U.S. DEPARTMENT OF THE INTERIOR 

U.S. GEOLOGICAL SURVEY

Loch Vale Watershed Project 

Quality Assurance Report: 1995-1998

By

U.S. Geological Survey

Eric J. Allstott2, Michael A. Bashkin2, Jill S. Baron1 

Open-File Report 99-111

Prepared in cooperation with the Natural Resource Ecology Laboratory 

and Colorado State University

This report is preliminary and has not been reviewed for conformity with the U.S.

Geological Survey editorial standards. Any use of trade, product or firm names is for

descriptive purposes and does not imply endorsement by the U.S. Government.

'Midcontinent Ecological Science Center

^

Natural Resource Ecology Laboratory

1999
Table of Contents

List of tables and figures.................................................................................................. 2

Introduction....................................................................................................................... 3

Comparison of Alter-Shielded and Nipher-Shielded Raingages.................................. 4

Methods......................................................................................................._^

Results and Discussion...................................................................................................................4

Conclusion...................................................................................................................................... 8

Comparison of BRD and WRD Loch Vale Weather Station Data............................. 10

Methods........................................................................................................................................ 10

Results and Discussion................................................................................................................. 11

Conclusion.................................................................................................................................... 14

Surface Water Chemistry............................................................................................... 15

USFS Water Quality Laboratory.................................................................................................. 15

Preliminary QA/QC Checks ......................................................................................................... 17

Bias and Contamination................................................................................................................ 18

Precision....................................................................................................................................... 19

Hydrology........................................................................................................................ 25

General Conclusions....................................................................................................... 29

References........................................................................................................................ 30
List of Tables and Figures

Table 1. P values for Bonferroni-adjusted paired t-test of Nipher-shielded and Alter-shielded gage

data by season and precipitation type from (1/1/95-12/11/97).

Table 2. Slopes and 95% CI for cumulative Alter/Nipher shielded gage data.

Table 3. Difference in Alter/Nipher shielded total complete and total incomplete cumulative

precipitation records by year and total period of analysis (1/1/95-12/11/97).

Table 4. Meteorological parameters recorded by BRD and WRD stations.

Table 5. P values and mean difference of temperature measured by BRD and WRD stations.

Table 6. P values and mean difference of solar radiation measured by BRD and WRD stations.

Table 7. Results of USGS Analytical Evaluation Program for USFS Biogeochemistry Laboratory.

Table 8. USGS Intersite Comparison Program results for CO98.

Table 9. Blank sample mean concentration.

Table 10. R-Square values for duplicate sample mean concentration vs. standard deviation.

Table 11. T-test differences between normal and duplicate Loch outlet samples.

Table 12. Number of samples taken at each site in Loch Vale.

Table 13. Summary of quality and actions.

Table 14. Water year deposition at Loch Outlet.

Table 15. Water year efflux at Loch Outlet.

Figure 1. Comparison of complete and incomplete Nipher-shielded gage data.

Figure 2. Comparison of complete and incomplete Alter-shielded gage data.

Figure 3. Comparison of incomplete Alter and Nipher-shielded gage data.

Figure 4. Comparison of complete Alter and Nipher-shielded gage data.

Figure 5. Estimated nitrogen deposition at CO98: NADP vs. LVWS calculations.

Figure 6. Difference of temperature measured at BRD and WRD stations.

Figure 7. Difference of relative humidity measured at BRD and WRD stations.

Figure 8. Difference of solar radiation measured at BRD and WRD stations.

Figure 9. Difference of windspeed measured at BRD and WRD stations.

Figure 10. Difference of wind direction measured at BRD and WRD stations.

Figures 11-22. Timeseries of streamwater chemical concentrations 1990-1998: Alk, Ca, Mg, K,

Na, NH4, SO4, NO3 , Cl, PO4, SiO2, and DOC.

Figure 23. Comparison of 1994 DPI 15 to L&S stripchart data.

Figure 24. Comparison of 1995 DPI 15 to L&S stripchart data.

Figure 25. Spurious 1992 streamflow data.
Introduction

The Loch Vale Watershed (LVWS) project was initiated in 1980 by the National 

Park Service with funding from the Aquatic Effects Research Program of the National 

Acid Precipitation Assessment Program. Initial research objectives were to understand 

the processes that would either mitigate or accelerate the effects of pollution on soil and 

surface water chemistry, and to build a record in which long-term trends could be 

identified and examined.

It is important for all data collected in Loch Vale to meet the high standards of 

quality set forth in previous LVWS QA/QC reports and LVWS Methods Manuals. Given 

the ever-widening usage of data collected in Loch Vale, it is equally important to provide 

users of that data with a report assuring that all data are sound. Parameters covered in 

this report are the quality of meteorological measurements, hydrological measurements, 

surface water chemistry, and similarities in catch efficiency of two raingage types in 

Loch Vale for the period of 1995-1998.

Routine sampling of weather conditions, precipitation chemistry, and stream/lake 

water chemistry began in 1982. Since then, all samples and data have been analyzed 

according to widely accepted and published methods. Weather data have been collected, 

analyzed, and stored by LVWS project personnel. Methods for the handling of 

meteorological data are well documented (Denning 1988, Edwards 1991, Newkirk 

1995,and Allstott 1995). Precipitation chemistry has always been collected according to 

National Atmospheric Deposition Program protocol (Bigelow 1988), and analyzed at the 

Central Analytical Laboratory of the Illinois State Water Survey in Champaign, IL. 

QA/QC procedures of the National Atmospheric Deposition Program are well 

documented (Aubertin 1990). Protocols for sampling surface waters are also well 

documented (Newkirk 1995). Analysis of surface water chemistry has been performed 

using standard EPA protocol at the US Forest Service's Rocky Mt. Station 

Biogeochemistry Laboratory since 1993.
Comparison of Alter-Shielded and Nipher-Shielded Raingages

An Alter-shielded Belfort raingage was installed in Loch Vale during September 

1983 as part of the National Atmospheric Deposition Program's (NADP) CO98 network 

site. A Nipher-shielded Belfort raingage was added as a backup gage in October 1987. 

The two gages are approximately 5 meters apart, and should receive the same amount of 

precipitation. The gages may differ in their collection efficiency due to the physical 

properties of each shield type. Comparisons of catch efficiency between Nipher- and 

Alter-shielded Belfort raingages (from October 1987 - April 1989) revealed a slightly 

greater snow catch (10%) from the Nipher-shielded gage (Bigelow et al. 1990).

NADP has adopted the Alter-shielded gage as standard equipment. Niphershielded data were reported to NADP from the Loch Vale site instead of the Altershielded data from 1/1/95 - 12/11/97. The purpose of this analysis is twofold: 1) to 

analyze the preparation of Alter-shielded gage data from 1/1/95 - 12/11/97 for possible 

substitution into the NADP database, and 2) to compare the daily total and cumulative 

precipitation by season and precipitation type between the two shields.

Methods

Precipitation data from the Nipher-shielded gage were recorded continuously on 

strip charts. These have been summed by hand to yield a daily total. Error in the Niphershielded precipitation record may be caused by changes in temperature, windshake, snow 

buildup on shield, and human recording error. Precipitation data from the Alter-shielded 

gage were recorded every fifteen minutes and transmitted hourly to Wallops Island, Va. 

via the GOES West satellite network. The data are made available through the USGS 

Water Resources Division DOMSAT Receive Station located in the Denver Federal 

Center. Sources of error in the Alter-shielded data include windshake, changes in 

temperature, problems with satellite transmission, weather station voltage, and state of 

the DCP's calibration and human interpretation. Raw data from the Alter-shielded gage 

have many false dips and spikes due to noise in the voltage transducer. The dips and 

spikes were smoothed by hand to derive a cumulative record.

Various running medians were applied to smooth the data (1:3 through 1:50). No 

one was able to simultaneously smooth small and large oscillations. Each data point was 

evaluated in relation to surrounding data and corrected when necessary. For example, 

when data oscillated continuously, the mean was assigned to all respective data. When a 

large dip or spike appeared it was flattened out to conform to the surrounding data points. 

The smoothed data were converted to a daily total by subtracting the midnight value from 

the previous day's midnight value.

Results and Discussion

The smoothed daily total Alter-shielded and Nipher-shielded gage data were not 

statistically different (paired t-test: p = 0.34, n= 975). The data were further tested for 

differences by season and precipitation type using Bonferroni-adjusted paired t-tests to 

control for Type 1 error. There were no significant differences between winter (10/1 - 

4/14), spring (4/15 - 7/14), summer (7/15 - 9/30), and rain or unknown precipitation types
(Table 1). However, the Nipher-shielded gage reported 50 mm more precipitation as 

snow (p = 0.0001, n = 310). This is similar to results from Bigelow et al. (1990) and 

Goodison et al. (1989). Winter and snow results can be different because the winter 

comparison uses all days (n = 460) whether or not there was precipitation, while the 

comparison based on snow uses only days when precipitation occurs (n = 310).

Table 1. P values for Bonferroni-adjusted paired t-test of Nipher-shielded and Altershielded gage data by season and precipitation type from 1/1/95 -12/11/97.

Season / Type

All Data

winter

spring

summer

rain

unknown

snow

P Value

0.34

0.18

0.78

0.96

0.48

0.56

0.0001

n*

975

460

230

199

109

60

310

*The total number of days is 1077. The total number of possible comparisons is 975 because of missing 

data. For comparisons based on precipitation type, only a subset of the data had precipitation type 

recorded.

Correcting for Missing Data

Because missing data may bias the cumulative record, we compared the record 

from the Alter-shielded and the Nipher-shielded gages when the data were substituted, 

and one when the record was incomplete. The incomplete record is the smoothed Altershielded gage and raw Nipher-shielded gage data. The complete record uses data from 

one gage when the other gage is missing points. For example, the Alter-shielded gage 

data were not transmitted on day 121, so the Nipher-shielded gage data were used as a 

proxy for that day. However, problems of auto-correlation may appear when comparing 

the cumulative records. The Alter-shielded gage missed 37 days out of 1077 days (3.4%) 

between 1/1/95 and 12/11/97. The Nipher-shielded gage missed 65 out of 1077 (6%). 

Given these low percentages the problem of auto-correlation is negligible.

To compare the cumulative records, 95% confidence intervals were calculated for 

the slopes of the incomplete/complete Alter-shielded and Nipher-shielded records. 

Figures 1 through 4 show the comparisons between gages and between complete and 

incomplete data from the same gage. None of the confidence intervals overlapped, 

suggesting all slopes are statistically different (Table 2). This is the opposite effect 

detected with the daily comparisons when using paired t-tests. However, the paired t-test 

is a more robust comparison because each pair is considered an independent sample. 

Comparison of slopes may be prone to error because an error early in the data is 

perpetuated through out the entire data set.

Table 2. Slopes and 95% CI for cumulative Alter & Nipher-shielded gage data.

Record

Incomplete Alter-shielded 

Complete Alter-shielded 

Incomplete Nipher-shielded 

Complete Nipher-shielded

Slope

0.137 

0.143 

0.126 

0.134

Upper 95%limit

0.138 

0.144 

0.127 

0.135

Lower 95% limit

0.136 

0.142 

0.125 

0.133
Figure 1. Comparison of complete and incomplete Nipher data.

4000

3600

X-V

I 3200

"c 2800 

O

2400

2000 

<u

Q- 1600

'5.

I' *- 

JO

D 

|

1200

800

400

Complete Nipher: 

Slope=0.134

Incomplete Nipher 

Slope=0.126

0 100 200 300 400 500 600 700 800 900 1000 1100

Julian Days Since 1/1/95

Figure 2. Comparison of complete and incomplete Alter data.

4000

3600

3200

2800

 § 

0)

0

1

3 

|

O

2000

1600

1200

800

400

0

Complete Alter: 

Slope=0.143

Incomplete Alter: 

Slope=0.137

100 200 300 400 500 600 700 800 900 1000 1100

Julian Days Since 1/1/95
Figure 3. Comparison of incomplete Alter and Nipher data.

4000

3600

p 3200

C 2800 

O

TO 2400 'a

O 2000 

Q) CL 1600

§£ 1200

ro

3 800

o 40°

Incomplete Alter: 

Slope=0.137

Incomplete Nipher 

Slope=0.126

100 200 300 400 500 600 700 800

Julian Days Since 1/1/95

Figure 4. Comparison of complete Alter and Nipher data.

4000

3600

^ 3200

E

E, 2800

c

.2 2400

^

*& 2000

2 1600

900 1000 1100

JO

D

E

D

O

1200

800

400

0

Complete Alter: 

Slope=0.143

Complete Niphen 

Slope=0.134

0 100 200 300 400 500 600 700 800 900 1000 1100

Julian Days Since 1/1/95
Differences in total cumulative precipitation between complete and incomplete 

data from both gages suggest missing data (< 6%) may slightly bias cumulative 

precipitation records (Table 3). The total difference between the complete and incomplete 

Alter-shielded and Nipher-shielded gage is 168 mm (4.5 % of total record) and 240 mm 

(6.9 % of total record) respectively.

Table 3. Difference in Alter-shielded and Nipher-shielded total complete and total 

incomplete cumulative precipitation records, by year and total period of analysis (1/1/95 - 

12/13/97). Data are expressed in millimeters.

Record

Incomplete Alter-shielded

Complete Alter-shielded

Incomplete Nipher-shielded

Complete Nipher-shielded

Cumulative

precipitation

1995

1255

1414

1226

1332

Cumulative

precipitation

1996

1345

1357

1151

1176

Cumulative

precipitation

1997

1196

1193

1099

1208

Total

Cumulative

precipitation

3796

3964

3476

3716

Conclusion

There was no difference between the Alter-shielded and Nipher-shielded gages 

when daily records were compared with a paired t-test, except when snow was tested 

separately. The Nipher-shielded gage reported 18% more snow than the Alter-shielded 

gage. This is similar to Bigelow et al. (1990) who reported 10% more snowfall from the 

Loch Vale Nipher -shielded gage. Goodison et al. (1989) reported 15% greater snow 

catch from Canadian sites. Previous studies suggest the Nipher-shielded gage is better at 

estimating snowfall, while the Alter-shielded gage under-represents snowfall (Goodison 

etal. 1983).

There was no overall difference between the two gages and the percentage of 

missing data was low (< 6%). Therefore, we suggest substituting for missing data is a 

sensible practice to better estimate cumulative precipitation.

Substituting for missing or corrupt data allows a more accurate calculation of annual 

chemical input budgets. Since under-reporting precipitation amount drives deposition 

down, it only makes sense to report all available precipitation data.

An amendment to modify NADP protocol is before the review committee as of 

this date. This amendment, if approved, would allow pre-approved sites to substitute 

Nipher data in the absence of Alter data. This will be an important change, if approved, 

because the threat of invalidation of our 1995-97 precipitation data will be lifted.

LVWS precipitation records are more complete than NADP's since Nipher data 

has always been included in our database. Use of LVWS precipitation records in the 

calculation of chemical deposition values produces more realistic estimates than when 

NADP records are used. NADP's conservative use of precipitation data causes a 

significant under calculation of chemical deposition. This is seen in the case of Nitrogen 

deposition where a t-test produced a P-value of 0.001- an underestimation of N 

deposition by NADP of 1.37 times (Figure 5).
Figure 5. Estimated nitrogen deposition at CO98: NADP vs. LVWS calculation.

4.00

3.00

2.00

1.00

0.00

Shields were exchanged during summer 1998 so the Alter shield now resides on the gage 

used to collect weekly precipitation amounts. The Nipher shield is now on the gage 

connected to the AeroChem event recorder. This gage collects data pertaining only to 

timing and duration of weekly precipitation- not amount. The as-of-yet-invalid shield 

type is not an issue because of the modified function of this gage. Function of both gages 

will be combined into one summer 2000. This will bring collection of CO98 data into 

line with the other NADP network sites.
Comparison of BRD and WRD Loch Vale Weather Station Data

There are four weather stations in LVWS. One is near the base of the 

Sharkstooth, and another is in Andrews Meadow. The two others, which are the focus of 

this section, are co-located near the confluence of Icy Brook and Andrews Creek. These 

two stations are ~30m apart. One station, established in 1983, was maintained by the 

USGS-Biological Resources Division (BRD). The second weather station, established in 

1991, is maintained by the USGS-Water Resources Division (WRD).

The BRD station was shut down on Nov. 24, 1998 for several reasons. The 

quality of data from all measured parameters declined even after each sensor was 

recalibrated and the data collection platform reprogrammed. Other reasons for 

decommissioning the BRD station include reduction of growing equipment costs, lack of 

available replacement components, lack of certified repair service, and the importance of 

a more standard method of data collection. Data from the WRD station will be included 

in the LVWS database. Merging the two station's data sets into one is prudent only if 

data from each measured parameter proves to be statistically similar. This report 

compares weather data from both stations from 1/1/93 -12/7/97.

The BRD station was a solar powered remote area weather station (RAWS). 

Weather parameters measured by this station were wind speed, wind direction, relative 

humidity, ambient air temperature, solar radiation, and barometric pressure. Parameters 

were measured every 15 minutes by a Handar 524 data collection platform (DCP). These 

data were relayed hourly to the National Oceanic Atmospheric Administration (NOAA) 

receive station at Wallops Island, VA via the Geostationary Operational Environmental 

Satellite West (GOES) satellite network.

Data were quality checked and edited by LVWS personnel before loading into the 

master database for two reasons: 1. the program that loaded data into the database could 

only process the data in one particular format; and 2. so that incomplete or erroneous 

transmissions would not be included in the database. These data were imported weekly 

the LVWS master database.

The WRD station scans every 15 seconds and calculates average hourly and daily 

values. The average hourly and daily values are recorded to Campbell Scientific data 

module that is collected and exchanged for a new module every two to three months. 

The data are available through an FTP link to the WRD.

Methods

The weather stations record many types of data, but only five variables are 

common to both stations (Table 4). The variables compared in this analysis are 

temperature, solar radiation, relative humidity, wind speed, and wind direction. Average 

daily values from both stations were used for comparison. The data were converted into 

the appropriate units for comparison when necessary. Data were adjusted to the nearest 

possible value when obviously erroneous. For example, in some cases, the BRD relative 

humidity was 150% or -10%; these values were adjusted to 100 and 0% respectively. 

Data were tested for significant differences with paired t-tests, and subsets of the data 

were tested for differences using Bonferroni-adjusted paired t-tests to control for Type 1 

error.

10
Table 4. Meteorological parameters recorded by WRD- BRD weather stations.

WRD STATION VARIABLES

Daily Ave. QS radiation in

Daily Ave. QS radiation out

Daily Ave. QA radiation in

Daily Ave. QA radiation out

Daily Ave. net radiation

Minimum 6 & 2 m air temperature.

Average 6 & 2 m air temperature.

Maximum 6 & 2 m air temperature.

Minimum 6 & 2 m relative hum.

Average 6 & 2 m relative hum.

Maximum 6 & 2 m relative hum.

Maximum 6 & 2 m windspeed

6 & 2 m EPA windspeed

6 & 2 m Campbell wind speed

6 & 2 m Campbell vector magnitude

6 & 2 m EPA UT vector dir.

6 & 2 m EPA vector dir. std. dev.

6 & 2 m Campbell vector dir.

6 & 2 m Camp, vector dir. std. dev

UNITS

Langleys/hour

Langleys/hour

Langleys/hour

Langleys/hour

Langleys/hour

Degrees C

Degrees C

Degrees C

%

%

%

mph

mph

mph

mph

360 Degrees

360 Degrees

360 Degrees

360 Degrees

BRD STATION VARIABLES

Hourly incoming QS rad.

2m air temp.

Relative humidity

6m wind speed

6m wind dir.

Barometric pressure

UNITS

Watts/mz

Degrees C

%

Meters/sec.

360 Degrees

Millibars

Results and Discussion

Temperature

On day 1357 (and continuing through the data set), the BRD station temperature 

data became spurious (Figure 7). Before that, WRD daily average temperature was 0.17 

C lower then the BRD station (p < 0.0001, n = 1352). Although the difference is 

statistically significant, 0.17 C is within the sensor's accuracy range (+/- 1 degree F). 

Temperature data were divided by year to determine if differences in temperature are at a 

constant significance level. P-values steadily decreased from 0.2290 in 1993 to <0.0001 

in 1997. The difference between stations markedly increased starting late in 1995 (Figure 

6 and Table 5). Since the BRD temperature/humidity sensor was replaced with a 

reconditioned one in 1994, 1996, and 1997, it appears the problem was with BRD 

station's DCP motherboard.

Figure 6. Difference of temperature measured at BRD and WRD stations.

20 -

.5 15 -

00

D

Q

10 -

5 -

-5 - --5

365 730 1095 

day (1 = 1/1/93)

1460

11
Table 5. P values and mean difference by year for temperature measured by the WRD 

and BRD weather stations. P values reported are Bonferroni adjusted to protect against 

Type 1 errors. Mean difference is WRD minus BRD.

Year

93

94

95

96

97

p value

0.2290

0.0310

O.0001

O.0001

O.0001

mean difference

-0.054

-0.062

-0.309

1.513

15.574

Humidity

Relative humidity from the BRD station reported very high values, often > 100% 

starting day 960, and then reported low (real?) values from day 1561 to the end of the 

record. However, prior to this period the average difference between the two stations was 

4.1% (p < 0.0001, n = 960) (Figure 7). Relative humidity is difficult to measure 

accurately due to glazing of water and or ice on the sensor itself.

Figure 7. Difference of relative humidity measured at BRD and WRD stations.

60

-100

365 730 1095 

Day (1=1/1/93)

1460

Solar Radiation

The BRD pyranometer appeared to malfunction on day 1323 (Figure 8). When 

these data were excluded from statistical comparison, the WRD station on average 

reported 1.9 watts/m2 more then the BRD station (p = 0.002; n = 1323). Solar radiation 

data were further divided by year to determine if difference was at a constant significance 

level over time. The BRD pyranometer was reconditioned and calibrated on July 1, 1997, 

yet spurious measurements persisted. P-values decrease from 1993 to 1997, again 

suggesting problems with the BRD DCP motherboard (Table 6).

12
Figure 8. Difference of solar radiation measured at BRD and WRD stations.

200 . 200

-600_ ..-600

730 1095 1460

day (1=1/1/93)

Table 6. P values and mean difference by year for solar radiation measured by the WRD 

and BRD weather stations. P values reported are Bonferroni adjusted to protect against 

Type 1 errors. Mean difference is WRD minus BRD.

Year

93

94

95

96

97

p value

0.1870

0.0320

0.0400

0.0450

O.0001

mean difference watts/m^/day

1.68

2.64

3.15

-8.26

35.32

Wind Speed

The BRD anemometer malfunctioned between days 728 and 1055. Excluding 

erroneous data, wind at the WRD station was an average of 1.7 m/s greater than at the 

BRD station (p O.0001, n = 1135) (Figure 9). WRD wind speeds were greater for the 

majority of days, suggesting a difference in prevailing wind direction/speed or in sensor 

calibration.

Figure 9. Difference of wind speed measured at BRD and WRD stations. 

15-'

10-

5-

52 

fi 0

a

-5-1

A 15 

10

5

0

-5

-10- -10

365 730 1095 

day (1=1/1/93)

1460

13
Wind Direction

Wind direction measurements are the only ones at the BRD station that don't 

show conclusive signs of malfunction. Wind direction was different between the two 

stations, with 84% of the WRD wind direction coming between 180-210 degrees, while 

the BRD station wind direction reported 81% wind direction coming from between 180 - 

30 degrees (Figure 10). The BRD wind direction record showed more variability than the 

WRD record, perhaps due to topographic differences between the two stations. There is 

nothing to suggest that either atmometer was malfunctioning. Several atmometers may 

be needed to capture the variability of wind direction within LVWS.

Figure 10. Prevailing wind direction at BRD and WRD stations.

North

330

300

West East

240 120

210 160

South

Conclusion

Temperature and solar radiation were similar until the BRD station began to fail. 

Both temperature and solar radiation became increasingly different with time, pointing to 

a progressive degradation of the BRD station. The BRD record shows erratic relative 

humidity and wind speed measurements throughout the record, suggesting intermittent 

station malfunctions. Microclimatological variability seems to drive differences in wind 

direction.

A new set of fields will be set up in the database for the inclusion of WRD station 

data. Requests for Loch Vale weather data will be filled with BRD data from Sept. 8, 

1982 until Dec. 31,1994 and from Jan. 1, 1995 - on from the WRD station.

14
Surface Water Chemistry

Surface water samples are routinely collected throughout the entire watershed. 

The focus of this section is on quality control/quality assurance (QA/QC) samples 

collected from the outlet of the Loch. Twelve percent of the total numbers of samples 

taken from the outlet (from 1995-1998) were QA/QC samples. All QA/QC procedures 

used in the preparation, collection, processing, and shipping of samples have been 

described in the LVWS Methods Manual (Newkirk, 1995), and by Denning (1988 

QA/QC), Edwards (1991 QA/QC), and Allstott (1994 QA/QC). Small procedural 

changes since 1995 will be updated in the forthcoming 1999 version of the methods 

manual.

USFS Water Quality Laboratory

Chemical analyses of water samples were performed by Louise O'Deen at the US 

Forest Service's Rocky Mt. Station Biogeqchemistry Laboratory, Fort Collins, CO. The 

USFS lab participates in a national blind audit round-robin sampling program sponsored 

by the USGS. Results from these tests provide laboratories with information about their 

analytical precision and accuracy. The USFS lab has always (with four exceptions) 

exceeded minimum standard requirements in the analysis of standard reference samples 

(USGS Open-File Reports 96-138, 96-436, 98-52, and 98-391). The cause of these 

exceptions is most probably because most labs that participate in the comparison report 

values gained from using atomic absorption methods, while the USFS laboratory reports 

values from their ion chromatography methods. A summary of results from 1995-1998 is 

listed in Table 7.

15
Table 7. Results of USGS Analytical Evaluation Program for Lab #2 (US Forest 

Service's Rocky Mt. Station Biogeochemistry Laboratory). 4=Excellent, 3=Good, 

2=Satisfactory, l=Marginal, 0=Unsatisfactory.

1995

1996

1997

1998

Constituent

Ca

Cl

F 

K

Mg

Na

S04

pH

Ca

Cl 

F 

K

Mg 

Na 

SO4 

pH

Ca

Cl

F

K

Mg

Na

S04

pH

Ca

Cl

F

K

Mg

Na

S04

pH

Reported Value

1.84

1.39

Not Reported 

0.06

0.40 

1.94

2.26

6.42

0.48

Not Reported 

Not Reported 

0.16

0.07 

Not Reported 

Not Reported 

4.68

1.87

0.16

0.03

0.35

0.59 

0.80

1.05

6.83

0.11

0.20

0.20

0.14

0.02 

0.34

0.41

5.41

Most Probable

1.67

1.30

Not Reported 

0.55

0.35 

1.28

2.34

6.52

0.45

Not Reported 

Not Reported 

0.15

0.06 

Not Reported 

Not Reported 

4.70

1.84

0.20

0.06

0.37

0.57 

0.66

1.10

6.85

0.13

0.23

0.21

0.14

0.03 

0.34

0.40

5.35

Rating

1

3

Not Reported 

3

0 

0

4

4

4

Not Reported 

Not Reported 

3

3 

Not Reported 

Not Reported

4

4

4

3

4

3 

0

4

4

3

4

4

4

4 

4

4

4

16
NREL Water Quality Laboratory

The Loch Vale water quality laboratory participates in the USGS Intersite 

Comparison Program in which conductivity and pH measurements are periodically tested 

on samples of known chemical properties. Results from past studies are listed in Table 8. 

We have met all accuracy goals with one exception. The measured pH in Study #41 was 

.02 over the upper limit of acceptable values. The source of the error was determined to 

be the pH probe itself, which was replaced within the week.

Table 8. USGS Intersite Comparison Program Results for C098 (LVWS).

Comp #

#35

#36

#37

#38

#39

#40

#41

#42

Date

May-95

Nov-95

May-96

Dec-96

May-97

Nov-97

May-98

Dec-98

Exp.

4.95

4.92

4.47

4.22

4.78

4.12

4.62

4.38

pH Meas. pH

5.02

4.98

4.51

4.25

4.80

4.17

4.76

4.39

Met 

Goal?

yes

yes

yes

yes

yes

yes

no

yes

Expected Cond.

15.7

5.3

26.3

26.8

13.0

33.9

20.1

26.9

Measured 

Cond.

18.0

5.2

28.0

27.0

14.4

35.0

21.0

25.9

Met 

Goal?

yes

yes

yes

yes

yes

yes

yes

yes

The pH meter used since the mid-eighties became impossible to calibrate in 

January 1999. The meter was replaced within the week with a new VWR 8000 model 

(approved by NADP). We continue to use pH probes supplied by NADP for all samples.

Samples to be analyzed for dissolved organic carbon are collected and processed 

according to standard methods (LVWS Methods Manual, 1995). Filtered samples are 

delivered bi-weekly to George Aiken's Boulder, CO USGS laboratory.

Preliminary OA/OC Checks

Results of chemical analyses are screened by USFS laboratory personnel and 

LVWS staff. The USFS uses the ion percent difference (IPD = (sum of anions + sum of 

cations)/total ion concentration) as a general indicator of analytical accuracy. Samples 

with an IPD > 15% are flagged and rerun. If the IPD is still out of acceptable range after 

being rerun, each sample is checked ion by ion for possible contamination. If one analyte 

is the clear cause of the imbalance, it may be dropped from the record (as long as the rest 

of the analytes look normal for that time of year). Twenty-two of 342 normal samples 

(6.4%) fell outside the 15% IPD margin from 1995 to 1998. Nineteen of these samples 

were taken between May and September of 1995. There is no apparent cause for this 

period of charge imbalance. Contamination introduced in the field or lab is the most 

probable cause of these errors.

17
Bias and Contamination

Bias and contamination of water samples are quantified by measuring elemental 

concentrations in field blank samples. Field blanks are deionized water samples that are 

processed from start to finish just as normal samples. These samples are taken every 

other third week. 5.8% of the total number of samples taken at the Loch outlet were field 

blanks. Sources of bias and/or contamination can include contamination of DI water 

columns, improper bottle washing procedures, errors in handling and processing of 

samples, and analytical bias in the lab. Mean concentrations of each analyte from field 

blank samples are presented in Table 9.

Table 9. Blank Sample Mean Concentration.

ANALYTE

FLDCOND

LABCOND

FLDPH

LABPH

ALK

Ca

Mg

Na

K

NH4

S04

N03

PO4

Cl

F

Si02

DOC

UNITS

us/cm

us/cm

pH

pH

ueq/1

mg/1

mg/1

mg/1

mg/1

mg/1

mg/1

mg/1

mg/1

mg/1

mg/1

mg/1

mg/1

MEANCONC.

1.31

1.66

5.84

5.30

-1.80

0.02

0.00

0.00

0.00

0.00

0.01

0.01

0.00

0.01

0.00

0.35

0.83

STDDEV.

1.25

1.09

0.31

0.21

3.27

0.03

0.00

0.02

0.01

0.00

0.03

0.02

0.00

0.03

0.01

0.52

0.73

N

18

20

17

20

20

20

20

20

20

20

20

20

20

20

20

17

17

The only known contamination of the DI water system since moving to the NESB 

building from the Grasslands Lab (in 1994) was a silica spike during the summer/fall of 

1996. The only blank sample from that period was taken on 8/13/96, and measured 44.83 

mg/1 (this value was not included in the average presented in Table 9). On 8/19/96, the 

USFS lab notified us that there was a problem with DI. DI water from the USFS 

Laboratory was used for all general laboratory practices from 8/19/96 until 9/11/96, at 

which time CSU Facilities repaired the faulty deionizing columns. No samples (besides 

the one blank) were effected by this contamination, as all samples were drawn from 

LVWS using bottles that had been stored with DI poured before 8/19/96.

Still, the average value of SiO2 in field blank samples is higher than would be 

expected. Because SiO2 carries little charge, DI scrubbing columns are not able to 

efficiently capture all of it. Higher than expected average DOC concentrations in field 

blank samples are likely due to the same cause.

18
Precision

Analytical precision is measured by quantifying differences between duplicate 

paired samples. Duplicate samples are taken every other third week at the outlet of the 

Loch using the identical technique as for normal samples. 6.2% of the total number of 

samples taken at the Loch outlet were duplicate samples.

Since precision often varies with concentration, plots of a duplicate pair's mean 

versus its standard deviation (SD) are useful in determining deficiencies in precision (US 

EPA, 1980). A problem with precision would be indicated by a relationship between all 

paired means and their respective SDs. The lack of relationship present in all regressions 

indicates good precision at varying concentrations. Table 10 describes the R-square 

value for each regression. The only analytes that showed any relationship between mean 

concentration and SD were Potassium (K), Silica (SiO2), and Phosphate (PO4). The SD 

of K (.34) and SiOz (.19) may indicate a slight lack of analytical precision for those 

solutes, or could be indicative of the smaller N value for each. The SD of PCU (.99) is 

due to the extremely low concentration of PO4 in LVWS sample waters (a mean of -0.0 

produces a SD of ~0.0, and the relationship between the two lends a very high R-square 

value).

Table 10. R-Square value for duplicate pair mean vs. duplicate pair standard deviation

Analyte

Field Conductivity

Lab Conductivity

Field pH

LabpH

ALK

Ca

Mg

Na

K

NH4

S04

NO3

PO4

F

Cl

SiO2

DOC

R-Square Value

0.04

0.01

0.00

0.12

0.03

0.01

0.00

0.14

0.34

0.12

0.02

0.02

0.99

0.06 .

0.09

0.19

0.02

19
Another method for examining analytical precision is to calculate the statistical 

difference between normal and duplicate pairs. Paired two-tailed t-tests were used to 

generate the results shown in Table 11.

Table 1 1 . T-test differences between normal

Analyte

FLDCOND

LABCOND

FLDpH

LABpH

ALK

Ca

Cl

DOC

K

Mg

Na

NH4

N03

PO4

Si02

S04

Normal Mean

14.48

12.66

6.38

6.31

69.45

1.61

0.14

1.83

0.18

0.27

0.73

0.02

0.87

0.002

2.44

1.62

Dupe Mean

14.58

12.66

6.49

6.29

68.56

1.58

0.13

1.75

0.18

0.27

0.74

0.01

0.87

0.001

2.39

1.62

and duplicate Loch.O samples.

N Pear son Correlation t-test P

18

16

18

16

17

17

17

15

17

17

17

17

17

16

9

17

0.99

1.00

0.94

0.83

1.00

0.98

0.95

0.97

0.99

0.98

0.98

0.91

0.99

1.00

0.87

1.00

0.44

0.97

O.0001

0.42

0.23

0.31

0.30

0.31

0.66

0.30

0.51

0.12

0.94

0.33

0.70

0.92

Most pairs are statistically similar. T-test P values are high with the exceptions of 

NH4 and field pH. Although not significant, the difference between paired NFLt 

measurements (p= .12) is most likely due to low sample concentrations that are at, or 

below analytical detection limits. All approaches to the determination of detection limits 

are based on a statistical statement of where "signal" exceeds "noise" (MacTaggart, 

1998). This limit will vary between different methods and instruments. The accuracy of 

any measurement of concentration below this threshold is suspect; yet still useful in the 

fact that we know the concentration is exceedingly small.

The only statistically significant difference found is between field pH normal and 

duplicate samples (p= .00005). Causes of this error could be due to a faulty pH probe, a 

faulty pH meter, or error in the calibration/usage of the meter. However, paired lab pH 

measurements (splits of the same pairs used for field pH) show a much higher degree of 

similarity (p= .42). These results suggest that pH measurements from the USFS lab are 

more accurate and reproducible.

20
The total number of normal samples taken at each site in Loch Vale is described 

in Table 12.

Table 12. Number of samples taken at each site in Loch Vale.

Sample Site

Andrews Creek

Andrews Tarn

Emerald Outlet

Glass Outlet

Haiyaha Outlet 

Husted Surface

Little Loch Creek

Loch Hypolimnion 

Loch Inlet

Loch Outlet

Loch Surface

Louise Inlet

Louise Outlet

Sky Hypolimnion 

Sky Inlet (North) 

Sky Inlet (South) 

Sky Outlet 

Sky Surface

Times Sampled (1995-1998)

13

1

3

13

3 

4

12

8 

13

208

9

1

4

5 

11 

12 

12 

4

While reviewing time-series charts of concentration data, it became apparent that 

some data points were unrealistic, and likely incorrect. Forty-nine suspicious points were 

identified from throughout the entire LVWS data set (1982-98). Data were reviewed on a 

point-by-point basis. Twenty data points proved to be erroneous, and were corrected or 

deleted. Common instances included blank samples recorded as normal samples, samples 

that were out of the +/-15 percentage IPD margin, contamination errors, and data 

entry/transfer errors. Corrected time series data (1990-1998) are presented in Figures 11- 

22.

Figure 11. Alkalinity.

120.00

21
Figure 12. Calcium.

2.50

1.50

0.50

r-.

* .

- < f-

.*.

<N <*) /95 <£>

-V-*1

Figure 13. Magnesium.

O)

0.45

0.35

0.25

0.15

0.05

* f .f ».

V l

'o tM ib 005

Figure 14. Potassium.

O)

0.50

0.10

Figure 15. Sodium.

O)

1.60

1.20

0.80

0.40

0.00

^

v^

 ^ *-

N /94 od 

5

22
Figure 16. Ammonium.

0.14

O)

0.10

Figure 17. Sulfate.

6.00

O)

2.00 -»

0.00

Figure 18. Nitrate.

2.00

D)

1.00 -f

0.00

* --

 * * V-v^ «/ "V- *» V %' ' -y % <

'O N c*)

9?

rO

/95 (6

Figure 19. Chloride.

0.70

O) 0.50

/97- CO

5?

23
Figure 20. Phosphate.

O)

0.10

0.06

0.02

O)

op

o 

92 92 

o

CM

92

CO

92 92T~

CD

10

92

CO

92 92

CD

oo 

92

Figure 21. Silica.

D)

4.50

Figure 22. Dissolved Organic Carbon.

5.00

O>

£ 3.00

O) 

CO 92 

o

CM

92

co 

92 92To

92

co 

92 92TO

oo 

92

24
Hydrology

The outlet of the Loch is located at the northeastern edge of the basin, and has 

been gaged with a Parshall flume and stilling well since 1983. The accuracy of a Parshall 

Flume is ~ 5% (Winter, 1981). Prior to 1994, it was estimated that an additional 5% 

uncertainty was introduced by water flowing around or under the frame structure. 

Frequent examination of the flume's condition reveals that, since some minor repairs in 

1994, flow around and under the flume is insignificant. A recent low-water inspection of 

the inside of the flume revealed that it is still of its original dimensions (extremely 

important when calculating flow volumes and rates), and that it is structurally sound.

Until 1997, stage height data were collected both mechanically (with a Leupold & 

Stevens chart recorder) and electronically (with an Omnidata DPI 15 datalogger). 

Necessary corrections to DPI 15 data (due to equipment and/or operator error) were 

executed and noted after reducing raw data from the data storage module (DSM). The 

data were then run through a Fortran program that calculates discharge as a flow rate of 

cubic meters/second (CMS) using a formula provided by the Thompson Pipe and Steel 

Co.

As a quality spot-check of flow data, weekly checks of actual stage height are 

recorded after observing a staff gage located just inside the flume as flow and snow 

permits. Stage height is converted to flow rate, and compared to the mechanically and 

electronically collected values.

Use of the Omnidata DPI 15 was discontinued at the end of the 1997 water year. 

This decision was due to a number of factors: 1) its overly cumbersome method of 

operation, 2) the many possible sources of error introduced in the process of reducing 

discharge data from the DPllS's DSM, and 3) the impossibility of attaining a proper 

offset factor from the 1997 data.

The 1997 and 1998 hydrographs were created by reading instantaneous values at 

maximum and minimum flow each day from the Leupold & Stevens chart recorder 

stripcharts. These values were averaged into daily mean CMS.

Before accepting this method of estimating flow, and including the data in our 

database, its validity was put to test. Several intervals of stripchart daily averages were 

compared to stage data gathered via the DP 115. In light of some significant differences 

found, the next step was to recalculate all flow from all years using the L&S stripcharts to 

make certain that historical data was correct. Years 1984 - 1991, 1993, and 1996 

matched very well (T-test p values ranging from 0.85 to 0.93). However, there were 

significant differences in 1994 (p=0.008) and 1995 (p=0.026) between calculated 

(DP 115) and observed flow (from charts and fieldbooks). These errors resulted in a 

serious underestimation of flow (Figures 23 and 24).

25
daily mean cms

to

p b

950401*1 

9504091 

950417= 

950425] 

950503= 

9505111 

950519J 

950527! 

950604J 

950612; 

950620! 

950628| 

9507061 

950714= 

9507221 

950730! 

950807! 

950815! 

95 082 31 

950831! 

950908; 

950916J 

950924; 

951002| 

951010; 

951018! 

9510261

OQ

bonoI

daily me

C/3

CA 

ff.

T3

Sp b

940401^ 

940409^ 

9404171 

940425J 

940503J 

940511J 

940519J 

94052 7| 

940604[ 

940612J 

940620J 

940628J 

940706] 

940714! 

940722J 

940730J 

940807J 

940815| 

9408231 

940831! 

940908J 

940916J 

940924J 

941002= 

941010; 

941018J 

9410261
A unique adjustment factor for each erroneous period during 1994 and 1995 was 

calculated by subtracting DPI 15 flow data from L&S chart data. Each factor was then 

added to its respective erroneous interval. This corrected flow was then rechecked 

against data from field notebook and the L&S charts. A new master flow file was created 

using all the corrected data and imported into the Loch Vale database.

In discussion following these actions, the question was raised as to whether or not 

two values per day would lend an accurate daily average. Ten days of flow from 1996 

(evenly distributed throughout the hydrograph) were calculated using different numbers 

of hourly measurements for averages. The most measurements used in a single day's 

average were twelve. Averages built on twelve observations per day were not 

significantly different from those built on two (max/min) (p= 0.83). Because maximum 

flow usually occurs within an hour of midnight, and minimum flow usually occurs within 

an hour of noon, there was no significant difference between max/min and midnight/noon 

averages (p=0.96). This is useful because it is easier to work through the stripcharts 

using midnight to noon values that it is to use maximum and minimum values.

The problems with the DPI 15 were caused by its inability to "remember" the 

proper offset adjustment. The Fortran code that reduces flow data from the raw DSM 

output required a single factor to act as an offset adjustment (equivalent to zeroing a 

balance). When the DPI 15 was new, one offset factor could be entered for the entire 

year. As the datalogger aged, a drift developed in the logger's memory that made offset 

change from week to week, or in some cases from day to day. This made it impossible to 

acquire one, or even several factors to input to the Fortran reduction code. Although 

there is no documentation of the actions taken, a past data manager spent several weeks 

with the 1996 hydrograph data. It is believed that he went through similar contortions (as 

previously described).

There was an erroneous period in 1992 of unknown origin. Data from this period 

was substituted with stripchart data (Figure 25) and entered into Oracle.

Figure 25. Spurious 1992 data.

erroneous data 

DP115

27
A number of errors were identified in the flow record from 1984-1991, 1993, and 

1996. Although none of these errors had significant bearing on the total estimate of 

yearly efflux, they were changed in the database and documented in the archive of yearly 

flow files.

A Campbell Scientific CR500 datalogger and an EnviroSystems shaft encoder 

will be installed in a new stilling well at the onset of flow in 1999. This recorder will be 

much easier to operate than the DPI 15. The CR500 will provide instantaneous, hourly, 

and daily flow measurements without having to manipulate any data. Extensive testing 

and calibration of the CR500 has been performed to ensure the quality of all data 

collected.

28
General Conclusions

In general, quality of LVWS data was good through the period of analysis. 

A summary of all actions taken is presented in Table 13.

Table 13. Summary of quality and actions taken.

Quality Action Taken

Met Station Insufficient/failing. decommissioned Nov. 24, 1998 

switched to WRD station

Aerochem Sensor not responding 

(November 98).

replaced regulator, added 

80amp/hr battery 

replaced motorbox 

replaced sensor

Belfort Raingages Non-standard (Nipher) winddrop shield. 

Missing points from NADP.

installed standard (Alter) shield

Combined all precip data from 

FORFs, charts, and database.

Stream Gage/Flow Underestimates/spurious points. 

Omnidata datalogger bad.

Recalculated discharge 1984-1997. 

Installed new Campbell Sci. 

CR500.

NREL/LVWS 

Laboratory

Duplicate analysis- good.

Blank analysis- good.

Si contamination in DI (8/19/96

-9/11/96).

pH probe failed. 

pH meter failed.

N/A

N/A

Imported clean DI water from

USFS lab.

DI columns were replaced.

Replaced November 1998.

Replaced January 1999.

USFS Laboratory Water quality- good. N/A

In spite of some major equipment failures, no data was lost due to backup devices. 

Decommissioning the Omnidata stream recorder and RAWS were important steps to 

insure the quality of future data collected. The new systems should be faster, more 

reliable, and less expensive to use/maintain.

Water quality measurements were very accurate, with the exception of a short 

period when our DI showed signs of SiCh contamination. The water quality database was 

examined virtually point by point. Several points were either corrected or deleted. This, 

combined with refinements to the streamflow and precipitation records, allow us the 

ability to construct the most accurate chemical input/output budgets for LVWS to date.

29
References

Allstott, E.J. Quality Assurance Report: 1991-1994, Loch Vale Watershed Project. Natural Resource 

Ecology Laboratory, Colorado State University, Fort Collins, CO. (1995).

Aubertin, G.M.; Bigelow, D.S.; Malo, B.A. Quality Assurance Plan NADP/NTN Deposition Monitoring. 

National Atmospheric Deposition Program. (1990)

Bigelow, D.S.; Dossett, S.R. Instruction Manual NADP/NTN Site Operation. NADP/CAL, (1988- updated 

frequently)

Bigelow, D. S.; Denning, S. A.; Baron, J. Differences between Nipher and Alter Shielded Universal Belfort 

Precipitation Gages at Two Colorado Deposition Monitoring Sites. Environ. Sci. and Tech. 1990, 24, 758- 

760.

Denning, A.S. Quality Assurance Report: 1982-1987. Loch Vale Watershed Project. Natural Resource 

Ecology Laboratory, Colorado State University, Fort Collins, CO. (1988).

Edwards, R. Quality Assurance Report: 1989-1990, Loch Vale Watershed Project. Natural Resource 

Ecology Laboratory, Colorado State University, Fort Collins, CO. (1991).

Goodison, B. E.; Turner, V. R.; Metcalfe, J. R. Proceeding: Conference on Meteorological Observation and 

Instrumentation; American Meteorological Society: Boston, MA, 1983; pp. 21-26.

Goodison, B. E.; Vet, R. J. In Atmospheric Deposition; Delleur, J. W., Ed.; IAHS Publication No. 179; 

International Association of Hydrological Sciences: 1989; pp. 47-55.

MacTaggart, D. Guest Editorial: Realistic detection limits. American Environmental Laboratory, 4:10/98, 

1998.

Newkirk, B.K. LVWS Methods Manual. Loch Vale Watershed Project. Natural Resource Ecology 

Laboratory, Colorado State University, Fort Collins, CO. (1995).

USGS Open-File Reports 96-138. Results of the US Geological Survey's Analytical Evaluation Program 

for Standard Reference Samples. (1996)

USGS Open-File Reports 96-436. Results of the US Geological Survey's Analytical Evaluation Program 

for Standard Reference Samples. (1996)

USGS Open-File Reports 98-52. Results of the US Geological Survey's Analytical Evaluation Program for 

Standard Reference Samples. (1998)

USGS Open-File Reports 98-391. Results of the US Geological Survey's Analytical Evaluation Program 

for Standard Reference Samples. (1998)

U.S. Environmental Protection Agency, Interim Guidelines and Specifications for Preparing Quality 

Assurance Project Plans, Office of Monitoring Systems and Quality Assurance, Office of Research and 

Development, QAMS-005/80, Washington. DC (1980).

30