1 

Loch Vale Watershed Long-Term Ecological 

Research and Monitoring Program: 

Quality Assurance Report, 2003-09

By Eric E. Richer and Jill S. Baron

Open-File Report 2011-1137

U.S. Department of Interior

U.S. Geological Survey
ii

U.S. Department of the Interior

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director 

U.S. Geological Survey, Reston, Virginia 2011

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Suggested citation:

Richer, E.E., and Baron, J.S., 2011, Loch Vale Watershed Long-Term Ecological Research and 

Monitoring Program: Quality Assurance Report, 2003-09: U.S. Geological Survey Open-File Report 

2011-1137, 22 p. 

Any use of trade, product, or firm names is for descriptive purposes only and does not imply 

endorsement by the U.S. Government.

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

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

Contents 

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

Research Objectives ......................................................................................................................................... 2

Program Objectives .......................................................................................................................................... 2

Purpose and Scope .......................................................................................................................................... 2

Approach........................................................................................................................................................... 3

Precipitation Data ................................................................................................................................................. 5

Discharge Data ..................................................................................................................................................... 8

Surface-Water Chemistry Data ...........................................................................................................................11

Natural Resource Ecology Laboratory ............................................................................................................11

U.S. Forest Service Rocky Mountain Research Station Water Chemistry Laboratory ....................................12

Data Outliers ...................................................................................................................................................14

Ion and Specific Conductance Balances .........................................................................................................14

Measures of Contamination ............................................................................................................................16

Measures of Precision.....................................................................................................................................16

Changes in Field and Laboratory Procedures during 2003-09 ...........................................................................18

Summary ............................................................................................................................................................19

Acknowledgments ..............................................................................................................................................20

References Cited ................................................................................................................................................20

Figures 

1. Map showing Loch Vale watershed project monitoring sites in Rocky Mountain National Park 

(RMNP) sampled during 2003-09..............................................................................................................4

2. Graph showing cumulative precipitation measured at the colocated Belfort and NOAH IV rain gages 

at the Loch Vale CO98 National Atmospheric Deposition Program site during 2008-09 ...........................5

3. Graph showing relation between observed discharge at Andrews Creek and the Loch Outlet during 

2000-09 used to estimate discharge for the Loch Outlet from October 18, 2005, to August 17, 

2006 ..........................................................................................................................................................8

4. Graph showing discharge at three streamflow stations in the Loch Vale watershed during water 

year 2003 ..................................................................................................................................................9

5. Graph showing discharge at three streamflow stations in the Loch Vale watershed during water 

year 2004 ..................................................................................................................................................9

6. Graph showing discharge at three streamflow stations in the Loch Vale watershed during water 

year 2005 ................................................................................................................................................10

7. Graph showing discharge at three streamflow stations in the Loch Vale watershed during water 

year 2006 ................................................................................................................................................10
iv

Tables 

1.

2.

3.

4.

5.

6.

7.

8.

9.

Summary of Loch Vale watershed data collected during 2003-09.............................................................3

Annual catch efficiency of the CO98 site Aerochem Metrics precipitation collector relative to the 

Alter shielded rain gage by season during 2003-09 ..................................................................................6

National Atmospheric Deposition Program Central Analytical Laboratory instrumentation for 

measuring concentrations of precipitation analytes during 2003-09..........................................................6

National Atmospheric Deposition Program Central Analytical Laboratory detection limits for 

precipitation analytes during 2003-09........................................................................................................7

Annual sample validity for National Atmospheric Deposition Program site CO98 during 2003-09 ............7

Detection limits for carbon, nitrogen, and silica at the Natural Resource Ecology Laboratory 

during 2009 .............................................................................................................................................12

Detection limits for U.S. Forest Service Rocky Mountain Research Station Water Chemistry 

Laboratory ...............................................................................................................................................12

Analytical results for precipitation Standard Reference Samples analyzed at the U.S. Forest Service 

Rocky Mountain Research Station Water Chemistry Laboratory during 2003-09....................................13

Data outliers removed from the Loch Vale watershed surface-water records for 2003-09......................14

10. Surface-water sample reanalysis criteria for ion percent difference and conductance percent 

difference ................................................................................................................................................15

11. Samples that failed to meet quality criteria for conductance percent difference after reanalysis.............16

12. Analyte concentration percentiles for field blanks and environmental samples collected for the Loch 

Vale watershed project during 2003-09...................................................................................................17

13. Ratio of median absolute differences for normal/duplicate sample pairs to the 10th-percentile value 

for all environmental samples collected during 2003-09..........................................................................18
v

0BConversion Factors

SI to Inch/Pound

Multiply By To obtain

Length

centimeter (cm) 0.3937 inch (in.)

meter (m) 3.281 foot (ft) 

kilometer (km) 0.6214 mile (mi)

Area

square kilometer (km2) 247.1 acre

square kilometer (km2) 0.3861 square mile (mi2)

Volume

liter (L) 33.82 ounce, fluid (fl. oz)

liter (L) 2.113 pint (pt)

liter (L) 1.057 quart (qt)

liter (L) 0.2642 gallon (gal)

cubic meter (m3) 264.2 gallon (gal) 

cubic meter (m3) 0.0002642 million gallons (Mgal) 

cubic meter (m3) 35.31 cubic foot (ft3)

cubic meter (m3) 0.0008107 acre-foot (acre-ft) 

Flow rate

cubic meter per second (m3/s) 70.07 acre-foot per day (acre-ft/d) 

cubic meter per second (m3/s) 35.31 cubic foot per second (ft3/s)

cubic meter per second (m3/s) 22.83 million gallons per day (Mgal/d) 

Mass

gram (g) 0.03527 ounce, avoirdupois (oz)

kilogram (kg) 2.205 pound avoirdupois (lb)

Pressure

kilopascal (kPa) 0.01 bar

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). Altitude, as 

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

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

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

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

per liter (μeq/L).
vi

1BAbbreviations

ANC Acid neutralizing capacity

ARML Air Resource Management Laboratory

Ca2+ Calcium

CAL Central Analytical Laboratory

Cl- Chloride

CPD Conductance percent difference

CSU Colorado State University

DI Deionized 

DOC Dissolved organic carbon

F

-

Fluoride

IPD Ion percent difference

K

+

Potassium

LVWS Loch Vale Watershed

Mg2+ Magnesium

Na+

Sodium

NADP National Atmospheric Deposition Program

NH4

+ Ammonium as ammonium

NO3

- Nitrate as nitrate

NPS National Park Service

NREL Natural Resource Ecology Laboratory

PO4

3- Orthophosphate

QA Quality assurance

QAP Quality-assurance plan

QMP Quality-management plan

RMNP Rocky Mountain National Park

RMRS Rocky Mountain Research Station

SC Specific conductance

SiO2 Dissolved silica as silicon dioxide

SO4

-

Sulfate as sulfate

SRS Standard reference sample

TDN Total dissolved nitrogen

TN Total nitrogen

TOC Total organic carbon

TP Total phosphorus

USEPA U.S. Environmental Protection Agency

USFS U.S. Forest Service

USGS U. S. Geological Survey

WEBB Water, Energy, and Biogeochemical Budgets

WMI Western Mountain Initiative

WY Water year
1

Loch Vale Watershed Long-Term Ecological Research 

and Monitoring Program: Quality Assurance Report, 

2003-09

By Eric E. Richer0F0F

1 and Jill S. Baron1F1F2

2BAbstract

The Loch Vale watershed project is a long-term research and monitoring program located 

in Rocky Mountain National Park that addresses watershed-scale ecosystem processes, 

particularly as they respond to atmospheric deposition and climate variability. Measurements of 

precipitation depth, precipitation chemistry, discharge, and surface-water quality are made within 

the watershed and elsewhere in Rocky Mountain National Park. As data collected for the 

program are used by resource managers, scientists, policy makers, and students, it is important 

that all data collected in Loch Vale watershed meet high standards of quality. In this report, data 

quality was evaluated for precipitation, discharge, and surface-water chemistry measurements

collected during 2003-09. Equipment upgrades were made at the Loch Vale National 

Atmospheric Deposition Program monitoring site to improve precipitation measurements and 

evaluate variability in precipitation depth and chemistry. Additional solar panels and batteries 

have been installed to improve the power supply, and data completeness, at the NADP site. As a 

result of equipment malfunction, discharge data for the Loch Outlet were estimated from October 

18, 2005, to August 17, 2006. Quality-assurance results indicate that more than 98 percent of all 

surface-water chemistry measurements were accurate and precise. Records that did not meet 

quality criteria were removed from the database. Measurements of precipitation depth, 

precipitation chemistry, discharge, and surface-water quality were all sufficiently complete and 

consistent to support project data needs. 

3BIntroduction

The National Park Service (NPS) initiated the Loch Vale watershed (LVWS) project in 

1982 with funding from the Aquatic Effects Research Program of the National Acid Precipitation 

Assessment Program. The LVWS is a 7-km2(square kilometer) basin located within Rocky 

Mountain National Park (RMNP) in the Colorado Front Range. The project is currently a 

cooperative effort of the NPS, U.S. Geological Survey (USGS), and Colorado State University

(CSU). The long-term research and monitoring program addresses watershed-scale ecosystem 

processes, particularly as they respond to atmospheric deposition and climate variability. 

 

1Natural Resource Ecology Laboratory, Colorado State University, Fort Collins, Colorado

2U.S. Geological Survey, Fort Collins Science Center, Fort Collins, Colorado; and Natural Resource Ecology 

Laboratory, Colorado State University, Fort Collins, Colorado
2

Monitoring of climate, hydrology, precipitation chemistry, and surface-water quality allows

analysis of long-term trends and distinction between natural and human-caused disturbances. 

Research efforts are diverse, and include vegetation responses to nitrogen deposition, algal 

response to nitrogen availability, microbial activity in subalpine and alpine soils, hydrologic flow 

paths, and the response of aquatic organisms to disturbance. These research activities provide 

knowledge about the broad range of processes that influence high-altitude ecosystems in the 

Rocky Mountains.

1BResearch Objectives

1. To understand and differentiate natural processes from unnatural, human-caused drivers 

of change.

2. To understand and quantify the effects of atmospheric deposition and climate change on 

high-altitude ecosystems.

12BProgram Objectives

1. To share knowledge gained from research activities with the public, scientific 

community, and natural-resource managers.

2. To offer a program of graduate education and research that develops future scientists and 

knowledgeable resource managers. 

3. To maintain the LVWS long-term ecological research project as a successful example of 

ecosystem-study design, interdisciplinary collaboration, long-term monitoring, and 

sustainable natural-resource management. 

As results from the long-term monitoring and research program are used by resource 

managers, scientists, policy makers, and students, it is important that all data collected in LVWS

meet high standards of quality. Therefore, the USGS must ensure the integrity of all data 

collected as part of the program. 

13BPurpose and Scope

This report describes quality assurance (QA) procedures and results used in support of 

long-term data-collection efforts in the LVWS. Since 1982, all LVWS samples and data have 

been analyzed according to standard methods. This report addresses data collected from January 

1, 2003, through December 31, 2009. Previous QA reports evaluated the quality of data collected

during 1983-87 (Denning, 1988), 1989-90 (Edwards, 1991), 1991-94 (Allstott, 1995), 1995-98 

(Allstott and others, 1999), and 1999-2002 (Botte and Baron, 2004). Variables addressed in this 

report include precipitation depth and chemistry, hydrologic measurements, and surface-water

chemistry. Support for sampling in the LVWS is jointly provided by USGS Western Mountain 

Initiative (WMI) and Water, Energy, and Biogeochemical Budgets (WEBB) programs. The WMI 

supports LVWS personnel, which includes USGS employees, CSU employees, and NPS 

volunteers. LVWS personnel monitor precipitation depth, precipitation chemistry, and surfacewater chemistry, which are the focus of this report. Meteorological, streamflow, and additional 

water-chemistry measurements are made within the LVWS and evaluated for data quality as part 

of the WEBB program. 
3

14BApproach

Streamflow data were collected and processed by LVWS personnel during 1983-2006. In 

August 2006, responsibility for collection and QA of all discharge data in the LVWS was 

transferred from LVWS personnel to the WEBB program. Surface-water samples were collected 

weekly at the Loch Outlet and less frequently at many other sites in RMNP (fig. 1). Surfacewater chemistry was determined according to U.S. Environmental Protection Agency (USEPA) 

protocols at the U.S. Forest Service Rocky Mountain Research Station (USFS-RMRS) Water 

Chemistry Laboratory and Natural Resource Ecology Laboratory (NREL) at CSU in Fort 

Collins, Colorado. Protocols for sampling and for measuring surface-water chemistry are 

documented in Richer and others (2011).

Precipitation depth and chemistry were monitored at the Loch Vale National 

Atmospheric Deposition Program (NADP) site, CO98 (fig. 1). Precipitation samples were 

collected according to NADP protocols (Dossett and Bowersox, 1999), and analyzed at the 

NADP Central Analytical Laboratory (CAL) in Champaign, Illinois. QA procedures for 

precipitation samples are outlined in the NADP Quality Assurance Plan (QAP; National 

Atmospheric Deposition Program, 2009a) and Quality Management Plan (QMP; National 

Atmospheric Deposition Program, 2009b). To further evaluate the quality of data collected at 

CO98, a colocated NADP site, CO89, was installed in October 2009.

LVWS data are available at multiple locations on the Internet (table 1), or by request

from the Principal Investigator of the Loch Vale research program, U.S. Geological Survey, Fort 

Collins, Colorado. 

Table 1. Summary of Loch Vale watershed data collected during 2003-09. 

Web site Available data

Loch Vale watershed: Water, Energy, and 

Biogeochemical Budgets (WEBB)

http://co.water.usgs.gov/lochvale/

http://waterdata.usgs.gov/nwis

Hydrology: Andrews Creek, Icy Brook, and Loch Outlet

Surface-water chemistry: Andrews Creek, Icy Brook, and 

Loch Outlet

Meteorology: Main Loch Vale weather station, Andrews 

Meadow, and Sharkstooth

National Atmospheric Deposition Program

http://nadp.sws.uiuc.edu/

Precipitation depth and chemistry: Rocky Mountain National 

Park–Loch Vale (CO98 and CO89)

Natural Resource Ecology Laboratory: 

Loch Vale Watershed Research Project

http://www.nrel.colostate.edu/projects/lvws/

pages/homepage.htm

Hydrology: Loch Outlet

Surface-water chemistry: Andrews Creek, Emerald Lake 

Outlet, Lake of Glass Outlet, Lake Haiyaha Outlet, Lake 

Husted, Loch Inlet, Loch Outlet, Lake Louise Inlet, Lake 

Louise Outlet, Sky Pond Inlet North, Sky Pond Inlet South, 

Sky Pond Outlet

Meteorology: Loch Vale remote area weather station
4

Figure 1. Loch Vale watershed project monitoring sites in Rocky Mountain National Park (RMNP)

sampled during 2003-09. (NADP, National Atmospheric Deposition Program)

Alpine tundra

Subalpine forest

Montane forest

Wetland

Lake

Rock

Talus

Glacier

Rock glacier

------ Loch Vale watershed

 Stream

Streamgage

Streamgage and water chemistry

Water chemistry

Weather station
5

4BPrecipitation Data

Precipitation was monitored at the Loch Vale NADP sites using rain gages and 

precipitation collectors. Cumulative precipitation depth was recorded to a data logger every 15 

minutes, whereas precipitation samples were collected weekly. Precipitation depth was measured 

with an Alter shielded weighing bucket rain gage. Two types of rain gages were used at the Loch 

Vale NADP site during 2003-09. An Alter shielded Belfort Model 5-780 rain gage measured 

precipitation depth from August 1983 to August 2010. NADP resolved to upgrade all 

precipitation gages in 2006, and an Alter shielded ETI NOAH IV electronic rain gage (e-gage) 

was installed at the CO98 NADP site on June 18, 2007. After more than 2 years of colocated 

precipitation data collection, the Belfort rain gage was dismantled on August 9, 2010. Analysis 

of the colocated precipitation data for CO98 revealed that the NOAH IV captured approximately 

7 percent more precipitation than the Belfort (fig. 2), which is within the expected margin of 

error associated with interpretation of Belfort strip charts. To compare variability in precipitation 

depth and chemistry between sites, a colocated NADP site, CO89, was installed in October 2009 

but was not fully operational until January 2010. The Loch Vale NADP sites, CO98 and CO89,

are located at an altitude of 3,160 m. 

Aerochem Metrics Model 301 precipitation collectors were used at NADP sites to capture 

precipitation for chemical analysis. Although precipitation depth is reported for collector 

buckets, the catch efficiency of the Aerochem Metrics wet deposition sampler is limited because 

the sampler is not shielded, especially during winter months when precipitation falls as snow

Figure 2. Cumulative precipitation measured at the colocated Belfort and NOAH IV rain gages at the 

Loch Vale CO98 National Atmospheric Deposition Program site during 2008-09. (The light grey line 

represents the 1:1 line.)

0

20

40

60

80

100

120

140

160

180

200

220

0 20 40 60 80 100 120 140 160 180 200 220

NOAH IV PRECIPITAION, IN CENTIMETERS

BELFORT PRECIPITATION, IN CENTIMETERS

Cumulative precipitation
6

(table 2). Alter shielded rain gages are more effective than the Aerochem collectors for catching 

solid precipitation in wind-prone areas. The World Meteorological Organization reports that 

Alter shielded rain gages capture approximately 75 percent of winter precipitation, whereas

unshielded gages similar to the Aerochem collector capture approximately 57 percent (Goodison 

and others, 1998). CO98 collector catch efficiency ranged from 99 percent in the summer to just 

33 percent in the winter on average (table 2). Poor winter catch efficiency can invalidate samples 

as a result of inadequate sample volume for complete chemical analysis. 

Table 2. Annual catch efficiency of the CO98 site Aerochem Metrics precipitation collector relative to the 

Alter shielded rain gage by season during 2003-09. 

Season Relative catch efficiency, in percent

2003 2004 2005 2006 2007 2008 2009 Average

Winter 51 27 25 27 47 29 22 33

Spring 44 66 62 50 58 56 57 56

Summer 99 100 97 107 101 96 98 99

Fall 50 68 40 66 86 62 61 62

Annual 57 70 62 62 73 61 54 63

Chemical analysis and quality assurance for all precipitation samples were conducted in 

accordance with NADP protocols (National Atmospheric Deposition Program, 2009a; 2009b). 

The quality-control program includes weekly blanks, check samples, blind network replicates, 

and internal blind audits with predetermined samples. The CAL was in compliance with the 

NADP QAP and QMP during 2003-09 (Rothert, 2008a; Rothert, 2008b; Rothert, 2009; Rothert,

2010; Dombek, 2011). Instruments used at CAL for chemical analysis of precipitation samples 

are listed in table 3. In 2004, CAL switched from a flame atomic absorption spectrometer to an

inductively coupled plasma-optical emission spectrometer for analysis for calcium (Ca2+), 

potassium (K

+

), magnesium (Mg2+), and sodium (Na+), and began using a Broadly-James 

electrode to measure pH. Detection limits for all ions measured at CAL are listed in table 4.

As part of the project, 363 precipitation samples were collected from CO98 for chemical 

analysis from December 31, 2002, to December 29, 2009. Of these 363 samples, 271 (75 

percent) were considered valid according to NADP criteria. Only valid samples with adequate 

sample volume were used to calculate annual precipitation-weighted mean concentrations, 

deposition, and data completeness. Annual sample validity is summarized in table 5. Of the 92

Table 3. National Atmospheric Deposition Program Central Analytical Laboratory instrumentation for 

measuring concentrations of precipitation analytes during 2003-09. 

[K+, potassium; Na+, sodium; Ca2+, calcium; Mg2+, magnesium; NH4

+

, ammonium as ammonium; Cl-, chloride; NO3

-

, nitrate as nitrate; SO4

2-

, sulfate as sulfate; PO4

3-

, orthophosphate as orthophosphate; SC, specific conductance; 

instrumentation data from Rothert (2010) and Dombeck (2011)]

Analyte Instrument Years of service

K

+

, Na+, Ca2+, Mg2+ Flame atomic absorption spectrometer

Inductively coupled plasma-optical emission spectrometer

1978-2003

2004-2009

NH4

+

Phenate (flow injection colorimetry) 1978-2009

Cl-, NO3

-

, SO4

2-

Ion chromatography, dionex 1985-2009

PO4

3- Ascorbic acid (flow injection colorimetry) 1978-2009

pH Corning pH meter

Broadly-James electrode

1978-2003

2004-2009

SC YSI conductivity meter 2003-2009
7

Table 4. National Atmospheric Deposition Program Central Analytical Laboratory detection limits for 

precipitation analytes during 2003-09. 

[K

+

, potassium; Na+, sodium; Ca2+, calcium; Mg2+, magnesium; NH4

+

, ammonium as ammonium; Cl-, chloride; 

NO3

-

, nitrate as nitrate; SO4

2-

, sulfate as sulfate; PO4

3-

, orthophosphate as orthophosphate; values from Rothert 

(2008a), Rothert (2008b), Rothert (2009), Rothert (2010), and Dombek (2011)]

Analyte

Detection limit (milligrams per liter)

2003 2004 2005 2006 2007 2008 2009

K

+

0.003 0.001 0.001 0.002 0.001 0.001 0.001

Na+0.003 0.003 0.003 0.002 0.001 0.001 0.001

Ca2+ 0.009 0.002 0.002 0.002 0.002 0.006 0.006

Mg2+ 0.003 0.001 0.001 0.001 0.001 0.001 0.001

NH4

+

0.020 0.020 0.005 0.003 0.004 0.006 0.003

Cl0.005 0.005 0.008 0.005 0.003 0.004 0.004

NO3

-

0.010 0.010 0.009 0.015 0.017 0.009 0.006

SO4

2-

0.010 0.010 0.013 0.015 0.010 0.007 0.004

PO4

3-

0.009 0.009 0.006 0.005 0.004 0.004 0.002

Table 5. Annual sample validity for National Atmospheric Deposition Program site CO98 during 2003-09. 

Reason for invalidation 2003 2004 2005 2006 2007 2008 2009

Inadequate volume 1 3 3 6 7 5 8

Contaminated sample 5 4 0 4 7 6 4

Undefined sample 0 0 0 7 3 2 2

Bulk sample 0 0 0 0 0 7 4

Extended sampling interval 1 0 1 0 0 0 1

Field protocol departure 0 0 0 1 0 0 0

Number of invalid samples 7 7 4 18 17 20 19

Number of valid samples 44 45 48 34 34 32 34

Total number of samples 51 52 52 52 51 52 53

Percent valid samples 86 87 92 65 67 62 64

invalid samples, 33 were invalid because the sample volume was inadequate for analysis, 30 

were contaminated, 14 were undefined (that is, the collector was open when no precipitation 

occurred), 11 were invalid because the collector was open continuously (that is, the sample was a 

bulk sample), 3 were invalid because the sampling interval was greater than 8 days, and 1 was 

invalid as a result of a departure from field protocol.

Inadequate sample volume was the most common reason for sample invalidation. There 

are three primary reasons for inadequate sample volume: (1) inadequate precipitation depth, (2) 

failure of the precipitation collector to open during snow storms due to insensitivity of the 

precipitation sensor, and (3) loss of sample when snow is blown back out of the collector bucket. 

Contamination was the second most common reason for sample invalidation. The most common 

types of contamination were dirt particles and plant matter. In the fall of 2009, approximately 20

trees around the Loch Vale NADP site were trimmed or felled to reduce sample contamination 

from plant matter. Cloudy or discolored samples, which may result from natural dust events, or

the presence of insects in the collector bucket also contaminated samples. Of all precipitation 

samples sent to NADP during 2003-09, 7 percent were invalidated as a result of equipment 

malfunction (that is, bulk and undefined samples). Additional solar panels and batteries were 

installed in 2010 to reduce equipment malfunction from power loss.
8

5BDischarge Data

The Loch Outlet is located at the northeastern edge of the basin at an altitude of 3,105 m

(fig. 1). Discharge at the Loch Outlet has been monitored with a Parshall flume and stilling well 

since 1983. Accuracy of the Parshall flume is estimated at ± 5 percent (Winter, 1981). In this 

section, discharge data for water years (WY) 2003-06 are evaluated. In August 2006, 

responsibility for collection and QA of discharge data at the Loch Outlet was transferred from 

LVWS personnel to the WEBB program. Stage was recorded with a Leupold and Stevens chart 

recorder through 2006. The chart recorder has since been replaced with a pressure transducer. As 

a quality check of flow data, stage height was recorded weekly from a staff gage located inside 

the flume, unless the flume was covered with snow.

Because stage records were incomplete as a result of a malfunctioning chart recorder, 

discharge data for the Loch Outlet from October 18, 2005, to August 17, 2006, were estimated

from observed flows at the Andrews Creek streamgage. Discharge data for Andrews Creek and 

the Loch Outlet during 2000-09 were used to develop the simple linear model with an R2value 

of 0.89 (fig. 3). Qualitative analysis of hydrographs for 2003-06 shows that estimated discharge 

values agree with streamflow patterns observed in the watershed (figs. 4-7). These qualitative 

comparisons of discharge at the Andrews Creek, Icy Brook, and Loch Outlet streamgages show 

that runoff generally peaked within 1 week at the three sites. Discharge values were greatest at 

the Loch Outlet as a result of the larger contributing area, which includes both the Andrews 

Creek and Icy Brook subbasins. (Discharge data are available from the USGS National Water 

Information Web site at http://waterdata.usgs.gov/nwis.)

Figure 3. Relation between observed discharge at Andrews Creek and the Loch Outlet during 2000-09 

used to estimate discharge for the Loch Outlet from October 18, 2005, to August 17, 2006. 

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50

LOCH OUTLET DISCHARGE, IN CUBIC 

METERS PER SECOND

ANDREWS CREEK DISCHARGE, IN CUBIC METERS PER SECOND

Loch Outlet discharge = 2.91 x Andrews Creek discharge + 0.01

R2 = 0.89
9

Figure 4. Discharge at three streamflow stations in the Loch Vale watershed during water year 2003. 

Figure 5. Discharge at three streamflow stations in the Loch Vale watershed during water year 2004.

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1-Oct 1-Nov 1-Dec 1-Jan 1-Feb 1-Mar 1-Apr 1-May 1-Jun 1-Jul 1-Aug 1-Sep

DISCHARGE, IN CUBIC METERS PER 

SECOND

WATER YEAR 2003

Loch Outlet

Icy Brook

Andrews Creek

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1-Oct 1-Nov 1-Dec 1-Jan 1-Feb 1-Mar 1-Apr 1-May 1-Jun 1-Jul 1-Aug 1-Sep

DISCHARGE, IN CUBIC METERS PER 

SECOND

WATER YEAR 2004

Loch Outlet

Andrews Creek

Icy Brook
10

Figure 6. Discharge at three streamflow stations in the Loch Vale watershed during water year 2005.

Figure 7. Discharge at three streamflow stations in the Loch Vale watershed during water year 2006. 

(Loch Outlet discharge data for October 18, 2005, to August 17, 2006, were estimated.)

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1-Oct 1-Nov 1-Dec 1-Jan 1-Feb 1-Mar 1-Apr 1-May 1-Jun 1-Jul 1-Aug 1-Sep

DISCHARGE, IN CUBIC METERS PER 

SECOND

WATER YEAR 2005

Loch Outlet

Icy Brook

Andrews Creek

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1-Oct 1-Nov 1-Dec 1-Jan 1-Feb 1-Mar 1-Apr 1-May 1-Jun 1-Jul 1-Aug 1-Sep

DISCHARGE, IN CUBIC METERS PER 

SECOND

WATER YEAR 2006

Loch Outlet (observed)

Loch Outlet (estimated)

Icy Brook

Andrews Creek
11

6BSurface-Water Chemistry Data

Water samples from the Loch Outlet were collected and processed weekly; sample 

collection from the other sites was less frequent. During 2003-09, 565 samples were collected,

55 (10 percent) of which were QA samples. Data quality was evaluated using field blanks, field 

duplicates, charge balance calculations (that is, ion percent difference), and theoretical 

conductance (that is, conductance percent difference). Sample-collection and -processing

procedures were assessed through the use of blank and duplicate samples. Field blanks were used 

to examine contamination from collection and processing procedures, whereas precision was 

evaluated with field duplicate samples. Differences in constituent concentrations in normal, 

blank, and duplicate samples highlight deficiencies in the analytical process. Quality-control 

check samples and laboratory blanks were analyzed every 10 samples to ensure internal quality 

control for each laboratory. All protocols used in the preparation, collection, processing, and 

shipment of samples are described in the LVWS methods manual (Richer and others, 2011).

Changes in laboratory and field procedures during 2003-09 are summarized farther on in this 

report.

15BNatural Resource Ecology Laboratory

LVWS surface-water samples were processed at the NREL before delivery to the RMRS 

laboratory. Specific conductance at 25°C (that is, field conductivity) and water temperature were 

measured prior to sample collection with a Thermo Orion 105Aplus conductivity meter, which 

was checked against standard reference solutions weekly and calibrated as needed. Water 

samples were analyzed at the NREL for dissolved organic carbon (DOC) and total dissolved 

nitrogen (TDN) with a Schimadzu TOC-V CPN Total Organic Carbon Analyzer. The Schimadzu 

measures total organic carbon (TOC) and total nitrogen (TN) but, because the samples were 

filtered prior to analysis, the analytes measured are operationally defined as dissolved organic 

carbon (DOC) and total dissolved nitrogen (TDN). Dissolved silica (as SiO2) was measured with 

a Thermo Spectronic 20D+spectrophotometer using the silicomolybdate method adapted from 

Clesceri and others (1998). 

Detection limit is the lowest quantity of a substance that can be distinguished from the

absence of that substance. This limit is defined as three times the standard deviation of signals 

produced by 10 nonconsecutive blank samples (U.S. Environmental Protection Agency, 1987).

Detection limits for all analyses conducted at NREL were calculated in 2009 (table 6). Prior to 

2009, detection limits were not evaluated annually. The calculated detection limits for DOC and 

TDN are below the required USEPA values (U.S. Environmental Protection Agency, 1987). The 

NREL detection limit for SiO2 is just slightly higher than the estimated detection limit for the 

method, which is 0.3 mg SiO2/L. Because phosphorus concentrations in LVWS waters were 

dilute, measurements of total phosphorus (TP) and orthophosphate (PO4

3-

) at NREL were

suspended because detection limits have proved inadequate for these analyses (for example, 

greater than 0.001 mg/L for PO4

3-

). TP samples were acidified and stored at 4°C until analytical 

capabilities improve or another laboratory with a lower TP detection limit is identified. pH 

analyses at NREL were discontinued in January 2010 because they were redundant with pH 

measurements made at the RMRS laboratory. 
12

Table 6. Detection limits for carbon, nitrogen, and silica at the Natural Resource Ecology Laboratory

during 2009. 

[mg/L, milligrams per liter; DOC, dissolved organic carbon; TDN, total dissolved nitrogen; SiO2, dissolved silica as 

silicon dioxide]

Analyte Detection limit (mg/L) Method of analysis

DOC 0.06 Oxidative combustion-infrared analysis

TDN 0.05 Oxidative combustion-chemiluminescence

SiO2 0.4 Spectrophotometry-silicomolybdate

16BU.S. Forest Service Rocky Mountain Research Station Water Chemistry Laboratory

Major cations and anions were measured at the RMRS Water Chemistry Laboratory.

Specific conductance at 25°C (that is, laboratory conductivity), pH, and acid neutralizing 

capacity (ANC) were also determined at the RMRS. Samples were delivered to the RMRS, 

where they were stored in a cold, dark environment, within 48 hours of collection and were 

processed in accordance with USEPA guidelines. Guidelines established in the Handbook of 

Methods for Acid Deposition Studies (U.S. Environmental Protection Agency, 1987) and the 

Standard Methods for the Examination of Water and Wastewater (Clesceri and others, 1998)

were followed for all analyses at the RMRS laboratory. Control charts and control samples were 

utilized daily to monitor internal quality control. Field and laboratory blanks were analyzed as 

well as lab duplicates and check standards (every 10 samples). The lab manager, lab analyst, and 

data analyst checked, verified, and archived all data collected. The published detection limits for 

the RMRS laboratory, which was formerly affiliated with the Air Resource Management 

Laboratory (ARML), are listed in table 7. The detection limit for ANC is difficult to quantify as 

a result of the gran titration method used for the analysis and seasonality of the data, which vary 

widely throughout the year.

The performance of USGS, cooperator, and contractor analytical laboratories that 

measure chemical constituents in environmental samples is evaluated in the Standard Reference 

Sample (SRS) project. SRS testing is performed at the RMRS laboratory every 6 months to 

assess the quality of laboratory methods and procedures while evaluating analytical precision and

Table 7. Detection limits for U.S. Forest Service Rocky Mountain Research Station Water Chemistry

Laboratory.

[mg/L, milligrams per liter; ANC, acid neutralization capacity; K

+

, potassium; Na+, sodium; Ca2+, calcium; Mg2+, 

magnesium; NH4

+

, ammonium as ammonium; F

-

, fluoride; Cl-, chloride; NO3

-

, nitrate as nitrate; SO4

2-

, sulfate as 

sulfate; PO4

3-

, orthophosphate as orthophosphate; ND, no data; values from Air Resource Management Laboratory 

(2010)]

Analyte Detection limit (mg/L) Method of analysis

ANC ND Gran titration 

K

+

0.01 Monovalent/divalent column

Na+0.02 Monovalent/divalent column

Ca2+ 0.04 Monovalent/divalent column

Mg2+ 0.01 Monovalent/divalent column

NH4

+

0.01 Monovalent/divalent column

F

-

0.01 Ion chromatography with separator column

Cl0.02 Ion chromatography with separator column

NO3

-

0.03 Ion chromatography with separator column

SO4

2-

0.04 Ion chromatography with separator column

PO4

3-

0.04 Ion chromatography with separator column
13

accuracy. All pertinent SRS information and data are available at http://bqs.usgs.gov/srs/. SRS

results for the RMRS laboratory (SRS lab #2) during 2003-09 are listed in table 8. The RMRS 

laboratory performed well for all SRS samples, with the exception of PO4

3-

and NH4

+

measurements. Results for PO4

3-

have been variable over the years, and the RMRS laboratory has 

chosen not to report some values because they are typically below detection limit. NH4

+

concentrations are generally very low for LVWS waters. In addition, high Na+concentrations 

make it difficult for the chromatography program to separate Na+and NH4

+

peaks. As a result of

the problem associated with determining NH4

+

concentrations when Na+concentrations are high, 

the effective detection limit for NH4

+

in LVWS surface waters is 0.05 mg/L (Derek Pierson, U.S. 

Forest Service, written commun., 2010). Therefore, NH4

+

values less than 0.05 mg/L cannot be 

resolved. 

Table 8. Analytical results for precipitation Standard Reference Samples analyzed at the U.S. Forest 

Service Rocky Mountain Research Station Water Chemistry Laboratory during 2003-09. 

[SC, specific conductance; K

+

, potassium; Na+, sodium; Ca2+, calcium; Mg2+, magnesium; NH4

+

, ammonium as 

ammonium; F-, fluoride; Cl-, chloride; SO4

2-

, sulfate as sulfate; PO4

3-

, orthophosphate as phosphorus; RV, reported 

value in milligrams per liter; MPV, most probable value in milligrams per liter; %Diff, percent difference between 

RV and MPV; ND, no data reported]

Period Statistic pH SC K+ Na+ Ca2+ Mg2+ F

- Cl- SO42- PO43-

Fall RV 3.950 57.9 ND 0.511 0.547 0.052 0.098 5.596 0.258 ND

2003 MPV 3.941 58.7 ND 0.480 0.550 0.054 0.107 5.878 0.320 ND

%Diff 0.2 -1.4 ND 6.5 -0.5 -3.7 -8.4 -4.8 -19.4 ND

Spring RV 3.932 65.7 0.331 0.313 0.499 0.048 0.112 5.821 0.283 ND

2004 MPV 3.900 63.2 0.325 0.304 0.495 0.048 0.110 6.120 0.344 ND

%Diff 0.8 4.0 1.8 3.0 0.8 0.0 1.8 -4.9 -17.7 ND

Fall RV 4.003 55.8 0.242 0.269 0.552 0.058 0.041 4.818 0.457 ND

2004 MPV 3.990 51.7 0.180 0.235 0.530 0.042 0.048 4.895 0.536 ND

%Diff 0.3 7.9 34.4 14.5 4.2 39.4 -14.8 -1.6 -14.7 ND

Spring RV 5.138 18.2 0.962 1.018 0.517 0.100 0.099 2.248 1.156 ND

2005 MPV 5.130 17.3 0.950 0.990 0.520 0.094 0.090 2.330 1.140 ND

%Diff 0.2 5.2 1.3 2.8 -0.6 6.4 10.0 -3.5 1.4 ND

Spring RV 4.143 39.9 0.459 0.703 0.464 0.073 0.136 4.375 0.517 ND

2006 MPV 4.160 42.4 0.445 0.652 0.452 0.050 0.140 4.380 0.555 ND

%Diff -0.4 -5.8 3.1 7.8 2.7 46.0 -2.9 -0.1 -6.8 ND

Fall RV 6.696 20.2 0.174 1.777 1.496 0.123 0.071 3.924 0.172 ND

2006 MPV 6.650 20.0 0.190 1.760 1.450 0.123 0.080 3.630 0.190 ND

%Diff 0.7 1.1 -8.4 1.0 3.2 0.0 -11.3 8.1 -9.5 ND

Fall RV 6.870 15.2 0.121 0.543 1.585 0.095 0.192 1.096 0.625 ND

2007 MPV 6.870 15.9 0.130 0.540 1.920 0.100 0.180 1.120 0.600 ND

%Diff 0.0 -4.6 -6.9 0.6 -17.5 -4.7 6.8 -2.2 4.1 ND

Spring RV 6.330 12.8 0.302 0.605 0.890 0.227 0.114 1.586 0.857 0.047

2008 MPV 6.320 14.4 0.301 0.610 0.898 0.232 0.120 1.580 0.844 0.048

%Diff 0.2 -10.9 0.5 -0.9 -0.9 -2.3 -5.4 0.3 1.6 -2.1

Fall RV 6.180 12.8 0.234 1.270 0.332 0.297 0.173 1.174 1.910 0.000

2008 MPV 6.170 13.5 0.237 1.240 0.330 0.300 0.174 1.240 1.990 0.015

%Diff 0.2 -5.2 -1.3 2.4 0.6 -1.0 -0.6 -5.3 -4.0 -100.0

Spring RV 4.782 13.6 0.738 0.239 0.433 0.061 0.092 1.926 0.211 ND

2009 MPV 4.880 14.0 0.650 0.230 0.415 0.057 0.100 1.780 0.210 ND

%Diff -2.0 -2.7 13.5 3.9 4.3 7.0 -8.0 8.2 0.2 ND

Fall RV 6.670 9.7 0.093 0.336 0.761 0.348 0.042 1.080 0.425 0.047

2009 MPV 6.700 10.0 0.080 0.321 0.741 0.340 0.040 1.050 0.418 0.026

%Diff -0.4 -3.0 15.8 4.6 2.7 2.4 3.8 2.9 1.7 80.8
14

17BData Outliers

Outliers are defined as points that markedly deviate from all other data in the sample. 

Only two erroneous points were detected (table 9) from graphical analysis of the 2003-09 data. 

The low field conductance value reported on December 8, 2009, is indicative of a frozen probe. 

The NH4

+

concentration reported on May 17, 2005, is an outlier. Although no other ion 

concentrations in this sample appear suspicious, the reported value is substantially higher than all 

other NH4

+

concentrations. This result indicates possible sample contamination or an analytical 

error. Given the extremely low NH4

+

concentrations in LVWS waters, a single breath can

contaminate a sample for NH4

+

. Both of the outlying data points in table 9 were removed from 

LVWS data records and replaced as missing data. 

Table 9. Data outliers removed from the Loch Vale watershed surface-water records for 2003-09. 

[NH4+, ammonium as ammonium; S/cm, microsiemens per centimeter at 25° Celsius; mg/L, milligrams per liter]

Analyte Units Site Date Reported value Mean value (2003-09)

Field conductivity S/cm Loch Outlet 12/8/2009 0.7 18.3

NH4

+ mg/L Loch Outlet 5/17/2005 0.21 0.02

18BIon and Specific Conductance Balances 

Loch Vale surface-water samples were checked for ion percent difference (IPD) and

specific conductance percent difference (CPD) (U.S. Environmental Protection Agency, 1987; 

Stednick and Gilbert, 1998; U.S. Environmental Protection Agency, 2004). Because all samples 

are electrically neutral, the sum of the measured cations should equal the sum of the measured 

anions, if it is assumed that all major ions are measured. The ion balance is expressed by the 

IPD, which is calculated as:

(1)

where

Σ cations = [Ca

2+] + [Mg2+] + [Na+] + [K+] + [NH4+] + [H+],

Σ anions = [SO4

2-] + [Cl-] + [F-] + [NO3-] + [HCO3-], and

HCO3

- = ANC + H+

with all concentrations expressed in microequivalents per liter.

A negative IPD represents an excess of anions and a positive IPD represents an excess of 

cations. The IPD is an indicator of analytical accuracy and samples that fall outside criteria in 

table 11 are flagged and the analysis rerun. If the IPD is still outside the acceptable range after 

the sample has been reanalyzed, each sample is checked, ion by ion, for possible contamination.

If one analyte is the obvious cause of the charge imbalance, it can be dropped from the record as 

long as the concentrations of the remaining analytes are normal for that time of year.
15

The theoretical conductance of a water sample is calculated by the formula:

(2)

Theoretical conductance = ([Ca

2+]59.47 + [Mg2+]53.0 + [Na+]50.08 + [K+]73.48 + [NH4+]73.50 + 

[H+]349.65 + [SO4

2-]80.0 + [Cl-]76.31 + [NO3-]71.42 + [HCO3-]44.5)/1000

with all concentrations expressed in microequivalents per liter.

The CPD is calculated as:

(3)

CPD calculations were performed for all surface-water samples using the specific 

conductance measured at the RMRS laboratory (that is, laboratory conductivity). Positive CPD 

values indicate that theoretical conductance exceeds the laboratory measured value, and can 

indicate an analytical error in one or more of the solute measurements. Negative CPD values 

indicate an unmeasured or under measured ion. Deviations from zero also can result from errors 

in specific conductance measurements. CPD values that fall outside the ranges reported in table 

10 are flagged and the sample reanalyzed. 

Of the 534 non-blank environmental samples (that is, normal and duplicate samples) 

collected during 2003-09, no samples were flagged for IPD after reanalysis. Three samples, all of 

which had positive CPD values, did not meet quality criteria for CPD after reanalysis (table 11), 

which could indicate an analytical error in one of the measurements. However, none of the 

samples flagged for CPD were flagged for IPD, which indicates that the solute analyses were 

complete and balanced. Therefore, data associated with these samples (table 11) were not 

removed from the database, but are reported here for completeness.

Table 10. Surface-water sample reanalysis criteria for ion percent difference and conductance percent 

difference. 

ueq/L, microequivalents per liter; IPD, ion percent difference; S/cm, microsiemens per centimeter at 25° Celsius; 

CPD, conductance percent difference; <, less than; ≥, greater than or equal to; criteria from U.S. Environmental 

Protection Agency, 1987]

Ion percent difference

Total ionic strength (μeq/L) Maximum IPD (percent)

<50 60

≥50<100 30

≥100 15

Conductance percent difference

Measured specific conductance (μS/cm) Maximum CPD (percent)

<5 50

≥5<30 30

≥30 20
16

Table 11. Samples that failed to meet quality criteria for conductance percent difference after reanalysis. 

S/cm, microsiemens per centimeter at 25o Celsius; CPD, Conductance percent difference]

Site Date Sample type

Theoretical 

conductance (μS/cm)

Measured

conductance (μS/cm)

CPD 

(percent)

Andrews Creek 09/23/03 Normal 19.7 14.5 35.9

Glass Outlet 09/23/03 Normal 25.9 18.5 40.1

Sky Inlet South 09/16/08 Normal 22.2 16.7 33.1

19BMeasures of Contamination

Contamination of low-ionic-strength streamwater samples is quantified by measuring 

solute concentrations in field blank samples. Field blanks consist of deionized (DI) water that is 

processed with the same methods used for environmental water samples (that is, normal and field 

duplicate samples). Sources of contamination can include improper bottle-washing procedures, 

errors in the handling and processing of samples, and contamination of DI water columns.

Twenty-seven field blanks were collected at the Loch Outlet during 2003-09. No known 

instances of contamination of the NREL DI water system occurred during 2003-09 (Dan Reuss, 

Natural Resource Ecology Laboratory, oral commun., 2010). The 25th- and 75th-percentile

concentrations of each analyte for field blanks and environmental samples are listed in table 12. 

The blank concentration values of most concern are those for DOC, as noted in previous 

QA reports (Allstott and others, 1999; Botte and Baron, 2004). Elevated DOC values are most 

likely caused by the inability of the DI water filtration system to effectively remove all organic 

carbon from the water. SiO2 has also been detected in NREL DI water in the past (Allstott and 

others, 1999), but the concentrations reported in table 12 are well below the reported detection 

limit of 0.4 mg/L. SiO2 concentrations greater than 11 mg/L were reported for three consecutive 

blank samples collected during December 2004-April 2005. As no instances of DI water 

contamination were reported at NREL during this time period, the abnormally high values are 

likely the result of operator error. Therefore, these three SiO2 values were removed from the 

LVWS database and were not used in calculating values in table 12. 

20BMeasures of Precision 

Analytical precision is quantified by determining differences between analyte 

concentrations in normal samples and field duplicates. Field duplicates are samples collected 

from the same location as normal samples, with identical methods and as close to the same time 

as possible. Twenty-eight duplicate samples were collected from the Loch Outlet during 2003-

09. Duplicate samples are processed and analyzed exactly as are normal samples. Median 

absolute differences (MADs) for each analyte were calculated for paired normal and duplicate 

samples. Precision can be calculated by determining the ratio of MAD values for the 

normal/duplicate sample pairs to the 10th-percentile concentration value for the analyte in 

environmental samples from all sites. Analytical precision ranged from ±0.6 percent of the 10th-

percentile value for fluoride to ±9.2 percent of the 10th-percentile value for DOC (table 13). 

Analytical precision for all analyses was acceptable at less than ±10 percent of the 10th-percentile 

value for all constituents. 
17

Table 12. Analyte concentration percentiles for field blanks and environmental samples collected for the 

Loch Vale watershed project during 2003-09. 

[P25, 25th percentile; P75, 75th percentile; n, sample size; NREL, Natural Resource Ecology Laboratory; RMRS, 

Rocky Mountain Research Station Water Chemistry Laboratory; ANC, acid neutralization capacity; K

+

, potassium; 

Na+, sodium; Ca2+, calcium; Mg2+, magnesium; NH4

+

, ammonium as ammonium; F-, fluoride; Cl-, chloride; NO3

-

, 

nitrate as nitrate; SO4

2-

, sulfate as sulfate; PO4

3-

, orthophosphate as orthophosphate; DOC, dissolved organic carbon; 

TDN, total dissolved nitrogen; SiO2; dissolved silica as silicon dioxide; S/cm, microsiemens per centimeter at 25°

Celsius; ueq/L, microequivalents per liter; mg/L, milligrams per liter]

Field blank samples Environmental samples

Analyte Units P25 P75 n P25 P75 n

Field conductivity μS/cm 0.8 1.3 26 12.1 21.8 525

Lab conductivity μS/cm 1.00 1.39 27 13.00 22.60 532

NREL pH Standard 5.30 5.80 25 6.40 6.84 525

RMRS pH standard 5.49 5.69 27 6.56 6.74 532

ANC ueq/L -7.45 2.10 27 40.1 97.3 532

K

+ mg/L 0.00 0.00 27 0.17 0.25 532

Na+ mg/L 0.00 0.02 27 0.52 1.04 532

Ca2+ mg/L 0.00 0.02 27 1.45 2.47 532

Mg2+ mg/L 0.00 0.00 27 0.22 0.38 532

NH4

+ mg/L 0.00 0.01 27 0.00 0.03 531

F

- mg/L 0.00 0.02 27 0.09 0.13 532

Cl- mg/L 0.01 0.02 27 0.11 0.24 532

NO3

- mg/L 0.00 0.00 27 1.04 1.88 532

SO4

2- mg/L 0.00 0.00 27 1.73 3.25 532

PO4

3- mg/L 0.00 0.00 27 0.00 0.00 532

DOC mg/L 0.12 0.32 27 0.60 0.99 519

TDN mg/L 0.02 0.05 27 0.34 0.51 519

SiO2 mg/L 0.00 0.08 24 1.80 3.17 525
18

Table 13. Ratio of median absolute differences for normal/duplicate sample pairs to the 10th-percentile

value for all environmental samples collected during 2003-09. 

[MAD, median absolute difference; P10, 10th percentile for environmental samples; NREL, Natural Resource 

Ecology Laboratory; RMRS, Rocky Mountain Research Station Water Chemistry Laboratory; ANC, acid 

neutralization capacity; K

+

, potassium; Na+, sodium; Ca2+, calcium; Mg2+, magnesium; NH4

+

, ammonium as 

ammonium; F-, fluoride; Cl-, chloride; NO3

-

, nitrate as nitrate; SO4

2-

, sulfate as sulfate; PO4

3-

, orthophosphate as 

orthophophate; DOC, dissolved organic carbon; TDN, total dissolved nitrogen; SiO2; dissolved silica as silicon 

dioxide; S/cm, microsiemens per centimeter at 25° Celsius; ueq/L, microequivalents per liter; mg/L, milligrams per 

liter; BDL, below detection limit]

Analyte Units MAD P10 MAD/P10 (percent)

Field conductivity S/cm 0.1 10.2 1.0

Lab conductivity S/cm 0.20 11.14 1.8

NREL pH Standard 0.06 6.27 1.0

RMRS pH Standard 0.01 6.44 0.2

ANC eq/L 1.36 32.02 4.2

K

+ mg/L 0.010 0.140 7.1

Na+ mg/L 0.020 0.450 4.4

Ca2+ mg/L 0.030 1.201 2.5

Mg2+ mg/L 0.010 0.177 5.6

NH4

+ mg/L BDL BDL BDL

F

- mg/L 0.001 0.080 0.6

Cl- mg/L 0.007 0.090 8.1

NO3

- mg/L 0.010 0.709 1.4

SO4

2- mg/L 0.020 1.457 1.4

PO4

3- mg/L BDL BDL BDL

DOC mg/L 0.037 0.399 9.2

TDN mg/L 0.009 0.271 3.4

SiO2 mg/L 0.040 1.405 2.8

7BChanges in Field and Laboratory Procedures during 2003-09

Changes in the LVWS field operating procedures:

Sky Outlet was not sampled during 2003-06.

Louise Inlet was not sampled during 2005-07 and 2009.

Sky Inlet North sampling was discontinued in 2006.

A NOAH IV electronic rain gage was installed at Loch Vale NADP site CO98 on 

June 18, 2007.

Colocated NADP site (CO89), with Aerochem Metric precipitation collector and 

NOAH IV electronic rain gage, was installed on September 29, 2009.

Changes in LVWS laboratory procedures:

Orthophosphate and total phosphorus measurements at NREL were suspended in 

2005. Samples are still collected, acidified, and stored at 4°C for measurement of 

total phosphorus concentrations until analytical capabilities improve or an alternate 

laboratory is identified. 
19

NADP discontinued support for field chemistry measurements (that is, pH and 

specific conductance) effective January 1, 2005. LVWS continued to measure pH of

all precipitation and surface-water samples at NREL through December 2009. 

The Milton Roy Spectronic 301 Photo spectrometer was replaced with a Thermo 

Spectronic 20D+spectrometer in 2007.

The ion chromatographs for Na+and NH4

+ were modified in 2009 to improve 

detection of NH4

+

in the presence of Na+. Because of the influence of Na+on 

detection of NH4

+

, the effective detection limit for NH4

+

is estimated at 0.05 mg/L. 

In 2010, all NREL pH measurements were discontinued because pH is also measured 

at the CAL and RMRS. 

8BSummary

Measurements of precipitation depth, precipitation chemistry, discharge, and surfacewater quality were all sufficiently complete and consistent to support project data needs. 

Bias of new e-gages for precipitation-depth measurement at the Loch Vale National 

Atmospheric Deposition Program (NADP) site CO98 was approximately +7 percent. Annual 

average wet-deposition collector catch efficiency ranged from 54 to 73 percent. The percentage 

of valid weekly NADP wet-deposition samples ranged from 62 to 92 percent. Approximately 25

percent of precipitation samples collected during 2003-09 did not meet NADP criteria for valid 

samples. The primary reasons for sample invalidation were inadequate sample volume, 

contamination, and equipment malfunction. 

Improvements were made to field instrumentation at the Loch Vale site CO98 and in the 

laboratories of the NADP Central Analytical Laboratory (CAL). In accordance with NADP site 

criteria, trees surrounding the CO98 site were trimmed or felled to reduce sample contamination 

from plant matter. Additional solar panels and batteries were installed to minimize equipment 

malfunction from power loss at the NADP site. Field instruments are now (2011) more reliable 

and provide more accurate precipitation measurements. A colocated site, CO89, was installed in

2009 to quantify the overall variability in NADP measurements of precipitation depth and 

chemistry at Loch Vale. Laboratory instruments currently used have lower detection limits to 

resolve low chemical concentrations in wet-deposition samples. The NADP CAL continues to 

produce accurate and precise data for the Loch Vale watershed (LVWS) long-term monitoring 

and research program. 

As a result of equipment malfunction, discharge data for the Loch Outlet were estimated

from October 18, 2005, to August 17, 2006. Discharge records are consistent among the three 

streamgaging stations for each water year during 2003-09.

More than 98 percent of all LVWS surface-water samplers met project quality criteria. 

Failures to meet quality criteria were attributable to sample contamination or analytical error. 

Rocky Mountain Research Station (RMRS) and Natural Resource Ecology Laboratory (NREL)

data were quality assured using ion balance, specific conductance balance, blank samples, and 

duplicate samples. Quality-assurance results indicate all analyses were accurate and precise. The

U.S. Forest Service (USFS)-RMRS Water Chemistry Laboratory and NREL continue to produce 

accurate and precise data for the LVWS long-term monitoring and research program. 
20

9BAcknowledgments

The authors thank Louise O’Deen (U.S. Forest Service, Air Resource Management 

Laboratory) and Derek Pierson (U.S. Forest Service, Rocky Mountain Research Station) for their 

years of high-quality laboratory work, the many volunteers and field technicians who helped

collect samples, and Shenavia Balcom and Matt Schoolmeester-Winnick for their help with lab 

work at the NREL. We also appreciate the helpful insight and constructive criticism from our 

peer reviewers, Greg Wetherbee and David Clow (U.S. Geological Survey).

10BReferences Cited

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Collins, Colorado, Colorado State University, Natural Resource Ecology Laboratory, 22 p.

Allstott, E.J., Bashkin, M.A., and Baron, J.S., 1999, Quality assurance report: 1995-1998, Loch 

Vale watershed project: U.S. Geological Survey Open-File Report 99-111, 30 p.

Botte, J.A., and Baron J.S., 2004, Quality assurance report: Loch Vale watershed, 1999-2002:

U.S. Geological Survey Open-File Report 2004-1306, 17 p. 

Clesceri, L.S., Greenberg, A.E., and Eaton, A.D., eds., 1998, Standard methods for the 

examination of water and wastewater, 20th ed.: Washington, D.C., American Public Health 

Association, 1,325 p.

Denning, A.S., 1988, Quality assurance report: 1982-1987, Loch Vale watershed project: Fort 

Collins, Colorado, Colorado State University, Natural Resource Ecology Laboratory, 19 p.

Dombek, T., 2011, Quality assurance report, National Atmospheric Deposition Program, 2009:

Champaign, Illinois, Illinois State Water Survey, Central Analytical Laboratory, 22 p.

Dossett, S.R., and Bowersox, V.C., 1999, National Trends Network site operation manual:

Champaign, Illinois, Illinois State Water Survey, National Atmospheric Deposition Program 

Office, NADP Manual 1999-01, 99 p.

Edwards, R.L., 1991, Quality assurance report: 1989-1990, Loch Vale watershed project: Fort 

Collins, Colorado, Colorado State University, Natural Resource Ecology Laboratory, 22 p.

Goodison, B.E., Louie, P.Y.T., and Yang, D., 1998, WMO solid precipitation measurement 

intercomparison final report: World Meteorological Organization, Instruments and Observing 

Methods Report No. 67, WMO/TN–No. 872, 318 p. 

National Atmospheric Deposition Program (NADP), Central Analytical Laboratory, 2009a, 

NADP network quality assurance plan: Champaign, Illinois, NADP Network QAP 2009-09, 

29 p., available at http://nadp.sws.uiuc.edu/. 
21

National Atmospheric Deposition Program (NADP), Central Analytical Laboratory, 2009b, 

NADP quality management plan: Champaign, Illinois, NADP QMP 2009-09, 30 p., available 

at http://nadp.sws.uiuc.edu/.

Richer, E.E., Botte, J.A., and Baron, J., 2011, Loch Vale watershed long-term monitoring and 

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