—USEPA Method 200.7 

Iron, dissolved 10 μg/L CDPHE—USEPA Method 200.7 

Lead, dissolved 1 μg/L CDPHE—USEPA Method 200.8 

Manganese, dissolved 4 μg/L CDPHE—USEPA Method 200.8 

Mercury, dissolved - CDPHE—USEPA Method 245.1

Mercury, total 0.2 μg/L CDPHE—USEPA Method 245.1

Selenium, dissolved 1 μg/L CDPHE—USEPA Method 200.8 

Silver, dissolved 0.2 μg/L CDPHE—USEPA Method 200.8 

Sulfate, total - CDPHE—USEPA Method 300

Zinc, dissolved 10 μg/L CDPHE—USEPA Method 200.8 

Dissolved solids - CDPHE—USEPA Method 160.1

Total suspended solids 10 mg/L CDPHE—USEPA Method 160.2

Total Kjeldahl nitrogen - CDPHE—USEPA Method 351.2

Ammonia, total 0.05 mg/L CDPHE—USEPA Method 350.1

Nitrate + nitrite, total - CDPHE—USEPA Method 353.2

Phosphorus, total - CDPHE—USEPA Method 365.1

Los Piños River above Vallecito Reservoir near Bayfield, CO

Alkalinity 5 mg/L EPA Method 310.1

Aluminum, dissolved and total 45 μg/L EPA Method 200.7 (ICP)

Arsenic, dissolved and total 1 μg/L EPA Method 200.8 (ICP/MS) or 200.9 (AAGF)

Cadmium, dissolved and total 0.5 μg/L EPA Method 200.7 (ICP) or 200.8 (ICP/MS)

Chloride, dissolved and total 0.5 mg/L EPA Method 300

Copper dissolved and total 1 μg/L EPA Method 200.8 (ICP/MS) or 200.9 (AAGF)

Chromium, dissolved and total 0.8 μg/L EPA Method 200.7 (ICP)
34 Water-Quality Data Collected from Vallecito Reservoir, Its Inflows and Outflow, Southwestern Colorado, 1999–2002 

Table 7. Constituents and properties measured in the water-quality monitoring of Vallecito Reservoir, its inflows and outflow, 

1999–2002.—Continued

[μS/cm, microsiemens per centimeter at 25o Celsius; mg/L, milligrams per liter; μg/L, micrograms per liter; nm, nanometers; --, no data]

Constituents and properties Reporting limit Analytical laboratory and method

Los Piños River above Vallecito Reservoir near Bayfield, CO—Continued

Fluoride, dissolved and total 0.2 mg/L EPA Method 300

Iron, dissolved and total 5 μg/L EPA Method 200.7 (ICP)

Lead, dissolved and total 1.5 μg/L EPA Method 200.7 (ICP)

Manganese, dissolved and total 3 μg/L EPA Method 200.7 (ICP) or 200.8 (ICP/MS)

Mercury, dissolved and total 0.2 μg/L EPA Mehtod 245.1 (CVAA)

Nickel, dissolved and total 10 μg/L EPA Method 200.7 (ICP) or 200.8 (ICP/MS)

Potassium, dissolved and total 2 mg/L EPA Method 200.7 (ICP)

Silver, dissolved and total 0.8 μg/L EPA Method 200.7 (ICP)

Silica, dissolved and total 1 mg/L EPA Method I-2700-85

Sulfate, dissolved and total 1.0 mg/L EPA Method 300

Total suspended solids 4 mg/L EPA Method 160.2

Zinc, dissolved and total 4 μg/L EPA Method 200.7 (ICP) or 200.8 (ICP/MS)

Dissolved organic carbon 0.33 mg/L USGS National Water-Quality Laboratory

Ultraviolet absorbance at 254 nm - USGS National Water-Quality Laboratory

Nitrogen, ammonia dissolved 0.002 mg/L USGS National Water-Quality Laboratory

Nitrogen, ammonia + organic nitrogen, total 0.10 mg/L USGS National Water-Quality Laboratory

Nitrogen, ammonia + organic nitrogen, dissolved 0.10 mg/L USGS National Water-Quality Laboratory

Nitrogen, nitrite + nitrate, dissolved 0.005 mg/L USGS National Water-Quality Laboratory

Total phosphorus 0.008 mg/L USGS National Water-Quality Laboratory

Phosphorus, dissolved 0.006 mg/L USGS National Water-Quality Laboratory

Phosphorus, phosphate, ortho, dissolved 0.001 mg/L USGS National Water-Quality Laboratory

Suspended sediment 0.5 mg/L USGS Sediment Laboratory

Los Piños River above Vallecito Reservoir

Aluminum, dissolved 50 μg/L CDPHE—USEPA Method 200.7 

Arsenic, dissolved 1 μg/L CDPHE—USEPA Method 200.8 

Cadmium, dissolved 0.3 μg/L CDPHE—USEPA Method 200.8 

Copper, dissolved 4 μg/L CDPHE—USEPA Method 200.8 

Hardness - CDPHE—USEPA Method 200.7 

Iron, total recoverable 10 μg/L CDPHE—USEPA Method 200.7 

Iron, dissolved 10 μg/L CDPHE—USEPA Method 200.7 

Lead, dissolved 1 μg/L CDPHE—USEPA Method 200.8 

Manganese, dissolved 4 μg/L CDPHE—USEPA Method 200.8 

Mercury, dissolved - CDPHE—USEPA Method 245.1

Mercury, total 0.2 μg/L CDPHE—USEPA Method 245.1

Selenium, dissolved 1 μg/L CDPHE—USEPA Method 200.8 

Silver, dissolved 0.2 μg/L CDPHE—USEPA Method 200.8 

Sulfate, total - CDPHE—USEPA Method 300

Zinc, dissolved 10 μg/L CDPHE—USEPA Method 200.8 

Dissolved solids - CDPHE—USEPA Method 160.1

Total suspended solids 10 mg/L CDPHE—USEPA Method 160.2

Total Kjeldahl nitrogen - CDPHE—USEPA Method 351.2

Ammonia, total 0.05 mg/L CDPHE—USEPA Method 350.1

Nitrate + nitrite, total - CDPHE—USEPA Method 353.2

Phosphorus, total - CDPHE—USEPA Method 365.1

Vallecito Reservoir south sampling site

Alkalinity 5 mg/L EPA Method 310.1

Aluminum, dissolved and total 45 μg/L EPA Method 200.7 (ICP)

Arsenic, dissolved and total 1 μg/L EPA Method 200.8 (ICP/MS) or 200.9 (AAGF)

Cadmium, dissolved and total 0.5 μg/L EPA Method 200.7 (ICP) or 200.8 (ICP/MS)

Chloride, dissolved and total 0.5 mg/L EPA Method 300

Copper dissolved and total 1 μg/L EPA Method 200.8 (ICP/MS) or 200.9 (AAGF)
Field Blank and Field Replicate Data Collection and Interpretation 35

Table 7. Constituents and properties measured in the water-quality monitoring of Vallecito Reservoir, its inflows and outflow, 

1999–2002.—Continued

[μS/cm, microsiemens per centimeter at 25o Celsius; mg/L, milligrams per liter; μg/L, micrograms per liter; nm, nanometers; --, no data]

Constituents and properties Reporting limit Analytical laboratory

Vallecito Reservoir south sampling site—Continued

Chromium, dissolved and total 0.8 μg/L EPA Method 200.7 (ICP)

Fluoride, dissolved and total 0.2 mg/L EPA Method 300

Iron, dissolved and total 5 μg/L EPA Method 200.7 (ICP)

Lead, dissolved and total 1.5 μg/L EPA Method 200.7 (ICP)

Manganese, dissolved and total 3 μg/L EPA Method 200.7 (ICP) or 200.8 (ICP/MS)

Mercury, dissolved and total 0.2 μg/L EPA Mehtod 245.1 (CVAA)

Nickel, dissolved and total 10 μg/L EPA Method 200.7 (ICP) or 200.8 (ICP/MS)

Potassium, dissolved and total 2 mg/L EPA Method 200.7 (ICP)

Silver, dissolved and total 0.8 μg/L EPA Method 200.7 (ICP)

Silica, dissolved and total 1 mg/L EPA Method I-2700-85

Sulfate, dissolved and total 1.0 mg/L EPA Method 300

Total suspended solids 4 mg/L EPA Method 160.2

Zinc, dissolved and total 4 μg/L EPA Method 200.7 (ICP) or 200.8 (ICP/MS)

Dissolved organic carbon 0.33 mg/L USGS National Water-Quality Laboratory

Ultraviolet absorbance at 254 nm - USGS National Water-Quality Laboratory

Nitrogen, ammonia dissolved 0.002 mg/L USGS National Water-Quality Laboratory

Nitrogen, ammonia + organic nitrogen, total 0.10 mg/L USGS National Water-Quality Laboratory

Nitrogen, ammonia + organic nitrogen, dissolved 0.10 mg/L USGS National Water-Quality Laboratory

Nitrogen, nitrite + nitrate, dissolved 0.005 mg/L USGS National Water-Quality Laboratory

Total phosphorus 0.008 mg/L USGS National Water-Quality Laboratory

Phosphorus, dissolved 0.006 mg/L USGS National Water-Quality Laboratory

Phosphorus, phosphate, ortho, dissolved 0.001 mg/L USGS National Water-Quality Laboratory

Chlorophyll-a 0.001 mg/L USGS National Water-Quality Laboratory

Los Piños River below Vallecito Reservoir near Bayfield, CO

Alkalinity 5 mg/L EPA Method 310.1

Aluminum, dissolved and total 45 μg/L EPA Method 200.7 (ICP)

Arsenic, dissolved and total 1 μg/L EPA Method 200.8 (ICP/MS) or 200.9 (AAGF)

Cadmium, dissolved and total 0.5 μg/L EPA Method 200.7 (ICP) or 200.8 (ICP/MS)

Chloride, dissolved and total 0.5 mg/L EPA Method 300

Copper dissolved and total 1 μg/L EPA Method 200.8 (ICP/MS) or 200.9 (AAGF)

Chromium, dissolved and total 0.8 μg/L EPA Method 200.7 (ICP)

Fluoride, dissolved and total 0.2 mg/L EPA Method 300

Iron, dissolved and total 5 μg/L EPA Method 200.7 (ICP)

Lead, dissolved and total 1.5 μg/L EPA Method 200.7 (ICP)

Manganese, dissolved and total 3 μg/L EPA Method 200.7 (ICP) or 200.8 (ICP/MS)

Mercury, dissolved and total 0.2 μg/L EPA Mehtod 245.1 (CVAA)

Nickel, dissolved and total 10 μg/L EPA Method 200.7 (ICP) or 200.8 (ICP/MS)

Potassium, dissolved and total 2 mg/L EPA Method 200.7 (ICP)

Silver, dissolved and total 0.8 μg/L EPA Method 200.7 (ICP)

Silica, dissolved and total 1 mg/L EPA Method I-2700-85

Sulfate, dissolved and total 1.0 mg/L EPA Method 300

Total suspended solids 4 mg/L EPA Method 160.2

Zinc, dissolved and total 4 μg/L EPA Method 200.7 (ICP) or 200.8 (ICP/MS)

Dissolved organic carbon 0.33 mg/L USGS National Water-Quality Laboratory

Ultraviolet absorbance at 254 nm - USGS National Water-Quality Laboratory

Nitrogen, ammonia dissolved 0.002 mg/L USGS National Water-Quality Laboratory

Nitrogen, ammonia + organic nitrogen, total 0.10 mg/L USGS National Water-Quality Laboratory

Nitrogen, ammonia + organic nitrogen, dissolved 0.10 mg/L USGS National Water-Quality Laboratory

Nitrogen, nitrite + nitrate, dissolved 0.005 mg/L USGS National Water-Quality Laboratory

Total phosphorus 0.008 mg/L USGS National Water-Quality Laboratory

Phosphorus, dissolved 0.006 mg/L USGS National Water-Quality Laboratory

Phosphorus, phosphate, ortho, dissolved 0.001 mg/L USGS National Water-Quality Laboratory
36 Water-Quality Data Collected from Vallecito Reservoir, Its Inflows and Outflow, Southwestern Colorado, 1999–2002 

Site name Date Time

Potassium,

total

(mg/L)

Chloride,

dissolved

(mg/L)

Sulfate,

dissolved

(mg/L)

Fluoride,

dissolved

(mg/L)

Bromide,

dissolved

(mg/L)

Silica,

dissolved

(mg/L)

Nitrogen

ammonia,

dissolved

(mg/L as N)

Vallecito Creek near Bayfield, CO 09/06/1996 0930 - - - - - <0.02 <0.002

Los Piños River above Vallecito 

Reservoir near Bayfield, CO

08/13/1996 1450 - - - - - - <0.002

Vallecito Reservoir South 10/23/1996 1015 - - - - - - <0.002

Vallecito Reservoir South 07/01/1997 1040 - - - - - - <0.002

Vallecito Creek near Bayfield, CO 04/21/1999 1300 - <0.01 <0.01 <0.01 <0.01 <0.02 <0.002

Vallecito Creek near Bayfield, CO 08/23/1999 1130 - <0.01 <0.01 <0.01 <0.01 <0.02 <0.002

Vallecito Reservoir South 05/19/2000 1115 <0.2 - - - - - 0.008

Vallecito Reservoir South 06/06/2000 1000 <0.2 - - - - - -

Vallecito Reservoir South 07/11/2000 0930 <0.2 - - - - - -

Vallecito Reservoir South 08/22/2000 0935 - - - - - - -

Vallecito Reservoir South 05/17/2001 1005 - - - - - - 0.009

Vallecito Reservoir South 06/14/2001 0930 <0.2 - - - - - 0.003

Vallecito Reservoir South 07/17/2001 0950 <0.2 - - - - - 0.005

Vallecito Reservoir South 08/16/2001 1005 <0.2 - - - - - -

Vallecito Reservoir South 09/18/2001 1010 0.22 - - - - - 0.002

Vallecito Reservoir South 10/17/2001 1005 <0.2 - - - - - <0.015

Vallecito Reservoir South 05/22/2002 0850 - - - - - - <0.015

Table 8. Field blanks collected from stream and reservoir sampling sites, 1999–2002.

[μS/cm, microsiemens per centimeter; mg/L, milligrams per liter; μg/L, micrograms per liter; <, less than; -, no data]

Site name Date Time

pH,

laboratory

(standard units)

Specific

conductance

(μS/cm)

Calcium,

dissolved

(mg/L)

Magnesium,

dissolved

(mg/L)

Sodium,

dissolved

(mg/L)

Potassium,

dissolved

(mg/L)

Vallecito Creek near Bayfield, CO 09/06/1996 0930 - 1 0.003 <0.001 <0.03 -

Los Piños River above Vallecito 

Reservoir near Bayfield, CO

08/13/1996 1450 - - - - - -

Vallecito Reservoir South 10/23/1996 1015 - - - - - -

Vallecito Reservoir South 07/01/1997 1040 - - - - - -

Vallecito Creek near Bayfield, CO 04/21/1999 1300 5.62 1.17 <0.002 <0.001 <0.025 -

Vallecito Creek near Bayfield, CO 08/23/1999 1130 - 1.06 <0.002 <0.001 <0.025 -

Vallecito Reservoir South 05/19/2000 1115 - - - - - <0.2

Vallecito Reservoir South 06/06/2000 1000 - - - - - -

Vallecito Reservoir South 07/11/2000 0930 - - - - - -

Vallecito Reservoir South 08/22/2000 0935 - - - - - <0.2

Vallecito Reservoir South 05/17/2001 1005 - - - - - -

Vallecito Reservoir South 06/14/2001 0930 - - - - - <0.2

Vallecito Reservoir South 07/17/2001 0950 - - - - - <0.2

Vallecito Reservoir South 08/16/2001 1005 - - - - - <0.2

Vallecito Reservoir South 09/18/2001 1010 - - - - - <0.2

Vallecito Reservoir South 10/17/2001 1005 - - - - - <0.2

Vallecito Reservoir South 05/22/2002 0850 - - - - - -
Field Blank and Field Replicate Data Collection and Interpretation 37

Table 8. Field blanks collected from stream and reservoir sampling sites, 1999–2002.—Continued

[μS/cm, microsiemens per centimeter; mg/L, milligrams per liter; μg/L, micrograms per liter; <, less than; -, no data]

Site name Date Time

Nitrogen

nitrite,

dissolved

(mg/L as N)

Nitrogen

nitrate,

dissolved

(mg/L as N)

Nitrogen

NO2 + NO3,

dissolved

(mg/L as N)

Nitrogen

Amn + Org,

dissolved

(mg/L as N)

Nitrogen

Amn + Org,

total

(mg/L as N)

Vallecito Creek near Bayfield, CO 09/06/1996 0930 <0.001 - <0.005 - -

Los Piños River above Vallecito 

Reservoir near Bayfield, CO

08/13/1996 1450 <0.001 - <0.005 <0.2 <0.2

Vallecito Reservoir South 10/23/1996 1015 <0.001 - <0.005 <0.2 <0.2

Vallecito Reservoir South 07/01/1997 1040 0.001 - 0.005 0.233 <0.2

Vallecito Creek near Bayfield, CO 04/21/1999 1300 <0.001 <0.01 0.004 - -

Vallecito Creek near Bayfield, CO 08/23/1999 1130 <0.001 <0.01 <0.005 - -

Vallecito Reservoir South 05/19/2000 1115 <0.001 - <0.005 <0.1 <0.1

Vallecito Reservoir South 06/06/2000 1000 - - - - -

Vallecito Reservoir South 07/11/2000 0930 - - - - -

Vallecito Reservoir South 08/22/2000 0935 - - - - -

Vallecito Reservoir South 05/17/2001 1005 <0.001 - <0.005 <0.1 0.041

Vallecito Reservoir South 06/14/2001 0930 <0.001 - <0.005 <0.1 <0.08

Vallecito Reservoir South 07/17/2001 0950 0.001 - 0.006 <0.1 <0.08

Vallecito Reservoir South 08/16/2001 1005 - - - - -

Vallecito Reservoir South 09/18/2001 1010 0.001 - 0.014 0.081 0.126

Vallecito Reservoir South 10/17/2001 1005 <0.002 - <0.013 <0.1 <0.1

Vallecito Reservoir South 05/22/2002 0850 <0.002 - <0.013 <0.1 <0.1

Site name Date Time

Phosphorus,

total

(mg/L as P)

Phosphorus,

dissolved

(mg/L as P)

Phosphorus,

ortho,

dissolved

(mg/L as P)

Organic

carbon,

dissolved

(mg/L as C)

UV

absorbance

(254 nm)

Vallecito Creek near Bayfield, CO 09/06/1996 0930 - - 0.001 - -

Los Piños River above Vallecito 

Reservoir near Bayfield, CO

08/13/1996 1450 <0.001 0.003 <0.001 - -

Vallecito Reservoir South 10/23/1996 1015 0.006 0.001 <0.001 - -

Vallecito Reservoir South 07/01/1997 1040 0.001 0.001 0.002 - -

Vallecito Creek near Bayfield, CO 04/21/1999 1300 - - 0.001 <0.1 -

Vallecito Creek near Bayfield, CO 08/23/1999 1130 - - <0.001 <0.1 -

Vallecito Reservoir South 05/19/2000 1115 <0.008 <0.006 <0.001 - -

Vallecito Reservoir South 06/06/2000 1000 - - - - -

Vallecito Reservoir South 07/11/2000 0930 - - - - -

Vallecito Reservoir South 08/22/2000 0935 - - - - -

Vallecito Reservoir South 05/17/2001 1005 <0.004 <0.006 <0.007 2.3 0.002

Vallecito Reservoir South 06/14/2001 0930 <0.004 <0.006 <0.007 1.7 0.002

Vallecito Reservoir South 07/17/2001 0950 <0.004 <0.006 <0.007 0.4 0.003

Vallecito Reservoir South 08/16/2001 1005 - - - - -

Vallecito Reservoir South 09/18/2001 1010 0.003 <0.006 <0.007 - -

Vallecito Reservoir South 10/17/2001 1005 <0.004 <0.004 <0.007 - -

Vallecito Reservoir South 05/22/2002 0850 0.003 <0.004 <0.007 0.3 -
38 Water-Quality Data Collected from Vallecito Reservoir, Its Inflows and Outflow, Southwestern Colorado, 1999–2002 

Table 8. Field blanks collected from stream and reservoir sampling sites, 1999–2002.—Continued

[μS/cm, microsiemens per centimeter; mg/L, milligrams per liter; μg/L, micrograms per liter; <, less than; -, no data]

Site name Date Time

Aluminum,

dissolved

(μg/L)

Aluminum,

total

(μg/L)

Antimony,

dissolved

(μg/L)

Arsenic,

dissolved

(μg/L)

Arsenic,

total

(μg/L)

Barium,

dissolved

(μg/L)

Vallecito Creek near Bayfield, CO 09/06/1996 0930 2.2 - <0.2 - - <0.2

Los Piños River above Vallecito 

Reservoir near Bayfield, CO

08/13/1996 1450 - - - - - -

Vallecito Reservoir South 10/23/1996 1015 - - - - - -

Vallecito Reservoir South 07/01/1997 1040 - - - - - -

Vallecito Creek near Bayfield, CO 04/21/1999 1300 <0.3 - <0.2 - - <0.2

Vallecito Creek near Bayfield, CO 08/23/1999 1130 <0.3 - <0.2 - - <0.2

Vallecito Reservoir South 05/19/2000 1115 <10 <10 - <1 <1 -

Vallecito Reservoir South 06/06/2000 1000 - <10 - - <1 -

Vallecito Reservoir South 07/11/2000 0930 - <10 - - <1 -

Vallecito Reservoir South 08/22/2000 0935 <10 - - <1 - -

Vallecito Reservoir South 05/17/2001 1005 - - - - - -

Vallecito Reservoir South 06/14/2001 0930 <10 <10 - <1 <1 -

Vallecito Reservoir South 07/17/2001 0950 <10 <10 - <1 <1 -

Vallecito Reservoir South 08/16/2001 1005 <10 <10 - <1 <1 -

Vallecito Reservoir South 09/18/2001 1010 <10 <10 - <1 <1 -

Vallecito Reservoir South 10/17/2001 1005 <10 <10 - <1 <1 -

Vallecito Reservoir South 05/22/2002 0850 <15 - - - - -

Site name Date Time

Beryllium,

dissolved

(μg/L)

Boron,

dissolved

(μg/L)

Cadmium,

dissolved

(μg/L)

Cadmium,

total

(μg/L)

Chromium,

dissolved

(μg/L)

Chromium,

total

(μg/L)

Vallecito Creek near Bayfield, CO 09/06/1996 0930 <0.2 3 <0.3 - <0.2 -

Los Piños River above Vallecito 

Reservoir near Bayfield, CO

08/13/1996 1450 - - - - - -

Vallecito Reservoir South 10/23/1996 1015 - - - - - -

Vallecito Reservoir South 07/01/1997 1040 - - - - - -

Vallecito Creek near Bayfield, CO 04/21/1999 1300 <0.2 <2.0 <0.3 - <0.2 -

Vallecito Creek near Bayfield, CO 08/23/1999 1130 <0.2 <2.0 <0.3 - <0.2 -

Vallecito Reservoir South 05/19/2000 1115 - - <0.2 <0.2 <0.4 <0.4

Vallecito Reservoir South 06/06/2000 1000 - - - <0.2 - <0.4

Vallecito Reservoir South 07/11/2000 0930 - - - <0.2 - <0.4

Vallecito Reservoir South 08/22/2000 0935 - - <0.2 - <0.4 -

Vallecito Reservoir South 05/17/2001 1005 - - - - - -

Vallecito Reservoir South 06/14/2001 0930 - - <0.3 <0.3 <0.4 <0.4

Vallecito Reservoir South 07/17/2001 0950 - - <0.3 <0.3 <0.4 <0.4

Vallecito Reservoir South 08/16/2001 1005 - - <0.3 <0.3 <0.4 <0.4

Vallecito Reservoir South 09/18/2001 1010 - - <0.3 <0.3 <0.4 <0.4

Vallecito Reservoir South 10/17/2001 1005 - - <0.3 <0.3 <0.4 <0.4

Vallecito Reservoir South 05/22/2002 0850 - - - - - -
Field Blank and Field Replicate Data Collection and Interpretation 39

Table 8. Field blanks collected from stream and reservoir sampling sites, 1999–2002.—Continued

[μS/cm, microsiemens per centimeter; mg/L, milligrams per liter; μg/L, micrograms per liter; <, less than; -, no data]

Site name Date Time

Cobalt,

dissolved

(μg/L)

Copper,

dissolved

(μg/L)

Copper,

total

(μg/L)

Iron,

dissolved

(μg/L)

Iron,

total

(μg/L)

Lead,

dissolved

(μg/L)

Vallecito Creek near Bayfield, CO 09/06/1996 0930 <0.2 <0.2 - <3 - <0.3

Los Piños River above Vallecito 

Reservoir near Bayfield, CO

08/13/1996 1450 - - - - - -

Vallecito Reservoir South 10/23/1996 1015 - - - - - -

Vallecito Reservoir South 07/01/1997 1040 - - - - - -

Vallecito Creek near Bayfield, CO 04/21/1999 1300 <0.2 <0.2 - <3.0 - <0.3

Vallecito Creek near Bayfield, CO 08/23/1999 1130 <0.2 <0.2 - <3.0 - <0.3

Vallecito Reservoir South 05/19/2000 1115 - 0.9 <0.6 <4 <4 <1.5

Vallecito Reservoir South 06/06/2000 1000 - - <2 - <4 -

Vallecito Reservoir South 07/11/2000 0930 - - <2 - <4 -

Vallecito Reservoir South 08/22/2000 0935 - <2 - <4 - <1.5

Vallecito Reservoir South 05/17/2001 1005 - - - - - -

Vallecito Reservoir South 06/14/2001 0930 - 1.0 1.0 <4 <4 <2

Vallecito Reservoir South 07/17/2001 0950 - 3.0 1.0 <4 <4 <2

Vallecito Reservoir South 08/16/2001 1005 - 1.2 0.7 <4 <4 <2

Vallecito Reservoir South 09/18/2001 1010 - 0.5 1.9 <4 <4 <2

Vallecito Reservoir South 10/17/2001 1005 - 0.7 0.5 <4 <4 <2

Vallecito Reservoir South 05/22/2002 0850 - - - <10 - -

Site name Date Time

Lead

total

(μg/L)

Manganese,

dissolved

(μg/L)

Manganese,

total

(μg/L)

Mercury,

dissolved

(μg/L)

Mercury,

total

(μg/L)

Molybdenum,

dissolved

(μg/L as Mo)

Vallecito Creek near Bayfield, CO 09/06/1996 0930 - <0.1 - - - <0.2

Los Piños River above Vallecito 

Reservoir near Bayfield, CO

08/13/1996 1450 - - - - - -

Vallecito Reservoir South 10/23/1996 1015 - - - - - -

Vallecito Reservoir South 07/01/1997 1040 - - - - - -

Vallecito Creek near Bayfield, CO 04/21/1999 1300 - <0.1 - - - <0.2

Vallecito Creek near Bayfield, CO 08/23/1999 1130 - <0.1 - - - <0.2

Vallecito Reservoir South 05/19/2000 1115 <1.5 0.3 <0.3 - <0.02 -

Vallecito Reservoir South 06/06/2000 1000 <1.5 - <0.3 - <0.02 -

Vallecito Reservoir South 07/11/2000 0930 <1.5 - <0.3 - <0.02 -

Vallecito Reservoir South 08/22/2000 0935 - <0.3 - - - -

Vallecito Reservoir South 05/17/2001 1005 - - - - - -

Vallecito Reservoir South 06/14/2001 0930 <2 <0.4 <0.4 <0.1 <0.1 -

Vallecito Reservoir South 07/17/2001 0950 <2 <0.4 <0.4 <0.2 <0.2 -

Vallecito Reservoir South 08/16/2001 1005 <2 <0.4 <0.4 <0.2 <0.2 -

Vallecito Reservoir South 09/18/2001 1010 <2 <0.4 <0.4 <0.2 <0.2 -

Vallecito Reservoir South 10/17/2001 1005 <2 <0.4 <0.4 <0.2 <0.2 -

Vallecito Reservoir South 05/22/2002 0850 - <2 - - - -
40 Water-Quality Data Collected from Vallecito Reservoir, Its Inflows and Outflow, Southwestern Colorado, 1999–2002 

Table 8. Field blanks collected from stream and reservoir sampling sites, 1999–2002.—Continued

[μS/cm, microsiemens per centimeter; mg/L, milligrams per liter; μg/L, micrograms per liter; <, less than; -, no data]

Site name Date Time

Nickel,

dissolved

(μg/L)

Nickel,

total

(μg/L)

Selenium,

dissolved

(μg/L)

Selenium,

total

(μg/L)

Silver,

dissolved

(μg/L)

Silver,

total

(μg/L)

Vallecito Creek near Bayfield, CO 09/06/1996 0930 <0.5 - - - <0.2 -

Los Piños River above Vallecito 

Reservoir near Bayfield, CO

08/13/1996 1450 - - - - - -

Vallecito Reservoir South 10/23/1996 1015 - - - - - -

Vallecito Reservoir South 07/01/1997 1040 - - - - - -

Vallecito Creek near Bayfield, CO 04/21/1999 1300 <0.5 - - - <0.2 -

Vallecito Creek near Bayfield, CO 08/23/1999 1130 <0.5 - - - <0.2 -

Vallecito Reservoir South 05/19/2000 1115 <0.4 <0.4 <1 <1 <0.2 <0.2

Vallecito Reservoir South 06/06/2000 1000 - <0.4 - - - <0.8

Vallecito Reservoir South 07/11/2000 0930 - 2.6 - - - <0.8

Vallecito Reservoir South 08/22/2000 0935 <0.4 - - - <0.8 -

Vallecito Reservoir South 05/17/2001 1005 - - - - - -

Vallecito Reservoir South 06/14/2001 0930 <0.4 <0.4 - - <0.8 <0.8

Vallecito Reservoir South 07/17/2001 0950 <0.4 <0.4 - - <0.8 <0.8

Vallecito Reservoir South 08/16/2001 1005 <0.4 <0.4 - - <0.8 <0.8

Vallecito Reservoir South 09/18/2001 1010 <0.4 0.4 - - <0.8 <0.8

Vallecito Reservoir South 10/17/2001 1005 <0.4 <0.4 - - <0.8 <0.8

Vallecito Reservoir South 05/22/2002 0850 - - - - - -

Site name Date Time

Strontium,

dissolved

(μg/L)

Thallium,

dissolved

(μg/L)

Thallium,

total

(μg/L)

Uranium,

dissolved

(μg/L)

Zinc,

dissolved

(μg/L)

Zinc,

total

(μg/L)

Vallecito Creek near Bayfield, CO 09/06/1996 0930 <0.1 - - <0.2 <0.5 -

Los Piños River above Vallecito 

Reservoir near Bayfield, CO

08/13/1996 1450 - - - - - -

Vallecito Reservoir South 10/23/1996 1015 - - - - - -

Vallecito Reservoir South 07/01/1997 1040 - - - - - -

Vallecito Creek near Bayfield, CO 04/21/1999 1300 <0.1 <0.1 - <0.2 <0.5 -

Vallecito Creek near Bayfield, CO 08/23/1999 1130 <0.1 <0.1 - <0.2 <0.5 -

Vallecito Reservoir South 05/19/2000 1115 - - - - <2 3.1

Vallecito Reservoir South 06/06/2000 1000 - - - - - <2

Vallecito Reservoir South 07/11/2000 0930 - - - - - 8.3

Vallecito Reservoir South 08/22/2000 0935 - - - - <2 -

Vallecito Reservoir South 05/17/2001 1005 - - - - - -

Vallecito Reservoir South 06/14/2001 0930 - - - - <2 <2

Vallecito Reservoir South 07/17/2001 0950 - - - - <2 <2

Vallecito Reservoir South 08/16/2001 1005 - - - - <2 <2

Vallecito Reservoir South 09/18/2001 1010 - - - - <2 <2

Vallecito Reservoir South 10/17/2001 1005 - - - - <2 <2

Vallecito Reservoir South 05/22/2002 0850 - - - - <1 -
Field Blank and Field Replicate Data Collection and Interpretation 41

Table 9. Field replicates collected from stream and reservoir sampling sites, 1999–2002.

[μS/cm, microsiemens per centimeter; mg/L, milligrams per liter; μg/L, micrograms per liter; nm, nanometers; <, less than; -, no data]

Site name Date Time Sample

type

pH

laboratory

(standard

units)

pH

field

(standard 

units)

Specific

conductance

laboratory

(μS/cm)

Specific

conductance

field

(μS/cm)

Calcium

dissolved

(mg/L)

Magnesium

dissolved

(mg/L)

Los Pinos River above Vallecito 

Reservoir near Bayfield, CO

08/13/1996 1520 Environmental - - - - - -

Los Pinos River above Vallecito 

Reservoir near Bayfield, CO

08/13/1996 1525 Replicate - - - - - -

Vallecito Reservoir South @ 2 feet 10/23/1996 1035 Environmental - - - - - -

Vallecito Reservoir South @ 2 feet 10/23/1996 1100 Replicate - - - - - -

Vallecito Reservoir Center @ 2 feet 07/01/1997 1330 Environmental - - - - - -

Vallecito Reservoir Center @ 2 feet 07/01/1997 1335 Replicate - - - - - -

Los Pinos River below Vallecito 

Reservoir near Bayfield , CO

07/02/1997 910 Environmental - - - - - -

Los Pinos River below Vallecito 

Reservoir near Bayfield , CO

07/02/1997 915 Replicate - - - - - -

Vallecito Creek near Bayfield, CO 05/13/1999 10:45 Environmental 7.88 7.65 71.3 70.0 9.04 1.85

Vallecito Creek near Bayfield, CO 05/13/1999 10:46 Replicate 7.65 7.72 70.9 70.0 - -

Vallecito Creek near Bayfield, CO 06/08/1999 10:45 Environmental 7.32 7.47 56 53 6.99 1.55

Vallecito Creek near Bayfield, CO 06/08/1999 10:46 Replicate - 7.47 - 53 - -

Vallecito Reservoir North @ 31.5 feet 08/24/1999 9:30 Environmental - - - - - -

Vallecito Reservoir North @ 31.5 feet 08/24/1999 9:35 Replicate - - - - - -

Vallecito Reservoir South @ 53 feet 09/21/1999 9:32 Environmental - - - - - -

Vallecito Reservoir South @ 53 feet 09/21/1999 9:37 Replicate - - - - - -

Site name Date Time Sample

type

Sodium

dissolved

(mg/L)

Potassium

dissolved

(mg/L)

Potassium

total

(mg/L)

Bicarbonate

dissolved

(mg/L)

Alkalinity

dissolved

(mg/L as

CaCO3)

Chloride

dissolved

(mg/L)

Los Pinos River above Vallecito 

Reservoir near Bayfield, CO

08/13/1996 1520 Environmental - - - - - -

Los Pinos River above Vallecito 

Reservoir near Bayfield, CO

08/13/1996 1525 Replicate - - - - - -

Vallecito Reservoir South @ 2 feet 10/23/1996 1035 Environmental - - - - - -

Vallecito Reservoir South @ 2 feet 10/23/1996 1100 Replicate - - - - - -

Vallecito Reservoir Center @ 2 feet 07/01/1997 1330 Environmental - - - - - -

Vallecito Reservoir Center @ 2 feet 07/01/1997 1335 Replicate - - - - - -

Los Pinos River below Vallecito 

Reservoir near Bayfield , CO

07/02/1997 910 Environmental - - - - - -

Los Pinos River below Vallecito 

Reservoir near Bayfield , CO

07/02/1997 915 Replicate - - - - - -

Vallecito Creek near Bayfield, CO 05/13/1999 10:45 Environmental 0.70 0.46 - 32.9 27 0.26

Vallecito Creek near Bayfield, CO 05/13/1999 10:46 Replicate - - 32.9 27 -

Vallecito Creek near Bayfield, CO 06/08/1999 10:45 Environmental 0.48 0.31 - 20.7 17 0.33

Vallecito Creek near Bayfield, CO 06/08/1999 10:46 Replicate - - - - - -

Vallecito Reservoir North @ 31.5 feet 08/24/1999 9:30 Environmental - - 0.7 - - -

Vallecito Reservoir North @ 31.5 feet 08/24/1999 9:35 Replicate - - 0.7 - - -

Vallecito Reservoir South @ 53 feet 09/21/1999 9:32 Environmental - - 0.7 - - -

Vallecito Reservoir South @ 53 feet 09/21/1999 9:37 Replicate - - 0.7 - - -
42 Water-Quality Data Collected from Vallecito Reservoir, Its Inflows and Outflow, Southwestern Colorado, 1999–2002 

Table 9. Field replicates collected from stream and reservoir sampling sites, 1999–2002.—Continued

[μS/cm, microsiemens per centimeter; mg/L, milligrams per liter; μg/L, micrograms per liter; nm, nanometers; <, less than; -, no data]

Site name Date Time Sample

type

Sulfate,

dissolved

(mg/L)

Fluoride,

dissolved

(mg/L)

Silica,

dissolved

(mg/L)

Aluminum,

dissolved

(μg/L)

Aluminum,

total

(μg/L)

Antimony,

dissolved

(μg/L)

Los Pinos River above Vallecito 

Reservoir near Bayfield, CO

08/13/1996 1520 Environmental - - - - - -

Los Pinos River above Vallecito 

Reservoir near Bayfield, CO

08/13/1996 1525 Replicate - - - - - -

Vallecito Reservoir South @ 2 feet 10/23/1996 1035 Environmental - - - - - -

Vallecito Reservoir South @ 2 feet 10/23/1996 1100 Replicate - - - - - -

Vallecito Reservoir Center @ 2 feet 07/01/1997 1330 Environmental - - - - - -

Vallecito Reservoir Center @ 2 feet 07/01/1997 1335 Replicate - - - - - -

Los Pinos River below Vallecito 

Reservoir near Bayfield , CO

07/02/1997 910 Environmental - - - - - -

Los Pinos River below Vallecito 

Reservoir near Bayfield , CO

07/02/1997 915 Replicate - - - - - -

Vallecito Creek near Bayfield, CO 05/13/1999 10:45 Environmental 4.90 0.20 3.61 45.0 - <1.0

Vallecito Creek near Bayfield, CO 05/13/1999 10:46 Replicate - - - 44.8 - <1.0

Vallecito Creek near Bayfield, CO 06/08/1999 10:45 Environmental 5.72 0.15 2.73 45.7 - <1.0

Vallecito Creek near Bayfield, CO 06/08/1999 10:46 Replicate - - - - - -

Vallecito Reservoir North @ 31.5 feet 08/24/1999 9:30 Environmental - - - - 50 -

Vallecito Reservoir North @ 31.5 feet 08/24/1999 9:35 Replicate - - - - 55 -

Vallecito Reservoir South @ 53 feet 09/21/1999 9:32 Environmental - - - - <45 -

Vallecito Reservoir South @ 53 feet 09/21/1999 9:37 Replicate - - - - <45 -

Site name Date Time Sample

type

Antimony,

total

(μg/L)

Arsenic,

dissolved

(μg/L)

Arsenic,

total

(μg/L)

Barium,

dissolved

(μg/L)

Beryllium,

dissolved

(μg/L)

Cadmium,

dissolved

(μg/L)

Los Pinos River above Vallecito 

Reservoir near Bayfield, CO

08/13/1996 1520 Environmental - - - - - -

Los Pinos River above Vallecito 

Reservoir near Bayfield, CO

08/13/1996 1525 Replicate - - - - - -

Vallecito Reservoir South @ 2 feet 10/23/1996 1035 Environmental - - - - - -

Vallecito Reservoir South @ 2 feet 10/23/1996 1100 Replicate - - - - - -

Vallecito Reservoir Center @ 2 feet 07/01/1997 1330 Environmental - - - - - -

Vallecito Reservoir Center @ 2 feet 07/01/1997 1335 Replicate - - - - - -

Los Pinos River below Vallecito 

Reservoir near Bayfield , CO

07/02/1997 910 Environmental - - - - - -

Los Pinos River below Vallecito 

Reservoir near Bayfield , CO

07/02/1997 915 Replicate - - - - - -

Vallecito Creek near Bayfield, CO 05/13/1999 10:45 Environmental - <1.0 - 13.3 <1.0 <1.0

Vallecito Creek near Bayfield, CO 05/13/1999 10:46 Replicate - <1.0 - 13.3 <1.0 <1.0

Vallecito Creek near Bayfield, CO 06/08/1999 10:45 Environmental - <1.0 - 9.96 <1.0 <1.0

Vallecito Creek near Bayfield, CO 06/08/1999 10:46 Replicate - - - - - -

Vallecito Reservoir North @ 31.5 feet 08/24/1999 9:30 Environmental - - <2 - - -

Vallecito Reservoir North @ 31.5 feet 08/24/1999 9:35 Replicate - - <2 - - -

Vallecito Reservoir South @ 53 feet 09/21/1999 9:32 Environmental - - <2 - - -

Vallecito Reservoir South @ 53 feet 09/21/1999 9:37 Replicate - - <2 - - -
Field Blank and Field Replicate Data Collection and Interpretation 43

Table 9. Field replicates collected from stream and reservoir sampling sites, 1999–2002.—Continued

[μS/cm, microsiemens per centimeter; mg/L, milligrams per liter; μg/L, micrograms per liter; nm, nanometers; <, less than; -, no data]

Site name Date Time Sample

type

Cadmium,

total

(μg/L)

Chromium,

dissolved

(μg/L)

Chromium,

total

(μg/L)

Cobalt,

dissolved

(μg/L)

Copper,

dissolved

(μg/L)

Copper,

total

(μg/L)

Los Pinos River above Vallecito 

Reservoir near Bayfield, CO

08/13/1996 1520 Environmental - - - - - -

Los Pinos River above Vallecito 

Reservoir near Bayfield, CO

08/13/1996 1525 Replicate - - - - - -

Vallecito Reservoir South @ 2 feet 10/23/1996 1035 Environmental - - - - - -

Vallecito Reservoir South @ 2 feet 10/23/1996 1100 Replicate - - - - - -

Vallecito Reservoir Center @ 2 feet 07/01/1997 1330 Environmental - - - - - -

Vallecito Reservoir Center @ 2 feet 07/01/1997 1335 Replicate - - - - - -

Los Pinos River below Vallecito 

Reservoir near Bayfield , CO

07/02/1997 910 Environmental - - - - - -

Los Pinos River below Vallecito 

Reservoir near Bayfield , CO

07/02/1997 915 Replicate - - - - - -

Vallecito Creek near Bayfield, CO 05/13/1999 10:45 Environmental - <1.0 - <1.0 <1.0 -

Vallecito Creek near Bayfield, CO 05/13/1999 10:46 Replicate - <1.0 - <1.0 <1.0 -

Vallecito Creek near Bayfield, CO 06/08/1999 10:45 Environmental - - - <1.0 <1.0 -

Vallecito Creek near Bayfield, CO 06/08/1999 10:46 Replicate - - - - - -

Vallecito Reservoir North @ 31.5 feet 08/24/1999 9:30 Environmental <0.1 - <5 - - <1

Vallecito Reservoir North @ 31.5 feet 08/24/1999 9:35 Replicate <0.1 - <5 - - <1

Vallecito Reservoir South @ 53 feet 09/21/1999 9:32 Environmental <0.1 - <5 - - <1

Vallecito Reservoir South @ 53 feet 09/21/1999 9:37 Replicate <0.1 - <5 - - <1

Site name Date Time Sample

type

Iron,

dissolved

(μg/L)

Iron,

total

(μg/L)

Lead,

dissolved

(μg/L)

Lead,

total

(μg/L)

Manganese,

dissolved

(μg/L)

Manganese,

total

(μg/L)

Los Pinos River above Vallecito 

Reservoir near Bayfield, CO

08/13/1996 1520 Environmental - - - - - -

Los Pinos River above Vallecito 

Reservoir near Bayfield, CO

08/13/1996 1525 Replicate - - - - - -

Vallecito Reservoir South @ 2 feet 10/23/1996 1035 Environmental - - - - - -

Vallecito Reservoir South @ 2 feet 10/23/1996 1100 Replicate - - - - - -

Vallecito Reservoir Center @ 2 feet 07/01/1997 1330 Environmental - - - - - -

Vallecito Reservoir Center @ 2 feet 07/01/1997 1335 Replicate - - - - - -

Los Pinos River below Vallecito 

Reservoir near Bayfield , CO

07/02/1997 910 Environmental - - - - - -

Los Pinos River below Vallecito 

Reservoir near Bayfield , CO

07/02/1997 915 Replicate - - - - - -

Vallecito Creek near Bayfield, CO 05/13/1999 10:45 Environmental 11.4 - <1.0 - 8.11 -

Vallecito Creek near Bayfield, CO 05/13/1999 10:46 Replicate - - <1.0 - 8.24 -

Vallecito Creek near Bayfield, CO 06/08/1999 10:45 Environmental 12.6 - <1.0 - 20.0 -

Vallecito Creek near Bayfield, CO 06/08/1999 10:46 Replicate - - - - - -

Vallecito Reservoir North @ 31.5 feet 08/24/1999 9:30 Environmental - 70 - <1 - 7

Vallecito Reservoir North @ 31.5 feet 08/24/1999 9:35 Replicate - 70 - <1 - 8

Vallecito Reservoir South @ 53 feet 09/21/1999 9:32 Environmental - 50 - <1 - 20

Vallecito Reservoir South @ 53 feet 09/21/1999 9:37 Replicate - 50 - <1 - 20
44 Water-Quality Data Collected from Vallecito Reservoir, Its Inflows and Outflow, Southwestern Colorado, 1999–2002 

Table 9. Field replicates collected from stream and reservoir sampling sites, 1999–2002.—Continued

[μS/cm, microsiemens per centimeter; mg/L, milligrams per liter; μg/L, micrograms per liter; nm, nanometers; <, less than; -, no data]

Site name Date Time Sample

type

Mercury,

total

(μg/L)

Molybdenum,

dissolved

(μg/L)

Nickel,

dissolved

(μg/L)

Nickel,

total

(μg/L)

Selenium,

dissolved

(μg/L)

Los Pinos River above Vallecito 

Reservoir near Bayfield, CO

08/13/1996 1520 Environmental - - - - -

Los Pinos River above Vallecito 

Reservoir near Bayfield, CO

08/13/1996 1525 Replicate - - - - -

Vallecito Reservoir South @ 2 feet 10/23/1996 1035 Environmental - - - - -

Vallecito Reservoir South @ 2 feet 10/23/1996 1100 Replicate - - - - -

Vallecito Reservoir Center @ 2 feet 07/01/1997 1330 Environmental - - - - -

Vallecito Reservoir Center @ 2 feet 07/01/1997 1335 Replicate - - - - -

Los Pinos River below Vallecito 

Reservoir near Bayfield , CO

07/02/1997 910 Environmental - - - - -

Los Pinos River below Vallecito 

Reservoir near Bayfield , CO

07/02/1997 915 Replicate - - - - -

Vallecito Creek near Bayfield, CO 05/13/1999 10:45 Environmental - <1.0 <1.0 - <1.0

Vallecito Creek near Bayfield, CO 05/13/1999 10:46 Replicate - <1.0 1.04 - <1.0

Vallecito Creek near Bayfield, CO 06/08/1999 10:45 Environmental - <1.0 1.48 -

Vallecito Creek near Bayfield, CO 06/08/1999 10:46 Replicate - - - - -

Vallecito Reservoir North @ 31.5 feet 08/24/1999 9:30 Environmental - - - <5 -

Vallecito Reservoir North @ 31.5 feet 08/24/1999 9:35 Replicate - - - <5 -

Vallecito Reservoir South @ 53 feet 09/21/1999 9:32 Environmental <0.1 - - <5 -

Vallecito Reservoir South @ 53 feet 09/21/1999 9:37 Replicate <0.1 - - <5 -

Site name Date Time Sample

type

Silver,

dissolved

(μg/L)

Silver,

total

(μg/L)

Uranium,

dissolved

(μg/L)

Zinc,

dissolved

(μg/L)

Zinc,

total

(μg/L)

Los Pinos River above Vallecito 

Reservoir near Bayfield, CO

08/13/1996 1520 Environmental - - - - -

Los Pinos River above Vallecito 

Reservoir near Bayfield, CO

08/13/1996 1525 Replicate - - - - -

Vallecito Reservoir South @ 2 feet 10/23/1996 1035 Environmental - - - - -

Vallecito Reservoir South @ 2 feet 10/23/1996 1100 Replicate - - - - -

Vallecito Reservoir Center @ 2 feet 07/01/1997 1330 Environmental - - - - -

Vallecito Reservoir Center @ 2 feet 07/01/1997 1335 Replicate - - - - -

Los Pinos River below Vallecito 

Reservoir near Bayfield , CO

07/02/1997 910 Environmental - - - - -

Los Pinos River below Vallecito 

Reservoir near Bayfield , CO

07/02/1997 915 Replicate - - - - -

Vallecito Creek near Bayfield, CO 05/13/1999 10:45 Environmental <1.0 - <1.0 1.17 -

Vallecito Creek near Bayfield, CO 05/13/1999 10:46 Replicate <1.0 - <1.0 1.06 -

Vallecito Creek near Bayfield, CO 06/08/1999 10:45 Environmental <1.0 - <1.0 3.02 -

Vallecito Creek near Bayfield, CO 06/08/1999 10:46 Replicate - - - - -

Vallecito Reservoir North @ 31.5 feet 08/24/1999 9:30 Environmental - <0.1 - - <5

Vallecito Reservoir North @ 31.5 feet 08/24/1999 9:35 Replicate - <0.1 - - <5

Vallecito Reservoir South @ 53 feet 09/21/1999 9:32 Environmental - <0.1 - - <5

Vallecito Reservoir South @ 53 feet 09/21/1999 9:37 Replicate - <0.1 - - <5
Field Blank and Field Replicate Data Collection and Interpretation 45

Table 9. Field replicates collected from stream and reservoir sampling sites, 1999–2002.—Continued

[μS/cm, microsiemens per centimeter; mg/L, milligrams per liter; μg/L, micrograms per liter; nm, nanometers; <, less than; -, no data]

Site name Date Time Sample

type

Nitrogen

ammonia,

dissolved

(mg/L as N)

Nitrogen

nitrite,

dissolved

(mg/L as N)

Nitrogen

NO2 + NO3,

dissolved

(mg/L as N)

Nitrogen

Amn + Org,

dissolved

(mg/L as N)

Nitrogen

Amn + Org,

total

(mg/L as N)

Los Pinos River above Vallecito 

Reservoir near Bayfield, CO

08/13/1996 1520 Environmental <0.002 <0.001 0.018 <0.2 <0.2

Los Pinos River above Vallecito 

Reservoir near Bayfield, CO

08/13/1996 1525 Replicate <0.002 <0.001 0.016 <0.2 <0.2

Vallecito Reservoir South @ 2 feet 10/23/1996 1035 Environmental 0.014 <0.001 <0.005 <0.2 <0.2

Vallecito Reservoir South @ 2 feet 10/23/1996 1100 Replicate 0.012 <0.001 <0.005 <0.2 <0.2

Vallecito Reservoir Center @ 2 feet 07/01/1997 1330 Environmental <0.002 0.001 0.007 <0.2 <0.2

Vallecito Reservoir Center @ 2 feet 07/01/1997 1335 Replicate <0.002 0.001 0.008 <0.2 <0.2

Los Pinos River below Vallecito 

Reservoir near Bayfield , CO

07/02/1997 910 Environmental 0.008 0.001 0.037 0.278 <0.2

Los Pinos River below Vallecito 

Reservoir near Bayfield , CO

07/02/1997 915 Replicate 0.008 0.001 0.036 0.207 <0.2

Vallecito Creek near Bayfield, CO 05/13/1999 10:45 Environmental 0.002 <0.001 0.087 0.056 0.117

Vallecito Creek near Bayfield, CO 05/13/1999 10:46 Replicate - - - - -

Vallecito Creek near Bayfield, CO 06/08/1999 10:45 Environmental 0.003 0.001 0.119 0.070 <0.1

Vallecito Creek near Bayfield, CO 06/08/1999 10:46 Replicate 0.002 0.001 0.119 0.093 <0.1

Vallecito Reservoir North @ 31.5 feet 08/24/1999 9:30 Environmental - - - - -

Vallecito Reservoir North @ 31.5 feet 08/24/1999 9:35 Replicate - - - - -

Vallecito Reservoir South @ 53 feet 09/21/1999 9:32 Environmental - - - - -

Vallecito Reservoir South @ 53 feet 09/21/1999 9:37 Replicate - - - - -

Site name Date Time Sample

type

Phosphorus,

total

(mg/L as P)

Phosphorus,

dissolved

(mg/L as P)

Phosphorus,

ortho,

dissolved

(mg/L as P)

Organic

carbon,

dissolved

(mg/L as C)

Los Pinos River above Vallecito 

Reservoir near Bayfield, CO

08/13/1996 1520 Environmental 0.008 0.005 <0.001 -

Los Pinos River above Vallecito 

Reservoir near Bayfield, CO

08/13/1996 1525 Replicate 0.004 0.005 <0.001 -

Vallecito Reservoir South @ 2 feet 10/23/1996 1035 Environmental 0.005 0.002 <0.001 -

Vallecito Reservoir South @ 2 feet 10/23/1996 1100 Replicate 0.005 0.004 <0.001 -

Vallecito Reservoir Center @ 2 feet 07/01/1997 1330 Environmental 0.005 0.002 0.002 -

Vallecito Reservoir Center @ 2 feet 07/01/1997 1335 Replicate 0.004 0.003 0.001 -

Los Pinos River below Vallecito 

Reservoir near Bayfield , CO

07/02/1997 910 Environmental 0.005 0.002 0.002 -

Los Pinos River below Vallecito 

Reservoir near Bayfield , CO

07/02/1997 915 Replicate 0.006 0.002 0.001 -

Vallecito Creek near Bayfield, CO 05/13/1999 10:45 Environmental 0.007 <0.004 <0.001 2.3

Vallecito Creek near Bayfield, CO 05/13/1999 10:46 Replicate - - - -

Vallecito Creek near Bayfield, CO 06/08/1999 10:45 Environmental 0.005 0.004 0.001 1.4

Vallecito Creek near Bayfield, CO 06/08/1999 10:46 Replicate 0.005 <0.004 <0.001 -

Vallecito Reservoir North @ 31.5 feet 08/24/1999 9:30 Environmental - - - -

Vallecito Reservoir North @ 31.5 feet 08/24/1999 9:35 Replicate - - - -

Vallecito Reservoir South @ 53 feet 09/21/1999 9:32 Environmental - - - -

Vallecito Reservoir South @ 53 feet 09/21/1999 9:37 Replicate - - - -
46 Water-Quality Data Collected from Vallecito Reservoir, Its Inflows and Outflow, Southwestern Colorado, 1999–2002 

Table 9. Field replicates collected from stream and reservoir sampling sites, 1999–2002.—Continued

[μS/cm, microsiemens per centimeter; mg/L, milligrams per liter; μg/L, micrograms per liter; nm, nanometers; <, less than; -, no data]

Site name Date Time Sample

type

pH,

laboratory

(standard

units)

pH,

field

(standard 

units)

Specific

conductance,

laboratory

(μS/cm)

Specific

conductance,

field

(μS/cm)

Calcium,

dissolved

(mg/L)

Magnesium,

dissolved

(mg/L)

Vallecito Reservoir Center @ 2 feet 10/19/1999 9:45 Environmental - - - - - -

Vallecito Reservoir Center @ 2 feet 10/19/1999 9:46 Replicate - - - - - -

Vallecito Reservoir Center @ 2 feet 11/30/1999 11:10 Environmental - - - - - -

Vallecito Reservoir Center @ 2 feet 11/30/1999 11:15 Replicate - - - - - -

Vallecito Reservoir South @ 2 feet 05/19/2000 11:00 Environmental - - - - - -

Vallecito Reservoir South @ 2 feet 05/19/2000 11:05 Replicate - - - - - -

Vallecito Reservoir South @ 85 feet 05/19/2000 11:00 Environmental - - - - - -

Vallecito Reservoir South @ 85 feet 05/19/2000 11:20 Replicate - - - - - -

Vallecito Reservoir South @ 2 feet 06/06/2000 10:00 Environmental - - - - - -

Vallecito Reservoir South @ 2 feet 06/06/2000 10:05 Replicate - - - - - -

Vallecito Reservoir South @ 25 feet 07/11/2000 10:00 Environmental - - - - - -

Vallecito Reservoir South @ 25 feet 07/11/2000 10:05 Replicate - - - - - -

Vallecito Reservoir South @ 2 feet 08/22/2000 9:30 Environmental - - - - - -

Vallecito Reservoir South @ 2 feet 08/22/2000 9:35 Replicate - - - - - -

Vallecito Creek near Bayfield, CO 08/22/2000 16:00 Environmental 7.89 7.42 64.8 61.0 7.69 1.71

Vallecito Creek near Bayfield, CO 08/22/2000 16:05 Replicate 8.14 - 66.2 61 7.85 1.75

Vallecito Reservoir South @ 2 feet 05/17/2001 10:00 Environmental - - - - - -

Vallecito Reservoir South @ 2 feet 05/17/2001 10:10 Replicate - - - - - -

Vallecito Reservoir South @ 2 feet 06/14/2001 9:15 Environmental - - - - - -

Vallecito Reservoir South @ 2 feet 06/14/2001 9:20 Replicate - - - - - -

Site name Date Time Sample

type

Sodium,

dissolved

(mg/L)

Potassium,

dissolved

(mg/L)

Potassium,

total

(mg/L)

Bicarbonate,

dissolved

(mg/L as

HCO3)

Alkalinity,

dissolved

(mg/L as

CaCO3)

Chloride,

dissolved

(mg/L)

Vallecito Reservoir Center @ 2 feet 10/19/1999 9:45 Environmental - - 1.1 - - -

Vallecito Reservoir Center @ 2 feet 10/19/1999 9:46 Replicate - - 1.1 - - -

Vallecito Reservoir Center @ 2 feet 11/30/1999 11:10 Environmental - - 0.39 - - -

Vallecito Reservoir Center @ 2 feet 11/30/1999 11:15 Replicate - - 0.42 - - -

Vallecito Reservoir South @ 2 feet 05/19/2000 11:00 Environmental - 0.8 1.00 - - -

Vallecito Reservoir South @ 2 feet 05/19/2000 11:05 Replicate - 0.8 0.88 - - -

Vallecito Reservoir South @ 85 feet 05/19/2000 11:00 Environmental - - - - -

Vallecito Reservoir South @ 85 feet 05/19/2000 11:20 Replicate - - - - -

Vallecito Reservoir South @ 2 feet 06/06/2000 10:00 Environmental - 0.76 0.79 - - -

Vallecito Reservoir South @ 2 feet 06/06/2000 10:05 Replicate - - 0.78 - - -

Vallecito Reservoir South @ 25 feet 07/11/2000 10:00 Environmental - 0.74 0.79 - - -

Vallecito Reservoir South @ 25 feet 07/11/2000 10:05 Replicate - 0.78 0.74 - - -

Vallecito Reservoir South @ 2 feet 08/22/2000 9:30 Environmental - 0.87 0.94 - - -

Vallecito Reservoir South @ 2 feet 08/22/2000 9:35 Replicate - 0.81 0.92 - - -

Vallecito Creek near Bayfield, CO 08/22/2000 16:00 Environmental 0.73 0.5 - 23 19 0.14

Vallecito Creek near Bayfield, CO 08/22/2000 16:05 Replicate 0.74 0.5 - 23 19 0.14

Vallecito Reservoir South @ 2 feet 05/17/2001 10:00 Environmental - - - - - -

Vallecito Reservoir South @ 2 feet 05/17/2001 10:10 Replicate - - - - - -

Vallecito Reservoir South @ 2 feet 06/14/2001 9:15 Environmental - 0.65 0.70 - - -

Vallecito Reservoir South @ 2 feet 06/14/2001 9:20 Replicate - 0.70 0.69 - - -
Field Blank and Field Replicate Data Collection and Interpretation 47

Table 9. Field replicates collected from stream and reservoir sampling sites, 1999–2002.—Continued

[μS/cm, microsiemens per centimeter; mg/L, milligrams per liter; μg/L, micrograms per liter; nm, nanometers; <, less than; -, no data]

Site name Date Time Sample

type

Sulfate,

dissolved

(mg/L)

Fluoride,

dissolved

(mg/L)

Silica,

dissolved

(mg/L)

Aluminum,

dissolved

(μg/L)

Aluminum,

total

(μg/L)

Antimony,

dissolved

(μg/L)

Vallecito Reservoir Center @ 2 feet 10/19/1999 9:45 Environmental - - - - 62 -

Vallecito Reservoir Center @ 2 feet 10/19/1999 9:46 Replicate - - - - 63 -

Vallecito Reservoir Center @ 2 feet 11/30/1999 11:10 Environmental - - - - <10 -

Vallecito Reservoir Center @ 2 feet 11/30/1999 11:15 Replicate - - - - 10.0 -

Vallecito Reservoir South @ 2 feet 05/19/2000 11:00 Environmental - - - 27.0 43.0 -

Vallecito Reservoir South @ 2 feet 05/19/2000 11:05 Replicate - - - 23.0 43.0 -

Vallecito Reservoir South @ 85 feet 05/19/2000 11:00 Environmental - - - - - -

Vallecito Reservoir South @ 85 feet 05/19/2000 11:20 Replicate - - - - - -

Vallecito Reservoir South @ 2 feet 06/06/2000 10:00 Environmental - - - 45.0 59.0 -

Vallecito Reservoir South @ 2 feet 06/06/2000 10:05 Replicate - - - - 57.0 -

Vallecito Reservoir South @ 25 feet 07/11/2000 10:00 Environmental - - - 17.0 24.0 -

Vallecito Reservoir South @ 25 feet 07/11/2000 10:05 Replicate - - - 19.0 23.0 -

Vallecito Reservoir South @ 2 feet 08/22/2000 9:30 Environmental - - - 24.0 44.0 -

Vallecito Reservoir South @ 2 feet 08/22/2000 9:35 Replicate - - - 20.0 41.0 -

Vallecito Creek near Bayfield, CO 08/22/2000 16:00 Environmental 7.95 <0.1 3.19 30.2 - <1.0

Vallecito Creek near Bayfield, CO 08/22/2000 16:05 Replicate 7.96 0.29 3.27 41.0 - <1.0

Vallecito Reservoir South @ 2 feet 05/17/2001 10:00 Environmental - - - - - -

Vallecito Reservoir South @ 2 feet 05/17/2001 10:10 Replicate - - - - - -

Vallecito Reservoir South @ 2 feet 06/14/2001 9:15 Environmental - - - 57.0 91.0 -

Vallecito Reservoir South @ 2 feet 06/14/2001 9:20 Replicate - - - 55.0 84.0 -

Site name Date Time Sample

type

Arsenic,

dissolved

(μg/L)

Arsenic,

total

(μg/L)

Barium,

dissolved

(μg/L)

Barium,

total

(μg/L)

Beryllium,

dissolved

(μg/L)

Cadmium,

dissolved

(μg/L)

Vallecito Reservoir Center @ 2 feet 10/19/1999 9:45 Environmental - <1 - - - -

Vallecito Reservoir Center @ 2 feet 10/19/1999 9:46 Replicate - <1 - - - -

Vallecito Reservoir Center @ 2 feet 11/30/1999 11:10 Environmental - <1 - - - -

Vallecito Reservoir Center @ 2 feet 11/30/1999 11:15 Replicate - <1 - - - -

Vallecito Reservoir South @ 2 feet 05/19/2000 11:00 Environmental <1 <1 - - - <0.2

Vallecito Reservoir South @ 2 feet 05/19/2000 11:05 Replicate <1 <1 - - - <0.2

Vallecito Reservoir South @ 85 feet 05/19/2000 11:00 Environmental - - - - - -

Vallecito Reservoir South @ 85 feet 05/19/2000 11:20 Replicate - - - - - -

Vallecito Reservoir South @ 2 feet 06/06/2000 10:00 Environmental <1 <1 - - - <0.2

Vallecito Reservoir South @ 2 feet 06/06/2000 10:05 Replicate - <1 - - - -

Vallecito Reservoir South @ 25 feet 07/11/2000 10:00 Environmental <1 <1 - - - <0.2

Vallecito Reservoir South @ 25 feet 07/11/2000 10:05 Replicate <1 <1 - - - <0.2

Vallecito Reservoir South @ 2 feet 08/22/2000 9:30 Environmental <1 <1 - - - <0.2

Vallecito Reservoir South @ 2 feet 08/22/2000 9:35 Replicate <1 <1 - - - <0.2

Vallecito Creek near Bayfield, CO 08/22/2000 16:00 Environmental <2.0 - 12.5 - <1.0 <1.0

Vallecito Creek near Bayfield, CO 08/22/2000 16:05 Replicate <2.0 - 12.5 - <1.0 <1.0

Vallecito Reservoir South @ 2 feet 05/17/2001 10:00 Environmental - - - - - -

Vallecito Reservoir South @ 2 feet 05/17/2001 10:10 Replicate - - - - - -

Vallecito Reservoir South @ 2 feet 06/14/2001 9:15 Environmental <1 <1 - - - <0.3

Vallecito Reservoir South @ 2 feet 06/14/2001 9:20 Replicate <1 1.3 - - - <0.3
48 Water-Quality Data Collected from Vallecito Reservoir, Its Inflows and Outflow, Southwestern Colorado, 1999–2002 

Table 9. Field replicates collected from stream and reservoir sampling sites, 1999–2002.

[μS/cm, microsiemens per centimeter; mg/L, milligrams per liter; μg/L, micrograms per liter; nm, nanometers; <, less than; -, no data]

Site name Date Time Sample

type

Cadmium,

total

(μg/L)

Chromium,

dissolved

(μg/L)

Chromium,

total

(μg/L)

Cobalt,

dissolved

(μg/L)

Copper,

dissolved

(μg/L)

Copper,

total

(μg/L)

Vallecito Reservoir Center @ 2 feet 10/19/1999 9:45 Environmental <0.1 - <5 - - <1

Vallecito Reservoir Center @ 2 feet 10/19/1999 9:46 Replicate <0.1 - <5 - - <1

Vallecito Reservoir Center @ 2 feet 11/30/1999 11:10 Environmental <0.2 - <0.4 - - 2.2

Vallecito Reservoir Center @ 2 feet 11/30/1999 11:15 Replicate <0.2 - <0.4 - - 4.4

Vallecito Reservoir South @ 2 feet 05/19/2000 11:00 Environmental <0.2 <0.4 <0.4 - 0.8 1.1

Vallecito Reservoir South @ 2 feet 05/19/2000 11:05 Replicate <0.2 <0.4 <0.4 - 1.5 0.8

Vallecito Reservoir South @ 85 feet 05/19/2000 11:00 Environmental - - - - - -

Vallecito Reservoir South @ 85 feet 05/19/2000 11:20 Replicate - - - - - -

Vallecito Reservoir South @ 2 feet 06/06/2000 10:00 Environmental <0.2 <0.4 0.6 - <2 2.7

Vallecito Reservoir South @ 2 feet 06/06/2000 10:05 Replicate <0.2 - <0.4 - - <2

Vallecito Reservoir South @ 25 feet 07/11/2000 10:00 Environmental <0.2 <0.4 <0.4 - <2 <2

Vallecito Reservoir South @ 25 feet 07/11/2000 10:05 Replicate <0.2 <0.4 <0.4 - <2 <2

Vallecito Reservoir South @ 2 feet 08/22/2000 9:30 Environmental <0.2 <0.4 <0.4 - 0.7 1.6

Vallecito Reservoir South @ 2 feet 08/22/2000 9:35 Replicate <0.2 <0.4 <0.4 - 0.6 1.1

Vallecito Creek near Bayfield, CO 08/22/2000 16:00 Environmental - <0.8 - <1.0 <1.0 -

Vallecito Creek near Bayfield, CO 08/22/2000 16:05 Replicate - <0.8 - <1.0 <1.0 -

Vallecito Reservoir South @ 2 feet 05/17/2001 10:00 Environmental - - - - - -

Vallecito Reservoir South @ 2 feet 05/17/2001 10:10 Replicate - - - - - -

Vallecito Reservoir South @ 2 feet 06/14/2001 9:15 Environmental <0.3 <0.4 <0.4 - 1.2 1.8

Vallecito Reservoir South @ 2 feet 06/14/2001 9:20 Replicate <0.3 <0.4 <0.4 - 1.1 1.6

Site name Date Time Sample

type

Iron,

dissolved

(μg/L)

Iron,

total

(μg/L)

Lead,

dissolved

(μg/L)

Lead,

total

(μg/L)

Manganese,

dissolved

(μg/L)

Manganese,

total

(μg/L)

Mercury,

dissolved

(μg/L)

Vallecito Reservoir Center @ 2 feet 10/19/1999 9:45 Environmental - 40 - <1 - 18 -

Vallecito Reservoir Center @ 2 feet 10/19/1999 9:46 Replicate - 40 - <1 - 18 -

Vallecito Reservoir Center @ 2 feet 11/30/1999 11:10 Environmental - 28 - <1.5 - 6.8 -

Vallecito Reservoir Center @ 2 feet 11/30/1999 11:15 Replicate - 34 - <1.5 - 7.8 -

Vallecito Reservoir South @ 2 feet 05/19/2000 11:00 Environmental 6.0 43.0 <1.5 <1.5 1.0 8.1 -

Vallecito Reservoir South @ 2 feet 05/19/2000 11:05 Replicate 6.0 35.0 <1.5 <1.5 1.2 7.0 -

Vallecito Reservoir South @ 85 feet 05/19/2000 11:00 Environmental - - - - - - -

Vallecito Reservoir South @ 85 feet 05/19/2000 11:20 Replicate - - - - - - -

Vallecito Reservoir South @ 2 feet 06/06/2000 10:00 Environmental 9.0 39.0 <1.5 <1.5 1.3 5.9 -

Vallecito Reservoir South @ 2 feet 06/06/2000 10:05 Replicate - 40.0 - <1.5 - 5.7 -

Vallecito Reservoir South @ 25 feet 07/11/2000 10:00 Environmental 9.0 33.9 <1.5 <1.5 24.3 43.8 -

Vallecito Reservoir South @ 25 feet 07/11/2000 10:05 Replicate 8.6 32.6 <1.5 <1.5 24.8 47.3 -

Vallecito Reservoir South @ 2 feet 08/22/2000 9:30 Environmental 7.3 36.1 <1.5 <1.5 1.0 14.6 -

Vallecito Reservoir South @ 2 feet 08/22/2000 9:35 Replicate 5.8 38.2 <1.5 <1.5 0.8 14.5 -

Vallecito Creek near Bayfield, CO 08/22/2000 16:00 Environmental <10.0 - <1.0 - 6.88 - -

Vallecito Creek near Bayfield, CO 08/22/2000 16:05 Replicate <10.0 - <1.0 - 6.88 - -

Vallecito Reservoir South @ 2 feet 05/17/2001 10:00 Environmental - - - - - - -

Vallecito Reservoir South @ 2 feet 05/17/2001 10:10 Replicate - - - - - - -

Vallecito Reservoir South @ 2 feet 06/14/2001 9:15 Environmental 14.4 42.8 <2 <2 1.5 4.1 <0.1

Vallecito Reservoir South @ 2 feet 06/14/2001 9:20 Replicate 13.3 43.6 <2 <2 1.6 4.1 <0.1
Field Blank and Field Replicate Data Collection and Interpretation 49

Table 9. Field replicates collected from stream and reservoir sampling sites, 1999–2002.—Continued

[μS/cm, microsiemens per centimeter; mg/L, milligrams per liter; μg/L, micrograms per liter; nm, nanometers; <, less than; -, no data]

Site name Date Time Sample

type

Mercury,

total

(μg/L)

Molybdenum,

dissolved

(μg/L)

Nickel,

dissolved

(μg/L)

Nickel,

total

(μg/L)

Selenium,

dissolved

(μg/L)

Vallecito Reservoir Center @ 2 feet 10/19/1999 9:45 Environmental <0.1 - - <5 -

Vallecito Reservoir Center @ 2 feet 10/19/1999 9:46 Replicate <0.1 - - <5 -

Vallecito Reservoir Center @ 2 feet 11/30/1999 11:10 Environmental <0.05 - - <0.4 -

Vallecito Reservoir Center @ 2 feet 11/30/1999 11:15 Replicate <0.05 - - 0.4 -

Vallecito Reservoir South @ 2 feet 05/19/2000 11:00 Environmental <0.02 - 0.8 0.9 <1

Vallecito Reservoir South @ 2 feet 05/19/2000 11:05 Replicate <0.02 - 1.0 0.7 <1

Vallecito Reservoir South @ 85 feet 05/19/2000 11:00 Environmental - - - -

Vallecito Reservoir South @ 85 feet 05/19/2000 11:20 Replicate - - - -

Vallecito Reservoir South @ 2 feet 06/06/2000 10:00 Environmental 0.12 - 0.9 1.8 -

Vallecito Reservoir South @ 2 feet 06/06/2000 10:05 Replicate <0.02 - - 0.9 -

Vallecito Reservoir South @ 25 feet 07/11/2000 10:00 Environmental <0.02 - 0.9 0.9 -

Vallecito Reservoir South @ 25 feet 07/11/2000 10:05 Replicate <0.02 - 0.9 0.9 -

Vallecito Reservoir South @ 2 feet 08/22/2000 9:30 Environmental <0.04 - 0.6 0.9 -

Vallecito Reservoir South @ 2 feet 08/22/2000 9:35 Replicate <0.04 - 0.9 0.9 -

Vallecito Creek near Bayfield, CO 08/22/2000 16:00 Environmental - 1.03 <1.0 - <2.4

Vallecito Creek near Bayfield, CO 08/22/2000 16:05 Replicate - 1.03 <1.0 - <2.4

Vallecito Reservoir South @ 2 feet 05/17/2001 10:00 Environmental - - - - -

Vallecito Reservoir South @ 2 feet 05/17/2001 10:10 Replicate - - - - -

Vallecito Reservoir South @ 2 feet 06/14/2001 9:15 Environmental <0.1 - 0.9 0.7 -

Vallecito Reservoir South @ 2 feet 06/14/2001 9:20 Replicate <0.1 - 0.7 0.8 -

Site name Date Time Sample

type

Selenium,

total

(μg/L)

Silver,

dissolved

(μg/L)

Silver,

total

(μg/L)

Uranium,

dissolved

(μg/L)

Zinc,

dissolved

(μg/L)

Zinc,

total

(μg/L)

Vallecito Reservoir Center @ 2 feet 10/19/1999 9:45 Environmental - - <0.1 - - 15

Vallecito Reservoir Center @ 2 feet 10/19/1999 9:46 Replicate - - <0.1 - - <5

Vallecito Reservoir Center @ 2 feet 11/30/1999 11:10 Environmental - - <0.8 - - 13.8

Vallecito Reservoir Center @ 2 feet 11/30/1999 11:15 Replicate - - <0.8 - - 17.2

Vallecito Reservoir South @ 2 feet 05/19/2000 11:00 Environmental <1 <0.2 <0.2 - 2.0 10.0

Vallecito Reservoir South @ 2 feet 05/19/2000 11:05 Replicate <1 <0.2 <0.2 - 2.1 5.4

Vallecito Reservoir South @ 85 feet 05/19/2000 11:00 Environmental - - - - - -

Vallecito Reservoir South @ 85 feet 05/19/2000 11:20 Replicate - - - - - -

Vallecito Reservoir South @ 2 feet 06/06/2000 10:00 Environmental - <0.8 <0.8 - <2 2.5

Vallecito Reservoir South @ 2 feet 06/06/2000 10:05 Replicate - - <0.8 - - 7.8

Vallecito Reservoir South @ 25 feet 07/11/2000 10:00 Environmental - <0.8 <0.8 - <2 <2

Vallecito Reservoir South @ 25 feet 07/11/2000 10:05 Replicate - <0.8 <0.8 - <2 <2

Vallecito Reservoir South @ 2 feet 08/22/2000 9:30 Environmental - <0.8 <0.8 - 4.3 3.4

Vallecito Reservoir South @ 2 feet 08/22/2000 9:35 Replicate - <0.8 <0.8 - 2.8 3.7

Vallecito Creek near Bayfield, CO 08/22/2000 16:00 Environmental - <1.0 - <1.0 <1.0 -

Vallecito Creek near Bayfield, CO 08/22/2000 16:05 Replicate - <1.0 - <1.0 1.24 -

Vallecito Reservoir South @ 2 feet 05/17/2001 10:00 Environmental - - - - - -

Vallecito Reservoir South @ 2 feet 05/17/2001 10:10 Replicate - - - - - -

Vallecito Reservoir South @ 2 feet 06/14/2001 9:15 Environmental - <0.8 <0.8 - <2 <2

Vallecito Reservoir South @ 2 feet 06/14/2001 9:20 Replicate - <0.8 <0.8 - <2 <2
50 Water-Quality Data Collected from Vallecito Reservoir, Its Inflows and Outflow, Southwestern Colorado, 1999–2002 

Table 9. Field replicates collected from stream and reservoir sampling sites, 1999–2002.—Continued

[μS/cm, microsiemens per centimeter; mg/L, milligrams per liter; μg/L, micrograms per liter; nm, nanometers; <, less than; -, no data]

Site name Date Time Sample

type

Nitrogen

ammonia,

dissolved

(mg/L as N)

Nitrogen

nitrite,

dissolved

(mg/L as N)

Nitrogen

NO2 + NO3,

dissolved

(mg/L as N)

Nitrogen

Amn + Org,

dissolved

(mg/L as N)

Nitrogen

Amn + Org,

total

(mg/L as N)

Vallecito Reservoir Center @ 2 feet 10/19/1999 9:45 Environmental - - - - -

Vallecito Reservoir Center @ 2 feet 10/19/1999 9:46 Replicate - - - - -

Vallecito Reservoir Center @ 2 feet 11/30/1999 11:10 Environmental - - - - -

Vallecito Reservoir Center @ 2 feet 11/30/1999 11:15 Replicate - - - - -

Vallecito Reservoir South @ 2 feet 05/19/2000 11:00 Environmental - - - - -

Vallecito Reservoir South @ 2 feet 05/19/2000 11:05 Replicate - - - - -

Vallecito Reservoir South @ 85 feet 05/19/2000 11:00 Environmental 0.009 <0.001 <0.005 0.079 0.1

Vallecito Reservoir South @ 85 feet 05/19/2000 11:20 Replicate 0.004 <0.001 <0.005 0.086 -

Vallecito Reservoir South @ 2 feet 06/06/2000 10:00 Environmental - - - - -

Vallecito Reservoir South @ 2 feet 06/06/2000 10:05 Replicate - - - - -

Vallecito Reservoir South @ 25 feet 07/11/2000 10:00 Environmental - - - - -

Vallecito Reservoir South @ 25 feet 07/11/2000 10:05 Replicate - - - - -

Vallecito Reservoir South @ 2 feet 08/22/2000 9:30 Environmental - - - - -

Vallecito Reservoir South @ 2 feet 08/22/2000 9:35 Replicate - - - - -

Vallecito Creek near Bayfield, CO 08/22/2000 16:00 Environmental <0.002 <0.001 0.141 <0.1 <0.1

Vallecito Creek near Bayfield, CO 08/22/2000 16:05 Replicate <0.002 <0.001 0.132 0.072 <0.1

Vallecito Reservoir South @ 2 feet 05/17/2001 10:00 Environmental 0.006 0.001 0.009 0.118 1.06

Vallecito Reservoir South @ 2 feet 05/17/2001 10:10 Replicate 0.01 0.002 0.009 0.1 0.178

Vallecito Reservoir South @ 2 feet 06/14/2001 9:15 Environmental <0.002 <0.001 0.021 0.1 0.11

Vallecito Reservoir South @ 2 feet 06/14/2001 9:20 Replicate 0.003 <0.001 0.025 0.084 0.117

Site name Date Time Sample

type

Phosphorus,

total

(mg/L as P)

Phosphorus,

dissolved

(mg/L as P)

Phosphorus,

ortho,

dissolved

(mg/L as P)

Organic

carbon,

dissolved

(mg/L as C)

UV

absorbance

(254 nm)

Vallecito Reservoir Center @ 2 feet 10/19/1999 9:45 Environmental - - - - -

Vallecito Reservoir Center @ 2 feet 10/19/1999 9:46 Replicate - - - - -

Vallecito Reservoir Center @ 2 feet 11/30/1999 11:10 Environmental - - - - -

Vallecito Reservoir Center @ 2 feet 11/30/1999 11:15 Replicate - - - - -

Vallecito Reservoir South @ 2 feet 05/19/2000 11:00 Environmental - - - - -

Vallecito Reservoir South @ 2 feet 05/19/2000 11:05 Replicate - - - - -

Vallecito Reservoir South @ 85 feet 05/19/2000 11:00 Environmental 0.006 <0.006 <0.001 1.8 0.037

Vallecito Reservoir South @ 85 feet 05/19/2000 11:20 Replicate - <0.006 <0.001 1.7 0.037

Vallecito Reservoir South @ 2 feet 06/06/2000 10:00 Environmental - - - - -

Vallecito Reservoir South @ 2 feet 06/06/2000 10:05 Replicate - - - - -

Vallecito Reservoir South @ 25 feet 07/11/2000 10:00 Environmental - - - - -

Vallecito Reservoir South @ 25 feet 07/11/2000 10:05 Replicate - - - - -

Vallecito Reservoir South @ 2 feet 08/22/2000 9:30 Environmental - - - - -

Vallecito Reservoir South @ 2 feet 08/22/2000 9:35 Replicate - - - - -

Vallecito Creek near Bayfield, CO 08/22/2000 16:00 Environmental <0.008 <0.006 <0.001 0.6 0.011

Vallecito Creek near Bayfield, CO 08/22/2000 16:05 Replicate <0.008 <0.006 0.001 0.7 0.012

Vallecito Reservoir South @ 2 feet 05/17/2001 10:00 Environmental 0.008 <0.006 <0.007 2.5 0.065

Vallecito Reservoir South @ 2 feet 05/17/2001 10:10 Replicate 0.012 <0.006 <0.007 2.1 0.065

Vallecito Reservoir South @ 2 feet 06/14/2001 9:15 Environmental 0.009 0.004 <0.007 2.2 0.073

Vallecito Reservoir South @ 2 feet 06/14/2001 9:20 Replicate 0.005 <0.006 <0.007 2.2 0.073
Field Blank and Field Replicate Data Collection and Interpretation 51

Table 9. Field replicates collected from stream and reservoir sampling sites, 1999–2002.—Continued

[μS/cm, microsiemens per centimeter; mg/L, milligrams per liter; μg/L, micrograms per liter; nm, nanometers; <, less than; -, no data]

Site name Date Time Sample

type

pH,

laboratory

(standard

units)

pH,

field

(standard 

units)

Specific

conductance,

laboratory

(μS/cm)

Specific

conductance,

field

(μS/cm)

Calcium,

dissolved

(mg/L)

Magnesium,

dissolved

(mg/L)

Vallecito Reservoir South @ 40 feet 07/17/2001 9:40 Environmental - - - - - -

Vallecito Reservoir South @ 40 feet 07/17/2001 9:45 Replicate - - - - - -

Vallecito Reservoir South @ 65 feet 08/16/2001 10:15 Environmental - - - - - -

Vallecito Reservoir South @ 65 feet 08/16/2001 10:20 Replicate - - - - - -

Vallecito Reservoir South @ 2 feet 09/18/2001 10:30 Environmental - - - - - -

Vallecito Reservoir South @ 2 feet 09/18/2001 10:35 Replicate - - - - - -

Vallecito Reservoir South @ 35 feet 10/17/2001 10:10 Environmental - - - - - -

Vallecito Reservoir South @ 35 feet 10/17/2001 10:15 Replicate - - - - - -

Los Pinos River above Vallecito 

Reservoir near Bayfield, CO

10/17/2001 10:15 Environmental - 7.42 - 95 - -

Los Pinos River above Vallecito 

Reservoir near Bayfield, CO

10/17/2001 10:16 Replicate - 7.42 - 95 - -

Vallecito Reservoir South @ 2 feet 05/22/2002 9:00 Environmental - - - - - -

Vallecito Reservoir South @ 2 feet 05/22/2002 9:10 Replicate - - - - - -

Vallecito Reservoir South @ 2 feet 07/31/2002 9:00 Environmental - - - - - -

Vallecito Reservoir South @ 2 feet 07/31/2002 9:05 Replicate - - - - - -

Vallecito Reservoir South @ 2 feet 08/29/2002 9:00 Environmental - - 130 - 18.8 2.84

Vallecito Reservoir South @ 2 feet 08/29/2002 9:05 Replicate - - 132.8 - 18.6 2.81

Site name Date Time Sample

type

Sodium,

dissolved

(mg/L)

Potassium,

dissolved

(mg/L)

Potassium,

total

(mg/L)

Bicarbonate,

dissolved

(mg/L 

as HCO3)

Alkalinity,

dissolved

(mg/L 

as CaCO3)

Chloride,

dissolved

(mg/L)

Vallecito Reservoir South @ 40 feet 07/17/2001 9:40 Environmental - 0.63 0.64 - - -

Vallecito Reservoir South @ 40 feet 07/17/2001 9:45 Replicate - 0.63 0.66 - - -

Vallecito Reservoir South @ 65 feet 08/16/2001 10:15 Environmental - 0.70 0.77 - - -

Vallecito Reservoir South @ 65 feet 08/16/2001 10:20 Replicate - 0.67 0.73 - - -

Vallecito Reservoir South @ 2 feet 09/18/2001 10:30 Environmental - 0.67 0.98 - - -

Vallecito Reservoir South @ 2 feet 09/18/2001 10:35 Replicate - 0.65 0.85 - - -

Vallecito Reservoir South @ 35 feet 10/17/2001 10:10 Environmental - 0.71 0.75 - - -

Vallecito Reservoir South @ 35 feet 10/17/2001 10:15 Replicate - 0.73 0.73 - - -

Los Pinos River above Vallecito 

Reservoir near Bayfield, CO

10/17/2001 10:15 Environmental - - - 48.1 39.4 -

Los Pinos River above Vallecito 

Reservoir near Bayfield, CO

10/17/2001 10:16 Replicate - - - 48.1 39.4 -

Vallecito Reservoir South @ 2 feet 05/22/2002 9:00 Environmental - - - - - -

Vallecito Reservoir South @ 2 feet 05/22/2002 9:10 Replicate - - - - - -

Vallecito Reservoir South @ 2 feet 07/31/2002 9:00 Environmental - - - - - -

Vallecito Reservoir South @ 2 feet 07/31/2002 9:05 Replicate - - - - - -

Vallecito Reservoir South @ 2 feet 08/29/2002 9:00 Environmental 1.56 1.11 - - 58.3 0.65

Vallecito Reservoir South @ 2 feet 08/29/2002 9:05 Replicate 1.53 1.02 - - 57.2 0.91
52 Water-Quality Data Collected from Vallecito Reservoir, Its Inflows and Outflow, Southwestern Colorado, 1999–2002 

Table 9. Field replicates collected from stream and reservoir sampling sites, 1999–2002.—Continued

[μS/cm, microsiemens per centimeter; mg/L, milligrams per liter; μg/L, micrograms per liter; nm, nanometers; <, less than; -, no data]

Site name Date Time Sample

type

Sulfate,

dissolved

(mg/L)

Silica,

dissolved

(mg/L)

Aluminum,

dissolved

(μg/L)

Aluminum,

total

(μg/L)

Vallecito Reservoir South @ 40 feet 07/17/2001 9:40 Environmental - - 42.0 49.0

Vallecito Reservoir South @ 40 feet 07/17/2001 9:45 Replicate - - 41.0 48.0

Vallecito Reservoir South @ 65 feet 08/16/2001 10:15 Environmental - - 11.0 31.0

Vallecito Reservoir South @ 65 feet 08/16/2001 10:20 Replicate - - 16 36

Vallecito Reservoir South @ 2 feet 09/18/2001 10:30 Environmental - - 26 38

Vallecito Reservoir South @ 2 feet 09/18/2001 10:35 Replicate - - 30 40

Vallecito Reservoir South @ 35 feet 10/17/2001 10:10 Environmental - - 11 21

Vallecito Reservoir South @ 35 feet 10/17/2001 10:15 Replicate - - 27 30

Los Pinos River above Vallecito 

Reservoir near Bayfield, CO

10/17/2001 10:15 Environmental - - - -

Los Pinos River above Vallecito 

Reservoir near Bayfield, CO

10/17/2001 10:16 Replicate - - - -

Vallecito Reservoir South @ 2 feet 05/22/2002 9:00 Environmental - - 15.8 -

Vallecito Reservoir South @ 2 feet 05/22/2002 9:10 Replicate - - 16.6 -

Vallecito Reservoir South @ 2 feet 07/31/2002 9:00 Environmental - - 12.7 -

Vallecito Reservoir South @ 2 feet 07/31/2002 9:05 Replicate - - <15 -

Vallecito Reservoir South @ 2 feet 08/29/2002 9:00 Environmental 6.35 2.29 6.68 26.1

Vallecito Reservoir South @ 2 feet 08/29/2002 9:05 Replicate 6.37 2.23 6.91 25.5

Site name Date Time Sample

type

Arsenic,

dissolved

(μg/L)

Arsenic,

total

(μg/L)

Cadmium,

dissolved

(μg/L)

Cadmium,

total

(μg/L)

Vallecito Reservoir South @ 40 feet 07/17/2001 9:40 Environmental <1 <1 <0.3 <0.3

Vallecito Reservoir South @ 40 feet 07/17/2001 9:45 Replicate <1 <1 <0.3 <0.3

Vallecito Reservoir South @ 65 feet 08/16/2001 10:15 Environmental <1 <1 <0.3 <0.3

Vallecito Reservoir South @ 65 feet 08/16/2001 10:20 Replicate <1 <1 <0.3 <0.3

Vallecito Reservoir South @ 2 feet 09/18/2001 10:30 Environmental <1 <1 <0.3 0.7

Vallecito Reservoir South @ 2 feet 09/18/2001 10:35 Replicate <1 <1 <0.3 <0.3

Vallecito Reservoir South @ 35 feet 10/17/2001 10:10 Environmental <1 <1 <0.3 <0.3

Vallecito Reservoir South @ 35 feet 10/17/2001 10:15 Replicate <1 <1 <0.3 <0.3

Los Pinos River above Vallecito 

Reservoir near Bayfield, CO

10/17/2001 10:15 Environmental - - - -

Los Pinos River above Vallecito 

Reservoir near Bayfield, CO

10/17/2001 10:16 Replicate - - - -

Vallecito Reservoir South @ 2 feet 05/22/2002 9:00 Environmental - - - -

Vallecito Reservoir South @ 2 feet 05/22/2002 9:10 Replicate - - - -

Vallecito Reservoir South @ 2 feet 07/31/2002 9:00 Environmental - - - -

Vallecito Reservoir South @ 2 feet 07/31/2002 9:05 Replicate - - - -

Vallecito Reservoir South @ 2 feet 08/29/2002 9:00 Environmental 0.732 3.52 <0.04 <0.04

Vallecito Reservoir South @ 2 feet 08/29/2002 9:05 Replicate 0.692 <2 <0.04 <0.04
Field Blank and Field Replicate Data Collection and Interpretation 53

Table 9. Field replicates collected from stream and reservoir sampling sites, 1999–2002.—Continued

[μS/cm, microsiemens per centimeter; mg/L, milligrams per liter; μg/L, micrograms per liter; nm, nanometers; <, less than; -, no data]

Site name Date Time Sample

type

Chromium,

dissolved

(μg/L)

Chromium,

total

(μg/L)

Copper,

dissolved

(μg/L)

Copper,

total

(μg/L)

Iron,

dissolved

(μg/L)

Iron,

total

(μg/L)

Vallecito Reservoir South @ 40 feet 07/17/2001 9:40 Environmental <0.4 <0.4 1.2 1.7 11.7 31.5

Vallecito Reservoir South @ 40 feet 07/17/2001 9:45 Replicate <0.4 <0.4 1.3 1.1 12.5 32.6

Vallecito Reservoir South @ 65 feet 08/16/2001 10:15 Environmental <0.4 <0.4 <0.6 <0.6 14.7 43.3

Vallecito Reservoir South @ 65 feet 08/16/2001 10:20 Replicate <0.4 <0.4 0.6 1.6 13.0 43.4

Vallecito Reservoir South @ 2 feet 09/18/2001 10:30 Environmental <0.4 <0.4 4.1 1.3 5.1 26.8

Vallecito Reservoir South @ 2 feet 09/18/2001 10:35 Replicate <0.4 <0.4 0.9 1.6 4.0 27.7

Vallecito Reservoir South @ 35 feet 10/17/2001 10:10 Environmental <0.4 <0.4 0.5 2.7 6.5 37.3

Vallecito Reservoir South @ 35 feet 10/17/2001 10:15 Replicate <0.4 <0.4 1.0 2.7 6.4 38.2

Los Pinos River above Vallecito 

Reservoir near Bayfield, CO

10/17/2001 10:15 Environmental - - - - - -

Los Pinos River above Vallecito 

Reservoir near Bayfield, CO

10/17/2001 10:16 Replicate - - - - - -

Vallecito Reservoir South @ 2 feet 05/22/2002 9:00 Environmental - - - - 8.83 -

Vallecito Reservoir South @ 2 feet 05/22/2002 9:10 Replicate - - - - 9.92 -

Vallecito Reservoir South @ 2 feet 07/31/2002 9:00 Environmental - - - - <10 -

Vallecito Reservoir South @ 2 feet 07/31/2002 9:05 Replicate - - - - <10 -

Vallecito Reservoir South @ 2 feet 08/29/2002 9:00 Environmental - - 0.447 0.549 7.00 52.2

Vallecito Reservoir South @ 2 feet 08/29/2002 9:05 Replicate - - 0.461 0.488 8.30 51.5

Site name Date Time Sample

type

Lead,

dissolved

(μg/L)

Lead,

total

(μg/L)

Manganese,

dissolved

(μg/L)

Manganese,

total

(μg/L)

Mercury,

dissolved

(μg/L)

Vallecito Reservoir South @ 40 feet 07/17/2001 9:40 Environmental <2 <2 7.0 12.0 <0.2

Vallecito Reservoir South @ 40 feet 07/17/2001 9:45 Replicate <2 <2 7.6 12.8 <0.2

Vallecito Reservoir South @ 65 feet 08/16/2001 10:15 Environmental <2 <2 4.7 29.1 <0.2

Vallecito Reservoir South @ 65 feet 08/16/2001 10:20 Replicate <2 <2 4.2 30.2 <0.2

Vallecito Reservoir South @ 2 feet 09/18/2001 10:30 Environmental <2 <2 0.9 9.1 <0.2

Vallecito Reservoir South @ 2 feet 09/18/2001 10:35 Replicate <2 <2 0.5 7.5 <0.2

Vallecito Reservoir South @ 35 feet 10/17/2001 10:10 Environmental <2 <2 0.5 20.8 <0.2

Vallecito Reservoir South @ 35 feet 10/17/2001 10:15 Replicate <2 <2 <0.4 21.3 <0.2

Los Pinos River above Vallecito 

Reservoir near Bayfield, CO

10/17/2001 10:15 Environmental - - - - -

Los Pinos River above Vallecito 

Reservoir near Bayfield, CO

10/17/2001 10:16 Replicate - - - - -

Vallecito Reservoir South @ 2 feet 05/22/2002 9:00 Environmental - - 3.75 - -

Vallecito Reservoir South @ 2 feet 05/22/2002 9:10 Replicate - - 3.92 - -

Vallecito Reservoir South @ 2 feet 07/31/2002 9:00 Environmental - - 12.7 - -

Vallecito Reservoir South @ 2 feet 07/31/2002 9:05 Replicate - - 11.5 - -

Vallecito Reservoir South @ 2 feet 08/29/2002 9:00 Environmental <0.08 <1 9.57 63.9 -

Vallecito Reservoir South @ 2 feet 08/29/2002 9:05 Replicate <0.08 <1 11.0 61.3 -
54 Water-Quality Data Collected from Vallecito Reservoir, Its Inflows and Outflow, Southwestern Colorado, 1999–2002 

Table 9. Field replicates collected from stream and reservoir sampling sites, 1999–2002.—Continued

[μS/cm, microsiemens per centimeter; mg/L, milligrams per liter; μg/L, micrograms per liter; nm, nanometers; <, less than; -, no data]

Site name Date Time Sample

type

Mercury

total

(μg/L)

Nickel

dissolved

(μg/L)

Nickel

total

(μg/L)

Silver

dissolved

(μg/L)

Silver

total

(μg/L)

Vallecito Reservoir South @ 40 feet 07/17/2001 9:40 Environmental <0.2 1.2 1.2 <0.8 <0.8

Vallecito Reservoir South @ 40 feet 07/17/2001 9:45 Replicate <0.2 1.3 1.1 <0.8 <0.8

Vallecito Reservoir South @ 65 feet 08/16/2001 10:15 Environmental <0.2 0.8 1.1 <0.8 <0.8

Vallecito Reservoir South @ 65 feet 08/16/2001 10:20 Replicate <0.2 0.9 1.1 <0.8 <0.8

Vallecito Reservoir South @ 2 feet 09/18/2001 10:30 Environmental <0.2 0.7 0.7 <0.8 <0.8

Vallecito Reservoir South @ 2 feet 09/18/2001 10:35 Replicate <0.2 0.7 0.6 <0.8 <0.8

Vallecito Reservoir South @ 35 feet 10/17/2001 10:10 Environmental <0.2 0.8 0.8 <0.8 <0.8

Vallecito Reservoir South @ 35 feet 10/17/2001 10:15 Replicate 0.22 0.6 1.2 <0.8 <0.8

Los Pinos River above Vallecito 

Reservoir near Bayfield, CO

10/17/2001 10:15 Environmental - - - - -

Los Pinos River above Vallecito 

Reservoir near Bayfield, CO

10/17/2001 10:16 Replicate - - - - -

Vallecito Reservoir South @ 2 feet 05/22/2002 9:00 Environmental - - - - -

Vallecito Reservoir South @ 2 feet 05/22/2002 9:10 Replicate - - - - -

Vallecito Reservoir South @ 2 feet 07/31/2002 9:00 Environmental - - - - -

Vallecito Reservoir South @ 2 feet 07/31/2002 9:05 Replicate - - - - -

Vallecito Reservoir South @ 2 feet 08/29/2002 9:00 Environmental - - - - -

Vallecito Reservoir South @ 2 feet 08/29/2002 9:05 Replicate - - - - -

Site name Date Time Sample

type

Zinc

dissolved

(μg/L)

Zinc

total

(μg/L)

Nitrogen

ammonia

dissolved

(mg/L as N)

Nitrogen

nitrite

dissolved

(mg/L as N)

Vallecito Reservoir South @ 40 feet 07/17/2001 9:40 Environmental <2 <2 0.019 0.003

Vallecito Reservoir South @ 40 feet 07/17/2001 9:45 Replicate <2 <2 0.018 0.003

Vallecito Reservoir South @ 65 feet 08/16/2001 10:15 Environmental <2 2.5 0.002 <0.001

Vallecito Reservoir South @ 65 feet 08/16/2001 10:20 Replicate <2 2.9 0.003 <0.001

Vallecito Reservoir South @ 2 feet 09/18/2001 10:30 Environmental <2 4.5 - -

Vallecito Reservoir South @ 2 feet 09/18/2001 10:35 Replicate <2 <2 - -

Vallecito Reservoir South @ 35 feet 10/17/2001 10:10 Environmental <2 <2 <0.015 <0.002

Vallecito Reservoir South @ 35 feet 10/17/2001 10:15 Replicate <2 <2 <0.015 <0.002

Los Pinos River above Vallecito 

Reservoir near Bayfield, CO

10/17/2001 10:15 Environmental - - <0.015 <0.002

Los Pinos River above Vallecito 

Reservoir near Bayfield, CO

10/17/2001 10:16 Replicate - - <0.015 <0.002

Vallecito Reservoir South @ 2 feet 05/22/2002 9:00 Environmental <1 - <0.015 <0.002

Vallecito Reservoir South @ 2 feet 05/22/2002 9:10 Replicate 3.48 - <0.015 <0.002

Vallecito Reservoir South @ 2 feet 07/31/2002 9:00 Environmental <1 - <0.015 <0.002

Vallecito Reservoir South @ 2 feet 07/31/2002 9:05 Replicate <1 - <0.015 <0.002

Vallecito Reservoir South @ 2 feet 08/29/2002 9:00 Environmental 1.82 <1 <0.015 <0.002

Vallecito Reservoir South @ 2 feet 08/29/2002 9:05 Replicate 3.94 <1 <0.015 <0.002
Field Blank and Field Replicate Data Collection and Interpretation 55

Table 9. Field replicates collected from stream and reservoir sampling sites, 1999–2002.—Continued

[μS/cm, microsiemens per centimeter; mg/L, milligrams per liter; μg/L, micrograms per liter; nm, nanometers; <, less than; -, no data]

Site name Date Time Sample

type

Nitrogen

NO2 + NO3

dissolved

(mg/L as N)

Nitrogen

Amn + Org

dissolved

(mg/L as N)

Nitrogen

Amn + Org

total

(mg/L as N)

Phosphorus

total

(mg/L as P)

Vallecito Reservoir South @ 40 feet 07/17/2001 9:40 Environmental 0.032 0.089 0.102 0.004

Vallecito Reservoir South @ 40 feet 07/17/2001 9:45 Replicate 0.032 0.135 0.11 <0.004

Vallecito Reservoir South @ 65 feet 08/16/2001 10:15 Environmental 0.064 0.088 0.107 0.004

Vallecito Reservoir South @ 65 feet 08/16/2001 10:20 Replicate 0.067 0.116 0.111 0.004

Vallecito Reservoir South @ 2 feet 09/18/2001 10:30 Environmental - - - -

Vallecito Reservoir South @ 2 feet 09/18/2001 10:35 Replicate - - - -

Vallecito Reservoir South @ 35 feet 10/17/2001 10:10 Environmental <0.013 <0.1 0.085 0.008

Vallecito Reservoir South @ 35 feet 10/17/2001 10:15 Replicate <0.013 0.074 0.095 0.004

Los Pinos River above Vallecito 

Reservoir near Bayfield, CO

10/17/2001 10:15 Environmental 0.019 <0.1 <0.1 <0.004

Los Pinos River above Vallecito 

Reservoir near Bayfield, CO

10/17/2001 10:16 Replicate 0.020 <0.1 <0.1 <0.004

Vallecito Reservoir South @ 2 feet 05/22/2002 9:00 Environmental <0.013 0.074 0.066 0.006

Vallecito Reservoir South @ 2 feet 05/22/2002 9:10 Replicate <0.013 0.069 0.062 0.005

Vallecito Reservoir South @ 2 feet 07/31/2002 9:00 Environmental <0.013 <0.1 0.136 0.01

Vallecito Reservoir South @ 2 feet 07/31/2002 9:05 Replicate <0.013 0.065 0.115 0.009

Vallecito Reservoir South @ 2 feet 08/29/2002 9:00 Environmental <0.013 0.123 0.164 0.018

Vallecito Reservoir South @ 2 feet 08/29/2002 9:05 Replicate <0.013 0.102 0.153 0.017

Site name Date Time Sample

type

Phosphorus

dissolved

(mg/L as P)

Phosphorus

ortho

dissolved

(mg/L as P)

Organic

carbon

dissolved

(mg/L as C)

UV

absorbance

(254 nm)

Vallecito Reservoir South @ 40 feet 07/17/2001 9:40 Environmental <0.006 <0.007 3.4 0.060

Vallecito Reservoir South @ 40 feet 07/17/2001 9:45 Replicate <0.006 <0.007 2.5 0.061

Vallecito Reservoir South @ 65 feet 08/16/2001 10:15 Environmental <0.006 <0.007 2.1 0.052

Vallecito Reservoir South @ 65 feet 08/16/2001 10:20 Replicate 0.005 <0.007 2.0 0.051

Vallecito Reservoir South @ 2 feet 09/18/2001 10:30 Environmental - - - -

Vallecito Reservoir South @ 2 feet 09/18/2001 10:35 Replicate - - - -

Vallecito Reservoir South @ 35 feet 10/17/2001 10:10 Environmental 0.004 <0.007 1.4 0.037

Vallecito Reservoir South @ 35 feet 10/17/2001 10:15 Replicate 0.003 <0.007 1.5 -

Los Pinos River above Vallecito 

Reservoir near Bayfield, CO

10/17/2001 10:15 Environmental <0.004 <0.007 0.8 0.020

Los Pinos River above Vallecito 

Reservoir near Bayfield, CO

10/17/2001 10:16 Replicate <0.004 <0.007 0.8 0.018

Vallecito Reservoir South @ 2 feet 05/22/2002 9:00 Environmental 0.002 <0.007 1.5 0.028

Vallecito Reservoir South @ 2 feet 05/22/2002 9:10 Replicate <0.004 <0.007 1.5 0.030

Vallecito Reservoir South @ 2 feet 07/31/2002 9:00 Environmental 0.005 <0.007 1.4 0.036

Vallecito Reservoir South @ 2 feet 07/31/2002 9:05 Replicate 0.004 0.014 1.6 0.037

Vallecito Reservoir South @ 2 feet 08/29/2002 9:00 Environmental 0.008 <0.007 1.7 0.042

Vallecito Reservoir South @ 2 feet 08/29/2002 9:05 Replicate 0.008 0.004 1.6 0.042
56 Water-Quality Data Collected from Vallecito Reservoir, Its Inflows and Outflow, Southwestern Colorado, 1999–2002 

Analysis of Field Blanks

Under ideal conditions any contamination present in field 

blanks would be so small that concentrations would be less 

than the detection limit. In practice, although concentrations 

measured in many field blanks are less than the detection limit, 

some blanks contain concentrations greater than the detection limit. Therefore, as stated in Mueller and Titus (2005), 

“The objective in analyzing data from blanks is to determine 

the amount of contamination that is not likely to be exceeded 

in a large percentage of the water samples represented by the 

blanks.” This objective can be achieved by calculating an upper 

confidence limit (UCL) for a high percentile of contamination 

in the population of water samples represented by the blanks. 

This UCL is the maximum contamination expected in the specified percentage of water samples. For example, the 95-percent 

UCL for the 90th percentile of concentrations in blanks is the 

maximum contamination expected in 90 percent of all water 

samples. In other words, there is 95 percent confidence that this 

amount of contamination would be exceeded in no more than 

10 percent of all samples (including environmental samples) 

that were collected, processed, and analyzed in the same manner as the blanks. This calculation was completed for the field 

blanks shown in table 8 using the formula given in Mueller and 

Titus (2005), and the results of calculation are given in table 10.

A review of the metal field blank data in table 8 for 

Vallecito Reservoir shows that all the blanks analyzed for dissolved and total aluminum, arsenic, cadmium, chromium, iron, 

Table 10. Upper confidence limits for contamination by nutrients and metals in specified percentiles of all samples based on data for 

field blanks.—Continued

[Vallecito Reservoir field blanks—UCL for the 60th percentile (5 blanks), 70th percentile (7 blanks), and 75th percentile (8 and 9 blanks) of concentration in 

blanks. mg/L, milligrams per liter; μg/L, micrograms per liter; <, less than; -, no data]

Analyte Number 

of blanks

Most 

common 

detection 

limit

5 blanks

Upper 

92-percent 

confidence 

limit 

7 blanks

Upper 

92-percent 

confidence 

limit

8 blanks

Upper 

90-percent 

confidence 

limit

9 blanks

Upper 

92-percent 

confidence 

limit

Ammonia, dissolved, mg/L 9 0.015 - - - <0.015

Nitrate + nitrite, dissolved, mg/L 9 0.013 - - - 0.014

Ammonia + organic nitrogen, dissolved, mg/L 9 0.1 - - - 0.233

Ammonia + organic nitrogen, total, mg/L 9 0.1 - - - <0.2

Phosphorus, total, mg/L 9 0.004 - - - <0.008

Phosphorus, dissolved, mg/L 9 0.006 - - - <0.006

Orthophosphate, dissolved, mg/L 9 0.007 - - - <0.007

Aluminum, dissolved, μg/L 8 10 - - <15 -

Aluminum, total, μg/L 8 10 - - <10 -

Arsenic, dissolved, μg/L 7 1 - <1 - -

Arsenic, total, μg/L 8 1 - - <1 -

Cadmium, dissolved, μg/L 7 0.3 - <0.3 - -

Cadmium, total, μg/L 8 0.3 - - <0.3 -

Chromium, dissolved, μg/L 7 0.4 - <0.4 - -

Chromium, total, μg/L 8 0.4 - - <0.4 -

Copper, dissolved, μg/L 7 2 - 3.0 - -

Copper, total, μg/L 8 2 - - <2 -

Iron, dissolved, μg/L 8 4 - - <4 -

Iron, total, μg/L 8 4 - - <4 -

Lead, dissolved, μg/L 7 2 - <2 - -

Lead, total, μg/L 8 2 - - <2 -

Manganese, dissolved, μg/L 8 0.4 - - <2 -

Manganese, total, μg/L 8 0.4 - - <0.4 -

Mercury, dissolved, μg/L 5 0.2 <0.2 - - -

Mercury, total, μg/L 8 0.2 - - <0.2 -

Nickel, dissolved, μg/L 7 0.4 - <0.4 - -

Nickel, total, μg/L 8 0.4 - - 2.6 -

Potassium, dissolved, μg/L 7 0.2 - <0.2 - -

Potassium, total, μg/L 8 0.2 - 0.22 - -

Silver, dissolved, μg/L 7 0.8 - <0.8 - -

Silver, total, μg/L 8 0.8 - - <0.8 -

Zinc, dissolved, μg/L 8 2 - - <2 -

Zinc, total, μg/L 8 2 - - 8.3 -
Field Blank and Field Replicate Data Collection and Interpretation 57

lead, manganese, mercury, and silver and dissolved nickel and 

zinc were reported as less than the reporting limit. A review 

of the data in table 10 indicates that there is 88–94 percent 

confidence (depending on the number of field blanks) that 

potential contamination is no greater than the detection limit 

for each of these constituents in at least 60–75 percent of all 

samples. For example, for dissolved and total iron in Vallecito 

Reservoir there is 90 percent confidence that contamination is 

no greater than 4 μg/L in at least 75 percent of all samples. For 

dissolved cadmium in Vallecito Reservoir there is 92 percent 

confidence that contamination is no greater than 0.3 μg/L in 

at least 70 percent of all samples. Two out of eight blanks 

for total nickel had measurable amounts of nickel (0.4 μg/L 

and 2.6 μg/L) and two out of eight blanks for total zinc had 

measurable amounts of zinc (3.1 μg/L and 8.3 μg/L). The 

information provided in table 10 for total zinc indicates that 

there is 90 percent confidence that contamination is no greater 

than 8.3 μg/L in at least 75 percent of all samples. For total 

nickel there is 90 percent confidence that contamination is no 

greater than 2.6 μg/L in at least 75 percent of all samples.

A review of the nutrient field blank data in table 10 for 

Vallecito Reservoir indicates that there is 92 percent confidence that contamination is no greater than the detection limit 

for dissolved ammonia, total ammonia plus organic nitrogen, total phosphorus, dissolved phosphorus, and dissolved 

orthophosphate in at least 75 percent of all samples. There is 

90 percent confidence that contamination is no greater than 

0.014 mg/L for dissolved nitrite plus nitrate and no greater 

than 0.233 mg/L for dissolved ammonia plus organic nitrogen 

in at least 75 percent of all samples.

All field blanks collected at Vallecito Creek near 

Bayfield, Colo., and Los Piños River above Vallecito Reservoir 

near Bayfield, Colo., and analyzed for metals and nutrients had 

concentrations that were less than the reporting limit except for 

one aluminum field blank and one boron field blank. Therefore, 

except for aluminum and boron, for constituents analyzed in 

three field blanks, there is 88 percent confidence that contamination is no greater than the detection limit in at least 50 percent 

of all samples. For constituents analyzed in four field blanks 

there is 94 percent confidence that contamination is no greater 

than the detection limit in at least 50 percent of all samples.

The results of the analysis of the field blank samples given 

in table 10 can then be compared to environmental concentrations to determine the likelihood that contamination has affected 

the interpretation of the environmental data in samples collected from Vallecito Reservoir. For all constituents measured 

in Vallecito Reservoir, with the exception of total nickel and 

zinc, there is a high degree of confidence that contamination 

is not greater than the detection limit or is only slightly greater 

than the detection limit. However, because the environmental 

concentrations are close to the detection limit for all constituents and the range of samples that could be affected by 

contamination varies from 25 to 40 percent, some effects 

from contamination cannot be ruled out. For example, with 

respect to orthophosphate, there is 92 percent confidence 

Table 10. Upper confidence limits for contamination by nutrients and metals in specified percentiles of all samples based on data for 

field blanks.—Continued

[Vallecito Creek and Los Piños River field blanks—UCL for the 50th percentile of concentration in blanks. mg/L, milligrams per liter; μg/L, micrograms per 

liter; <, less than; -, no data]

Analyte Number 

of blanks

Most common 

detection limit

3 blanks

Upper 88-percent 

confidence limit

4 blanks

Upper 94-percent 

confidence limit

Ammonia, dissolved, mg/L 4 0.002 - <0.002

Nitrate + nitrite, dissolved, mg/L 4 0.005 - <0.005

Orthophosphate, dissolved, mg/L 4 0.001 - <0.001

Aluminum, dissolved, μg/L 3 0.3 2.2 -

Antimony, dissolved, μg/L 3 0.2 <0.2 -

Barium, dissolved, μg/L 3 0.2 <0.2 -

Beryllium, dissolved, μg/L 3 0.2 <0.2 -

Boron, dissolved, μg/L 3 2.0 3.0 -

Cadmium, dissolved, μg/L 3 0.3 <0.3 -

Chromium, dissolved, μg/L 3 0.2 <0.2 -

Cobalt, dissolved, μg/L 3 0.2 <0.2 -

Copper, dissolved, μg/L 3 0.2 <0.2 -

Iron, dissolved, μg/L 3 3.0 <3.0 -

Lead, dissolved, μg/L 3 0.3 <0.3 -

Manganese, dissolved, μg/L 3 0.1 <0.1 -

Molybdenum, dissolved, μg/L 3 0.2 <0.2 -

Nickel, dissolved, μg/L 3 0.5 <0.5 -

Silver, dissolved, μg/L 3 0.2 <0.2 -

Zinc, dissolved, μg/L 3 0.5 <0.5 -
58 Water-Quality Data Collected from Vallecito Reservoir, Its Inflows and Outflow, Southwestern Colorado, 1999–2002 

that contamination is less than the detection limit in at least 

75 percent of samples; however, the potential contamination 

in the remaining 25 percent is not known. Although there is 

no evidence that contamination accounts for any of the measured orthophosphate, environmental concentrations are low 

in comparison to the detection limit, and some effects from 

contamination cannot be ruled out. The environmental concentrations of total iron and total manganese, however, are usually 

at least 10 times greater than the detection limit. It is unlikely 

that contamination as great as 4 mg/L in 25 percent of all 

samples (total iron) and as great as 0.4 mg/L in 25 percent of all 

samples (total manganese) will affect the interpretation of the 

total iron and manganese concentrations in the environmental 

samples. The amount of potential contamination for total nickel 

and total zinc shown in table 10 exceeds the concentration of 

these constituents in most of the environmental samples so that 

contamination probably has compromised the interpretation of 

the environmental data for these two constituents.

The same analysis of the data presented in table 10 applies 

to the environmental data collected from Vallecito Creek near 

Bayfield, Colo., and Los Piños River above Vallecito Reservoir 

near Bayfield, Colo. There is a high degree of confidence that 

contamination is not greater than the detection limit or is only 

slightly greater than the detection limit but because the environmental concentrations are close to the detection limit for all 

constituents and the range of samples that could be affected by 

contamination is 50 percent, some effects from contamination 

cannot be ruled out. For example, with respect to orthophosphate, we can state with 94 percent confidence that contamination is less than the detection limit in at least 50 percent of 

samples; however, the potential contamination in the remaining 

50 percent is not known. Although there is no evidence that 

contamination accounts for any of the measured orthophosphate, environmental concentrations are low in comparison 

to the detection limit, and some effects from contamination 

cannot be ruled out. The concentration of dissolved manganese 

in Vallecito Creek near Bayfield, Colo., and Los Piños River 

above Vallecito Reservoir near Bayfield, Colo., is usually at 

least 10 times greater than the detection limit. It is unlikely that 

contamination as great as 0.1 mg/L in 50 percent of all samples 

will affect the interpretation of the dissolved manganese concentrations in the environmental samples.

Analysis of Field Replicates

The field replicate data were analyzed to assess the amount 

of variability present in the environmental data by the method 

given in Mueller and Titus (2005). This method involved 

calculating a standard deviation for each field replicate pair 

and examining graphs of the standard deviation of each replicate 

pair as a function of the average concentration of each field 

replicate pair to determine if the standard deviation is constant 

over the range of concentrations measured. Typically, the higher 

the constituent concentration, the greater the standard deviation, however, the relation between standard deviation of each 

replicate pair was constant over the range in concentration 

measured for each constituent. This consistency most likely is a 

result of relatively little variation in the environmental concentrations for all constituents (that is concentrations were generally quite low and similar to each other). Therefore, the average 

standard deviation of the replicate pairs for each constituent was 

substituted into the following equation to calculate a 95 percent 

confidence interval about a single sample:

Cinterval = Csample ± Z0.95SD

where

Cinterval is the confidence interval about a single 

measurement = 100(1–α);

Csample is the concentration of a single sample;

SD is the average standard deviation of the 

replicate pairs;

and

Z0.95 is the statistic for the 95-percentage point of 

the standard normal curve = 1.96

When one of the replicate pairs was reported as less than the 

reporting limit but the other had measurable amounts of a 

constituent reported, the sample with a value of less than the 

reporting limit was assigned a value of one-half the reporting 

limit to perform the calculation.

The 95-percent confidence interval data about a single 

sample are presented in table 11 and can be interpreted in the 

following manner. There is 95 percent confidence that the true 

value of any individual measurement for any constituent listed 

in table 11 will lie within the range given in table 11. To determine the minimum significant difference that can be detected 

between any two individual measurements the following 

formula was used:

∆C (difference in concentration between

two samples) ≥ 1.96 * √2 * SD

If the difference in concentration between any two 

samples is equal to or greater than the values listed in table 11, 

there is a 95 percent probability that the difference is significant. This calculation has shown that, for the nutrient constituents, the minimum concentration difference that can be considered significant among the sampling sites (reservoir and the 

three stream sites) and over time at any given sampling site is 

small, ranging from 1 μg/L to 32 μg/L, except for total ammonia + organic nitrogen in the reservoir (minimum difference of 

0.186 mg/L) and DOC in the reservoir (minimum difference of 

0.4 mg/L). For the total and dissolved metal constituents there 

were only sufficient data to perform this calculation for the 

Vallecito Reservoir South sampling site. At this site, the minimum concentration difference that can be considered significant over time is small as well, ranging from 0.3 to 7.9 μg/L, 

depending on the metal and whether it is expressed as a total 

or dissolved analysis. The minimum concentration difference 

that can be considered significant for the CDPHE sampling 

sites is also small.
Analysis of pH and Specific Conductance Standard Reference Samples by the Hydrolab 59

Analysis of pH and Specific 

Conductance Standard Reference 

Samples by the Hydrolab

Quality control for the Hydrolab involved measuring 

the pH of a low ionic-strength solution provided by the USGS 

Standard Reference Sample Program (Farrar, 1999) and the 

specific conductance of a potassium chloride solution provide 

by the USGS water-quality service unit in Ocala, Fla., after 

calibration. The low ionic-strength solution is a snowmelt 

sample (P-31) with a most probable pH value of 7.44. The 

specific-conductance value of the potassium chloride solution varied from 48, 50, or 52 microsiemens per centimeter at 

25 degrees Celsius depending on availability from the USGS 

water-quality service unit in Ocala, Fla. The accuracy of the 

water temperature probe was not checked during this study. 

In the future a quality-control procedure to use for the water 

temperature probe would be to compare the water temperature 

measured with the Hydrolab to the water temperature measured with a National Institute of Standards rated thermometer 

capable of measuring to 0.1 degree Celsius.

The quality of the Hydrolab pH data was evaluated by 

determining if bias was present in the values measured by 

the Hydrolab of a Low Ionic Strength Solution. There does 

appear to be a low bias in the pH measurements made by the 

Hydrolab as the majority of the pH measurements are below 

7.44 (fig. 2 and table 12). The following hypotheses were 

evaluated with a t-test to determine if bias is present in the 

Hydrolab measurements:

Null Hypothesis (HO)—The mean of the differences 

between the Hydrolab measurements of the Low Ionic 

Strength Standard and the accepted pH value of the Low Ionic 

Strength Standard is equal to zero.

Alternative Hypothesis (HA)—The mean of the differences between the Hydrolab measurements of the Low Ionic 

Strength Standard and the accepted pH value of the Low Ionic 

Strength Standard is not equal to zero.

The p-value for the t-test is 0.0013, indicating that the 

null hypothesis is rejected for any α > 0.0013. Alpha (α) is 

the level of significance of a hypothesis test and represents the 

maximum probability of rejecting the null hypothesis when it 

is true. Therefore, by rejecting the null hypothesis at α = 0.01 

we have 99-percent confidence (the null hypothesis will be 

rejected when it is true only one time in a hundred) that bias is 

present in the pH measurements by the Hydrolab and that the 

Hydrolab measurements underestimate pH by 0.47 pH units at 

a pH of 7.44. Technically this conclusion of low bias applies 

only to a pH of 7.44, and the same calculation would need to 

be done on other standard reference solutions that bracket the 

pH measured in Vallecito Reservoir to calculate the bias at all 

pH values. However, since most of the measured pH values are 

around a pH of 7.44 (table 4), it is probably safe to conclude 

that the Hydrolab pH measurements presented in this report are 

Table 11. Ninety-five percent confidence intervals about a 

single sample.

[+/–, plus or minus; μg/L, micrograms per liter; mg/L, milligrams per liter]

Parameter and 

reporting unit

95% Confidence 

interval about 

a single sample

(+/–)

Minimum 

significant

difference 

between samples

Vallecito Reservoir

Aluminum, dissolved, 

μg/L

5.6 7.9

Aluminum, total, μg/L 4.1 5.8

Copper, dissolved, μg/L 0.8 1.1

Copper, total, μg/L 0.7 1.0

Iron, dissolved, μg/L 1.1 1.6

Iron, total, μg/L 2.3 3.2

Manganese, dissolved, 

μg/L

0.7 1.0

Manganese, total, μg/L 1.3 1.9

Nickel, dissolved, μg/L 0.2 0.3

Nickel, total, μg/L 0.2 0.3

Zinc, dissolved, μg/L 0.8 1.2

Zinc, total, μg/L 3.0 4.2

Ammonia, dissolved, 

mg/L

0.002 0.003

Nitrate + nitrite, dissolved,

mg/L

0.001 0.001

Ammonia + organic nitrogen, 

dissolved, mg/L

0.023 0.032

Ammonia + organic nitrogen, 

total, mg/L

0.131 0.186

Phosphorus, total, mg/L 0.002 0.004

Phosphorus, dissolved, 

mg/L

0.001 0.001

Orthophosphorus, dissolved, 

mg/L

0.002 0.002

Organic carbon, dissolved,

mg/L

0.3 0.4

Stream sampling sites

Ammonia, dissolved, mg/L 0.001 0.001

Nitrate + nitrite, dissolved, 

mg/L

0.004 0.005

Ammonia + organic nitrogen, 

dissolved, mg/L

0.032 0.045

Phosphorus, total, mg/L 0.001 0.002

Phosphorus, dissolved, 

mg/L

0.001 0.001

Orthophosphorus, dissolved, 

mg/L

0.001 0.001

CDPHE stream sampling sites

Iron, total, μg/L 3 4

Iron, dissolved, μg/L 1 2

Sulfate, dissolved, mg/L 0.2 0.3

Nitrate + Nitrite, dissolved, 

mg/L 

0.003 0.005

Phosphorus, total, mg/L 0.021 0.029
60 Water-Quality Data Collected from Vallecito Reservoir, Its Inflows and Outflow, Southwestern Colorado, 1999–2002 

Table 12. Differences in the measurement of the pH and specificconductance (SC) standards by the Hydrolab.

Date pH 

standard

Hydrolab 

reading Difference Percentageof error

05/18/2000 7.44 7.77 –0.33 –4.4

06/06/2000 7.44 6.87 0.57 7.7

07/11/2000 7.44 6.02 1.42 19.1

07/25/2000 7.44 6.87 0.57 7.7

08/08/2000 7.44 6.65 0.79 10.6

08/22/2000 7.44 6.18 1.26 16.9

09/28/2000 7.44 6.56 0.88 11.8

05/17/2001 7.44 7.17 0.27 3.6

06/14/2001 7.44 7.44 0.00 0.0

06/27/2001 7.44 7.32 0.12 1.6

07/31/2001 7.44 7.40 0.04 0.5

08/16/2001 7.44 7.25 0.19 2.6

08/29/2001 7.44 7.15 0.29 3.9

09/18/2001 7.44 7.51 –0.07 –0.9

05/30/2002 7.44 7.51 –0.07 –0.9

06/05/2002 7.44 6.47 0.97 13.0

09/02/2002 7.44 6.17 1.27 17.1

09/19/2002 7.44 7.07 0.37 5.0

Mean 6.4

Median 4.4

Figure 2. Comparison of Hydrolab measurements of the low ionic strength standard to the accepted true value of the standard.

biased low by about 0.47 pH unit. However, pH values as high 

as 9.4 and as low as 6.2 were measured. At these pH values, 

the calculated bias of 0.47 unit is most likely not accurate, and 

measurements of a standard reference sample with these pH 

values would be needed to estimate the bias present (if it exists).

The quality of the Hydrolab specific-conductance data 

was evaluated by determining if bias was present in the values 

measured by the Hydrolab of a specific-conductance standard 

(fig. 3 and table 11). Since the differences in the Hydrolab 

measurements of the specific-conductance standard and the 

accepted true value of the specific-conductance standard were 

not normally distributed, a Wilcoxon Signed Ranks test was 

used to evaluate the following hypotheses to determine if bias 

is present in the Hydrolab measurements:

Null Hypothesis (HO)—The mean of the differences 

between the Hydrolab measurements of the specificconductance standard and the accepted value of the specificconductance standard is equal to zero.

Alternative Hypothesis (HA)—The mean of the differences between the Hydrolab measurements of the specificconductance standard and the accepted value of the of the 

specific-conductance standard is not equal to zero.

The p-value for this test is 0.1357, indicating that the null 

hypothesis can be accepted at α = 0.05, and we can conclude 

that there is no bias present in the measurement of specific 

conductance by the Hydrolab.

6.0

6.2

6.4

6.6

6.8

7.0

7.2

7.4

7.6

7.8

8.0

pH

05/18/200006/06/200007/11/200007/25/200008/08/200008/22/200009/28/200005/17/200106/14/200106/27/200107/31/200108/16/200108/29/200109/18/200105/30/200206/05/200209/2/200209/19/2002

pH standard

Hydrolab reading

EXPLANATION
Summary 61

Table 12. Differences in the measurement of the pH and specificconductance (SC) standards by the Hydrolab.—Continued

Date SC 

standard

Hydrolab 

reading Difference Percentage of error

05/18/2000 50 47 –3 6.0

06/06/2000 50 47 –3 6.0

06/20/2000 50 57 7 –14.0

07/11/2000 50 51 1 –2.0

07/25/2000 48 48 0 0.0

08/08/2000 48 48 0 0.0

08/22/2002 48 48 0 0.0

09/28/2000 50 50 0 0.0

05/17/2001 50 49 –1 2.0

06/14/2001 50 48 –2 4.0

06/27/2001 50 49 –1 2.0

07/31/2001 50 50 0 0.0

08/16/2001 50 49 –1 2.0

08/29/2001 50 50 0 0.0

09/18/2001 50 48 –2 4.0

10/01/2001 50 47 –3 6.0

05/30/2002 52 48 –4 7.7

06/05/2002 50 49 –1 2.0

09/02/2002 48 50 2 –4.2

09/19/2002 50 50 0 0.0

Mean 1.1

Median 1.0

Figure 3. Difference between the value of the specificconductance standard and the Hydrolab reading of the specific 

conductance standard.

Summary

The USGS, in cooperation with volunteers from 

the Pine River Watershed Stakeholders Group and the 

U.S. Environmental Protection Agency (USEPA), U.S. Bureau 

of Reclamation (BOR), Colorado Department of Public Health 

and Environment (CDPHE), Pine River Irrigation District, 

Southern Ute Tribe, San Juan Basin Health Department, and 

San Juan Resource Conservation and Development, collected water-quality samples from Vallecito Reservoir, its 

two major inflows, and its outflow between August 1999 and 

November 2002 at about monthly intervals from April through 

November. This report documents the (1) sampling sites and 

times of sample collection, (2) sample-collection methods, 

(3) laboratory analytical methods, and (4) responsibilities of 

each agency/group involved in the project. The report also 

provides the environmental and quality-control data collected 

during the project and provides an interpretation of the qualitycontrol data (field blanks and field duplicates) to assess the 

quality of the environmental data.

The study was initiated due to concern the Pine River 

Watershed Stakeholders Group expressed about the potential effects population growth and development within the 

Vallecito Reservoir watershed might have on the water quality 

of Vallecito Reservoir, its two major inflows (Vallecito Creek 

and Los Piños River), and Los Piños River downstream from 

the reservoir. To address this issue, the stakeholders envisioned 

a long-term water-quality monitoring project of the study 

area and initiated water-quality sampling in August 1999. 

The overall objectives of the water-quality monitoring are to 

(1) characterize the current water quality of the study area and 

(2) periodically monitor the water quality of the study area over 

time to document trends in water quality and the causes for the 

trends if they occur.

The water-quality samples were analyzed for total 

and dissolved metals (aluminum, arsenic, cadmium, copper, 

chromium, iron, lead, manganese, mercury, nickel, silver, 

and zinc), dissolved major ions (calcium, magnesium, sodium, 

potassium, chloride, bicarbonate, and sulfate), dissolved silica, 

dissolved organic carbon, ultraviolet absorbance at 254 and 

280 nanometers, nutrients (total organic nitrogen, dissolved 

organic nitrogen, dissolved ammonia, dissolved nitrate, total 

phosphorus, dissolved phosphorus, and orthophosphorus), 

chlorophyll-a (reservoir only), and suspended sediment 

(inflows to the reservoir only). Measurements of field properties (pH, specific conductance, water temperature, and 

dissolved oxygen) also were made at each sampling site 

each time a water-quality sample was collected.

An assessment of the field-blank data collected from 

Vallecito Reservoir showed that all constituents were either 

below or slightly above the detection limit in all field blanks. 

The only exceptions were one total nickel and one total zinc 

field blank in which the measured concentration of these two 

05/18/200006/06/200007/11/200007/25/200008/08/200008/22/200009/28/200005/17/200109/18/200110/01/200105/30/200206/05/2002

DIFFERENCE BETWEEN THE VALUE OF THE SC STANDARD

AND THE HYDROLAB READING OF THE SC STANDARD

(MICROSIEMENS PER CENTIMETER) –6

–4

–2

0

2

4

6

8

06/14/2001

06/27/200107/31/200108/16/2001

08/29/2001

09/02/2002

09/19/2002

EXPLANATION

Zero difference between 

 SC standard and Hydrolab

Difference between SC standard 

 and Hydrolab reading
62 Water-Quality Data Collected from Vallecito Reservoir, Its Inflows and Outflow, Southwestern Colorado, 1999–2002 

constituents were well above the detection limit. Thus, it was 

concluded with 88–94 percent confidence (depending on the 

number of field blanks) that potential contamination is no 

greater than the detection limit for each of these constituents 

in at least 60–75 percent of all samples. However, since the 

concentration of all constituents in the environmental samples is close to the detection limit and the range of samples 

that could be affected by contamination is 25–40 percent, 

some effects from contamination cannot be ruled out. The 

environmental concentrations of total iron and total manganese, however, are usually at least 10 times greater than the 

detection limit. It is unlikely that contamination as great as 

4 mg/L in 25 percent of all samples (total iron) and as great 

as 0.4 mg/L in 25 percent of all samples (total manganese) 

will affect the interpretation of the total iron and manganese 

concentrations in the environmental samples. The amount of 

potential contamination for total nickel and total zinc exceeds 

the concentration of these constituents in most of the environmental samples so that contamination probably has compromised the interpretation of the environmental data for these 

two constituents.

An assessment of the field blank data collected from 

Vallecito Creek and Los Piños River showed that all constituents were below the detection limit in all field blanks except 

for one aluminum field blank and one boron field blank. 

Therefore, except for aluminum and boron, for constituents 

analyzed in three field blanks, there is 88 percent confidence 

that contamination is no greater than the detection limit in at 

least 50 percent of all samples. For constituents analyzed in 

four field blanks, there is 94 percent confidence that contamination is no greater than the detection limit in at least 50 percent of all samples. However, since the concentration of all 

constituents in the environmental samples is close to the detection limit and the amount of samples that could be affected 

by contamination is 50 percent, some effects from contamination cannot be ruled out. The environmental concentration 

of dissolved manganese in Vallecito Creek near Bayfield, 

Colo., and Los Piños River above Vallecito Reservoir near 

Bayfield, Colo., is usually at least 10 times greater than the 

detection limit. It is unlikely that contamination as great as 

0.1 mg/L in 50 percent of all samples will affect the interpretation of the dissolved manganese concentrations in the 

environmental samples.

The analysis of the field blank data has shown that, 

except for total nickel and total zinc in samples collected from 

the Vallecito Reservoir South sampling site, there is no cause 

for concern about contamination; but these data are limited, so 

there is some uncertainty (particularly for the stream samples). 

Therefore, the environmental data collected from all sampling 

sites (Vallecito Reservoir and the three stream sites) can be 

considered comparable.

Variability present in the environmental data was estimated by calculating a 95 percent confidence interval about a 

single sample for each constituent and the minimum difference 

between any two samples that can be considered significant. 

The calculation of the minimum difference between any two 

samples that can be considered significant indicates that, for 

both the nutrient and metal constituents, the differences in concentration among the sampling sites and over time at a given 

sampling site (that can be detected) is small. For example, for 

the nutrient constituents the minimum concentration difference that can be considered significant ranges from 1 μg/L to 

32 μg/L, except for total ammonia + organic nitrogen in the 

reservoir (minimum difference of 0.186 mg/L) and DOC in the 

reservoir (minimum difference of 0.4 mg/L). For the total and 

dissolved metal constituents there were only sufficient data to 

perform this calculation for the Vallecito Reservoir South sampling site. At this site, the minimum concentration difference 

that can be considered significant is small as well and ranges 

from 0.3 to 7.9 μg/L, depending on the metal and whether it is 

expressed as a total or dissolved analysis.

The CDPHE did not collect field blanks from Vallecito 

Creek near mouth and Los Piños River above Vallecito 

Reservoir but did collect a few field replicates from these 

sampling sites. The minimum concentration difference that 

can be considered significant for the CDPHE sampling sites is 

small (4 μg/L for total Fe, 2 μg/L for dissolved Fe, 5 μg/L as 

N for NO3 + NO2, 29 μg/L as P for total phosphorus, and less 

than 1 mg/L for sulfate) but it was not possible to determine 

if contamination has any effect on the interpretation of the 

environmental data collected from these sites.

An analysis of the quality-control data for the Hydrolab 

showed that, on average, the Hydrolab underestimated pH by 

0.47 pH units, and there was no bias in the measurement of 

specific conductance. The documentation of sampling dates, 

locations, field methods, and laboratory methods described 

in this report and the analysis of the field blank and field 

duplicate data allow the water-quality data collected during 

1999–2002 to serve as a baseline data set against which future 

changes in water quality can be assessed.

Acknowledgments

The USGS gratefully acknowledges the funding contribution made by Southern Ute Tribe for the majority of the work 

described in this report and the funding provided by the Bureau 

of Reclamation for the collection of water-quality samples following the Missionary Ridge Fire in June 2002. The USGS also 

acknowledges the contributions of the volunteers from the Pine 

River Watershed Stakeholders Group, USEPA, CDPHE, Pine 

River Irrigation District, San Juan Basin Health Department, 

and San Juan Resource Conservation and Development in the 

collection and analysis of water-quality data.
References Cited 63

References Cited

American Public Health Association, 1998, 20th edition, Standard methods for the examination of water and wastewater: 

American Public Health Association, variously paged.

Britton, L.J., and Greeson, P.E., 1987, eds., Methods for collection and analysis of aquatic biological and microbiological samples: Techniques of Water-Resources Investigations 

of the U.S. Geological Survey, book 5, chap. A4, 363 p.

Carlson, R.E., 1977, A trophic state index for lakes: Limnology and Oceanography, v. 22, no. 2, p. 361–369.

Cobb, E.D., and Biesecker, J.E., 1971, The national hydrologic bench-mark network: U.S. Geological Survey 

Circular 460–D, 38 p.

Colorado Department of Public Health and Environment, 

1994, Quality assurance project plan for the Colorado 

nonpoint-source monitoring program, variously paged.

Edwards, T.K., and Glysson, G.D., 1988, Field methods for 

measurement of fluvial sediment: U.S. Geological Survey 

Open-File Report 86–531, 118 p.

Farrar, J.W., 1999, Results of the U.S. Geological Survey’s 

analytical evaluation program for standard reference samples: T-155 (trace constituents), M-148 (major constituents), 

N-59 (nutrient constituents), N-60 (nutrient constituents), 

P-31) low ionic strength constituents), GWT-4 (groundwater trace constituents), and Hg-27 (mercury) distributed 

in September 1998: U.S. Geological Survey Open-File 

Report 99–71, 143 p.

Fishman, M.J., 1993, Methods of analysis by the U.S. Geological Survey National Water Quality Laboratory—

Determination of inorganic and organic constituents in 

water and fluvial sediments: U.S. Geological Survey OpenFile Report 93–125, 217 p.

Horowitz, A.J., Demas, C.R., Fitzgerald, K.K., Miller, T.L., 

and Rickert, D.A., 1994, U.S. Geological Survey protocol 

for the collection and processing of surface-water samples 

for the subsequent determination of inorganic constituents in filtered water: U.S. Geological Survey Open-File 

Report 94–539, 57 p.

Hydrolab Corporation, 1993, Technical manual: Austin, Tex., 

130 p.

Keith, L.H., ed., 1996, Compilation of EPA’s sampling and analysis methods, 2d ed.: New York, Lewis Publishers, 1696 p.

Mueller, D.K., and Titus, C.J., 2005, Quality of nutrient data 

from streams and ground water sampled during water years 

1992–2001: U.S. Geological Survey Scientific Investigations Report 2005–5106, 27 p.

Ranalli, A.J., and Evans, J.B., 1999, Water quality of Vallecito 

Reservoir and its inflows, southwestern Colorado, 1996–97: 

U.S. Geological Survey Water-Resources Investigations 

Report 99–4092, 37 p.

Rantz, S.E., and others, 1982, Measurement and computation of 

streamflow, volume 1, Measurement of stage and discharge: 

U.S. Geological Survey Water-Supply Paper 2175, 284 p.

Wilde, F.D., and Radtke, D.F., 1998, National field manual for 

the collection of water-quality data: U.S. Geological Survey 

Techniques of Water-Resources Investigations, book 9, 

chap. A5, variously paged.
Appendix 65

Appendix Table. Field property data measured in Vallecito Reservoir, 2000–2002.—Continued

[ft, feet; μS/cm, microsiemens per centimeter; oC, degrees Celsius; mg/L, milligrams per liter]

Date Time

Reservoir 

sample depth,

ft

Field specific 

conductance, 

μS/cm @ 25°C

Field pH, 

standard units

Temperature,

 °C

Dissolved 

oxygen (DO),

mg/L

Vallecito Reservoir at South End

05/19/00 10:36 0 87 7.9 10.7 9.3

05/19/00 10:37 5 84 7.9 10.6 9.7

05/19/00 10:39 10 84 7.9 10.4 9.4

05/19/00 10:40 15 84 7.8 10.2 9.1

05/19/00 10:41 20 84 7.8 10.1 9.2

05/19/00 10:43 30 83 7.8 10 9.1

05/19/00 10:44 40 84 7.7 9.6 8.6

05/19/00 10:45 50 84 7.7 9.2 8.6

05/19/00 10:46 60 86 7.5 8.5 8.8

05/19/00 10:47 70 87 7.5 8 8.6

05/19/00 10:49 80 88 7.4 7.8 8.9

05/19/00 10:50 85 88 7.4 7.7 9.4

06/06/00 10:00 2 84 8.3 16 8.25

06/06/00 9:32 5 78 8.3 15.8 8.3

06/06/00 9:34 10 77 8.3 15.7 8.2

06/06/00 9:36 15 77 8.3 15.6 8.3

06/06/00 9:38 20 77 8.3 15.5 8.2

06/06/00 10:15 25 76 7.5 11.3 7.9

06/06/00 9:40 30 75 7.4 10.4 7.8

06/06/00 9:41 35 75 7.4 9.9 7.7

06/06/00 9:42 40 74 7.3 9.7 7.6

06/06/00 9:43 50 78 7.2 9.2 7.5

06/06/00 9:45 60 78 7.2 9 7.3

06/06/00 9:46 70 78 7.2 8.9 7.2

06/06/00 9:47 80 79 7.2 8.9 7.2

06/06/00 9:48 90 79 7.2 8.8 7.2

06/06/00 10:30 100 81 7.1 8.6 7

06/20/00 10:00 0 87 8.2 17.2 8.5

06/20/00 10:01 5 87 8.4 17.2 8.6

06/20/00 10:02 10 87 8.4 17 8.7

06/20/00 10:03 15 87 8.4 16.9 8.8

06/20/00 10:04 20 85 8.2 15.8 8.8

06/20/00 10:05 25 84 8.1 15.4 8.8

06/20/00 10:06 30 82 7.6 13.9 8.7

06/20/00 10:07 35 84 7.2 11.2 8.1

06/20/00 10:08 40 85 7.1 10.8 7.5

06/20/00 10:09 45 85 7 10.6 7.5

06/20/00 10:10 50 86 6.9 10.2 7.2

06/20/00 10:11 60 87 6.9 9.9 7

06/20/00 10:12 70 87 6.9 9.8 7

07/11/00 9:30 0 86 7.8 19.7 7

07/11/00 9:31 5 84 7.8 19.5 7.1

07/11/00 9:32 10 83 7.7 19.4 7.1

07/11/00 9:33 15 83 7.7 19.4 7.2

07/11/00 9:34 20 82 7.5 18.9 7.2

07/11/00 10:00 25 82 7.3 18.5 7.2

07/11/00 9:36 30 80 7 16.5 6.9

07/11/00 9:37 35 79 6.7 14.7 6.4

07/11/00 9:38 45 79 6.4 11.6 5.5

07/11/00 9:39 55 79 6.3 10.7 5.4

07/11/00 9:40 65 80 6.3 10.2 5.2

07/11/00 9:41 75 80 6.3 9.9 5.1

07/11/00 10:30 78 81 6.3 9.8 4.9
66 Water-Quality Data Collected from Vallecito Reservoir, Its Inflows and Outflow, Southwestern Colorado, 1999–2002 

Appendix Table. Field property data measured in Vallecito Reservoir, 2000–2002.—Continued

[ft, feet; μS/cm, microsiemens per centimeter; oC, degrees Celsius; mg/L, milligrams per liter]

Date Time

Reservoir 

sample depth,

ft

Field specific 

conductance, 

μS/cm @ 25°C

Field pH, 

standard units

Temperature,

 °C

Dissolved 

oxygen (DO),

mg/L

Vallecito Reservoir at South End—Continued

07/25/00 9:58 2 80 8 20 7.3

07/25/00 10:00 5 80 8 19.9 7.4

07/25/00 10:01 10 80 7.9 19.8 7.5

07/25/00 10:02 15 80 7.8 19.8 7.4

07/25/00 10:03 20 80 7.7 19.8 7.4

07/25/00 10:04 25 80 7.9 19.7 7.3

07/25/00 10:05 30 78 7.4 18.4 6.8

07/25/00 10:06 32 78 7.2 17.3 6.3

07/25/00 10:07 35 77 7.1 16.8 6.2

07/25/00 10:08 45 75 6.9 14.2 5.3

07/25/00 10:09 55 75 6.8 12.2 5

07/25/00 10:10 65 76 6.7 10.8 4.7

07/25/00 10:12 75 77 6.7 10 4.1

07/25/00 10:15 80 78 6.8 9.8 3.8

08/08/00 9:30 2 80 7.8 20.1 7.8

08/08/00 9:32 5 81 7.8 20 7.9

08/08/00 9:33 10 81 7.8 19.8 7.8

08/08/00 9:34 15 81 7.8 19.7 8

08/08/00 9:35 20 82 7.8 19.6 7.9

08/08/00 9:37 25 82 7.7 19.6 7.8

08/08/00 9:38 30 82 7.5 19.4 7.5

08/08/00 9:40 35 82 7.2 19 7

08/08/00 9:41 40 82 6.8 18 5.8

08/08/00 9:42 45 80 6.6 16.4 4.8

08/08/00 9:43 55 77 6.4 12.9 3.7

08/08/00 9:44 65 77 6.4 10.6 3.6

08/08/00 9:45 71 78 6.7 10.1 2.7

08/22/00 9:30 2 84 6.9 19.5 7.2

08/22/00 9:32 5 84 7.1 19.5 7.2

08/22/00 9:33 10 84 7.2 19.5 7.3

08/22/00 9:34 15 84 7.2 19.5 7.3

08/22/00 9:35 20 84 7.2 19.5 7.4

08/22/00 9:36 25 85 7.2 19.5 7.4

08/22/00 9:37 30 84 7.2 19.4 7.3

08/22/00 9:39 35 84 7.2 19.4 7.3

08/22/00 9:41 40 86 6.8 19.2 8.4

08/22/00 10:00 43 86 6.6 18.5 5.1

08/22/00 9:46 45 84 6.5 18 4.6

08/22/00 9:47 50 80 6.3 14 2.9

08/22/00 9:48 55 78 6.3 12 2.6

08/22/00 9:49 60 77 6.2 11 2.4

08/22/00 10:15 70 82 6.2 9.7 0.7

09/02/00 10:00 0 91 7.2 17.6 6.9

09/02/00 10:01 5.5 91 7.3 17.4 6.8

09/02/00 10:02 10 91 7.3 17.4 6.8

09/02/00 10:03 15 91 7.2 17.3 6.8

09/02/00 10:04 20 91 7.2 17.3 6.6

09/02/00 10:05 25 92 7.2 17.2 6.6

09/02/00 10:06 30 91 7.1 17.1 6.5

09/02/00 10:07 35 91 7.1 17 6.5

09/02/00 10:08 40 91 7 16.8 6.2

09/02/00 10:09 45 90 6.8 16.4 5.4

09/02/00 10:10 50 86 6.4 13.4 2.2
Appendix 67

Appendix Table. Field property data measured in Vallecito Reservoir, 2000–2002.—Continued

[ft, feet; μS/cm, microsiemens per centimeter; oC, degrees Celsius; mg/L, milligrams per liter]

Date Time

Reservoir 

sample depth,

ft

Field specific 

conductance, 

μS/cm @ 25°C

Field pH, 

standard units

Temperature,

 °C

Dissolved 

oxygen (DO),

mg/L

Vallecito Reservoir at South End—Continued

09/02/00 10:11 55 85 6.3 10.8 0.9

09/02/00 10:12 60 87 6.4 10.1 0.3

09/28/00 10:00 0.1 97 7.1 14.8 6.3

09/28/00 10:01 5 97 7.1 14.8 6.3

09/28/00 10:02 10 97 7.1 14.8 6.3

09/28/00 10:03 15 97 7.1 14.8 6.2

09/28/00 10:04 20 97 7.1 14.8 6.2

09/28/00 10:05 25 97 7 14.8 6.2

09/28/00 10:06 30 96 7 14.8 6

09/28/00 10:07 35 97 6.8 14.5 5.5

09/28/00 10:08 40 97 6.8 14.2 5.4

09/28/00 10:09 45 94 6.4 13.5 3.6

09/28/00 10:10 50 91 6.2 11.6 0.9

05/17/01 10:01 2 83 8.3 12.7 8.6

05/17/01 10:00 10 81 8.2 12.0 8.7

05/17/01 9:59 20 80 7.9 10.0 8.5

05/17/01 9:58 30 79 7.7 8.2 8.5

05/17/01 9:57 40 84 7.6 7.2 8.5

05/17/01 9:56 50 84 7.5 6.9 8.4

05/17/01 9:55 60 87 7.4 6.6 8.1

05/17/01 9:48 70.4 89 7.4 6.2 7.8

05/30/01 9:55 2.1 72 8.1 12.6 8

05/30/01 9:54 7 71 8.1 12.4 8.1

05/30/01 9:52 11.8 72 8.1 12.3 8.1

05/30/01 9:50 17 72 8 12.1 8

05/30/01 9:49 22 72 7.7 10.8 7.9

05/30/01 9:47 27.6 72 7.6 9.6 7.9

05/30/01 9:45 32.7 67 7.5 8.8 8

05/30/01 9:42 42 69 7.5 8.3 7.9

05/30/01 9:40 46.8 72 7.4 8.1 7.8

05/30/01 9:38 52.2 74 7.4 7.7 7.8

05/30/01 9:36 57.1 75 7.4 7.7 7.8

05/30/01 9:35 62.1 76 7.3 7.6 7.3

05/30/01 9:33 66.7 76 7.3 7.5 7.7

05/30/01 9:32 72.5 76 7.3 7.4 7.8

05/30/01 9:31 78 80 7.3 7.3 7.9

05/30/01 9:25 83.9 81 7.3 7.1 8.4

06/01/01 9:46 10 65 7.9 13.1 8.1

06/01/01 9:47 15 64 7.9 12.8 8.1

06/01/01 9:48 20 64 7.8 12.6 8.1

06/01/01 9:49 25 64 7.8 12.4 8.1

06/01/01 9:50 30 64 7.8 12.1 8.1

06/01/01 9:55 35 63 7.7 11.3 8.1

06/01/01 9:56 40 63 7.7 11.1 8

06/01/01 9:58 50 65 7.6 9.7 7.9

06/01/01 9:59 55 66 7.5 9.7 7.8

06/01/01 10:00 60 66 7.5 9.5 7.7

06/01/01 10:01 65 68 7.5 9.2 7.7

06/01/01 10:02 70 68 7.5 9 7.5

06/01/01 10:03 75 68 7.5 9 7.5

06/01/01 10:04 80 68 7.5 8.8 7.5

06/01/01 10:06 90 70 7.4 8.6 7.3

06/14/01 9:15 2 64 7.8 13.4 7.8
68 Water-Quality Data Collected from Vallecito Reservoir, Its Inflows and Outflow, Southwestern Colorado, 1999–2002 

Appendix Table. Field property data measured in Vallecito Reservoir, 2000–2002.—Continued

[ft, feet; μS/cm, microsiemens per centimeter; oC, degrees Celsius; mg/L, milligrams per liter]

Date Time

Reservoir 

sample depth,

ft

Field specific 

conductance, 

μS/cm @ 25°C

Field pH, 

standard units

Temperature,

 °C

Dissolved 

oxygen (DO),

mg/L

Vallecito Reservoir at South End—Continued

06/14/01 9:45 0.9 64 7.9 13.4 7.8

06/14/01 9:46 10 65 7.9 13.1 8.1

06/14/01 9:47 15 64 7.9 12.8 8.1

06/14/01 9:48 20 64 7.8 12.6 8.1

06/14/01 9:49 25 64 7.8 12.4 8.1

06/14/01 9:50 30 64 7.8 12.1 8.1

06/14/01 9:55 35 63 7.7 11.3 8.1

06/14/01 9:56 40 63 7.7 11.1 8.0

06/14/01 9:57 45 64 7.6 10.3 8.0

06/14/01 9:58 50 65 7.6 9.7 7.9

06/14/01 9:59 55 66 7.5 9.7 7.8

06/14/01 10:00 60 66 7.5 9.5 7.7

06/14/01 10:01 65 68 7.5 9.2 7.7

06/14/01 10:02 70 68 7.5 9.0 7.5

06/14/01 10:03 75 68 7.5 9.0 7.5

06/14/01 10:04 80 68 7.5 8.8 7.5

06/14/01 10:05 85 70 7.5 8.6 7.3

06/14/01 10:06 90 70 7.4 8.6 7.3

06/27/01 9:56 0.6 64 8.3 17.8 7.4

06/27/01 9:55 5.1 65 8.3 17.5 7.5

06/27/01 9:54 10 64 8.3 17.3 7.5

06/27/01 9:53 15 64 8.3 17.2 7.6

06/27/01 9:52 20.1 63 8 15.9 7.6

06/27/01 9:51 25 61 7.5 13.7 7.2

06/27/01 9:50 30.2 60 7.4 12.3 7.1

06/27/01 9:49 35.2 60 7.3 35.2 7

06/27/01 9:48 40.2 61 7.3 11 7

06/27/01 9:47 45.3 62 7.3 10.5 7

06/27/01 9:46 50 62 7.2 10.3 7

06/27/01 9:45 54.9 63 7.2 10.2 7

06/27/01 9:44 59.9 64 8.2 9.9 6.9

06/27/01 9:43 65.1 63 7.2 9.8 6.8

06/27/01 9:42 70.2 64 7.2 9.8 6.8

06/27/01 9:41 75.1 64 7.2 9.7 6.9

06/27/01 9:40 80 64 7.2 9.6 6.9

06/27/01 9:39 84.9 64 7.2 9.5 6.7

06/27/01 9:38 90.2 64 7.2 9.4 6.7

06/27/01 9:36 95.3 64 7.1 9.4 6.6

06/27/01 9:35 99.9 65 7.1 9.4 6.6

07/17/01 9:30 2 67 8.2 19.3 7.0

07/17/01 9:38 5 67 8.2 19.3 7.0

07/17/01 9:37 10 67 8.2 19.2 6.9

07/17/01 9:36 15 67 8.1 19.2 6.9

07/17/01 9:35 19.9 67 8.1 19.1 6.9

07/17/01 9:34 25 65 7.6 16.9 7.1

07/17/01 9:33 29.9 62 7.3 14.5 6.7

07/17/01 9:32 35 62 7.1 13.1 6.1

07/17/01 9:31 40 62 7.1 12.5 5.8

07/17/01 9:30 45 63 7.1 11.6 5.7

07/17/01 9:29 50 64 7.0 11.1 5.8

07/17/01 9:28 55 64 7.0 10.8 5.6

07/17/01 9:27 60 64 7.0 10.8 5.6

07/17/01 9:26 65.1 65 7.0 10.7 5.7

07/17/01 9:25 70.1 65 7.0 10.7 5.7
Appendix 69

Appendix Table. Field property data measured in Vallecito Reservoir, 2000–2002.—Continued

[ft, feet; μS/cm, microsiemens per centimeter; oC, degrees Celsius; mg/L, milligrams per liter]

Date Time

Reservoir 

sample depth,

ft

Field specific 

conductance, 

μS/cm @ 25°C

Field pH, 

standard units

Temperature,

 °C

Dissolved 

oxygen (DO),

mg/L

Vallecito Reservoir at South End—Continued

07/17/01 9:24 75 65 7.0 10.5 5.8

07/17/01 9:23 80 66 7.0 10.3 5.7

07/17/01 9:22 85 66 7.0 10.1 5.7

07/17/01 9:21 90 67 - 9.9 5.4

07/17/01 9:20 90.5 66 7.1 10.0 6.2

07/31/01 9:25 5.1 68 8.5 20.0 7

07/31/01 9:26 10 68 8.5 19.9 7.2

07/31/01 9:27 14.9 68 8.4 19.9 7.2

07/31/01 9:28 20.1 69 8.4 19.8 7.3

07/31/01 9:29 25 69 8 18.6 7.5

07/31/01 9:30 29.9 67 7.7 17.3 7.4

07/31/01 9:31 34.9 64 7.4 15.1 7

07/31/01 9:32 40.4 64 7.2 14.0 6.2

07/31/01 9:33 45.3 63 7.1 13.2 5.9

07/31/01 9:34 49.6 64 7 12.8 5.6

07/31/01 9:35 54.9 64 7 11.7 5.6

07/31/01 9:36 59.7 64 7 11.2 5.5

07/31/01 9:37 65.3 64 7 11.0 5.5

07/31/01 9:38 70.1 64 7 10.7 5.3

07/31/01 9:39 75.3 66 6.9 10.5 4.8

07/31/01 9:40 80.1 65 6.9 10.3 4.8

07/31/01 9:41 85.1 66 6.9 10.1 4.2

08/16/01 9:22 5 68 8.4 19.4 6.9

08/16/01 9:23 10 68 8.5 19.3 6.9

08/16/01 9:24 15 68 8.5 19.3 6.9

08/16/01 9:25 20 68 8.6 19.3 6.9

08/16/01 9:26 25 68 8.6 19.2 6.9

08/16/01 9:27 30 67 7.5 17.4 6.5

08/16/01 9:28 35 67 7.1 16.5 6.2

08/16/01 9:30 40 65 7.3 15.9 5.6

08/16/01 9:31 45 65 7.2 15.5 5.5

08/16/01 9:32 49.9 65 7.2 15 5.2

08/16/01 9:33 55 64 7.1 14.2 4.7

08/16/01 9:34 60 64 7.0 12.9 4.5

08/16/01 9:35 65 64 7.0 12.1 4.4

08/16/01 9:36 70 64 6.9 11.6 4.3

08/16/01 9:37 75 64 6.9 11.2 4.1

08/16/01 9:38 80 64 6.9 10.8 4.1

08/16/01 9:39 85 66 6.8 10.3 8.4

08/16/01 9:48 88 66 6.8 10.1 2.8

08/17/01 9:38 5 67 8.2 19.3 7

08/17/01 9:37 10 67 8.2 19.2 7

08/17/01 9:36 15 67 8.1 19.2 7

08/17/01 9:35 19.9 67 8.1 19.1 6.9

08/17/01 9:34 25 65 7.6 16.9 7.1

08/17/01 9:33 29.9 62 7.3 14.5 6.7

08/17/01 9:32 35 62 7.1 13.1 6.1

08/17/01 9:30 45 63 7.1 11.6 5.7

08/17/01 9:29 50 64 7.0 11.1 5.8

08/17/01 9:28 55 64 7.0 10.8 5.6

08/17/01 9:27 60 64 7.0 10.8 5.5

08/17/01 9:26 65.1 65 7.0 10.7 5.7

08/17/01 9:25 70.1 65 7.0 10.7 5.7
70 Water-Quality Data Collected from Vallecito Reservoir, Its Inflows and Outflow, Southwestern Colorado, 1999–2002 

Appendix Table. Field property data measured in Vallecito Reservoir, 2000–2002.—Continued

[ft, feet; μS/cm, microsiemens per centimeter; oC, degrees Celsius; mg/L, milligrams per liter]

Date Time

Reservoir 

sample depth,

ft

Field specific 

conductance, 

μS/cm @ 25°C

Field pH, 

standard units

Temperature,

 °C

Dissolved 

oxygen (DO),

mg/L

Vallecito Reservoir at South End—Continued

08/17/01 9:24 75 65 7.0 10.5 5.8

08/17/01 9:23 80 66 7.0 10.3 5.7

08/17/01 9:22 85 66 7.0 10.1 5.7

08/29/01 9:22 8 70 8.1 18.4 6.7

08/29/01 9:23 10 70 8.2 18.4 6.7

08/29/01 9:24 15 70 8.2 18.3 7.1

08/29/01 9:25 20 70 8.2 18.3 7.1

08/29/01 9:26 25 70 8.2 18.3 6.9

08/29/01 9:27 30 69 8.2 18.3 6.9

08/29/01 9:28 35 68 7.6 16.6 6.4

08/29/01 9:29 40 68 7.4 16.1 6.1

08/29/01 9:30 45 67 7.2 15.5 5.7

08/29/01 9:31 50 66 7.1 15.1 5.3

08/29/01 9:32 55 66 7.1 14.9 5

08/29/01 9:33 60 66 7 14.4 4.5

08/29/01 9:34 65 66 6.9 13.6 4.2

08/29/01 9:35 70 65 6.9 12.7 3.9

08/29/01 9:36 75 65 6.8 11.2 3.3

08/29/01 9:37 80 66 6.7 10.7 2.8

10/17/01 10:00 2 68 8 12.2 7.2

10/17/01 9:31 5 71 7.9 12.2 7.1

10/17/01 9:32 10 68 7.8 12.2 7

10/17/01 9:33 15 67 7.8 12.2 7

10/17/01 9:34 20 68 7.8 12.2 7

10/17/01 9:35 25 68 7.8 12.2 6.9

10/17/01 9:36 30 68 7.8 12.2 6.9

10/17/01 10:10 35 68 7.8 12.2 6.9

10/17/01 9:38 40 68 7.8 12.2 7.4

10/17/01 9:39 45 68 7.8 12.2 9.4

10/17/01 9:40 50 68 7.7 12.2 7.7

10/17/01 9:41 55 68 7.7 12.1 6.8

10/17/01 9:42 60 68 7.6 12.1 6.5

10/17/01 9:43 65 70 7.5 11.9 5.9

05/22/02 9:00 2 87 7.9 12.4 7.2

05/22/02 9:55 5 87 7.8 12.4 7.2

05/22/02 9:54 10 88 7.8 12.3 7.2

05/22/02 9:53 15 88 7.7 12.2 7.1

05/22/02 9:52 20 88 7.7 12.0 7.1

05/22/02 9:51 25 88 7.7 11.9 7.1

05/22/02 9:50 30 88 7.7 11.8 7.0

05/22/02 9:49 35 89 7.6 11.8 7.0

05/22/02 9:48 40 88 7.6 11.5 6.9

05/22/02 9:47 45 89 7.5 11.3 6.9

05/22/02 9:46 50 89 7.4 10.7 6.9

05/22/02 9:45 55 89 7.3 10.6 6.8

05/22/02 9:44 60 89 7.3 10.4 6.7

05/22/02 9:20 65 89 7.3 10.2 6.6

05/22/02 9:43 67.5 89 7.2 10.0 6.7

06/05/02 9:20 1 92 7.2 15.3 6.7

06/05/02 9:21 5 92 7.2 15.1 6.7

06/05/02 9:22 10 92 7.2 15.0 6.6

06/05/02 9:23 15 92 7.2 15.0 6.6

06/05/02 9:24 20 92 7.2 15.0 6.6
Appendix 71

Appendix Table. Field property data measured in Vallecito Reservoir, 2000–2002.—Continued

[ft, feet; μS/cm, microsiemens per centimeter; oC, degrees Celsius; mg/L, milligrams per liter]

Date Time

Reservoir 

sample depth,

ft

Field specific 

conductance, 

μS/cm @ 25°C

Field pH, 

standard units

Temperature,

 °C

Dissolved 

oxygen (DO),

mg/L

Vallecito Reservoir at South End—Continued

06/05/02 9:25 25 92 7.2 14.9 6.5

06/05/02 9:26 30 91 6.9 12.9 6.6

06/05/02 9:27 35 92 6.8 12.5 6.5

06/05/02 9:28 40 92 6.7 12.4 6.4

06/05/02 9:29 45 92 6.6 12.2 6.2

06/05/02 9:30 50 92 6.5 11.8 6.0

06/05/02 9:31 55 92 6.3 11.5 5.8

06/05/02 9:32 60 92 6.3 11.4 5.6

08/29/02 10:30 5 122 8.8 17.6 6.2

08/29/02 10:31 10 123 8.9 17.6 6.1

08/29/02 10:32 15 122 9 17.6 6

08/29/02 10:33 20 122 9.2 17.5 6.1

08/29/02 10:34 25 122 9.3 17.5 6.1

08/29/02 10:35 30 122 9.4 17.4 5.5

09/19/02 9:30 0.1 136 7.3 15.2 6.1

09/19/02 9:31 5 134 7.3 15.1 6

09/19/02 9:32 10 135 7.4 15.1 6

09/19/02 9:33 15 134 7.4 15.1 5.7

09/19/02 9:34 20 134 7.4 15 5.7

09/19/02 9:35 25 134 7.4 15.1 5.7

09/19/02 9:36 30 134 7.4 15.1 5.7

09/19/02 9:37 35 124 7.2 14.8 5

09/19/02 9:03 40 123 7.1 14.4 4.5

09/19/02 9:39 43 122 7 14.3 3.9

Vallecito Reservoir at Center

05/19/00 10:09 2 89 7.8 11.2 9

05/19/00 10:10 5 84 7.9 10.9 9.2

05/19/00 10:11 10 82 7.9 10.8 8.8

05/19/00 10:13 15 82 7.8 10.6 8.8

05/19/00 10:15 20 82 7.8 10.4 8.8

05/19/00 10:16 30 84 7.7 9.6 8.6

05/19/00 10:18 40 85 7.6 8.6 8.5

05/19/00 10:19 50 83 7.5 8.1 8.5

05/19/00 10:20 55 83 7.5 8 8.5

06/06/00 10:30 0 76 8.5 16.5 8.6

06/06/00 10:32 5 75 8.2 16.2 8.7

06/06/00 10:33 10 75 8.4 15.9 8.6

06/06/00 10:34 15 75 8.3 15.3 8.4

06/06/00 10:35 20 77 8 13.2 8.3

06/06/00 10:36 50 76 7.6 11.5 8.2

06/06/00 10:37 30 70 7.5 10.6 8.2

06/06/00 10:38 40 76 7.3 9.4 7.8

06/06/00 10:40 50 75 7.2 9.4 7.6

06/20/00 10:30 0 88 8.3 17.2 8.3

06/20/00 10:31 5 87 8.3 17.6 8.3

06/20/00 10:32 10 87 8.4 17.6 8.5

06/20/00 10:33 15 87 8.4 17.5 8.5

06/20/00 10:34 20 87 8.4 17.4 8.5

06/20/00 10:35 25 82 7.6 14.3 8.3

06/20/00 10:36 30 82 7.3 13.1 8.3

06/20/00 10:37 35 82 7.2 12.1 7.6

06/20/00 10:38 40 84 7 11 7.4

06/20/00 10:39 50 86 6.9 10.2 6.9
72 Water-Quality Data Collected from Vallecito Reservoir, Its Inflows and Outflow, Southwestern Colorado, 1999–2002 

Appendix Table. Field property data measured in Vallecito Reservoir, 2000–2002.—Continued

[ft, feet; μS/cm, microsiemens per centimeter; oC, degrees Celsius; mg/L, milligrams per liter]

Date Time

Reservoir 

sample depth,

ft

Field specific 

conductance, 

μS/cm @ 25°C

Field pH, 

standard units

Temperature,

 °C

Dissolved 

oxygen (DO),

mg/L

Vallecito Reservoir at Center—Continued

07/11/00 10:20 0 83 7.8 20.7 7.1

07/11/00 10:21 5 82 7.8 20.1 7.1

07/11/00 10:22 10 82 7.8 19.8 7.1

07/11/00 10:23 15 82 7.6 19.5 7.2

07/11/00 10:24 20 81 7.4 18.6 7.2

07/11/00 10:25 25 79 6.8 16.9 7

07/11/00 10:26 30 79 6.7 16.2 6.9

07/11/00 10:27 35 77 6.6 14.4 6.5

07/11/00 10:28 45 78 6.5 11.8 5.7

07/11/00 10:29 55 79 6.4 10.9 5.4

07/11/00 10:30 60 79 6.3 10.4 5.2

07/25/00 10:31 2 80 8 19.9 7.4

07/25/00 10:32 5 80 8 19.8 7.4

07/25/00 10:33 10 80 7.9 7.9 7.4

07/25/00 10:34 15 80 7.8 19.7 7.3

07/25/00 10:35 20 80 7.7 19.6 7.2

07/25/00 10:36 25 80 7.6 19.6 7.2

07/25/00 10:37 30 78 6.9 17.2 6.3

07/25/00 10:40 32 79 6.8 17 6

07/25/00 10:41 40 76 6.5 15 5.4

07/25/00 10:44 50 76 6.4 13.2 5

08/08/00 14:15 2 82 7.8 20.4 7.9

08/08/00 14:17 5 82 7.8 20.3 7.7

08/08/00 14:18 10 82 7.8 19.7 7.7

08/08/00 14:19 15 82 7.8 19.7 7.7

08/08/00 14:20 20 82 7.7 19.6 7.7

08/08/00 14:21 25 82 7.5 19.4 7.4

08/08/00 14:22 30 82 7.3 19 7.1

08/08/00 14:23 35 82 7.1 18.7 6.5

08/08/00 14:25 40 83 6.9 18.2 6

08/08/00 14:26 42 83 6.9 17.9 5.7

08/22/00 10:20 2 86 7.4 19.6 7.3

08/22/00 10:21 5 86 7.4 19.6 7.3

08/22/00 10:22 10 85 7.3 19.5 7.2

08/22/00 10:23 15 86 7.3 19.5 7.3

08/22/00 10:24 20 85 7.3 19.5 7.2

08/22/00 10:25 25 85 7.3 19.4 7.2

08/22/00 10:26 30 85 7.2 19.4 7

08/22/00 10:27 35 87 7 19.1 6.6

08/22/00 10:28 38 87 6.8 6.8 5.4

09/02/00 10:30 1.4 92 7.3 17.7 7.3

09/02/00 10:31 5 92 7.3 17.5 7.1

09/02/00 10:32 10 91 7.4 17.4 7

09/02/00 10:33 15 91 7.4 17.4 7.1

09/02/00 10:34 20 92 7.3 17.3 7

09/02/00 10:35 25 92 7.3 17.3 7

09/02/00 10:36 30 92 7.2 17.1 6.7

09/02/00 10:37 32 92 7.1 17 6.4

09/28/00 10:30 0.1 97 7.2 14.6 7

09/28/00 10:31 5 97 7.2 14.6 7

09/28/00 10:32 10 98 7.2 14.6 7.1

09/28/00 10:33 15 98 7.2 14.6 7

09/28/00 10:34 21 98 7.1 14.2 7
Appendix 73

Appendix Table. Field property data measured in Vallecito Reservoir, 2000–2002.—Continued

[ft, feet; μS/cm, microsiemens per centimeter; oC, degrees Celsius; mg/L, milligrams per liter]

Date Time

Reservoir 

sample depth,

ft

Field specific 

conductance, 

μS/cm @ 25°C

Field pH, 

standard units

Temperature,

 °C

Dissolved 

oxygen (DO),

mg/L

Vallecito Reservoir at Center—Continued

02/01/01 12:04 2.7 65 7.9 13.8 7.8

02/01/01 12:05 10 65 7.9 13.6 7.8

02/01/01 12:06 15 65 7.9 13.4 7.8

02/01/01 12:07 20 65 7.8 13.1 7.8

02/01/01 12:08 25 64 7.8 12.8 7.8

02/01/01 12:09 30 64 7.7 10.6 7.9

02/01/01 12:10 35 64 7.6 10.5 7.8

02/01/01 12:11 40 64 7.6 10.5 7.7

02/01/01 12:12 45 64 7.6 10.4 7.7

02/01/01 12:13 50 66 7.5 9.7 7.6

02/01/01 12:14 55 66 7.5 9.6 7.4

02/01/01 12:15 65 67 7.5 9.2 7.4

02/01/01 12:16 65 67 7.5 9.2 7.4

05/30/01 9:55 68 75 7.4 7.6 8.3

05/30/01 9:57 61.7 75 7.4 7.6 8

05/30/01 9:59 66.9 74 7.4 7.7 7.8

05/30/01 10:00 52 73 7.4 7.8 7.8

05/30/01 10:01 46.7 72 7.4 8 7.8

05/30/01 10:02 41.5 73 7.4 8 7.8

05/30/01 10:03 36.7 72 7.5 8.2 7.7

05/30/01 10:04 31.9 70 7.5 8.4 7.7

05/30/01 10:05 27.1 69 7.5 8.7 7.8

05/30/01 10:06 22.5 70 7.7 10.8 7.7

05/30/01 10:07 17.3 68 7.8 11.2 7.8

05/30/01 10:08 12.3 69 7.9 11.7 7.8

05/30/01 10:09 7 71 8.1 12.4 8.1

05/30/01 10:10 2.1 71 8.1 12.8 8

06/27/01 10:14 70 64 7.2 10 7.5

06/27/01 10:15 65.2 64 7.2 10 7.2

06/27/01 10:16 60.1 64 7.2 10.1 7.1

06/27/01 10:17 55 63 7.2 10.1 7

06/27/01 10:18 50.2 63 7.2 10.2 6.9

06/27/01 10:19 45 63 7.2 10.3 7

06/27/01 10:20 40.1 62 7.2 10.7 7

06/27/01 10:21 34.9 62 7.3 11 7

06/27/01 10:22 30.1 58 7.3 11.9 7

06/27/01 10:23 25.2 60 7.4 12.8 7

06/27/01 10:24 20.1 62 7.8 15 7.3

06/27/01 10:25 15 65 8.2 16.8 7.4

06/27/01 10:26 9.9 64 8.2 16.9 7.5

06/27/01 10:27 5.1 64 8.2 17.2 7.4

06/27/01 10:31 0.1 64 8.3 17.9 7.5

07/17/01 10:30 64 66 7.2 10.7 5.9

07/17/01 10:31 55 64 7.1 11.3 5.8

07/17/01 10:32 50 64 7.1 11.6 5.9

07/17/01 10:33 45 64 7 12 5.8

07/17/01 10:34 40 63 7 12.4 5.9

07/17/01 10:35 35 62 7.1 13.5 6.2

07/17/01 10:36 30 63 7.3 14.8 6.7

07/17/01 10:37 25 63 7.4 15.9 7

07/17/01 10:38 20 65 7.7 17.2 7.1

07/17/01 10:39 15 67 8 19.3 6.9

07/17/01 10:40 10 68 8.1 19.5 6.9
74 Water-Quality Data Collected from Vallecito Reservoir, Its Inflows and Outflow, Southwestern Colorado, 1999–2002 

Appendix Table. Field property data measured in Vallecito Reservoir, 2000–2002.—Continued

[ft, feet; μS/cm, microsiemens per centimeter; oC, degrees Celsius; mg/L, milligrams per liter]

Date Time

Reservoir 

sample depth,

ft

Field specific 

conductance, 

μS/cm @ 25°C

Field pH, 

standard units

Temperature,

 °C

Dissolved 

oxygen (DO),

mg/L

Vallecito Reservoir at Center—Continued

07/17/01 10:41 5 68 8.1 19.6 6.9

07/17/01 10:42 2 68 8.1 19.6 6.9

07/31/01 9:57 5 68 8.4 20.6 6.7

07/31/01 10:00 20.3 68 8.4 20.3 6.7

07/31/01 10:02 14.9 68 8.4 20.2 6.7

07/31/01 10:03 20.4 68 8.2 19.2 6.8

07/31/01 10:05 25.1 68 7.8 17.6 6.8

07/31/01 10:07 30.1 66 7.6 16.9 6.6

07/31/01 10:08 35 64 7.4 15.2 6.2

07/31/01 10:09 39.9 64 7.2 13.9 5.6

07/31/01 10:10 44.8 64 7.1 13.1 5.2

07/31/01 10:11 50 64 7.1 12.3 5

07/31/01 10:12 55.1 64 7.1 12 4.9

07/31/01 10:13 59.9 64 7 11.9 4.8

07/31/01 10:14 65 64 7 11.3 4.8

08/16/01 10:10 5 68 8.3 19.2 6.8

08/16/01 10:11 10 68 8.4 19.1 6.8

08/16/01 10:12 15 67 8.2 18.7 6.8

08/16/01 10:13 20 67 7.7 17.8 6.6

08/16/01 10:14 25 66 7.5 17.2 6.4

08/16/01 10:15 30 66 7.4 16.7 6.2

08/16/01 10:16 35 66 7.3 16.3 5.8

08/16/01 10:17 40 66 7.2 15.9 5.6

08/16/01 10:18 45 64 7.2 14.9 5.4

08/16/01 10:19 50 65 7.1 14.5 4.9

08/16/01 10:20 55 65 7 14 4.5

08/16/01 10:21 60 66 7 13.1 4.1

08/29/01 9:55 5 69 8 18.3 7

08/29/01 9:56 20 69 8 18.3 7.1

08/29/01 9:57 15 69 8.1 18.3 7.2

08/29/01 9:58 20 70 8.1 18.3 7.2

08/29/01 9:59 25 70 8.1 14.2 7

08/29/01 10:00 30 69 8.1 18.2 6.9

08/29/01 10:01 35 68 7.6 16.6 6.4

08/29/01 10:02 40 68 7.3 16.2 6

08/29/01 10:03 45 68 7.2 15.9 5.8

08/29/01 10:04 50 68 7.2 15.5 5.5

08/29/01 10:05 55 67 7.1 14.8 5.1

08/29/01 10:06 60 67 7 14.3 4.6

10/17/01 10:12 2 69 8 12.2 7.8

10/17/01 10:13 5 69 8 12.2 7.4

10/17/01 10:14 10 69 8 12.2 7.3

10/17/01 10:15 15 68 7.9 12.1 7.2

10/17/01 10:16 20 69 7.9 12.1 7.2

10/17/01 10:17 25 69 7.9 12.1 7.2

10/17/01 10:18 30 69 7.9 12.1 7.1

10/17/01 10:19 35 68 7.9 12.1 7.2

05/22/02 11:00 38 90 7.5 10.8 6.9

05/22/02 11:01 35 90 7.5 11 6.8

05/22/02 11:02 30 89 7.6 11.7 6.9

05/22/02 11:03 25 89 7.7 12.1 6.9

05/22/02 11:04 25 89 7.7 12.1 6.9

05/22/02 11:05 15 88 7.8 12.8 7
Appendix 75

Appendix Table. Field property data measured in Vallecito Reservoir, 2000–2002.—Continued

[ft, feet; μS/cm, microsiemens per centimeter; oC, degrees Celsius; mg/L, milligrams per liter]

Date Time

Reservoir 

sample depth,

ft

Field specific 

conductance, 

μS/cm @ 25°C

Field pH, 

standard units

Temperature,

 °C

Dissolved 

oxygen (DO),

mg/L

Vallecito Reservoir at Center—Continued

05/22/02 11:06 10 88 7.8 12.9 7

05/22/02 11:07 5 88 7.9 12.9 7

05/22/02 11:08 1 88 7.9 12.9 7

06/05/02 9:45 1 92 7.2 15.6 6.5

06/05/02 9:46 5 91 7.3 15.3 6.5

06/05/02 9:47 10 92 7.3 15.2 6.5

06/05/02 9:48 15 92 7.3 15.2 6.4

06/05/02 9:49 20 92 7.3 15.1 6.4

06/05/02 9:50 25 92 7.1 13.9 6.4

06/05/02 9:51 30 92 6.9 12.8 6.2

Vallecito Reservoir at North End

05/19/00 9:34 2 84 7.9 11.9 8.6

05/19/00 9:40 5 82 8 11.4 8.7

05/19/00 9:43 15 83 7.9 11 8.6

05/19/00 9:45 15 83 7.9 11 8.6

05/19/00 9:46 20 81 7.7 10.2 8.3

05/19/00 9:47 25 81 7.6 9.4 8.2

05/19/00 9:49 30 83 7.5 8.8 8.2

05/19/00 9:51 35 82 7.5 8.3 8.1

05/19/00 9:53 40 82 7.5 8.2 8.1

06/06/00 11:00 0 74 8.3 17.2 8.6

06/06/00 11:02 5 74 8.4 16.7 8.9

06/06/00 11:03 10 76 8.2 15.5 8.9

06/06/00 11:04 15 75 8.2 14.7 9.2

06/06/00 11:05 20 73 7.7 12.6 9.2

06/06/00 11:06 25 70 7.6 11.9 9.2

06/06/00 11:07 30 67 7.5 10.9 9.1

06/06/00 11:08 35 68 7.3 10.2 8.8

06/06/00 11:09 40 73 7.2 9.7 8.7

06/06/00 11:10 45 75 7.2 9.4 8.5

06/20/00 10:50 0 87 8.4 18.1 8.5

06/20/00 10:51 5 87 8.4 18.1 8.5

06/20/00 10:52 10 87 8.4 18 8.5

06/20/00 10:53 15 87 8.4 17.7 8.5

06/20/00 10:54 20 87 8.4 17.6 8.4

06/20/00 10:55 25 90 7.7 14.8 8.2

07/11/00 10:45 0 82 7.8 20.6 7.3

07/11/00 10:46 5 82 7.8 20.5 7.3

07/11/00 10:47 10 82 7.7 20.1 7.2

07/11/00 10:48 15 82 7.5 19.7 7.3

07/11/00 10:49 25 80 6.8 17.2 7.3

07/11/00 10:50 25 80 6.8 17.2 7.3

07/11/00 10:51 30 78 6.8 15.9 7

07/11/00 10:52 32 79 6.7 15.4 6.7

07/25/00 10:55 2 82 8 20.5 7.3

07/25/00 10:56 5 81 7.9 20 7.4

07/25/00 10:57 10 80 7.8 19.9 7.3

07/25/00 10:58 15 80 7.7 19.8 7.2

07/25/00 10:59 18 80 7.4 19.4 7

08/08/00 14:35 2 83 7.9 20.7 7.8

08/08/00 14:36 5 84 7.8 20.7 7.7

08/08/00 14:37 10 84 7.8 20.4 7.7

08/08/00 14:38 13 83 7.6 19.8 7.6

08/22/00 10:40 2 86 7.4 19.8 7.5
76 Water-Quality Data Collected from Vallecito Reservoir, Its Inflows and Outflow, Southwestern Colorado, 1999–2002 

Appendix Table. Field property data measured in Vallecito Reservoir, 2000–2002.—Continued

[ft, feet; μS/cm, microsiemens per centimeter; oC, degrees Celsius; mg/L, milligrams per liter]

Date Time

Reservoir 

sample depth,

ft

Field specific 

conductance, 

μS/cm @ 25°C

Field pH, 

standard units

Temperature,

 °C

Dissolved 

oxygen (DO),

mg/L

Vallecito Reservoir at North End—Continued

08/22/00 10:41 5 86 7.5 19.6 7.5

08/22/00 10:42 8 89 7.3 19.1 7.4

09/02/00 10:45 1.2 94 7.4 18 7.3

09/02/00 10:46 5.4 94 7.2 17.1 7.4

09/28/00 10:45 0.1 101 7.2 14 6.8

09/28/00 10:46 5 106 6.9 11.9 7

05/31/01 10:19 23.6 58 7.7 7.9 8.5

05/31/01 10:20 18.8 62 7.6 9.1 8.2

05/31/01 10:21 13.6 61 7.6 10 8.1

05/31/01 10:22 8.8 66 7.8 11.4 8

05/31/01 10:23 3.7 69 8 12.4 7.9

05/31/01 10:24 1.6 69 8.1 12.8 7.9

06/14/01 11:40 2 64 8 14.8 7.7

06/14/01 11:41 10 64 7.9 14.2 7.8

06/14/01 11:42 15 64 7.9 13.7 7.7

06/14/01 11:43 20 69 7.8 12.8 7.7

06/14/01 11:44 25 62 7.7 11.4 7.8

06/14/01 11:45 30 61 7.6 9.7 7.7

06/14/01 11:46 35 62 7.5 9.7 7.7

06/27/01 10:45 37 61 7.4 11.4 7.6

06/27/01 10:46 30.3 60 7.4 12.7 7.5

06/27/01 10:47 25.1 61 7.6 14.6 7.5

06/27/01 10:48 20.3 63 7.8 15.4 7.7

06/27/01 10:49 15.1 63 8 15.9 7.8

06/27/01 10:51 10.2 64 8.2 17 7.6

06/27/01 10:52 4.9 65 8.2 17.7 7.5

06/27/01 10:55 0.1 65 8.2 17.9 7.4

07/17/01 11:00 33 65 7.5 15.1 7

07/17/01 11:01 25 63 7.5 15.8 7.1

07/17/01 11:02 20 65 7.7 17.1 7.3

07/17/01 11:03 15 68 8.2 19.7 7.1

07/17/01 11:04 10 68 8.2 19.8 7.1

07/17/01 11:05 5 68 8.2 19.8 7

07/17/01 11:06 2 67 8.2 19.9 7.1

07/31/01 10:29 5 69 8.4 21.2 6.6

07/31/01 10:30 9.8 68 8.4 21 6.6

07/31/01 10:31 14.9 69 8.4 20.5 6.7

07/31/01 10:32 20 68 7.9 18.4 6.9

07/31/01 10:33 24.8 67 7.5 16.6 6.3

07/31/01 10:34 28.8 69 7.2 15.2 5.1

08/16/01 10:30 5 68 8.4 19.5 6.8

08/16/01 10:31 10 68 8.4 19.2 6.8

08/16/01 10:32 15 68 8.3 18.8 6.9

08/16/01 10:33 20 68 8 18.2 6.9

08/16/01 10:34 25 68 7.8 17.8 6.8

08/29/01 10:10 5 70 8 18.3 7

08/29/01 10:11 10 70 8.1 18.2 7

08/29/01 10:12 15 70 8.1 18.1 7

08/29/01 10:13 20 70 8 18 6.9

08/29/01 10:14 25 70 8 17.9 6.8

10/17/01 10:30 2 69 8.1 12.2 7.6

10/17/01 10:31 5 69 8 12.1 7.3

10/17/01 10:32 10 69 8 12.1 7.3

10/17/01 10:33 15 69 7.9 11.7 7.2