Agnes

Lost

English

North Fork 

Elk Creek

Trail

Dog

Creek

Creek

Creek

Creek

North Fork Elk River

Middle Fork 

Elk Creek

Elk River

Site 1

Site 2

Site 3

Site 4

Site 5

ROUTT CO

JACKSON CO

40o50'

40o45'

106o 106 40' o45'

0 1

0

2 MILES

1 2 KILOMETERS

LOCATION MAP

DENVER Grand 

Junction

C O L O R A D O

Milner

Study area

EXPLANATION

Mount Zirkel Wilderness Area

Routt National Forest

Stream

Lake

Secondary or logging road

Water-quality sampling site

Improved road or highway

Blowdown and salvage 

 logging zone

Private land

106o50' 106o35' 106o30'

40o55'

Clark

N

ABSTRACT

On October 25, 1997, in and around the Routt National Forest and the Mount Zirkel Wilderness Area, a winter snowstorm 

occurred in conjunction with heavy winds that resulted in the 

destruction of thousands of acres of old-growth tree stands. The 

U.S. Geological Survey, in cooperation with the U.S. Forest Service, collected water-quality data at five sites in the North Fork 

Elk River watershed where most of the blowdown occurred. In 

this report, these data are used to characterize water quality in 

areas affected by the blowdown compared to that of relatively 

undisturbed areas. No difference was detected between loads of 

the selected constituents from the five water-quality sampling 

sites. 

INTRODUCTION

On October 25, 1997, in and around the Routt National 

Forest and the Mount Zirkel Wilderness Area, a winter snowstorm occurred in conjunction with heavy winds that resulted in 

the destruction of thousands of acres of old-growth tree stands

(fig. 1). Maximum wind velocities of 120 miles per hour were 

recorded. This event, typically referred to as a "blowdown," is 

Data Summary and Loading Sources for Selected Water-Quality 

Characteristics of Streams in Blowdown Areas, North Fork 

Elk River Watershed, Colorado, March 1999–August 2000

Prepared in cooperation with the U.S. FOREST SERVICE

Figure 1. Water-quality sampling sites and area affected by blowdown in the North Fork Elk River watershed.

U.S. Department of the Interior

U.S. Geological Survey January 2003

FS–127–02
considered to be an anomaly usually associated with hurricaneforce winds. The abundance of old-growth canopy such as Engelmann spruce and subalpine fir in the region indicates the rarity of 

this type of event in this area (Snook, 1999). 

Trees over a large area were uprooted, which disrupted the 

air-soil interface (fig. 2). As a result, the potential for increased 

sediment yield and mass wasting increased. Increases in sediment 

yield have been linked to issues concerning stream and forest habitat, floodwater conveyance, and stream-chemistry imbalance 

(Elliott and DeFeyter, 1986). Disturbance from salvage logging 

may increase sediment yield and affect stream chemistry; however, disturbance from salvage logging likely will occur on a 

smaller scale relative to the disturbance from blowdown. 

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

U.S. Forest Service, collected water-quality data at sites in the 

North Fork Elk River watershed where most of the blowdown 

occurred. In this report, these data are used to characterize water 

quality in areas affected by the blowdown compared to that of relatively undisturbed areas.

SITE SELECTION AND DATA COLLECTION

Water-quality sampling sites (fig. 1, table 1) were selected to 

represent undisturbed, disturbed, and salvage-logging zones. 

Water-quality samples were collected and concurrent streamflow 

measurements made at each site from March 1999 to August 

2000. All water-quality and streamflow data were collected using 

USGS quality-assurance protocols (Wilde and Radtke, 1998; 

Rantz and others, 1982). Water-quality samples were analyzed for 

field parameters, major ions, dissolved nutrients, total phosphorus, total and dissolved metals, suspended sediment, and turbidity. 

The farthest upstream sampling site, on the North Fork Elk River 

just upstream from Agnes Creek (site 1), was chosen as a background site because blowdown was minimal in this subwatershed, 

and the site is upstream from a salvage-logging area. Site 2 was 

located on the North Fork Elk River upstream from the confluence with Trail Creek. The watershed for site 1 represents less 

blowdown than site 2. Both sites are upstream from where salvage logging is done. Igneous and metamorphic rocks underlie 

the watershed upstream from site 1. The geology that underlies 

site 1 continues into the watershed of site 2 and includes unconsolidated Pleistocene deposits and, to a limited extent, Mancos 

Shale (Tweto, 1979). The next two sites are on tributaries of the 

North Fork Elk River, Lost Dog Creek (site 3) and English Creek 

(site 4). Sites 3 and 4 were subjected to some of the heaviest 

blowdown outside of the Mount Zirkel Wilderness Area and represent basins where salvage logging is being done. The underlying geology in these basins is similar to that upstream from site 2 

with the addition of some sandstone and limestone (Tweto, 1979). 

North Fork Elk River above mouth near Clark (site 5) is an integrator site for the entire watershed. Comparison of water-quality 

information from site 5 with water-quality information from sites 

2, 3, and 4 characterizes water quality in the area affected by the 

blowdown and salvage logging and provides perspective on the 

water quality of tributary inflows from the west side of the watershed.

DATA SUMMARY

Summary statistics for field parameters, chemical constituents, and physical parameters are listed in table 2. All waterquality and streamflow data collected for this study are published 

in USGS annual data reports for Colorado (U.S. Geological Survey, 1999 and 2000). The Elk River and tributaries to the Elk 

River, including streams located within the Mount Zirkel Wilderness Area, are classified as “outstanding waters” by the State of 

Colorado and carry Aquatic-Use Class 1 and Recreation 1 designations (Colorado Department of Public Health and Environment, 

2001). 

Figure 2. Routt National Forest near North Fork Elk River after the 

blowdown of October 25, 1997.

Table 1. Sample collection site in North Fork Elk River watershed

[mi2, square miles; USGS, U.S. Geological Survey]

Site 

number

(fig. 1)

USGS station

number Site name

Drainage 

area

(mi2)

1 405057106451000 North Fork Elk River above 

Agnes Creek near Clark

12.3

2 404950106462700 North Fork Elk River above 

Trail Creek near Clark

19.3

3 40475106454200 Lost Dog Creek above 

mouth near Clark

3.2

4 404727106453700 English Creek above mouth 

near Clark

2.5

5 404620106461900 North Fork Elk River above 

mouth near Clark

41.4
Physical Parameters

Summary statistics for physical parameters are listed in 

table 2. These parameters are streamflow, suspended sediment, 

and turbidity. There are no State standards for suspended sediment or turbidity. However, comparison of suspended-sediment 

concentrations and turbidity between sites would indicate if 

there were any differences upstream from the major disturbance 

areas as compared to those measured downstream near the 

mouth of the North Fork Elk River. Suspended-sediment concentrations at site 1 ranged from less than 1 to 10 milligrams per 

liter and median concentration was 2.5 milligrams per liter. Suspended-sediment concentrations at site 5 ranged from less than 1 

to 21 milligrams per liter and median concentration was 2 milligrams per liter. Ranges of concentration and median concentrations for suspended sediment were similar at sites 2, 3, and 4. 

The similarity of suspended-sediment concentrations between 

sites upstream and downstream from the areas in the watershed 

affected by the blowdown indicates that there was no measurable 

effect of the blowdown on suspended-sediment concentrations. 

Turbidity values measured at sites 1 through 5 also were similar.

 Field Parameters

Field measurements were for dissolved oxygen, pH, specific conductance, and water temperature. Comparisons of summary statistics for each parameter at individual sites are listed in 

table 2. These data indicate that all values of dissolved oxygen or 

pH were in compliance with State instream standards. The State 

of Colorado Department of Public Health and Environment does 

not set standards for specific conductance or temperature for the 

North Fork Elk River watershed. Comparisons of the median 

specific-conductance values and water temperature values from 

the primarily undisturbed area (site 1) to those measured near 

the mouth of the North Fork Elk River downstream from watersheds that contained areas of blowdown (site 5) indicate that specific conductance and water temperature are similar at all sites.

Chemical Constituents 

Chemical constituents such as major ions, nutrients, and 

trace elements can originate from a variety of sources. The ways 

in which solutes occur in natural waters are influenced by many 

environmental factors, especially climate, underlying geology, 

and biochemical effects associated with life cycles of plants and 

animals (Hem, 1985). Because there is minimal human impact 

on the watershed of the North Fork Elk River, water-quality constituents are derived primarily from natural sources. 

Except for dissolved solids and aluminum, chemical constituents listed in table 2 have instream standards set by the State of 

Colorado. All constituents sampled at all sites had concentrations 

less than the instream standard. Based on the comparison of 

median concentrations for constituents listed in table 2, water quality among sites is similar. For example, at sites 1 through 5, 

median concentrations of total phosphorus ranged from less than 

0.004 to 0.007 milligram per liter. 

LOADING SOURCES

Constituent concentrations and field-parameter values were 

similar among all sampling sites; however, constituent loading (the 

product of streamflow, constituent concentration, and a coefficient) 

could be affected by surface disturbance associated with the blowdown in a particular subbasin. To evaluate constituent loading 

among the five sampling sites, constituent loading per square mile 

was calculated for selected constituents at each site to determine if 

any particular subbasin contributed more loading per unit area than 

other subbasins. Median constituent loads per square mile for dissolved nitrite plus nitrate, total phosphorus, dissolved zinc, dissolved solids, and suspended sediment were computed (table 3).

Because constituent concentration among sites is a function 

of runoff and drainage-basin area, analysis of loading between sites 

may be useful. Except for nitrite plus nitrate and dissolved zinc, 

Lost Dog Creek (site 3) had the largest median load for the selected 

constituents. Median dissolved nitrite plus nitrate and dissolved 

zinc loads decreased from upstream to downstream on the main 

stem of the North Fork Elk River (sites 1, 2, and 5, table 3). 

Loads for dissolved nitrite plus nitrate, total phosphorus, dissolved zinc, dissolved solids, and suspended sediment for the five 

water-quality sampling sites were compared using analysis of variance (ANOVA) (SPSS Inc., 1997). For the purpose of this analysis 

the data were ranked, and ANOVA was done on the ranks of the 

data (Conover and Iman, 1981). The grouped means of ranked data 

for the selected constituent loads among the five sites were not significantly different (p > 0.05). The study shows that there was no 

difference between loads of the selected constituents from the five 

water-quality sampling sites; therefore, the conclusion can be made 

that constituent loads from watersheds with large areas of blowdown and where salvage logging occurred were not different from 

loads in areas where minimal blowdown and no salvage logging 

occurred.
Table 2. Selected streamflow and water-quality data for sites located in North Fork Elk River study area

[ft3/s, cubic feet per second; mg/L, milligrams per liter; SC, specific conductance; NO2 + NO3, nitrite plus nitrate; μS/cm, microsiemens per centimeter; oC, degrees Celsius; μg/L, micrograms per liter; 

N, number of samples; NTU, nephelometric turbidity units; <, less than]

Summary 

statistics

Physical parameters Field parameters Chemical constituents

Instantaneous 

streamflow

(ft3/s)

Suspended 

sediment 

(mg/L)

Turbidity 

(NTU)

Oxygen, 

dissolved 

(mg/L)

pH, 

standard units

SC

(μS/cm)

Water 

temperature 

(° Celsius)

Sulfate, 

dissolved 

(mg/L as 

SO4)

NO2 + 

NO3,

dissolved 

(mg/L as 

N)

Phosphorus, 

total 

(mg/L as 

P)

Aluminum, 

dissolved 

(μg/L as 

Al)

Cadmium, 

dissolved 

(μg/L as 

Cd)

Copper, 

dissolved 

(μg/L as 

Cu)

Iron,

dissolved 

(μg/L as 

Fe)

Silver, 

dissolved 

(μg/L as 

Ag)

Zinc,

dissolved 

(μg/L as 

Zn)

Dissolved 

solids 

(μg/L)

North Fork Elk River above Agnes Creek 

(site 1)

N 11 10 11 11 11 11 11 11 11 11 6 6 6 6 6 6 11Median 11 2.5 0.5 8.9 7.2 35 5 1.6 0.08 <0.008 44.5 <1 <1 24 <0.60 <20 23.1

Maximum 218 10 2 10.9 7.5 43 11.6 4.5 0.18 0.01 51 <1 1 46 <1.0 <20 36.1Minimum 0.62 <1 0.3 7.9 6.6 21 0.5 1.1 0.05 <0.004 9 <1 <1 20 <0.20 <20 16.0

North Fork Elk River above Trail Creek

(site 2)

N 11 9 11 11 11 11 11 11 11 11 7 6 6 66 6 11Median 21 2 0.7 8.9 7.2 39 6.6 1.6 0.06 <0.004 24.0 <1 0.75 35 <0.60 <20 26.7

Maximum 282 79 2 11.3 7.8 52 14 2.9 0.14 0.034 60.6 <1 1 82 <1.0 <20 39.0

Minimum 5.9 <1 0.4 7.7 6.9 21 0.1 1.1 0.03 <0.004 <15 <1 <1 20 <0.20 <20 16.0

Lost Dog Creek 

(site 3)

N 11 11 11 11 11 11 11 11 11 11 6 6 6 6 6 6 7Median 9.1 2 0.7 10.1 7.4 35 3.5 1 0.033 0.006 61.3 <1 <1 78 <0.60 <20 28.0Maximum 41 10 8 11 7.8 44 10.5 1.3 0.120 0.010 78.1 <1 5 130 <1.0 <20 37.0

Minimum 2.2 <1 0.3 7.9 6.9 21 0.1 0.7 <0.005 <0.008 29.0 <1 <1 50 <0.20 <20 18.0

English Creek 

(site 4)

N 11 11 11 11 11 11 11 11 11 11 6 6 6 6 6 6 11Median 5 1 0.6 9.2 7.2 33 3.4 1.1 0.011 0.007 62.3 <1 <1 76.5 <0.60 <20 31.0

Maximum 26 9 2.4 10.6 7.6 39 10.9 1.4 0.093 0.010 75.6 <1 3 150 <1.0 <20 36.7

Minimum 1.2 <1 0.3 7.8 6.8 19 0.2 0.7 <0.005 <0.004 34 <1 <1 51 <0.20 <20 17.5

North Fork Elk River above Mouth 

(site 5)

N 11 11 11 11 11 11 11 11 11 11 6 6 6 66 6 11Median 44 2 0.6 9.8 7.5 54 3.9 2.5 0.033 0.007 40.8 <1 <1 55 <0.60 <20 38.0

Maximum 422 21 9 10.6 7.9 74 15.7 4.9 0.101 0.021 67.9 <1 <1 79 <1.0 <20 49.0

Minimum 16 <1 0.2 7.4 7.1 24 0 1.1 0.013 <0.004 12.0 <1 <1 30 <0.20 <20 19.1
REFERENCES

Colorado Department of Public Health and Environment, 2001, 

Classifications and numeric standards for Upper Colorado 

River Basin and North Platte River: Water Quality Control 

Commission, Regulation Number 33, 84 p.

Conover, W.J., and Iman, R.L., 1981, Rank transformations as a 

bridge between parametric and non-parametric statistics: 

The American Statistician, v. 35, no. 3, p. 124–129.

Elliott, J.G., and DeFeyter, K.L., 1986, Sediment-data sources 

and estimated annual suspended-sediment loads: U.S. 

Geological Survey Water-Resources Investigations Report 

86–4344, 147 p.

Hem, J.D., 1985, Study and interpretation of the chemical characteristics of natural water: (3d ed.): U.S. Geological Survey Water-Supply Paper 2254, 263 p. 

Rantz, S.E., and others, 1982, Measurement and computation of 

streamflow –Volume 1, measurement of stage and discharge: Volume 2, Computation of discharge: U.S. Geological Survey Water-Supply Paper 2175, 631 p.

Snook, J.S., 1999, The 1997 Rocky Mountain Forest blowdown 

event: February 1999, Forecast System Laboratory Forum, 

Web site URL: http://www.fsl.noaa.gov/~vondaust/f299/

f399a.html accessed January 2001.

SPSS Inc., 1997, SYSTAT 7.0—Statistics: Chicago, User's guide, 

751 p.

Tweto, Ogden, comp., 1979, Geologic map of Colorado: U.S. Geological Survey State Geological map, scale 1:500,000 

(reprinted).

U.S. Geological Survey, 1999–2000, Water resources data, Colorado water years 1999–2000, v. 2, Colorado River Basin: 

U.S. Geological Survey Water-Data Reports CO–99–2 

through CO–00–2.

Wilde, F.D., and Radtke, D.B., 1998, National field manual for collection of water-quality data: U.S. Geological Survey Techniques of Water-Resources Investigations, book 9, chap. A6, 

variously paged.

—Kenneth J. Leib and Paul von Guerard

Table 3. Median load for selected constituents per square mile of drainage area

[NO2 + NO3, nitrite plus nitrate; lb/d/mi2, pounds per day per square mile]

Site name

(fig.1)

NO2 + NO3,

dissolved

(lb/d/mi2)

Phosphorus, total

(lb/d/mi2)

Zinc, 

dissolved

(lb/d/mi2)

Dissolved 

solids

(lb/d/mi2)

Suspended 

sediment

(lb/d/mi2)

North Fork Elk River above Agnes Creek near Clark 0.60 0.02 0.49 186 12

North Fork Elk River above Trail Creek near Clark 0.32 0.02 0.53 222 12

Lost Dog Creek above mouth near Clark 0.60 0.09 0.45 465 33

English Creek above mouth near Clark 0.12 0.07 0.36 360 9.6

North Fork Elk River above mouth near Clark 0.25 0.04 0.35 169 4.9

For more information about this study, write to:

Subdistrict Chief

764 Horizon Drive

Room 125

Grand Junction, CO 81506

email: kjleib@usgs.gov

email: pbvongue@usgs.gov
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